They explain how to properly pour a strip foundation to ensure maximum structural life. Before filling the formwork with concrete, it is necessary to lay a sand cushion (if necessary), tie armored belts, and strengthen the formwork.
To prevent concrete from being destroyed during stripping, the inner surface of the formwork panels is covered with film, roofing felt or coated with a hydrophobic compound ( soap solution, cement or lime milk). Common mistakes Concreting with your own hands - cracks in the formwork panels larger than 3 mm, rusty deposits on the reinforcement rods, lack of compaction of the mixture. In this case, the house will not last long due to the delamination of the monolith.
Requirements of SNiP standards
Decorative concrete is prohibited from being dumped into the formwork from a height of more than 1 m, commercial concrete - 2 m. The recommended dumping height is 0.5 m, only in this case the house will not shrink due to delamination of the base. The basic requirements for concrete work are given in (clauses 2.10 – 2.14), which facilitates the work:
- laying in one direction;
- equal layer thickness (vibration compaction every 60 cm);
- the reinforcement must be well coated with the solution;
- technological break between laying layers is a maximum of 2 hours from the moment of mixing the concrete (during this time Bottom part must be compacted);
- It is not advisable to fill along the upper edge of the formwork; it is better to install it 5–7 cm higher and lower, and distribute the solution along a line marked on the inner surface of the panel.
Please note that concrete at 25 degrees begins to set two hours after mixing, i.e. not from the moment it was poured into the formwork, but from the moment water was added. Therefore, if concrete is produced at a factory, you need to order concrete with an expectation of no more than 1 hour for delivery in order to have time to lay and compact it.
If the height of the tape is not much more than 60 cm, it is recommended to divide it into two equal layers (for example, 80 cm = 40 + 40 cm).
Sudden rain leading to erosion of concrete causes work to stop. The defective layer is removed and replaced with new concrete with mandatory re-compaction. Mobile canopies and covering the poured tape after completion of work allow you to protect the structure from rain while gaining strength.
Hot and cold seam
Before you start pouring a monolithic base, you should calculate the work time. For large volumes, it is often impossible to fill the formwork with the mixture in one go (for example, a deep strip 2 m high along a 10 x 10 m perimeter). For these conditions, two technologies are used:
- hot joint - filling the tape halfway in depth with layer-by-layer tamping every 60 cm in height, covering the surface with film, resuming work the next day after washing off the exposed cement film from the surface of the concrete (after 7 hours, maximum);
- cold seam – installation of vertical lintels into the formwork (wooden, plywood board), resumption of work only after the concrete has gained strength (8 hours, minimum)
Changing these modes is fraught with a sharp loss of strength of the strip foundation. When a new portion is applied to concrete that has already lost its mobility, but has not yet gained strength, cracks form in the structure. Before continuing concrete works measure the strength of the poured structure; if it is slightly higher than 1.5 MPa, you can order a mixer or run a concrete mixer on site. Normal conditions for an eight-hour strengthening period are considered to be a temperature of +20 degrees and no precipitation.
The contact area (working seam) is cleaned of cement film in several ways:
- mechanical - scrapers, angle grinders with a diamond disc or equipment for concrete, a stream of air, water;
- chemical - special compounds called “chemical cutters” (usually acids);
- sandblasting - supplying quartz sand under pressure, then you need to remove dust from the surface.
Cold seams must be treated with materials that increase adhesion. The most effective primers deep penetration, strengthening concrete, changing its structure at the molecular level.
Highly effective injection insulation (for example, Penetron products) improves the waterproofing properties of the seam and increases frost resistance. Budget option waterproofing is swellable cords made of germite, bentonite, waterstop.
By default, concrete poured into formwork is saturated with air. After hardening, cavities, pores, and internal cavities are formed in it. Therefore, the house will rest on a reliable foundation only when the mixture is compacted manual tamper or a vibrator. The main mistakes when building a monolithic foundation are lack of compaction or an increase in the layer more than 60 cm.
Why compact concrete?
The main reasons for concrete vibration are:
- reduction of porosity - air escaping from the mixture increases water resistance, structural strength, and class of concrete (small amplitude, high frequency vibrators are recommended);
- increased fluidity (short-term) - periodic shaking of the solution with a vibrator improves the gravitational distribution of concrete inside the formwork.
