The construction of a foundation slab requires careful preparation and accurate calculations. If it needs to be built for a small bathhouse or garage, then you can do all the calculations for concreting yourself. If the structure will be built for a residential building, then in this case errors are unacceptable. Particular care must be taken when determining the load, type of foundation and depth. Such calculations are best left to specialists.
- Site preparation.
- Soil study.
- Excavation of the earth, arrangement of a pillow.
- Covering with waterproofing material.
- Warming and waterproofing.
- Reinforcing cage installation.
- Formwork.
- Concreting.
- Drainage and blind area.
- Soil removal.
The first step is site preparation. Trees are uprooted, garbage is taken out, entrances for equipment and places for storing building materials are being equipped, as well as living conditions for workers are being improved. Perhaps needed.
The cost of filling at this moment directly depends on the area. Experts determine the type of soil, the depth of groundwater. According to their results, the type of foundation is selected. Geotechnical studies allow you to find out the pressure that will be exerted on the base, a diagram is drawn up.
After studying the soil, they begin to calculate the load on the slab from the side of the house. The weight of everything that will be on it is taken into account - people, furniture, equipment, and so on. This work should be done by a design engineer. The depth of the foundation is determined, as well as how the drainage will be equipped and what building materials are best used. The bases can be brick, rubble, rubble concrete, concrete, reinforced concrete and piles.
According to the drawn up project, the site is marked, the locations of the walls and partitions are marked both from the outside and from the outside. The soil is excavated and the sand and gravel cushion is being laid.
At this stage, it is recommended to equip a rough screed for laying waterproofing material. Thanks to it, the insulation will not tear or shrink during concreting under pressure of the mixture and the reinforcing cage. To prevent cement milk from flowing out of the solution, use a plastic film or other waterproofing. In no case should you skip and save at this stage. Due to the lack of water, the concrete will set unevenly, which in the future will lead to its cracking.
The price of reinforcing work is determined according to the design of the building, it must indicate the volume and type of frame. But if there is no estimate, then some developers are trying to reduce cash costs by reducing the number and diameter of reinforcement. Rods make up a large part of the total cost, but you can’t save on them. If there is no diagram, then for 1 m2 of the base surface, at least 10 m of reinforcement with a diameter of 12 mm should be purchased. After installation of the frame, all connections must be carefully checked before concreting.
The next stage of foundation work is the assembly of formwork. Many developers may decide to save on its construction by doing the concreting in parts. They equip the formwork in one part, pour concrete, remove the boards and put them on the next site. The base made by this method will not be monolithic. Cold joints are formed at the joints, in which, after some time, wide and deep cracks will certainly appear. Also, because of this, the overall strength of the structure is reduced, and water from the soil can flow through the cracks into the house.
After the formwork is installed, the concrete solution is poured. The strength of the foundation completely depends on the correct implementation, it is necessary to comply with all building codes and GOST. The concrete mixture must be fed at the same speed and evenly distributed; it cannot be pulled apart with a shovel.
Depending on the climatic zone, before work on the arrangement of the frame and formwork, insulation is carried out. Thermal insulation increases the cost, but it fully justifies itself in winter, as it reduces heat loss through concrete. Extruded polystyrene foam, polyurethane foam and other materials are used as heaters. From above, they must be covered with waterproofing, for example, with plastic wrap, so that liquid does not flow out of the concrete solution.
If built with a cellar, it is recommended to make drainage to drain water from the house. This will avoid excess moisture, dampness and mold on the walls of the basement. A blind area is also laid, atmospheric precipitation will flow down it, preventing it from penetrating into the ground near the walls, thereby extending the life of the base. It will become protected from heaving, which will significantly reduce the load.
Once construction is completed, a large amount of soil and debris remains on the site. When making calculations, be sure to add the payment for their export to the total price.
Rates
The cost of pouring the foundation depends on many factors - the size and type of foundation, distance from the city, the level of groundwater rise, and so on.
| Type | Price, rubles |
| Monolithic works: | |
| Tape | 4600 m3 |
| Plate | 4350 m3 |
| overlap | 4850 m3 |
| Poles and support beams | 5100 m3 |
| Piles TISE | 3800 for 1 piece |
| Ground work: | |
| Extraction by machinery and by hand | 290 m3 |
| Seal | 270 m2 |
| Laying gravel | 590 m3 |
| Sand pad construction, compaction and spillage | 890 m3 |
| Waterproofing and thermal insulation: | |
| Installation of roll insulation | 170 m2 |
| Warming | 120 m2 |
You can also order drainage. A running meter of a pipe costs 150 rubles, installation of revision wells - 400 per 1 pc. Backfilling with soil - 790 rubles per m3. Monolithic work includes the manufacture and removal of formwork, the installation of a frame for reinforcement, the pouring of concrete mortar and compaction with a vibrator.
