The foundation determines the performance characteristics and service life of the house, so the selection and installation of the structure must be approached with great responsibility. A strip foundation is a strong and reliable foundation for buildings with heavy floors and simple architecture.
The strip foundation device consists of a strip that takes the load of the entire room. It does not require careful soil preparation and is suitable for liquefied, garden, forest or clay soil. Widely used in non-uniform soil.
The main advantage of a strip foundation is that it is suitable for building a house with a basement or ground floor. Laying is easier, but requires more cost and time than other types of foundation.
Types of strip foundation
- Shallow strip foundation is suitable for soil with moderate heaving and for soil that does not freeze below 1.5 meters. This is a profitable construction option, since the construction of the structure does not require a deep pit, which will save money and work time.
- Recessed the foundation is used to build houses with heavy walls and concrete floors, with a large basement or underground garage. For this type of construction, it is important to correctly calculate the depth. To do this, determine the level of soil freezing and subtract 30 centimeters from the indicator.
Both designs are suitable for building a wooden house. A shallow strip foundation is a more affordable and simpler option, which, thanks to easy installation, can be installed with your own hands. Shallow strip foundations are often used for light-weight buildings: country houses and small country cottages, bathhouses and gazebos.
Recessed and shallow strip foundations come in the form of a monolithic concrete structure or prefabricated reinforced concrete blocks. Experts recommend using the first option, as it is very durable and reliable with a service life of 100-150 years. Next, step-by-step instructions will tell you how to properly install the foundation with your own hands.
Preparatory work: soil study and marking
First of all, marking and calculation of the strip foundation is carried out. To calculate the required dimensions, volumes of materials and fittings, use a special online calculator. Such a calculator is easy to find on the Internet.
In addition, you can seek help from professional builders or consultants in a store that sells the necessary materials. Then they move on to marking.
To do the marking yourself, first remove debris from the land. Then you need to mark the internal and external boundaries of the structure using pegs, rope, reinforcement rods or other available items. For more accurate markings, laser levels are used.
How to achieve even markings:
- Establish the axis of the future structure;
- Use a plumb line to determine the first angle from which to pull the rope perpendicular to the other two angles;
- Use a square to mark the last fourth corner;
- Check the evenness of the corners and stretch the rope between them;
- Make the internal markings according to the same principle with an indentation of 40 centimeters from the outside. By the way, you can first mark the internal boundaries, and then the external ones. The sequence doesn't matter much
Before installation, be sure to study the soil characteristics, the degree of soil freezing and surface differences. You need to dig a pit from the lowest point. For the construction of a small house, bathhouse or gazebo, the depth of the trench is about 40 centimeters. You can dig a small pit with your own hands using a regular shovel. An excavator will save effort and time, but even in this case, you will have to use a shovel for final leveling.
Main works
sand cushion
A sand cushion with gravel in a layer about 15 centimeters high is placed in the finished pit. To increase density, a layer of sand and gravel is watered and compacted. Then a durable waterproofing film or geotextile is laid on the sand cushion.
Formwork
For formwork of shallow foundations, available materials are used: boards, plywood, bars and slate. The frame is knocked down on the inside, and the nails are bent on the outside. Due to this, the surface will become smooth, and it will be easier to remove the formwork later. Always check the vertical position while working! To arrange a small base or basement, make a frame at least 30 centimeters high from the ground.
The formwork must not be left unfilled in winter! Therefore, it is better to carry out work in the warm season.
Waterproofing
To enhance waterproofing, roofing felt is placed at the bottom of the pit. More efficient modern materials can also be used. For example, penetron. This mixture is characterized by increased resistance to moisture; it will prevent the formation of mold and mildew on the concrete foundation. To make the mixture, simply add Penetron to the concrete when pouring the foundation according to the instructions.
Reinforcement
Reinforcement of the strip foundation is carried out using bricks and reinforced mesh. Bricks are placed at the bottom of the trench, and steel reinforcement for the strip foundation is installed on top. To make a mesh, reinforcement rods are tied with special wire so that the cells are square with a side of about 40 centimeters. Reinforcement of the strip foundation is done with a distance of 50 mm from the edges of the pit.
The reinforcement bundle cannot be made with a welding machine, as corrosion will occur at the welding points!
Ventilation and communications
Then they begin to arrange communications in the wooden house. To do this, special holes are made for communication pipes that will bring the water supply and sewage system to the house. For the arrangement, plastic or asbestos-cement pipes are used, which are tied to fittings. To prevent the pipes from filling with concrete mortar during pouring, pour sand into it.
Pouring concrete: how to make a concrete mixture yourself
The concrete mixture is poured into the formwork gradually in layers 15-20 centimeters thick. The layers must be identical in composition! Then the concrete is compacted using a deep vibrator or wooden tamper. Tamping will help avoid empty spaces, which will increase the strength and reliability of the structure.
You can buy ready-mixed concrete or make the solution yourself. Mix cement, sand and crushed stone in a ratio of 1:3:5. Then the mass is diluted with water in the amount of 60% of the cement. In cold weather, warm water is poured, and in hot weather, cold water is poured. This will speed up hardening.
Also, be sure to add Penetron if you decide to use this waterproofing product. At sub-zero temperatures, frost-resistant substances are added to the mixture at the rate of 1.5% by weight of cement. At temperatures down to -10 degrees, table salt is suitable; in severe frosts, calcium chloride is used. But, as already noted, it is better to pour concrete in the warm season.
The poured concrete is covered with film. After 4-6 days, the formwork is removed, the foundation is covered with sand or clay and covered again with film. It is advisable to leave the film for 2-4 weeks, because in the first month after pouring the foundation gains 99% strength.
If you do not want to prepare the concrete mixture yourself, the solution can be purchased ready-made. It is extremely important to choose the right concrete, since the quality of the composition affects the strength, reliability and durability of the future foundation and structure.
How to choose the right concrete
First of all, pay attention to the brand of the product. It shows the ability of concrete to withstand certain loads.
Also, pay attention to other indicators. Marking in the form of the letter W indicates the level of water permeability of concrete. It varies between 2-12. The higher the coefficient, the more resistant the material is to moisture. This indicator is taken into account if groundwater is present on the site. The letter F characterizes resistance to cold and low temperatures. It shows how much freezing and defrosting concrete will withstand.
Is it necessary to insulate the foundation?
The step-by-step instructions for installing a strip foundation are over, but experts recommend insulating the structure after installation along the external and internal perimeter. But you can limit yourself to insulating only the external foundation. Thermal insulation protects concrete from freezing and cracking. After insulation, the foundation is less susceptible to temperature changes and the negative effects of moisture.
You can also insulate the foundation yourself. The step-by-step instructions offer three main methods:
- From the outside and inside, fill the foundation with expanded clay at least 0.5 meters thick;
- Place foamed polystyrene foam on the outside in a layer 5-10 centimeters thick. Choose medium-density polystyrene foam, fasten it with plastic dowels and a hammer;
- After hardening, the finished foundation is treated on the sides with sprayed polyurethane foam. This product evenly covers the surface and protects the structure from moisture, but it gradually dissolves under the influence of ultraviolet radiation.
Installing a foundation with your own hands is a labor-intensive process that may contain errors in calculations and installation. Violation of construction technologies will lead to serious design problems in a few years. To avoid this, contact professionals!
The masters of the MariSrub company will calculate the volume of consumables and select a high-quality concrete mixture, conduct a soil study on the land plot, and reliably and quickly install any type of foundation!