In the absence of a vibrator (a garden house built independently), reinforcing pins can be used. This bayonet technology is effective mainly for liquid concrete. In reinforced concrete foundation elements of complex configuration, it is recommended to re-compact an hour after laying the mixture, but before setting begins. When pouring layer-by-layer, the tip of the vibrator is immersed in the bottom layer by 5-10 cm for uniform mixing and the disappearance of the interlayer boundary.
The main requirements for working with a vibrator are:
- fast immersion + slow extraction (concrete should close on its own);
- overlap of circles from the vibrator by 10 cm or the step of rearranging the vibrating tool = one and a half radius of action.
The signs of satisfactory seal quality are:
- quick alignment of the concrete surface when removing the tip;
- no bubbles;
- fine-grained sand in cement laitance over the entire surface;
- cessation of subsidence.
Vibrator or manual bayonet
On straight sections monolithic structures concrete is definitely easier to compact with vibrators. In narrow places, with complex design shields, armored belts, the tip of the vibrating tool may not fit into the formwork, so you have to bayonet the mixture with pieces of reinforcement. Only in these cases does the house receive the maximum possible service life.
The most popular types of vibrators are:
- manual - the motor is built-in, the tip is heavy (29 - 22 kg), the working part is about 50 cm, the productivity is 7 - 18 cubic meters per hour;
- with a flexible shaft - the working body is extended, the length of the tip is 36 - 44 cm, weight 11.5 - 23 kg, productivity is half that of previous options (2 - 6 cubic meters per hour).
The electric drive is built into following models: IV 60, IV 100, IV 103. Modifications IV 47B, IV 112, IV 113 are equipped with a flexible shaft. The tip of the tool is called a vibrating mace; manufacturers produce equipment with a diameter of 2.5 - 10 cm for different operating conditions. In addition to deep instrument options, there are surface and external vibrators. The former are mounted on the surface of the concrete, the latter are fixed to the formwork, giving it oscillatory movements.
Pneumatic vibrators operate from a compressor and are professional equipment. They have a high service life and are designed for long-term operating conditions.
In order not to ask questions later on the forum about why the foundation cracked after pouring, we recommend reading.
Influence of weather conditions
To ensure normal conditions, the concrete should not be hot; the optimal solution temperature is within 35 degrees. At winter concreting the house will be provided with a high-strength foundation if the temperature inside the formwork is maintained at + 10 degrees for three days.
Specifics of summer concreting
In hot weather, concrete heats up intensely due to chemical processes taking place inside it. In this case, the linear expansion exceeds the permissible norm, which is fraught with the following defects:
- at the moment of expansion the volume increases;
- at the same time, setting begins (hydration);
- after natural cooling, compression begins, which is prevented by the structure of the material formed at the previous stage.
Residual stresses lead to rapid destruction of the reinforced concrete structure, the house loses its resource and strength. Therefore, when concreting in summer, it is necessary to use concrete whose grade is one and a half times higher than the design grade of concrete and add plasticizers.
Work is carried out in the evening or early in the morning during the hours of least heat. The work site is protected from solar ultraviolet radiation by canopies and awnings. Repeated vibration compaction can be used to save surfaces with emerging cracks no later than 1 hour after laying the mixture.
Pouring monolithic structures in winter
Already when the temperature drops to + 5 degrees, concrete will take twice as long as at + 20 degrees. Strength gain at 0 degrees practically stops, which destroys the structure of the reinforced concrete structure. Water stops participating in hydration and remains in the form of droplets that expand in cold weather. Crack formation along the entire depth of the foundation strip is ensured; it will not be possible to restore the structure. The main methods for winter concreting are:
- heating concrete components - steaming sand, crushed stone (within + 35 degrees), using warm water(+ 70 degrees, maximum);
- change in water/cement proportions - the amount of liquid is reduced, the amount of cement is increased;
- the use of R-cements - the letter in the marking means a rapid increase in strength, the rate of hydration increases without loss of properties;
- use of antifreeze - chemicals are added to water to reduce the freezing point;
- heating of formwork - cable inside the foundation strip, around the perimeter, heating of panels.
Polymer films covering the poured mixture and layers of insulation create the effect of a thermos. IN severe frost greenhouses are made above the formwork.
How to care for concrete
In order for the house to stand firmly, it is not enough to pour concrete into the formwork in compliance with the above requirements and remove it. Depending on the season and air temperature, it is necessary to provide conditions for gaining strength:
- reduce shrinkage to an acceptable minimum (vibration);
- prevent sudden drying out or freezing;
- prevent damage (chemical, mechanical).