It is better to entrust the construction company with budgeting and cost calculation. Specialists will accurately calculate the amount of materials, the size of the foundation, its type and other details, it is enough just to provide a building project.
If it is not possible to bring everything you need and build a foundation yourself, it is better to order a turnkey construction. Many companies purchase and deliver themselves. In this case, you can save money, as they buy goods at the cheapest points of sale. In addition, professional developers will purchase only high-quality material that will meet all standards.
Outwardly, 2 bases can look exactly the same - in structure and color, but at the same time completely different in cost. The differences lie in the materials used and the companies involved in its manufacture. The first will stand for more than one century, and the second will begin to collapse much earlier. Therefore, experts do not advise saving on the construction of a foundation for a turnkey house.
It is worth being prepared for the fact that 15-20% of the price of the entire building will have to be spent on its construction. If builders offer to make a base at prices almost equal to its cost, then their services should be abandoned.
Affects the cost of building a foundation and the time of year. In the summer, when such work is most carried out, it increases, as the price of building materials and the demand for them increase.
Foundation works consist in the construction of a supporting structure that perceives and distributes the main loads transmitted by the elements located above. The laying is carried out below the freezing level in order to prevent buckling. Works on the arrangement of reinforced concrete bases are allowed to be carried out at a temperature of +5°C.
Rules for carrying out foundation work
Activities for the construction of the foundation begin with the definition of the geometry of the structure, depending on the degree of strength of the materials used. The following steps are preliminarily performed:
Determining the size in the course of foundation work, the strength of materials, the depth of compaction, and the thickness of the pillow are calculated. The degree of strength of the upper layers of the soil is revealed, if such a need was identified during geological engineering surveys.
Foundation work using reinforced concrete pilesfastened with a grillage is carried out in stages using various technologies:
Types of piles used
It is recommended to use stuffed and driven piles in monolithic construction. Factories offer developers driven structures with an annular, rectangular or round section. Products are equipped with non-stressed or prestressed fittings. Supports with a square section are produced in lengths of 3 - 20 meters and have a cross section of 200 - 400 mm. Reinforcement of driven piles is carried out with A500SP non-tensioned reinforcement, which has limiting deformation parameters during compression.
The use of stuffed piles is associated with the formation of reinforced concrete supports with a broadened heel. Monolithic elements are concreted in pre-prepared wells up to 40 meters long.
The procedure for reinforcing piles and grillage
Reinforcement is carried out taking into account the loads acting on the supports. If there are exclusively compressive forces acting in the vertical plane, then constructive reinforcement is performed, organized in the upper segment of the element. It is required to use up to 12 rods 2 meters long with outlets of 400 mm, which provide reliable adhesion to the grillage. If the supports are subjected to horizontal loads, then the entire trunk will have to be reinforced.
Fig.1Pile reinforcement
The reinforcement process consists in creating a rigid frame, additionally reinforced with transverse reinforcement bars attached by welding, steel clamps.
Uniform distribution of the load of the pile foundation of reinforced concrete supports is ensured with the help of a grillage. Plates are reinforced in all directions. Separate welded meshes are used for these purposes, consisting of rods with a distance of 200 mm.
Rice. 2Pile pouring
Reinforcement anchoring is carried out at the ends of the mesh with a step of 25 mm using transversely located rods having a half diameter. When the upper segment of the piles is embedded in the grillage, it is necessary to insert the support into the body of the slab by 50 mm. It is necessary to lay a mesh of reinforcement over the head of the support. If the embedment depth is large, then the mesh rods that intersect with the pile are cut out, due to which a protective layer 50 mm thick is formed.
To compensate for the lack of removed rods, it is possible with the help of additional elements attached to the body of the main grid. If a grillage with mating piles is formed, then a conditional hinged support is created, sometimes replaced by a rigid pinch. The use of a hinged support located on top of the pile head implies the introduction of an element into the body of the grillage slab by 10 cm. When it becomes necessary to achieve a rigid pairing of the supports with the grillage, the pile head is embedded to a depth comparable to the length of the reinforcement anchorage.