Everyone knows the old proverb that a real man must do three things in his life: plant a tree, raise a son and build a house. With the last point, especially many questions arise - what material is better to use, choose a one- or two-story building, how many rooms to count on, with or without a veranda, how to install the foundation and many others. Among all these aspects, the foundation is fundamental, and this article will be devoted to its strip type, its features, differences, and construction technology.
Peculiarities
Despite the fact that there are several types of foundations for a house, preference in modern construction is given to strip foundations. Thanks to its durability, reliability and strength, it occupies a leading position in the construction industry around the world.
Already from the name it is clear that such a structure is a tape of a set width and height, laid in special trenches along the boundaries of the building under each of the external walls, thus forming a closed contour.
This technology gives the foundation extreme rigidity and strength. And through the use of reinforced concrete when forming the structure, maximum strength is achieved.
Among the key features of the strip foundation type are the following:
- the reliability and long service life already mentioned above;
- quick construction of the structure;
- accessibility in terms of cost relative to its parameters;
- the ability to install manually without the use of heavy equipment.
According to GOST 13580-85 standards, a strip foundation is a reinforced concrete slab, the length of which is from 78 cm to 298 cm, the width is from 60 cm to 320 cm and the height is from 30 cm to 50 cm. After calculations, the grade of the base with a load index of 1 is determined up to 4, which is an indicator of the pressure of the walls on the foundation.
In comparison with pile and slab types, the strip base, of course, wins. However, a columnar foundation overpowers the base with tape due to the significant consumption of materials and increased labor intensity.
This figure is influenced by:
- soil characteristics;
- total area of the ground floor;
- type and quality of building materials;
- depth;
- dimensions (height and width) of the tape itself.
The service life of a strip foundation directly depends on the correct choice of site for construction, compliance with all requirements and building codes. Taking into account all the rules will extend the service life for more than one decade.
An important feature in this matter is the choice of building material:
- a brick foundation will last up to 50 years;
- prefabricated structure - up to 75 years;
- Rubble and monolithic concrete in the manufacture of the base will increase the service life to 150 years.
Purpose
Tape foundation construction technology can be used:
- in the construction of monolithic, wooden, concrete, brick, frame structures;
- for a residential building, bathhouse, commercial or industrial building;
- for the construction of fences;
- if the building is located on a site with a slope;
- great if you decide to build a basement, veranda, garage or basement;
- for a house where the wall density is more than 1300 kg/m³;
- for both light and heavy buildings;
- in areas with unevenly layered soil, which leads to uneven shrinkage of the base of the structure;
- on loamy, clay and sandy soil.
Advantages and disadvantages
Among all the many advantages, it is worth mentioning some of the disadvantages of a strip foundation:
- Despite the simplicity of the design, the work itself is quite labor-intensive;
- difficulties with waterproofing when installed on wet ground;
- not a suitable option for soils with weak load-bearing properties due to the large mass of the structure;
- reliability and strength are guaranteed only with reinforcement (strengthening the concrete base with steel reinforcement).
Kinds
By classifying the selected type of foundation according to the type of device, we can distinguish between monolithic and prefabricated foundations.
Monolithic
Continuity of underground walls is assumed. They are characterized by low construction costs in relation to strength. This type is in demand when building a bathhouse or a small wooden house. The disadvantage is the large weight of the monolithic structure.
Monolithic foundation technology involves a reinforced metal frame, which is installed in a trench and then filled with concrete. It is due to the frame that the necessary rigidity of the foundation and resistance to loads is acquired.
Cost per 1 sq. m - approximately 5100 rubles (with characteristics: slab - 300 mm (h), sand cushion - 500 mm, concrete grade - M300). On average, a contractor will charge about 300-350 thousand rubles for pouring a 10x10 foundation, taking into account installation and the cost of materials.
Prefabricated
A prefabricated strip foundation differs from a monolithic one in that it consists of a complex of special reinforced concrete blocks connected to each other through reinforcement and masonry mortar, which are mounted using a crane at the construction site. Among the main advantages is a reduction in installation time. The downside is the lack of a unified design and the need to attract heavy equipment. In addition, the strength of a prefabricated foundation is inferior to a monolithic one by as much as 20%.
Such a foundation is used in the construction of industrial or civil buildings, as well as for cottages and private houses.
The main costs will be for transportation and hourly rental of a truck crane. 1 linear meter of prefabricated foundation will cost no less than 6,600 rubles. About 330 thousand will have to be spent on the base of a building with an area of 10x10. Laying wall blocks and pillows with a small distance will allow you to save money.
There is also a strip-slotted subtype of construction, which is similar in its parameters to a monolithic strip foundation. However, this base is adapted for pouring exclusively on clay and non-heaving soils. Such a foundation costs less due to the reduction of earthworks, since the installation takes place without formwork. Instead, they use a trench, which visually resembles a gap, hence the name. Slotted foundations allow you to equip a garage or utility room in low-rise, non-massive buildings.
Important! Concrete is poured into wet soil, since in a dry trench some of the moisture goes into the ground, which can cause the quality of the foundation to deteriorate. Therefore, it is better to use concrete of a higher grade.
Another subtype of prefabricated strip foundation is cross. It includes glasses for columns, support and intermediate plates. Such foundations are in demand in row building conditions - when a columnar foundation is located close to a base of the same type. This arrangement is fraught with subsidence of structures. The use of cross foundations involves the contact of the grid of end beams of the building under construction with an already constructed and stable structure, thereby allowing the load to be evenly distributed. This type of construction is applicable for both residential and industrial construction. Among the disadvantages is the labor intensity of the work.
Also, for a strip foundation type, a conditional division can be made regarding the laying depth. In this connection, according to the magnitude of the load, buried and shallow types are distinguished.
Deepening is carried out below the established level of soil freezing. However, within private low-rise buildings, a shallow foundation is acceptable.
The choice in this typing depends on:
- mass of the building;
- presence of a basement floor;
- soil type;
- height difference indicators;
- groundwater level;
- soil freezing level.
Determining the listed indicators will help in choosing the right type of strip foundation.
The recessed type of foundation is intended for a house made of foam blocks, heavy buildings made of stone, brick, or multi-story buildings. Such foundations are not afraid of significant differences in height. Perfectly suitable for buildings in which it is planned to equip the ground floor. It is erected 20 cm below the soil freezing level (for Russia this is 1.1-2 m).
It is important to take into account the frosty buoyancy forces of heaving, which should be less than the concentrated load from the house. To confront these forces, the foundation is set in the shape of an inverted "T".
The shallowly buried belt is distinguished by the ease of construction that will be located on it. In particular, these are wooden, frame or cellular structures. But its location on the ground with a high groundwater level (up to 50-70 cm) is undesirable.
The key advantages of a shallow foundation are the low cost of building materials, low labor intensity and short installation time, in contrast to a buried foundation. In addition, if it is possible to get by with a small cellar in the house, then such a foundation is an excellent and low-cost option.
Disadvantages include the inadmissibility of installation in unstable soils., and such a foundation will not be suitable for a two-story house.
Also, one of the features of this type of foundation is the small area of the lateral surface of the walls, and therefore the buoyant forces of frost heaving are not harmful to light construction.
Today, developers are actively introducing the Finnish technology for installing foundations without deepening - pile-grillage. The grillage consists of slabs or beams that connect the piles to each other above the ground. The new type of zero-level device does not require the installation of panels and the installation of wooden blocks. In addition, there is no need to dismantle the hardened concrete. It is believed that such a structure is not subject to heaving forces at all and the foundation is not deformed. Installed on formwork.
In accordance with the standards regulated by SNiP, the minimum depth of the strip foundation is calculated.