For example, possible leaks in the cracks of the formwork must be eliminated. It is advisable to cover the surface of the concrete with film immediately after vibration compaction (burlap, tarpaulin, sawdust are allowed). IN winter time It is necessary to heat the formwork and the building area in different ways.
In the heat, intense drying and dehydration occurs, which can lead to cracks along the perimeter of the tape. Therefore, periodic moisturizing is necessary in the first seven days. To do this, it is forbidden to use jet irrigation; it is better to use watering cans or hose attachments. A wet-drying compress will ensure no shrinkage, cracking, or peeling.
It is very important to use all of the above techniques and monolithic concreting technologies in combination. Violation of the regime at any stage will lead to an increase in the construction budget by at least 2.5 times - it will be necessary to first dismantle the poor-quality foundation, then re-fill it, and remove construction waste.
Advice! If you need builders to build a foundation, there is a very convenient service for selecting specialists from. Just fill out the order details, the specialists will respond themselves and you can choose who to cooperate with. Each specialist in the system has a rating, reviews and examples of work, which will help with the choice. Looks like a mini tender. Placing an application is FREE and does not oblige you to anything. Works in almost all cities of Russia.
If you are a master, then go to, register in the system and you will be able to accept orders.
Strip foundation has a lot of advantages, its technology has been proven for a long time, setting up a strip foundation is not a difficult task, the main thing is to follow all stages of the technology. This is the only option that allows you to include a full-fledged underground/ground floor in the project.
According to the SNiP standards of 1987, numbered, strip foundations are classified according to the following criteria:
- design - prefabricated from factory reinforced concrete FBS blocks on FL slabs; monolithic (pouring in place into formwork), laying the strip with brick or rubble stone;
- laying depth - shallow strip foundation (MZLF - 0.4 - 0.7 m), deep (below the freezing mark in the region).
IN individual construction Low-rise buildings usually use a monolithic type of this foundation.
Step-by-step instructions for installing a strip foundation
To ensure the maximum service life of the structure, it is not enough to pour the strip foundation into the formwork. It is necessary to rest it on non-heaving soil, remove moisture, and compensate for the forces of frost heaving. For this purpose, a cushion, drainage, hydro and thermal insulation are made, respectively. In order to do all operations correctly, you must follow the technology below:
Preparation
Soil samples before construction
In order for the strip foundation to last a long time, it is necessary to order surveys from specialized company. This will reveal the possibility of movement of layers, soil composition and depth of occurrence groundwater. Only in this case can the foundation of the house be done correctly. Survey data is necessary to calculate the cross-section of the reinforcement, the number of chords and the cross-section of the tape.
Marking
At this stage, it is necessary to remove the fertile layer from the entire building area (usually 0.4 - 0.6 m), and mark:
- cords on pegs along each wall;
- scheme lime mortar on the ground.
Marking trenches for strip foundations.
The stakes are mounted slightly further than the axes of the walls so that the cords do not sag when removing soil with a shovel. In projects of rectangular and square cottages, the diagonals must coincide, within 2 cm. If there are pilasters, porches or verandas, the geometry of each architectural element controlled additionally.
For heavy equipment (pumps, emergency generators), heating devices(boilers, furnaces weighing more than 0.4 tons), independent foundations not connected to the tape are marked. The distance between reinforced concrete structures should be more than 10 cm; after pouring concrete, it is covered with non-combustible material (crushed stone or sand).
Excavation
Depending on the depth of the tape, different heaving forces act on it:
- tangents - they try to move the structure sideways or push it tangentially upward;
- pushing out - only for MZLF that does not reach layers that do not swell in winter.
Therefore, in addition to the sand cushion under the sole of the tape, it is necessary to provide the side backfill of the foundation with non-metallic material (sand, crushed stone, ASG mixture).
Digging a trench for a strip foundation. In the future, the fertile soil layer inside the foundation must be removed.
To compensate for heaving forces and create normal operating conditions for the underground floor, the walls of which in 60% of cases are strip foundations, the outer surface concrete structure insulated with XPS expanded polystyrene sheets over a waterproofing layer. The layer of heat insulation is continued in a horizontal plane along the bottom of the trench for 0.6 - 0.8 m, spreading sheets of the same material.