Rice. 3Reinforcing cage pile
Stages of arranging the foundation
Schematically, the step-by-step technology for building a foundation from bored piles is as follows:
- preparation of points for pouring;
- well wall waterproofing;
- creating piles - if driven supports are used, then factory-made products will have to be used. Stuffed structures are made directly on the construction site;
- exposure of piles - the supports created on the site must harden;
- creation of formwork for grillage;
- the process of reinforcing and pouring the grillage.
Rice. 4 Stages of pile formation
Prices for foundation work
The calculation of the cost of erecting a pile foundation is carried out taking into account the costs for each stage of work. The determining factor is the price of stuffed piles:
| Support diameter (mm) | pile type | Price (RUB) |
| 150 | printed | 5800 |
| 200 | printed | 6500 |
| 250 | printed | 6900 |
| 300 | printed | 7100 |
Works related to the arrangement of the base include the cost of preliminary marking of the territory at a price of 100 rubles / m2. Earthworks, consisting in drilling wells, are estimated at 500 rubles. for 1 running meter. The process of waterproofing the walls of wells costs 250 rubles / m2
If it is required to expand the supports, then the price will be 500 rubles / m2. It is possible to expand the support up to 600 mm. The cost of arranging a grillage reaches 500 rubles per 1 running meter.
Traditionally, the cost of services for the arrangement of a pile foundation from stuffed reinforced concrete piles includes the following materials for specific parameters of the foundation:
- grillage - 400 x 600 cm;
- sand base - thickness 20 cm;
- stuffed piles - with a diameter of 250 mm;
- deepening of supports by 170 cm;
- and grillage - rods with a diameter of 12 mm;
- concrete - M-300.
Rice. five Completed foundation structure
The price of a running meter with installation under such conditions will be 4400 rubles. Additionally, you will have to pay for the following services:
- reducing the step between the supports - will inevitably lead to an increase in the number of piles used and the base cost of the foundation;
- an increase in the reinforcing diameter - strengthens the structure and increases the cost of work;
- increase in the depth of wells - increases the price in accordance with the quoted rates for earthworks;
- change in the brand of concrete - the price increases depending on the improvement in the quality of the building material;
- correction of grillage parameters.
It is necessary to take into account a large list of aspects in the process of organizing construction work. The arrangement of the base requires careful calculations and measurements to assess the characteristics of the soil. Technical operations associated with the preparation of wells and pouring piles must be carried out with filigree accuracy.
Order of foundation works in Moscow
It is recommended to turn to professionals, we are ready to take on the obligation to carry out the entire scope of work on driving piles for a pile foundation. If all aspects are taken into account, the foundation will last at least 50 years. By contacting us, our customers will be able to achieve cost minimization and quality improvement. We specialize only in pile foundations. Fill the form for application:
Related Articles
jQuery(document).ready(function()( jQuery("#plgjlcomments1 a:first").tab("show"); ));
When constructing a detached house, contractors for foundation work and for the construction of walls and roofs are sometimes selected separately. At the same time, not only prices, estimates and costs for the construction of the foundation, but also the timing of the work will depend on the optimal type and size of the foundation. The area of the house and the location of its main premises are also taken into account.
Principles for choosing the optimal type of foundation
According to the increasing complexity of their manufacture, foundations are distinguished:
slab;
tape;
pile;
screw
Therefore, before construction, it is necessary to at least roughly calculate the strength loads on the future house. For example, how many floors are planned in it, whether an attic will be built, whether basements are envisaged and what their main purpose will be (for example, the strength of the basement, where heating equipment is supposed to be installed, should be much higher than usual).
It should be noted that sometimes the choice of foundation is dictated by purely aesthetic requirements for the future house - for example, how its exterior is supposed to be, how the facade will be clad.
Comparison of common types of foundations for a house
The slab foundation by default has the greatest strength, since all operational loads will be taken by a massive concrete slab. It is only important to check the strength of the soil: whether groundwater is close, whether there is a risk of flooding the site in the spring with intensive snowmelt.