Materials
Strip foundations are mainly installed from brick, reinforced concrete, rubble concrete, using reinforced concrete blocks or slabs.
Brick is suitable if the house is to be built frame or with thin brick walls. Since brick material is very hygroscopic and easily destroyed due to moisture and cold, such a buried foundation is not welcome in places with high groundwater levels. It is important to provide a waterproofing coating for such a base.
The popular reinforced concrete base, despite its cheapness, is quite reliable and durable. The material contains cement, sand, crushed stone, which is reinforced with metal mesh or reinforcement rods. Suitable for sandy soil when constructing monolithic foundations of complex configuration.
A strip foundation made of rubble concrete is a mixture of cement, sand and large stone. A fairly reliable material with length parameters - no more than 30 cm, width - from 20 to 100 cm and two parallel surfaces up to 30 kg. This option is perfect for sandy soils. In addition, a prerequisite for the construction of a rubble concrete foundation must be the presence of a gravel or sand cushion 10 cm thick, which simplifies the process of laying the mixture and allows you to level the surface.
The foundation made of reinforced concrete blocks and slabs is a finished product manufactured at the enterprise. Among the distinctive features are reliability, stability, strength, and the ability to be used for houses of various designs and types of soil.
The choice of material for constructing a strip foundation depends on the type of device.
The prefabricated base is made:
- from blocks or slabs of the established brand;
- concrete mortar or even brick is used to seal cracks;
- everything is completed with materials for hydro- and thermal insulation.
- the formwork is constructed from wooden boards or expanded polystyrene;
- concrete;
- material for hydro- and thermal insulation;
- sand or crushed stone for a pillow.
Calculation and design rules
Before a project is drawn up and the parameters of the building’s foundation are determined, it is recommended to review the regulatory construction documents, which describe all the key rules for calculating the foundation and tables with established coefficients.
Among these documents:
GOST 25100-82 (95) “Soils. Classification";
GOST 27751-88 “Reliability of building structures and foundations. Basic provisions for calculation";
GOST R 54257 “Reliability of building structures and foundations”;
SP 131.13330.2012 “Building climatology”. Updated version of SN and P 23-01-99;
SNiP 11-02-96. “Engineering surveys for construction. Basic provisions";
SNiP 2.02.01-83 “Foundations of buildings and structures”;
Manual for SNiP 2.02.01-83 “Manual for designing foundations of buildings and structures”;
SNiP 2.01.07-85 “Loads and impacts”;
Manual for SNiP 2.03.01; 84. “Manual for designing foundations on a natural foundation for columns of buildings and structures”;
SP 50-101-2004 “Design and installation of foundations and foundations of buildings and structures”;
SNiP 3.02.01-87 “Earth structures, foundations and foundations”;
SP 45.13330.2012 “Earth structures, foundations and foundations.” (Updated edition of SNiP 3.02.01-87);
SNiP 2.02.04; 88 “Foundations and foundations on permafrost soils.”
Let us consider in detail and step by step the calculation plan for the construction of the foundation.
To begin with, a total calculation of the entire weight of the structure is made, including the roof, walls and ceilings, the maximum permissible number of residents, heating equipment and household installations, and the load from precipitation.
You need to know that the weight of the house is determined not by the material from which the foundation is made, but by the load that is created by the entire structure made of various materials. This load directly depends on the mechanical features and the amount of material used.
To calculate the pressure on the sole of the base, it is enough to sum up the following indicators:
The first point is calculated by using the formula snow load = roof area (from the project) x established parameter of snow cover mass (different for each region of Russia) x correction factor (which is affected by the angle of inclination of a single- or gable roof).
The established parameter of snow cover mass is determined according to the zoned map SN and P 2.01.07-85 “Loads and impacts”.
The next step is to calculate the potential payload. This category includes household appliances, temporary and permanent residents, furniture and bathroom equipment, communication systems, stoves and fireplaces (if available), and additional utility routes.
There is an established form for calculating this parameter, calculated with a margin: payload parameters = total structure area x 180 kg/m².
In the calculations of the last point (load of parts of the building), it is important to list as much as possible all the elements of the building, including:
- the reinforced base itself;
- ground floor of the house;
- load-bearing part of the building, window and door openings, stairs, if any;
- floor and ceiling surfaces, basement and attic floors;
- roof covering with all associated elements;
- floor insulation, waterproofing, ventilation;
- surface finishing and decorative elements;
- all the many fasteners and hardware.
Moreover, to calculate the sum of all the above elements, two methods are used - mathematical and the results of marketing calculations in the building materials market.
Of course, there is also the option of using a combination of both methods.
The first method's plan is:
- breaking complex structures into parts in a project, determining the linear dimensions of the elements (length, width, height);
- multiply the obtained data to measure volume;
- using all-Union technological design standards or in the manufacturer’s documents, establish the specific gravity of the building material used;
- Having established the parameters of volume and specific gravity, calculate the mass of each of the elements of the building using the formula: mass of a part of the building = volume of this part x parameter of the specific gravity of the material from which it is made;
- calculate the total mass allowed under the foundation by summing up the results obtained from the parts of the structure.
The marketing calculation method is based on data from the Internet, the media and reviews of professionals. The specified specific gravity is also summed up.
The design and sales departments of enterprises have accurate data, where it is possible to call them to clarify the nomenclature or use the manufacturer’s website.
The general parameter of the load on the foundation is determined by the summation of all calculated values - the load of parts of the structure, useful and snow.
approximate specific pressure = mass of the entire structure / dimensions of the base area.
Having determined these parameters, an approximate calculation of the geometric parameters of the strip foundation is permissible. This process occurs according to a certain algorithm established during research by specialists from the scientific and engineering department. The scheme for calculating the size of the foundation depends not only on the expected load on it, but also on the construction documented standards for deepening the foundation, which, in turn, are determined by the type and structure of the soil, groundwater level, and freezing depth.
Based on the experience gained, the developer recommends the following parameters:
Soil type | Soil within the calculated freezing depth | Interval from the planned mark to the groundwater level during the freezing period | Foundation installation depth |
Non-heaving | Coarse, gravelly sands, large and medium-sized | Not standardized | Any, regardless of the freezing limit, but not less than 0.5 meters |
Heaving | The sand is fine and dusty | Exceeds the freezing depth of more than 2 m | Same figure |
Exceeds the freezing depth by at least 2 m | Not less than ¾ of the calculated freezing level, but not less than 0.7 m. |
||
Loam, clay | Less than the calculated freezing depth | Not less than the calculated freezing level |
The width of the strip foundation should not be less than the width of the walls. The depth of the pit, which determines the height of the base, should be designed for a 10-15 centimeter sand or gravel cushion. These indicators allow further calculations to determine: The minimum width of the foundation base is calculated depending on the pressure of the building on the foundation. This size, in turn, determines the width of the foundation itself, which presses on the soil.
This is why it is so important to do a soil examination before starting to design a structure.
- amount of concrete to pour;
- volume of reinforcement elements;
- amount of material for the formwork.
Rubble stone:
- basement depth – 2 m:
- length of the basement wall – up to 3 m: wall thickness – 600, width of the foundation base – 800;
- The length of the basement wall is 3-4 m: the thickness of the wall is 750, the width of the base of the foundation is 900.
- basement depth – 2.5m:
- length of the basement wall – up to 3 m: wall thickness – 600, width of the foundation base – 900;
- The length of the basement wall is 3-4 m: the thickness of the wall is 750, the width of the base of the foundation is 1050.