To do hydro-thermal insulation correctly, builders need access to these surfaces located below ground level. This requires increasing the width of each trench around the perimeter of the house by 0.8 - 1 m. Installing a strip foundation with your own hands will take four times longer than using special equipment. For a shallow MZLF belt, work can be done manually; for depths below the freezing mark, it is better to use an excavator.
On last stage it is necessary to level the bottom of all trenches to the same level. However, the excavation work does not end there, since the tape must be protected from moisture in another way.
Drainage
Most manufacturers of expanded polystyrene have technological maps for insulated MZLF and deep-lying tapes. They provide step-by-step instructions for arranging drainage:
- along the outer perimeter of the trench expanded at the previous stage, a depression is created 30 cm below the bottom of the tape;
- a general slope of the system is created in one direction (3 - 4 degrees for gravity movement of wastewater);
- at the collection site, a sealed container with a neck extending to the surface is buried in the ground;
- the bottom of the recess is filled with crushed stone; if the soil is silty, it is necessary to lay geotextiles (a margin of 30 cm on each side for subsequent wrapping of the pipe), compacting the cushion with a vibrator or tamper is necessary;
- placed on a pillow drainage pipes(smooth or corrugated, with slotted or round perforation), they are launched into the wells, leaving free space into which, if clogged, a hose can be lowered to purge the system with high pressure;
- mounted in the corners inspection wells from corrugated or smooth pipe with plugs on top;
- the mini-trench is filled with crushed stone to the level of the bottom of the trench.
To make drains correctly, all the above conditions must be met. This will allow you to keep the reinforced concrete structures of the house buried in the ground dry. The drains should be located under the planned blind area so that the runoff from it does not flow into the drainage, but into the surface storm drain, which will relieve the reservoir from overflowing.
It is worth noting that drainage is not always provided for; if you are in doubt about whether or not to do underground drainage, then only soil geology can tell for sure which is worth ordering.
Sand substrate
To make a proper foundation pad, it is necessary to compact 15–20 cm of sand and the same amount of crushed stone in layers. Only in combination with drainage and tape insulation will the structure ensure a century-long life of the house without destruction. At the time of compaction, the non-metallic material must be wetted for better shrinkage.
- crushed stone and sand have drainage properties, that is, water can only seep through them downwards;
- There is no capillary rise from lower levels in these materials.
In the event of a sudden increase in groundwater level, roofing material will not protect concrete, since it is not associated with the lateral waterproofing of the structure. Moisture from the concrete does not go down during vibratory ramming, the cement laitance rises to the top, and large fractions go down. Therefore, it is better to make normal hydro- and thermal insulation of the base of the house after stripping the structure.
Formwork
The formwork must be securely fastened with braces and tied with wire through holes drilled in the panels.
Step-by-step instructions for installing classic removable formwork are as follows:
- production - from plywood, edged boards, chipboard or OSB, boards are knocked together (height from the bottom of the trench to the ground level + 40 - 50 cm of the base);
- installation - the boards are fastened with jumpers for a stable geometry when expanded from the inside with concrete, they are fixed from the outside with inclined bars resting on pegs;
- holes - in the base part, pipes of a suitable diameter for ventilation ducts are passed through the shields; similar sleeves are installed underground for input engineering systems(if floors are planned on the ground, ventilation ducts are not needed);
- processing - to facilitate stripping and improve the quality of the side surfaces of the concrete strip, the inside of the boards is sheathed with roofing felt or PVC film.
It is not recommended to pour concrete along the upper edge of the formwork; it is better that the level is 2–5 cm below it. This will prevent splashing during vibration compaction of the mixture and will allow the surface to be better leveled. Marking the horizon with a marker or cord on the inner surface of the boards will allow you to control the filling of the form with concrete.
Don’t forget to put plastic inserts into the formwork for ventilation and communications.
Technology permanent formwork slightly different from the previous version:
- instead of lumber, polystyrene blocks are used (assembly is similar to the construction set);
- there are no external supports, plastic ties are mounted from the inside;
- Thanks to the corrugated surface of polystyrene and internal ties, the insulation reliably adheres to the concrete.
Fixed formwork is always narrower than classic formwork, which makes it difficult to place an in-depth vibrator. When pouring MZLF, the formwork is filled with concrete at a time. If the depth of the foundation is below the freezing mark, 40–60 cm of formwork in height is assembled, concrete is poured, and compacted. Then the formwork is increased to the same height, and the operations are repeated.