With a minimum of labor intensity of its construction, a monolithic slab foundation is not such a cheap structure, which is associated with the consumption of steel reinforcement and the large height of the slab. foundation, prices, cost and cost estimates also include the cost of an increased volume of concrete work, as well as the need for subsequent effective insulation of such a foundation.
A strip foundation made of profiled slabs is noticeably more economical, although it requires some calculations. In this case, instead of a solid slab, concrete profiles (tapes) with stiffeners are used, poured into special forms. They also perceive the main loads. Such a foundation is easier, faster and more convenient to install. In this case, the construction of the foundation, the price, cost and cost estimate will include the cost of arranging a special one-time formwork, the main component of which is polystyrene foam.
The most expensive are considered pile and screw, for the construction of which special expensive equipment will be required. In addition, costs will increase due to the need to use high-quality piles - concrete or steel screw.
Thus, to select the appropriate type of foundation, you must:
Find out the value of the maximum load.
Correlate the choice with the possibilities of the soil in the construction area.
Decide on the level of your own technical capabilities or the capabilities of the company that will lay the foundation.
Establish deadlines for the construction of the foundation.
It is customary to call the foundation the underground part of a building or structure, which takes on all the loads, transferring them to the foundation. The foundation is chosen according to the features of the future structure and the type of soil at the construction site. In order to decorate the building in a style suitable for the landscape, any foundation technology is suitable. a lot:
- tape;
- columnar;
- monolithic;
- pile;
- slab (floating);
- screw.
Strip foundation technology
This type of foundation is often found in individual construction. It is such a foundation - a reinforced concrete strip with a pre-fixed height and width, which is located along the perimeter of the entire building. The tape must be placed under all external and internal walls of the building, the cross-sectional shape must be maintained along the entire perimeter of the base. This type of foundation is well suited for houses with heavy walls made of concrete or brick, with ceilings. Also this type of base is applicable for underground garage or basement.
They resort to the device of the tape base in the following cases:
- for houses with walls made of brick, concrete or stone, the density of which is equal to or more than 1000-1300 kg / m³;
- when it is planned to make heavy floors in houses, monolithic or prefabricated metal, reinforced concrete;
- if there is a threat of uneven settlement of the entire foundation as a whole, for example, if the site is composed of heaving loams in one part of the structure, and sands in the other part. In this case, the correct foundation device will work as a whole, redistributing the load and preventing the walls of the house from cracking and deforming;
- when a basement is planned in the house, while the walls of the strip foundation will be the walls of the basement.
According to their device, strip foundations are monolithic, poured directly on the construction site, and prefabricated. The device of prefabricated foundations is made from standard reinforced concrete blocks, which are produced at the factory and are mounted on the construction site with a crane. The device of such bases and foundations is made of pillows - reinforced concrete slabs and concrete blocks. The prefabricated type of base is inferior to the monolithic one in strength.
Back to index
Work order
After it is selected, the axes of the house are marked on the ground, where the location of the main axes of the foundation is fixed with the help of stakes and a cord or wire. If the site is with difficult terrain, accuracy and attention will be required, as well as the use of a building level and slats. The corners of a rectangular or square foundation are strictly checked, they must be 90º. The bottom of the trench is checked with a theodolite, especially in those places where the tapes will intersect, and in the corners of the house.
The leveled, prepared for construction site of the foundation for the foundations should be 2-2.5 m larger than the dimensions of the house in each direction.
The trench is dug manually or with an excavator; after the technique, the bottom must be cleaned manually. The pit is fenced and a pillow of 120-200 mm of sand or coarse gravel is laid on the bottom. Pillow for a tighter fit is poured with water and carefully rammed. Then waterproofing is laid on it, for example, a plastic film and poured with cement mortar. This is necessary so that water does not go into the ground from concrete and does not impair its strength.
From boards planed on one side, at least 40-50 mm thick, formwork is installed in the trench. It is also possible to use shield iron formwork, it is collapsible and convenient to use. The wooden formwork is thoroughly moistened with water, cleaned of chips and debris and rigidly fixed to the walls of the trench with spacers so that the walls do not swell. The verticality of the formwork walls is carefully calibrated with a plumb line, it is on this that the durability and strength of the foundation largely depends. Above the ground, the formwork is taken out at least 30 cm, this height is the base of the future house.
The arrangement of bases of this type involves the preliminary leaving of holes for water pipes and sewers. Otherwise, cutting through them, you can split the foundation. The top of the foundation is covered with waterproofing materials to protect the walls of the building from capillary moisture.