Rubble concrete:
- basement depth – 2 m:
- length of the basement wall – up to 3 m: wall thickness – 400, width of the foundation base – 500;
- Basement wall length – 3-4 m: wall thickness – 500, foundation base width – 600.
- basement depth – 2.5m:
- basement wall length up to 3 m: wall thickness – 400, foundation base width – 600;
- The length of the basement wall is 3-4 m: the thickness of the wall is 500, the width of the base of the foundation is 800.
Clay brick (ordinary):
- basement depth – 2 m:
- basement wall length up to 3 m: wall thickness – 380, foundation base width – 640;
- The length of the basement wall is 3-4 m: the thickness of the wall is 510, the width of the base of the foundation is 770.
- basement depth – 2.5m:
- basement wall length up to 3 m: wall thickness – 380, foundation base width – 770;
- The length of the basement wall is 3-4 m: the thickness of the wall is 510, the width of the base of the foundation is 900.
Concrete (monolith):
- basement depth – 2 m:
- basement wall length up to 3 m: wall thickness – 200, foundation base width – 300;
- The length of the basement wall is 3-4 m: the thickness of the wall is 250, the width of the base of the foundation is 400.
- basement depth – 2.5m;
- basement wall length up to 3 m: wall thickness – 200, foundation base width – 400;
- The length of the basement wall is 3-4 m: the thickness of the wall is 250, the width of the base of the foundation is 500.
Concrete (blocks):
- basement depth – 2 m:
- basement wall length up to 3 m: wall thickness – 250, foundation base width – 400;
- The length of the basement wall is 3-4 m: the thickness of the wall is 300, the width of the base of the foundation is 500.
- basement depth – 2.5m:
- basement wall length up to 3 m: wall thickness – 250, foundation base width – 500;
- The length of the basement wall is 3-4 m: the thickness of the wall is 300, the width of the base of the foundation is 600.
Next, it is important to optimally adjust the parameters by adjusting the norms of specific pressure on the soil of the sole in accordance with the calculated soil resistance - the ability to withstand a certain load of the entire structure without settling.
The calculated soil resistance must be greater than the parameters of the specific load from the building. This point represents a significant requirement in the process of designing the foundation of a house, according to which in order to obtain linear dimensions it is necessary to simply solve an arithmetic inequality.
When drawing up a drawing, it is important that this difference be 15-20% of the specific load of the structure in favor of the soil’s ability to withstand pressure from the building.
In accordance with the types of soil, the following calculated resistances are derived:
- Coarse soil, crushed stone, gravel - 500-600 kPa.
- Sand:
- gravelly and coarse – 350-450 kPa;
- medium size – 250-350 kPa;
- fine and dusty dense – 200-300 kPa;
- medium density – 100-200 kPa;
- Sandy loam is hard and plastic – 200-300 kPa;
- Loam is hard and plastic – 100-300 kPa;
- Clay:
- hard – 300-600 kPa;
- plastic – 100-300 kPa;
100 kPa = 1 kg/cm²
Having adjusted the results obtained, we obtain approximate geometric parameters of the foundation of the structure.
In addition, today's technologies make it possible to significantly simplify calculations using special calculators on developer websites. By indicating the dimensions of the base and the building material used, you can calculate the total cost of building the foundation.
Installation
To install a strip foundation with your own hands you will need:
- round and corrugated reinforcement elements;
- galvanized steel wire;
- sand;
- edged boards;
- wooden blocks;
- a set of nails, self-tapping screws;
- waterproofing material for foundation and formwork walls;
- concrete (mostly factory-made) and materials suitable for it.
Marking
When planning to build a structure on a site, it is worthwhile to first examine the site where construction is planned.
There are certain rules for choosing a place for the foundation:
- Immediately after the snow melts, it is important to pay attention to the presence of cracks (indicate the heterogeneity of the soil - freezing will lead to rise) or dips (indicate the presence of water veins).
- The presence of other buildings on the site makes it possible to assess the quality of the soil. You can make sure the soil is homogeneous by digging a trench at an angle of the house. The imperfection of the soil indicates an unfavorable location for construction. And if cracks are noticed on the foundation, then it is better to postpone construction.
- As mentioned above, conduct a hydrogeological assessment of the soil.
Having determined that the selected area complies with all standards, you should begin marking the area. First of all, it needs to be leveled and rid of weeds and debris.
For marking work you will need:
- marking cord or fishing line;
- roulette;
- wooden pegs;
- level;
- pencil and paper;
- hammer.
The first marking line is decisive - it is from it that all other boundaries will be measured. It is important to establish an object that will serve as a guide. This could be another structure, a road or a fence.
The first peg represents the right corner of the building. The second is installed at a distance equal to the length or width of the structure. The pegs are connected to each other with a special marking cord or tape. The rest are hammered in the same way.
Having defined the external boundaries, you can move on to the internal ones. For this, temporary pegs are used, which are installed at a distance of the width of the strip foundation on both sides of the corner markings. Opposite marks are also connected to each other by a cord.
Lines of load-bearing walls and partitions are installed using a similar method. Potential windows and doors are highlighted using pegs.
Excavation
When the marking stage is completed, the cords are temporarily removed and, following the marks on the ground, trenches are dug under the external load-bearing walls of the structure along the entire perimeter of the marking. The internal space is torn out only if a basement or basement is planned.
The established requirements for carrying out excavation work are specified in SNiP 3.02.01-87 on earthworks, foundations and foundations.
The depth of the trenches must be greater than the calculated depth of the foundation. Do not forget about the mandatory preparatory layer of concrete or bulk material. If the excavated excavation significantly exceeds the depth taking into account the reserve, this volume can be replenished with the same soil or crushed stone, sand. However, if the overshoot exceeds more than 50 cm, you should contact the designers.
It is important to take into account worker safety - the excessive depth of the pit requires strengthening the walls of the trench.
In accordance with regulatory documents, fastenings are not required if the depth is:
- for bulk, sandy and coarse soils – 1 m;
- for sandy loam – 1.25 m;
- for loam and clay – 1.5 m.
Typically, for the construction of a small building, the average trench depth is 400 mm.
The width of the excavation must correspond to the plan, which already takes into account the thickness of the formwork, the parameters of the underlying preparation, the protrusion of which beyond the lateral boundaries of the base is allowed at least 100 mm.
The usual parameters are the width of the trench equal to the width of the tape plus 600-800 mm.
Important! To ensure that the bottom of the pit is a perfectly flat surface, you should use a water level.
Formwork
This element represents the form for the intended foundation. Wood is most often used as the material for formwork due to its availability in terms of cost and ease of implementation. Removable or permanent metal formwork is also actively used.
In addition, depending on the material, the following types differ:
- aluminum;
- steel;
- plastic;
- combined.
Classifying formwork depending on the type of structure, there are:
- large shield;
- small shield;
- volumetric-adjustable;
- block;
- sliding;
- horizontally movable;
- lifting and adjustable.
Grouping the types of formwork according to thermal conductivity, they differ:
- insulated;
- uninsulated.
The structure of the formwork is:
- deck with shields;
- fasteners (screws, angles, nails);
- props, racks and frames for support.
For installation you will need the following materials:
- beacon board;
- shield board;
- scrum of longitudinal boards;
- tension hook;
- spring bracket;
- ladder;
- shovel;
- concreting site.
The amount of materials listed depends on the parameters of the strip foundation.