Reinforcement
To make an armored belt for the base of a house without errors, it is necessary to make a calculation (section, number of longitudinal bars, jumper spacing), and take into account the nuances:
- rods are prohibited from joining in corners, T-junctions, one rod is bent at a right angle (50 reinforcement diameters minimum), the second is attached to it on a straight section of the adjacent wall;
- It is not recommended that the diameter of longitudinal bars of periodic cross-section (corrugated) be less than 12 mm, distribution clamps or jumpers less than 6 mm (smooth reinforcement);
- 4–6 pieces of longitudinal rods are usually laid. in each frame (2-3 below, 2-3 above);
- in junctions and corners, the spacing of the jumpers is reduced threefold (20 cm instead of 60 cm);
- overlap is recommended 40 - 60 cm with double ligation with wire.
Scheme of reinforcing the corners of a strip foundation with U-shaped clamps.
Knowing the volume of formwork for ordering concrete, you can roughly estimate the consumption of reinforcement - 80 kg per cubic meter of mortar. It is prohibited to touch the armored belt to the formwork panels, from metal elements there should be at least 2 cm to them, 5 cm is better.
When using clamps (a closed element bent from a rod that follows the shape of the formwork), the installation productivity of the armored belt increases.
Fill
Basic rules of professional pouring strip base are:
- filling the formwork in one day with breaks within 1 - 2 hours (the beginning of setting depending on the weather);
- moving the mixer around the perimeter, rather than dispersing liquid concrete from one place over all walls (the mixture loses its properties);
- the horizontal of the upper plane of the tape is below the sides of the formwork panels, and do not interfere with them;
- it is prohibited to throw the solution from a height (maximum 2 m from the bottom of the trench);
- It is necessary to compact the concrete mixture with a vibrator.
To fill the formwork efficiently, it is necessary to move the mixer several times around the building spot to fill the height of 60 cm. Then go through all areas with a deep vibrator, repeat the operations until the design mark is reached. The norm for a vibrating tool is a compaction depth equal to 1.25 times the length of the tip.
Curing
To avoid wasting the construction budget at the foundation pit stage, the developer must know how long the concrete sits in the formwork and how to care for it. The main troubles that can happen with a reinforced concrete structure are:
- damage – chemical or mechanical;
- drying until completely hydrated - brittle structure, broken internal connections, possibly in the heat;
- cracking from temperature changes - important in late summer and autumn;
- shells on the surface - shrinkage due to the lack of plasticizers.
After pouring, the foundation is watered for a week and covered with film on top to prevent moisture evaporation.
Until the concrete has reached 2/3 of its design strength (can be identified by its grade), it cannot be stripped and must be protected from the specified influences. To do this, the building spot or the perimeter of the base is covered with PVC film, burlap or tarpaulin, and after 8 hours watering begins. The tape covered with loose materials retains moisture longer; it is recommended to sprinkle it with sand, sawdust, cover it with burlap and moisten these materials.
Stripping
When using permanent formwork technology, this structural element remains on the tape. In other cases, the panels are removed at 70% of the design strength of the concrete, which is a week in the summer. It is better to carry out the work together, holding the removed formwork elements in a canopy.
A home craftsman, when building a strip foundation with his own hands, will avoid serious mistakes when following these recommendations and save money. The foundation is too important an element of the building to risk its integrity and resource.
Advice! If you need builders to build a foundation, there is a very convenient service for selecting specialists from. Just fill out the order details, the specialists will respond themselves and you can choose who to cooperate with. Each specialist in the system has a rating, reviews and examples of work, which will help with the choice. Looks like a mini tender. Placing an application is FREE and does not oblige you to anything. Works in almost all cities of Russia.
If you are a master, then go to, register in the system and you will be able to accept orders.
The technology of pouring monolithic concrete foundations is in demand in private construction; the main advantage is the possibility of obtaining reliable design even when doing the work yourself. The requirements for the mortar, reinforced frame and other materials used are high; up to 30% of the budget is spent on laying this part of the building. The only way saving is pouring the foundation with your own hands, without or with minimal involvement of specialists. In most cases, the tape type is chosen.