The reinforcement is mounted in the trench at the same time as the formwork, by which time it should already be assembled into frames. Most often, the frame consists of two horizontal rows of reinforcement, while the number of vertical rows depends on the length of the foundation. After pouring concrete reinforcement allows you to get high strength characteristics.
Concrete is poured into the base gradually, in layers of 15-20 cm, in order to exclude voids, each layer is rammed with special wooden rammers, for the same purpose the formwork walls are carefully tapped. It is important to use concrete of the same concentration so that it does not separate into layers.
Often in the construction of foundations there are problems associated with the use of excessively liquid concrete. Such concrete is easier to pour, but as a result, aggregates often settle at the bottom, this entails the separation of concrete and a decrease in its strength. The concrete mixture is also subject to stratification when pouring it from a height of more than 1.5 m.
The formwork can be removed after 7-10 days, by which time the foundation reaches 70% of the planned strength. In order to, you can use a special mastic (bituminous), which is used to process all the outer walls and glue the waterproofing material, which is excellent for roofing material. The quality of the gluing must be checked after a while, making sure that the waterproofing does not peel off from the walls of the foundation.
After the waterproofing is done, it is necessary to backfill the bases and foundations. It is carried out with large clean sand, which is watered with water and rammed in layers.
Back to index
Pile foundation device
This type of foundation is designed for construction on very unstable soils, as well as for large-sized construction. The device of the pile foundation occurs with the use of piles with a pointed end. Each pile (reinforced concrete, wood or other materials) can withstand a load of 2 to 5 tons. The upper parts of the piles are interconnected by beams, thus forming the supporting foundations of the structure. In private construction, this type of bases and foundations is used extremely rarely, as it is very expensive.
Based on the weight of the future structure, the number of piles is determined. For the calculation, you need to find out the following parameters:
- foundation weight;
- wall weight;
- floor weight;
- roof weight with truss systems;
Back to index
Work order
Schemes of pile foundations from various materials.
Any work on the construction of the foundation begins with marking, pegs are hammered in at the places where the piles are supposed to be located. After that, wells are drilled. Piles for reinforcement are tied into a single three-dimensional frame, it can be square or round. The frame after assembly is lowered into the drilled hole. At the same time, the reinforcement should not touch the bottom and walls of the well, the protective layer is 30–50 cm.
After reinforcing the corners of the foundation, you can begin to collect the formwork. A protective layer must be maintained between the reinforcement and the formwork walls. It is best to pour all the piles in one stage. To eliminate the appearance of voids during the pouring process, you need to use a deep vibrator.
Loads on the pile foundation are possible no earlier than 3 weeks after its pouring.
Back to index
The device of monolithic foundations
In the construction of light wooden structures, monolithic bases are often used. There are no restrictions in the planning of structures with the device, and special equipment is not required to create it.
The constancy of the position of the monolithic foundation slab is its main advantage in the case of soil movements, this saves the structure from destruction. In the case of strong compression of the soil, this type of foundation is also applicable.
Back to index
Execution features
When constructing a monolithic foundation, reinforcing wire must be used in at least two layers. A trench is dug, the depth corresponding to the depth of laying the sole of the foundation. A sand cushion is laid at the bottom of it. To protect the foundation from erosion by groundwater, a layer of drainage is laid out on it, carefully leveled and rammed. Two layers of waterproofing are placed on a thin layer of concrete, and then reinforcement - also at least two layers. The pit is poured with concrete, which forms a slab of a monolithic foundation.
In order to act as a link with the walls of the future building, the ends of the reinforcement for this type of foundation must protrude beyond the monolithic foundation slab. When the slab hardens, the reinforcement frame for walls and formwork is mounted on them. At this stage, the wall reinforcement is connected to the foundation reinforcement, which is called the blind area.
Back to index
Column foundation device
Work on the device of the columnar foundation is carried out by placing in all corners and intersections of the walls of the planned construction of the pillars. This type of base is more economical than tape, but it can only be used for light structures and houses. This type of foundation is used only on soils that are not subject to heaving and movement, on immovable soils.
In order to create conditions for the operation of the pillars as a single structure and at the same time avoid their overturning and horizontal displacement, so that the supporting part of the basement is stable, a grillage is made between the pillars. It is also called strapping beams or randbalks.