The installation itself requires strict adherence to the established requirements:
- installation of formwork is preceded by thorough cleaning of the area from debris, stumps, plant roots, and elimination of any unevenness;
- the side of the formwork in contact with the concrete is ideally cleaned and leveled;
- fastening occurs in such a way as to prevent shrinkage during concreting - such deformation can negatively affect the entire structure as a whole;
- formwork panels are connected to each other as tightly as possible;
- All formwork fastenings are carefully checked - a barometer is used to check the compliance of the actual dimensions with the design ones, a level is used to control horizontality, and a plumb line is used to control verticality;
- If the type of formwork allows it to be removed, then for reuse it is important to clean the fasteners and panels from debris and traces of concrete.
Step-by-step instructions for arranging continuous formwork for a strip base:
- To level the surface, lighthouse boards are installed.
- At intervals of 4 m, formwork panels are attached on both sides, which are fastened using struts for rigidity and spacers, ensuring a fixed thickness of the base tape.
- The foundation will be level only if the number of shields between the lighthouse boards is the same.
- Scrums, which are longitudinal boards, are nailed to the sides of the boards for horizontal alignment and reliability.
- The fights are stabilized using inclined struts, which allow the shields to be vertically aligned.
- The panels are secured with tension hooks or spring clips.
- Solid formwork is usually more than a meter high, which requires the installation of stairs and platforms for concreting.
- If necessary, disassembly of the structure occurs in the reverse order.
The installation of a stepped structure goes through several stages. Each subsequent tier of formwork is preceded by another similar tier:
- first stage of formwork;
- concreting;
- second stage of formwork;
- concreting;
- The required parameters are installed using the same scheme.
Installation of stepped formwork is also possible at once, similar to the mechanism for assembling a continuous structure. In this case, it is important to adhere to the horizontal and vertical arrangement of the parts.
During the formwork construction phase, a significant issue is the layout of ventilation openings. Vents should be located at a minimum height of 20 cm from the ground surface. However, it is worth taking into account seasonal flooding and varying the location depending on this factor.
The best material for the ventilation hole is a round plastic or asbestos-cement pipe with a diameter of 110-130 mm. Wooden beams tend to stick to the concrete base, which makes them difficult to remove later.
The diameter of the vents is determined depending on the size of the building and can reach from 100 to 150 cm. These ventilation holes are located in the walls strictly parallel to each other at a distance of 2.5-3 m.
With all the need for vents, there are cases when the presence of holes is not required:
- the room already has ventilation vents in the floor of the building;
- between the foundation pillars a material with sufficient vapor permeability is used;
- there is a powerful and stable ventilation system;
- a vapor-proof material covers the sand or soil compacted in the basement.
The correct choice of reinforcement is facilitated by understanding the variety of material classifications.
Depending on the manufacturing technology, the fittings may vary:
- wire or cold rolled;
- rod or hot rolled.
Depending on the surface type, the rods:
- with a periodic profile (corrugations) ensuring maximum connection with concrete;
- smooth.
By purpose:
- rods used in conventional reinforced concrete structures;
- prestressing rods.
Most often, reinforcement in accordance with GOST 5781 is used for strip foundations - a hot-rolled element, applicable for conventional and prestressing reinforced structures.
In addition, in accordance with the grades of steel, and therefore the physical and mechanical properties, the reinforcement bars vary from A-I to A-VI. For the manufacture of elements of the initial class, low-carbon steel is used; in high classes, properties close to alloy steel are used.
In planned areas with the greatest load, mounting fittings are installed in the direction of the expected additional pressure. Such places are the corners of the structure, areas with the highest walls, the base under a balcony or terrace.
When installing a structure made of reinforcement, intersections, junctions and corners are formed. Such a poorly installed unit can lead to a crack or subsidence of the foundation.
That is why for reliability we use:
- legs - an L-shaped bend (internal and external), attached to the outer working part of the reinforcement frame;
- cross clamp;
- gain.
It is important to remember that each class of reinforcement has its own specific parameters for the permissible bending angle and curvature.
The parts are connected into a solid frame using two methods:
- Welding, which requires special equipment, the availability of electricity and a specialist who will do it all.
- Knitting is possible with a simple screw hook and mounting wire (30 cm per intersection). It is considered the most reliable method, although time-consuming. Its convenience also lies in the fact that, if necessary (bending load), the rod can be moved slightly, thereby reducing the pressure on the concrete layer and protecting it from damage.
You can make a hook if you take a thick and durable metal rod. A handle is made on one edge for more convenient use, the other is bent in the form of a hook. Fold the mounting wire in half to form a loop at one end. Then it should be wrapped around the reinforced knot, inserting the hook into the loop so that it rests on one of the “tails”, and the second “tail” is wrapped around the mounting wire, carefully tightening it around the reinforcing rod.
All metal parts are carefully protected with a layer of concrete (minimum 10 mm) to prevent acid corrosion.
Calculations of the amount of reinforcement that will be needed for the construction of a strip foundation require determining the following parameters:
- dimensions of the total length of the foundation strip (external and, if available, internal lintels);
- number of elements for longitudinal reinforcement (you can use the calculator on the manufacturers’ website);
- number of reinforcement points (number of corners and joints of foundation strips);
- parameters of overlap of reinforcing elements.
SNiP standards indicate the parameters of the total cross-sectional area of longitudinal reinforcement elements, which will be at least 0.1% of the cross-sectional area.
Fill
It is recommended to pour a monolithic foundation with concrete in layers 20 cm thick, after which the tier is compacted with a concrete vibrator to avoid voids. If you pour concrete in winter, which is undesirable, then you need to insulate it using available materials. In dry seasons, it is recommended to use water to create a damp effect, otherwise this may affect its strength.
The consistency of the concrete should be the same for each layer, and pouring should be done on the same day, since a low level of adhesion (a method of adhesion of surfaces of dissimilar solid or liquid consistencies) can lead to the formation of cracks. In the event that it is impossible to fill in one day, it is important to at least generously water the surface of the concrete and, in order to maintain dampness, cover the top with plastic film.
The concrete must settle. After 10 days, the outside walls of the base are treated with bitumen mastic and a waterproofing material (most often roofing felt) is glued to protect against water penetration.
The next stage is backfilling the cavities of the strip foundation with sand, which is also laid in layers, carefully compacting each tier. Before laying the next layer, the sand is watered.
A properly installed strip foundation is the key to long years of operation of the building.
It is important to strictly maintain a constant foundation depth over the entire area of the construction site, since minor deviations lead to differences in soil density and moisture saturation, which jeopardizes the reliability and durability of the foundation.
Among the common omissions during the construction of the foundation of a building are mainly inexperience, inattention and frivolity in installation, as well as:
- insufficiently thorough study of hydrogeological properties and ground level;
- use of cheap and low-quality building materials;
- the unprofessionalism of the builders is demonstrated by damage to the waterproofing layer, crooked markings, unevenly laid cushion, and violation of the angle;
- failure to comply with the deadlines for removing formwork, drying the concrete layer and other temporary stages.
To avoid such mistakes, it is fundamentally important to contact only specialists involved in installing the foundations of structures and try to follow the stages of construction. If you still plan to install the base yourself, before starting work it would be preferable to consult with specialists in this field.
An important topic when building a foundation is the question of the recommended time of year for such work. As mentioned above, winter and late autumn are considered undesirable times, since frozen and wet soil leads to inconvenience, slowdown of construction work, and, importantly, shrinkage of the foundation and the appearance of cracks in the finished structure. Professionals indicate that the optimal time for construction is warm and dry periods (depending on the region, these periods fall in different months).