The main nuance of the technology is the continuity of the process; the structure is poured into a single monolith. This and the need for the most homogeneous solution leads to the need to use special equipment. Manual mixing is not allowed; it is almost impossible to prepare high-quality concrete in a volume of 4-6 m3 yourself. The most popular device is a concrete mixer with a bowl capacity of at least 60 liters; on average, mixing one portion takes 5 minutes (provided the components are properly prepared).
When working with ready-made ready-mix mixtures, two types of machines are used: a mixer or a concrete pump. The first is used when pouring a large foundation; a prerequisite is the organization of access to the formwork and the preparation of chutes for supply. The more supply points, the easier it is to distribute the solution inside. The services of a concrete pump are required in the absence of an appropriate entrance; this special equipment is considered the most convenient due to its long hose (up to 50 m). The disadvantages include increasing costs; its one-time rental costs 15,000-20,000 rubles.
Next comes equipment for uniform distribution of concrete in the formwork, for example, deep vibrators. Their main purpose is to expel excess air from the solution and compact it. Renting is inexpensive (500-750 rubles per day), the use is considered justified (the characteristics of concrete correspond to its strength class, the reliability and durability of the structure increases). If this is not possible, air must be expelled manually - with a shovel or a special stick.
You will also need: a hook or a construction gun for tying the frame, formwork ( better surface obtained by using shields from moisture resistant plywood or plastics), spacers, plastic pipes for filling holes for future communications, a wheelbarrow for transporting mortar, a trowel for leveling the top layer of the foundation. Soil analysis and calculation of the amount of building materials and reinforcement are carried out in advance. When planning the timing, it is taken into account that most of the labor costs are spent on excavation work; special equipment can also be used to dig deep trenches and remove soil.
Step-by-step instructions for concreting the base
The standard guide includes the following steps:
1. Preparatory: clearing the area of debris, applying markings. Special attention is given to the corners, diagonal deviations are checked and eliminated.
2. Excavation work. The depth of the trench depends on the soil parameters, usually it varies from 0.5 to 1 m, the width is chosen 20 cm larger than the size of the tape. At the end of digging, the bottom is checked for evenness; level deviations are unacceptable.
3. Formation of the pillow: at least 15 cm of sand and 10 cm of crushed stone are poured in layers and compacted. The main purpose of these layers is to reduce the load from soil movements on the lower base of the foundation; in problem areas, their thickness is increased. In some cases, a layer is laid on top of carefully compacted crushed stone roll waterproofing, alternative option is the impregnation of screenings with bitumen. At high risk It is recommended to fill the top layer of the cushion with thin concrete (up to 10 cm).
4. Preparation and installation of formwork panels. At this stage, in addition to laying holes for communications, it is important to check and mark the level inside future design. To avoid backfilling with earth, the shields are made higher zero mark at least 30 cm; to simplify the procedure for removing them, they are lubricated with oil. All elements are securely fixed, the angles are checked again.
5. Frame assembly. The reinforcement scheme is selected based on the size of the foundation, the cross-section of the rods depends on the purpose of the building - for residential buildings the minimum for longitudinal rows is 12 mm, for baths - 10. The requirements for vertical and transverse ones are weaker; the use of rods with a diameter of 6 to 10 mm is allowed. It is not recommended to use welding to connect joints; for these purposes you will need plastic clamps or binding wire. Minimum number of longitudinal rows in a standard base shallow– 2, if the height of the structure is exceeded, they are increased (vertical placement interval – 70-80 cm). To prevent contact of the lower part with the pillow, pieces of brick or special plastic molds are placed under the rods.
6. Mixing in a concrete mixer. The ratio of binder to sand cannot be more than 1:3; the exact proportions are selected according to the required grade of concrete and type of building (from M200 and above). All components are prepared in advance; the permissible break between mixing new portions is 2 hours. The foundation must be poured in one day; if this condition cannot be met, a ready-made composition is ordered.
7. Distribution of the mixture in the formwork: in layers of 20 cm, with air forced out with a hoe, stick or using vibration equipment or piercing with reinforcement. The top layer is leveled with a trowel.
8. Curing of concrete in formwork with mandatory moisture maintenance and covering with film. The shields are removed after 1-2 weeks, and it is allowed to proceed to the next stage no earlier than after a month.
The given guide can be used for pouring a slab-type foundation, in this case the soil is removed along the entire perimeter of the building, the cushion, reinforced frame and concrete layer are placed over its entire area.
At independent batch the solution cannot be poured in one layer; it is distributed over squares. Materials and work are more expensive; this option is used when laying the slab shallowly or building a house with a basement is permissible.
What factors are taken into account when laying the foundation?
The process becomes more complicated when planning a basement, constructing an extension to an existing building, conducting construction on difficult soils, or the need to replace or restore a structure. The foundation is laid to a depth of 2-2.2 m in the case of a cellar; for buildings with basement areas, the total height of the tape is at least half a floor. A foundation with a basement for a house is more difficult to reinforce and fill; the cost of building materials and the effort to dig trenches or a foundation pit increase significantly; when designing, it is worth thinking about the feasibility of such a solution. An alternative is to lay the walls of the cellar from blocks, but this design is not suitable for all types of soil.
If it is necessary to lay a new foundation under an already operating building (old, or without tape under the internal walls), the following procedure is followed: excavating walls → clearing surfaces and corners, removing old concrete → reinforcing the reinforced frame using anchoring or tying to old rods → installing formwork → concreting. Replacement is carried out in separate segments up to 2 m wide, dismantling is carried out in one section, leaving a gap for waterproofing the top layer. When bookmarking under the old wooden house The walls are slightly lifted with jacks, starting from the most sagging corner.
When pouring tape for an extension or if there is no tape under the internal load-bearing walls a trench is dug with a depth no less than that of the monolith already in use. A properly executed connection is impossible without anchoring. For this purpose, a hole for reinforcement with a depth of at least 25 cm is drilled in the foundation wall, and it is deepened to the same distance into the new foundation. The brand of concrete used and the width of the tape are not lower than the old one.
How to properly pour a foundation: tips and tricks
To speed up the process, all proportions should be transferred to buckets. The recommended ratio of components is 1:3:5. In recalculation for the M250 brand, one 50 kg bag of M400 Portland cement requires 5 buckets of sand, 12 crushed stone and 3.5 liters of water. These proportions are indicated for a measuring container of 10 liters; checking the weight of the filler on site is mandatory.
Technology violations and actions that complicate the process include:
- Digging trenches in advance, when leaving them on long time the edges crumble, the markings get lost, and moisture accumulates at the bottom.
- Moisten the sand for the cushion before pouring it into the pit, otherwise the bottom will wash out.
- Construction of a foundation for an extension to a house without a rigid connection or laying an expansion joint.
- Exceeding the W/C ratio, using stale binder, lack of a concrete mixer.
- Welding reinforcement in the frame (the seams are susceptible to corrosion and are inferior in reliability to wire), ignoring the requirements for the arrangement of rods.
Strip foundations are widely used in private housing construction. This popularity is primarily due to the uncomplicated work to be done and the relatively low cost compared to prefabricated concrete foundations.
However, it is preferable to build strip foundations on non-heaving soils - in a shallow way. In this article we will try to tell you how to properly pour a strip foundation, what materials and tools will be required for this, and the procedure for carrying out excavation, reinforcement and concrete work.
Preparatory work
Before proceeding with the installation of a strip foundation, it is necessary to carry out a geodetic marking of the construction site and determine:
- soil properties;
- groundwater level;
- depth of soil freezing in winter.
Based on the data obtained, you can already decide whether to make a strip foundation or choose a more suitable option foundation installations to ensure maximum strength and reliability of the entire structure for many years.
This information, among other things, is the basis for calculating the strength of the foundation, choosing its size and type of reinforcement for the reinforcement cage.
Calculating the strength of the foundation is the main task before pouring a strip foundation. Since mistakes made in the future can result in irreparable changes in the design of the entire house and lead to its destruction. It is better to order the calculation of the foundation from specialists, as well as the preparation of the entire construction project.
Excavation
After the project is ready, they begin marking the future foundation on the ground. The construction site must be cleared of trees, bushes, construction and other debris, and planned as much as possible.
The foundation plan from the drawing is transferred to the ground. This is done using pegs, a cord and a level.
The correctness of the construction of the angles is checked by diagonal measurements. Both diagonals should be the same size.
Pegs are driven into the corners of the future foundation and a cord is pulled, which will mark the center line of the foundation.
On both sides of the axial line, the boundaries of the foundations and, even further, the boundaries of the trench or pit are marked.
When digging a trench or pit, their dimensions should allow the worker to move freely inside in order to position the formwork and reinforcement frame as conveniently as possible.
The bottom of the trench or pit must be level and correspond to the design marks.