Sometimes, after the foundation has been erected and the building has been in operation, the idea of expanding the living space of the house comes to mind. This issue requires a close analysis of the state of the foundation. If the construction is insufficiently strong, it can lead to the foundation bursting, sagging, or cracks appearing on the walls. Such an outcome can lead to the complete destruction of the building.
However, if the condition of the foundation does not allow you to complete the building, do not be upset. In this case, there are some tricks in the form of strengthening the foundation of the structure.
This process can be carried out in several ways:
- in case of minor damage to the foundation, it is sufficient to restore the hydro- and heat-insulating layer;
- it is more expensive to expand the foundation;
- they often use the method of replacing the soil under the foundation of the house;
- using various types of piles;
- by creating a reinforced concrete jacket that prevents collapse when cracks appear in the walls;
- reinforcement with monolithic clips strengthens the base throughout its entire thickness. This method involves the use of a double-sided reinforced concrete cage or tubes that inject a solution that freely fills all the voids in the masonry.
The most important thing when building any type of foundation is to correctly determine the required type, carry out a thorough calculation of all parameters, carry out all the steps exactly according to the instructions, follow the rules and advice of experts and, of course, enlist the support of assistants.
Strip foundation technology is in the next video.
To make the foundation correctly, you need to carefully study the options for construction types and their features. The construction of the underground part is carried out taking into account the following requirements:
- economic expediency;
- reliability;
- strength;
- durability;
- sustainability.
Before starting construction work, a soil study should be carried out. The choice of the right type of foundation is influenced by the total weight of the house, the strength of the soil and the groundwater level. A foundation that is carefully made and built in compliance with technology will last a long time and will not cause problems during operation.
Preparatory stage
It’s worth starting with pits or drilling. The main goal of this activity is to find out what soils are located on the site, as well as to find out the level of groundwater. The foundation must be laid in compliance with the rule: the mark of the sole must be at least 50 cm above the level of the water horizon.
How to do soil testing correctly? Two methods are used for this:
- excerpts of pits (deep holes, dimensions in plan are usually 1x2 m);
- manual drilling.
In the first case, the soil on the walls of the pit is examined. They also check to see if water has left the bottom. In the second option, the soil on the tool blades is examined.
Once you have determined what kind of soil is on the site, you will need to find its strength indicators. This can be done using special tables.
The cost of laying the foundation for a house can be up to 30% of the estimate for the entire building. To avoid cost overruns, you need to perform a calculation that will allow you to find the optimal design parameters that will simultaneously guarantee minimum costs, strength and reliability. For your convenience, you can use online payment.
Types of foundations
Building a foundation with your own hands involves the use of several technologies:
- ribbon;
- combined options.
Columnar supports have a low load-bearing capacity. It is possible to install monolithic pillars or assemble them into compact concrete blocks. Both options are great for DIY projects.
There are three types of pile foundation for a house:
- driven (not recommended for private buildings due to the need to attract equipment);
- (suitable for building a brick or concrete house);
- (ideal for light wooden buildings).
Piles make it possible to reduce the amount of excavation work. There is no need to dig trenches or a foundation pit or transport large amounts of soil outside the site. Thanks to this quality, installing this type of foundation is a very economical choice. The main disadvantage will be the impossibility of equipping a basement or underground for utilities. In this case, the base of the building is covered with decorative materials.
Another advantage of piles is the possibility of using them in wetlands. Even if the groundwater level is located close to the ground surface, the supports provide the necessary load-bearing capacity.
The next option is tape. It can be made monolithic or from blocks. The second option is rational to use for mass construction. Strip foundations are:
- recessed (for buildings with a basement, brick and concrete structures);
- (for wooden and frame houses);
- non-buried (technology of pouring foundations for small buildings on a solid foundation).
Before making a tape, it is worth checking the groundwater level and compliance with the rule that the sole cannot be closer than 50 cm to the groundwater horizon. Otherwise, there is a high probability of flooding of the basement, reducing the load-bearing capacity of the foundation and destruction of the materials of the supporting part of the building.
What to do with high groundwater level? If the structure is made independently from brick or stone, screw piles will not be suitable, and for bored piles it will be necessary to lower the water level. An excellent option would be filling. In this case, a non-recessed or slightly recessed base is made. The thickness of the slab is determined depending on the load, on average 300-400 mm.
How to pour a foundation for a house
Monolithic foundation type is the best option for private housing construction. In this case, laying can significantly save on transportation and installation of structures. There is no need to hire a crane to install elements in the designed position or a KamAZ truck to transport concrete blocks and slabs.
Monolithic foundations can be made from factory-made concrete or you can mix the solution yourself using a concrete mixer. The first option is recommended. The fact is that it is very difficult to strictly observe the proportions of the composition in artisanal conditions. For factory-mixed concrete, such a guarantor will be a passport, which indicates the verified indicators of the material.
To make the material yourself, you will need to prepare clean water, cement, sand and crushed stone (or gravel). They are mixed with each other strictly observing proportions, which depend on what grade of concrete needs to be obtained. If you add a little more sand or crushed stone to the composition than required, the strength of the supporting part of the building will suffer.
To properly pour the foundation, you need to familiarize yourself with the basic rules of concreting:
- Concrete must be poured in one go at time intervals of up to 1.5 hours. If you take long breaks in work, the solution sets and concreting joints form, which weaken the structure. The technology allows making horizontal seams if absolutely necessary. It is unacceptable to install vertical seams on a monolithic foundation, since in this case the support of the house will not be able to resist soil deformations.
- The class of concrete is chosen depending on the type of supporting part. For a columnar or pile foundation, class B 15 is sufficient. For tape, grades from B 15 to B 22.5 are needed. Construction of a house foundation using slab technology requires concrete grades B 22.5 or B 25.
- After pouring, the material should gain strength. On average, this takes 28 days. Construction work can continue after the structure reaches 70% of its original strength.
- It is better to carry out work in warm, dry weather. The ideal average daily temperature for concrete hardening is +25°C. At temperatures below +5°C the material practically does not harden. For normal hardening in this case, special additives and heating are used.
- The concrete must be maintained within 1-2 weeks after pouring. It involves wetting the surface with water.
- To mix the mixture yourself, you will need cement, sand, crushed stone (gravel) and clean water. The proportions depend on the strength class. The material is delivered from the factory using a concrete mixer truck - it allows you to extend the life of the solution and deliver it over relatively long distances.
How to pour the foundation correctly? In general, work is performed in this order:
- installation of formwork and reinforcement cage;
- laying waterproofing material in formwork;
- pouring concrete;
- its compaction by vibration or bayonet;
- curing;
- stripping works (if necessary).
To quickly complete the work, it is recommended to order a concrete pump together with a concrete mixer. Concrete manufacturers are usually willing to provide this technique. In this case, it is necessary to use a concrete mixture of grades P3 or P4 in terms of mobility. Otherwise, the equipment breaks down.
Step-by-step instructions for pouring a strip foundation
Concreting is considered using the example of a monolithic tape. To erect the supporting part of the structure, construction is necessary. To do this, use cast-offs and construction cord. You need to show the edges of the tape.
After marking, the soil is excavated. If there is no basement, it is enough to dig a trench. At its bottom you need to make a sand cushion. It performs several functions:
- ground leveling;
- prevention of frost heaving;
The edges of the trench must go exactly along the cord Next stage - . For this purpose, the material included in the estimate is used: boards (removable type) or polystyrene foam (non-removable). The second option serves not only as a form for pouring concrete, but also as insulation of the underground part of the building. When installing the formwork, I raise the base to the desired height.
If you want to build a high-quality foundation for your house that will last for many years and withstand heavy loads, then, undoubtedly, a strip foundation for your house is the best option. Since it is quite popular, there is plenty of information on how to complete all the work. All you have to do is study it and implement it.
We have collected useful information for you that will help you figure out how to build the right foundation yourself.
Features of strip foundation
First, let's give a brief overview and characteristics. A strip foundation is a monolithic structure that runs under the walls of a house. The tape itself can be made of blocks, slabs or concrete. The peculiarity of the building is that it can withstand heavy loads. The tape evenly transfers the load to the ground. In addition, this is the only foundation option with which you can make a garage or cellar under it. But working with such a foundation is not easy.
The thing is that the device requires a lot of time, effort and investment. The main part of the work comes down to digging a trench. If you use special equipment, there will be no problems. But for manual digging with shovels you need to try. Not only does it take a long time, it also takes energy, especially if the ground is rocky. As for pouring concrete, you will need to mix a high-quality solution, build formwork and wait about a month for the concrete solution to dry. And we don’t even mention how much money will be spent on materials.
If this information does not frighten you, and you continue to have the goal of building it, then know that a strip foundation for a house is a reliable structure that will serve you for many years. And thanks to the presence of a base, the room will be warm. So, let's look at where the construction of a strip foundation begins.
Preparation of tools and materials
The first thing you need to do is take care of an arsenal of tools and raw materials for working with the foundation. What does this list consist of? If we talk about materials, it is as follows:
- river sand of medium fraction;
- crushed stone or gravel;
- boards or plywood for formwork;
- reinforcement rods Ø10-12 mm and binding wire;
- pegs and rope for marking;
- a concrete solution consisting of sand, water and cement.
Now let's look at the list of tools:
- crowbar and shovel;
- tape measure, level, plumb line, level;
- hammer and nails or screwdriver with self-tapping screws;
- concrete mixer;
- buckets, wheelbarrow, shovel;
- vibration installation for concrete compaction;
- Master OK.
As you can see, the list is large, but all materials for strip foundations are easily available.
Note! If you do not want to prepare concrete for the foundation yourself on site, you can order it in advance from a specialized company. They will deliver you the right amount of high-quality mortar for pouring the foundation.
Preparatory work
If you have already stocked up on everything you need, then you can start practicing. You must have drawn up a foundation plan in advance, which indicates its layout, width, depth of the tape and other features. All this depends on the type of soil, the depth of soil freezing and the occurrence of groundwater. It is better to entrust such work to an experienced specialist who can draw up a high-quality plan.
Now you can work on the area where the foundation will be built. Rate it. Are there trees, bushes or other structures that will get in your way? They need to be removed. The work area should be free of debris, remains of old buildings, etc. It is desirable that the surface be relatively flat.
Advice! At the site you need to make lighting, take care of sockets and water supply.
After this, you can begin marking the future foundation. High-quality markings are essential. This way, you will make the future foundation perfectly even and of the correct shape. The ropes will serve as guides. You can read more about how to mark a strip foundation on our website. In general, the scheme looks like this.
We are trenching the foundation
It’s good if you are making a strip foundation for a country house. Then the depth of the tape will be small, since such houses are small, so the amount of work is reduced. Basically, the average depth of the tape reaches 70 cm. It can be 40 cm, or maybe 1.5 m. It all depends on groundwater and freezing. Be that as it may, the work of digging a pit will have to be done.
If you have the means, you can make the task easier for yourself. How? Hire special heavy equipment that can complete all the work in a matter of hours. The trench under the foundation will be perfectly level, and you can quickly get to work. But such an opportunity may not exist. And the reason for this is not only the means, but also the lack of possibility of bringing in heavy equipment. In this case, everything will have to be done manually.
To reduce labor costs and increase the speed of work, you can ask for help. Doing work with friends or family is much easier and more fun. As for the process itself, make sure you follow the markings. It is important to make the walls and bottom of the trench even, checking everything with a plumb line. And with a tape measure you can control the depth.
Foundation cushion installation
When the pit is ready, you can proceed to the next stage. The process is as follows:
- Sand is poured to the bottom.
- Water is added to thicken it.
- The surface is tamped with a special tamping tool to compact the sand.
- It is important to ensure that the sand level reaches 10 cm. You can make approximate marks on the walls.
- A layer of crushed stone or gravel is poured on top.
- They can also be tamped. The required layer is 10 cm.
Thanks to such a substrate, the foundation will not shift and will become more reliable and durable.
Installation of foundation formwork
It's time to go upstairs and build the formwork. This is the ground part of the structure that will form the base of the building. Its height depends on the desired base. For cold regions this figure can reach 50 cm, for warm regions 20-30 cm. The structure itself can be made of different materials, such as boards, plywood, asbestos-cement pipes, etc.
The types of formwork are also different. There are two options:
- Removable formwork, which is simply removed after pouring concrete.
- Fixed, which becomes part of the base.
As you understand, the first option will be cheaper. But it will take more time to set it up. The non-removable structure will serve as additional protection and act as insulation.
You can see the formwork diagram in the figure below. The main task is to make it perfectly smooth and reliable. Supports are installed on the sides, and a screed is packed on top. So, the concrete will not fall out of it.
Advice! To make the process of removing the formwork easier after pouring, and to prevent the concrete itself from seeping through the holes, you can cover it from the inside with a film.
Reinforcement as a guarantee of strength
To give the strip foundation rigidity, it needs to be reinforced with reinforcement. Everyone knows that reinforced concrete is many times stronger than simple concrete for foundations. Therefore, a frame in the form of a mesh is made from reinforcement rods. It is better to connect the elements not by welding, but by binding wire. The completed frame is installed in the formwork. There are several nuances here.
Do not install the frame on the ground. It should be at least 5 cm from the soil. The same applies to the side walls. Use stands to support the frame. This is what ideal strip foundation reinforcement looks like.
Filling the strip foundation
To make the strip foundation of the house yourself, all that remains is to fill it. Here you will need concrete, a lot of concrete. The solution is made in a concrete mixer. It is advisable to install it close to the trench itself that will need to be filled. The process is as follows:
That's all, now you know how to properly make a strip foundation with your own hands. All you have to do is wait until the concrete dries. This will take a month. After 15 days, you can remove the formwork, just do it carefully so as not to damage the foundation.
Advice! While the concrete is drying, cover it with polyethylene to protect it from external factors. After all, rain can wash it away.
Let's sum it up
As you can see, the process of constructing a strip foundation is really long and labor-intensive. But making a foundation with your own hands is not at all difficult. You must adhere to technology and follow instructions. The main thing in this work is to design everything correctly so that the finished strip foundation can withstand the load of the house and is not washed away by groundwater. Consider the depth of soil freezing and get to work!
What is a strip foundation is a question that seems easy to answer, but not every builder can formulate it correctly. A strip foundation is a closed loop constructed from reinforced concrete beams that are mounted (poured) under all load-bearing walls of the building.
Depending on the size of the beams and the depth of their placement in the ground, the strength of the structure and its load-bearing capacity are determined. Therefore, it is very important to calculate the foundation for all indicators at the stage of project creation.
Types of strip foundation
The device of a strip foundation is classified according to several indicators. By depth level:
- Recessed strip foundation- this is when a trench for a structure is dug below the soil freezing level by 30-50 cm.
- Shallow (MZLF)- this is when the depth of the trench is only 20-50 cm.
- Non-buried is a foundation for a house laid on the surface of the ground without digging trenches.
For obvious reasons, the buried option is more difficult to carry out the work and will be more expensive than the others. But it is it that is most often used in private housing construction. It is more reliable and can be used on almost any type of soil.