After this, they begin to construct a sand cushion. A layer of sand, gravel or crushed stone is placed at the bottom of the trench or pit. The height of the sand cushion should be at least 15-20 cm when we fill the strip foundation with our own hands. When using gravel or crushed stone, the height of the cushion can be reduced by half. The poured layer is moistened with water and compacted.
The width of the sand or gravel layer should be 30-40 cm greater than the base of the foundation so that the edges of the base of the foundation do not sag above the ground.
For residential buildings, the height of the strip foundation is usually taken to be no more than 1 meter, depending on the number of storeys and the material used for the walls. Based on this, the trench is dug to a depth of 60-70 cm.
Formwork and reinforcement cage
Can be used as formwork wooden boards from edged boards, moisture-resistant plywood, metal sheets and other materials.
The formwork can be:
- removable,
- non-removable, in this case it is left on the poured foundation.
After installing the formwork, they begin to create a reinforcement frame.
To do this you should stock up:
- periodic profile reinforcement with a diameter of 10-12 mm,
- annealed knitting wire,
- crochet
Vertical reinforcing bars are installed at the bottom of the trench every 30-50 cm on both sides, after which horizontal reinforcing bars are tied to them, retreating 5-7 cm upward from the sand cushion. This will be the bottom chord of the reinforcement cage.
Then, at a distance of 5 cm from the top of the future foundation, horizontal rods are laid upper belt. If possible, it is easier to knit the reinforcement frame on the ground and then lower it into the trench, placing pieces of concrete, brick or special plastic backing parts 5-7 cm thick under the lower belt.
The cells of the reinforcement frame are usually kept in dimensions of 30x30cm, this is quite enough to ensure the strength of the strip foundation of an individual residential building.
Videos on various construction sites and forums show clearly and intelligibly how to pour a strip foundation.
When installing the reinforcement cage, it is necessary to provide passage holes engineering communications(sewage, water supply systems), as well as for ventilation ground floor or underground.
To do this, holes are cut in the formwork and asbestos-cement or plastic pipes of the required diameter are inserted. The pipes are tied to the fittings with binding wire.
The reinforcement cage must be located in the formwork in such a way that the distance from it to the formwork walls, top and bottom is at least 5 cm. In this case, the reinforcement will be completely protected from corrosion.
Pouring concrete mixture
Before you start pouring the foundation with concrete, inside formwork, you need to make a horizontal mark, which will serve as the boundary of the upper level of the foundation.
Depending on how the foundation will be poured, it will be determined how much it costs to pour a strip foundation:
- concrete will be prepared on its own,
- will be ordered ready-made and delivered to the site by mixers
If the concrete mixture will be prepared directly on site, then it is necessary to buy or rent a concrete mixer, since mixing concrete manually with shovels is very hard work and the construction of the foundation can take a long time.
If ready-made concrete is ordered, the mixture is poured into the entire formwork as soon as possible. If the delivered concrete is not enough, then the entire perimeter of the foundation should be poured evenly. The poured layer of concrete mixture is compacted using special vibrators or manually using the bayonet method.
To do this, pierce the concrete with any metal rod, shaking it a little so that the air accumulated in the concrete can come out. Thus, the concrete acquires sufficient density; air chambers, which significantly reduces its strength.
The top of the poured concrete is smoothed using a rule along the intended horizontal mark on the inside of the formwork.
A freshly poured foundation must be covered with damp burlap or covered with sawdust. In hot, sunny weather, concrete must be periodically wetted to prevent cracks from uneven drying.
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 correct type of base is influenced by total weight houses, soil strength and groundwater levels. 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 overspending, you need to perform a calculation that will allow you to find optimal parameters designs 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 the construction of brick or concrete house);
- (ideal for light wooden buildings).
Piles allow you to reduce the volume earthworks. 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 basement flooding, reducing bearing capacity foundation and destruction of materials of the supporting part of the building.
What to do when 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. Great option there will 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 - 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 when emergency. Arrange Monolithic foundation vertical seams are unacceptable, 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 columnar or pile foundation Class B 15 is sufficient. For tape you need grades from B 15 to B 22.5. 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. Continue construction works It is possible after the structure reaches 70% brand strength.
- It is better to carry out work in warm, dry weather. Perfect average daily temperature for concrete hardening - +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 pure 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;
- styling waterproofing material into the 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 you need to use concrete mixture 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 proclaim supporting part buildings, construction needed. 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.