By type of structure:
- Monolithic is when concrete is poured into the installed formwork.
- Prefabricated strip foundation- This is a structure assembled from ready-made reinforced concrete products, specially manufactured in factories for foundations. Their installation requires the presence of heavy equipment at the construction site, which increases the cost of installation work.
Advantages and disadvantages
It’s not for nothing that strip foundations (monolithic) are so popular among private developers because:
- withstands huge loads;
- easy to construct, which makes it possible to carry out all construction operations with your own hands;
- it has a huge operational resource;
- I have an opportunity select according to the construction conditions from the presented classification list;
- the tape will not yield in terms of its reliability, the slab version;
- it's cheaper than a stove several times;
- there is an opportunity to conduct thermal insulation of floors by laying several layers of insulation between the beams.
And disadvantages:
- Not monolithic on all soils reinforced concrete strip foundation can be poured.
- If a big house is being built, then a large volume of concrete will have to be poured under it, which cannot be produced on a construction site in one day. And it must be poured in one day, so you will have to buy a ready-made solution, which costs more than if you make it yourself.
- Large amount of preparatory work under strip foundations, especially earthen ones. You will have to dig a deep trench, which may take several days. If you use the services of an excavator, the work will go faster, but you will have to pay for the equipment used.
Stages of strip foundation construction
Before making a strip foundation, you need to plan all the work and break it down into stages. The first stage is preparatory. What does it include:
- marking the structure on the ground;
- trench digging;
- preparation of trenches with backfill;
- installation of formwork;
- installation of a reinforcing frame.
Marking
The most crucial moment in the construction of a recessed strip foundation is the precise marking of the structure on the construction site. If the plot and the house are large, then it is very difficult to apply accurate markings yourself. There is a high probability that it will be applied incorrectly. Therefore, invite a specialist with a laser level who will mark the axes of the beams on the ground with reference to the boundaries of the site.
- Drive wedges along the axes and tie them with twine.
- Set aside half the thickness of the strip foundation from the axis in two directions. For example, if the thickness of the tape according to the project is 50 cm, then 25 cm should be set aside from the axis in each direction.
- Drive stakes along each side of the axle and tie them with twine as well. After this, you can remove the pegs and strings that define the axes. A foundation diagram for a private house is formed on the ground.
- Trenches are being dug taking into account the depth of the foundation structure. The walls of the trenches are aligned vertically as much as possible.
- The bottom is covered with sand a layer of 20-30 cm, which is well compacted. It is recommended to water it with water.
Formwork
The formwork is being assembled. Depending on the type of soil on the site, the formwork is selected to cover the entire height of the foundation or only for the basement part. If the soil is strong, then the second option is used, if it is loose, then the first. The formwork itself is assembled from flat materials: boards, plywood, OSB boards, corrugated sheets, metal sheets, slate, etc. The main requirement for it is the strength of the structure, which must withstand the pressure of concrete.
Reinforced frame
Now, as for the reinforcing frame. You can make it yourself or order it. The project calculates the dimensions of the frame and what reinforcement it should be made of. Therefore, making it yourself is not a problem, the main thing is to choose how to fasten its elements. This is electric welding or wire. It is recommended to knit the reinforcement.
Pay attention to how to properly install the frame in the formwork and trench. It should not be installed on a pillow, but on stands. Because according to the canons of construction, the frame must be located in the body of the foundation. Solid bricks, concrete blocks or specially made slingshots made of metal profiles (reinforcement, corners) are used as supports.
Calculations
Everything is ready, you can proceed to pouring the strip foundation. But before this, you need to decide on two questions: what brand of concrete is used in the construction of a strip structure, and how to calculate the amount of concrete for the foundation.
Everything is simple here. The grade of concrete for the strip foundation of a private house should not be less than M400. Therefore, when mixing the mortar on a construction site, use the following ratio:
- 1 volume of cement grade M400;
- 2 volumes of sand;
- 3 volumes of crushed stone of small or medium fraction;
- 0.4 volume of water.
As for calculating the amount of solution, to do this it is necessary to determine the volume of the structure itself. In cross-section it is a rectangle with sides - width and height. Multiplying them together, we obtain the cross-sectional area of the tape. Now you need to measure the length of the entire contour with all internal sections.
The total length is multiplied by the calculated cross-section value. This is the volume of concrete mass for the strip foundation. Serious construction portals offer calculators with which you can calculate the volume.
Pouring the foundation
The technology for constructing a strip foundation is based on the construction of a reinforced concrete structure, where the main component is concrete. It is necessary not only to make it correctly and decide what grade of concrete is needed for the strip foundation, but also to carry out the pouring correctly.
- It must be refilled continuously but if it takes time to mix the solution, then the time between pours should not be more than 4 hours.
- Concrete mortar distributed evenly throughout the foundation structure. Each poured volume is subjected to vibration, the main purpose of which is to remove air from the concrete mass. Because the air remaining in the mixture is after the concrete has hardened, shells and pores that reduce the strength of the stone. The second purpose of vibration is to compact the solution.
After pouring, the surface of the tape is covered with burlap or plastic film. You can choose any one. Now to the question of how long the foundation should stand. To gain its brand strength, the foundation needs to stand for 28 days. 7 days after pouring, the formwork can be removed.
Here is a not-so-simple step-by-step instruction for building a strip foundation with your own hands.
Foundation on a slope
Building a house on a slope using a strip structure is one of the options. True, a strip foundation on a slope is a rather complex structure that requires an increased amount of concrete mortar. But the most important thing is to dig the trenches correctly. On the high part of the site, a large amount of excavation work is carried out, because the foundation is deepened relative to the lowest point of the location. It is from this that the calculation of the depth of placement comes.
For example, if the difference between the ends of the foundation structure in height is half a meter, and the laying depth is 1.5 m, then on the high part of the slope you will have to dig trenches 2 m deep. It must be understood that in the lower part of the structure you will have to install formwork of greater height, and more specifically, half a meter in the lower edge.
The formwork will be beveled, so first of all the height of the tape is set, and then the dimensions of the panels are adjusted to it. This is about the question of how to properly make formwork for a foundation on a slope.
Let us add that if the formwork is installed only on the basement part, then at the highest section in height it will be small, or may be absent altogether. It all depends on the design of the foundation. For example, with the same difference of half a meter. If in the lower part of the slope the formwork for the plinth is 50 cm high, then there is no need to install it in the upper part.
Before pouring concrete, it is necessary to carry out all the preparatory operations that are required for a structure of this type. Regarding the question of what concrete to use for a strip foundation built on a slope, we choose M400. As in the previous case, the solution must stand for 28 days.
Often, a strip-grillage foundation is constructed on slopes. Grillage - what is it? This is still the same tape, only installed on poles. It is more difficult to calculate a strip foundation on piles, because support posts are added to the strip.
And the construction process itself becomes more complicated, because the load-bearing capacity of the piles will have to be taken into account, that is, it is necessary to accurately determine the laying depth and diameter of each columnar element. Be sure to lay a reinforcing frame in the pillars, and time is allocated for the foundation to settle for 28 days.
Conclusion on the topic
Although the foundation in the form of a tape is a simple structure, its construction must be approached from the position of strict adherence to the rules and regulations. Deviations in everything cannot be allowed. This applies to the proportions of the concrete solution, its correct mixing, and the proper distribution of the reinforcing mesh, its installation, and other nuances.
A slight deviation will definitely lead to a decrease in strength. And this cannot be allowed, because the foundation is the basis of the building, and how long the house will stand will depend on it.