The distance between the posts, as a rule, should be at least 1.5-2.5 m, but in some cases it may be more. The grillage is an ordinary reinforced jumper.
It is impossible to link together a terrace, a veranda, a porch attached to the main building into a single constructive solution. Each of these structures must have its own foundation, and they must be separated from the main structure by an expansion joint. This is due to the fact that the main building and the porch have very different loads and different draft.
The columnar foundation has several undoubted advantages in comparison with others.
Strengthening foundations with the help of injection wells: a - zone of distribution of the solution; b – drilling injection wells.
- Price. Foundations of other types make up from 15 to 30% of the cost of the building, while columnar foundations make up 15-18%.
- In terms of material consumption and labor costs, columnar foundations are 1.5-2 times more economical than strip foundations.
- Substrate soils work better under free-standing supports than under solid bands. Consequently, the sediment under them is much less under the condition of equal pressures on the ground.
- The forces of frost heaving are the most dangerous of the forces acting on the foundations of low-rise buildings. It is not for nothing that all foundations are considered primarily from the point of view of resisting heaving soils. It is believed that the foundation should be laid below the freezing depth, then deformations will not occur. For lightly loaded foundations, however, the heaving force exceeds the load from the house, and heaving still occurs.
With a large depth of soil freezing, anchor columnar or reinforced concrete monolithic foundations are most effective. The force of frost heaving acts on the side surfaces, which are small near the pillars.
- weak soils, horizontally moving soils, since columnar foundations are not sufficiently resistant to overturning;
- peat and other weakly bearing rocks are also not recommended for construction;
- construction of houses with heavy walls, brick with a thickness of more than 510 mm and reinforced concrete standard slabs and blocks;
- with limited financial or temporary opportunities for construction. Zabirka, namely filling the space between the pillars and the wall, is a very laborious process;
- in areas with sharp elevation changes, the device of a columnar foundation is not recommended.
Back to index
Work order
Work begins with cleaning the construction site of the foundation for the foundations, cutting off the vegetation layer from it with a width greater than the area of the planned foundation by 2-5 m. The soil is cut to a thickness of 10-30 cm, all debris and foreign objects are removed. The mounds are cut off, the required amount of soil is poured into the formed pits. Horizontal control is carried out using the building level.
Along the perimeter of the planned building, pillars are installed, which are called cast-off. They are installed 1-2 m from the planned walls. From the side of the future walls, wooden slats or boards are nailed to the pillars and parallel to them in level, on which the size of the individual parts of the pit, the foundation itself and future walls are marked. The breakdown of the center lines is controlled for accuracy with a tape measure. The corners of a rectangular and square foundation must be checked especially carefully at the corners of the house and at the intersection of the axes. Pillars should be installed under each crosshair of the walls.
Rectangular pits are dug by an excavator or manually. Then formwork is installed in them. Wide boards are not suitable for formwork; gaps are most often formed in them. You can use chipboard, waterproof plywood. The formwork is installed close to the walls of the pit, the perpendicularity of the bottom is checked by a plumb line.
If the soil of the walls is dry and does not crumble, you can do without formwork by laying out the walls of the pit with polyethylene.
The pillars are reinforced with longitudinal reinforcement 10-12 mm in diameter, installed vertically with the obligatory girth of clamps or wire to prevent sideways divergence. Above the top of the foundation, the reinforcement should extend 10-12 cm in order to weld the grillage reinforcement to it.
Concrete is laid in layers with the obligatory passage of each layer with building vibrators.
The construction of any house, bathhouse or even just a barn always begins with the preparation of the foundation. But making it is quite difficult, there are many potential problems that every builder, whether professional or amateur, is obliged to exclude. To begin with, it is worthwhile to understand what the foundation for a house actually is.
What it is?
The foundation is an underground, much less often underwater part of any structure, which transmits static and dynamic stresses to the soil base. Proper design implies such a transfer of impulses that it is impossible to exceed the shrinkage norms and accelerate the destruction of the house.
There are a number of methods by which this effect is achieved:
- dispersal of active forces over a large territory;
- removal of soil to a strong mass;
- overcoming the loose layer in some places due to piles;
- increasing the strength of the surface array.
The easiest option is to build on completely rocky soil, there is no shrinkage, or it is excessively small. It is much more difficult to create and design foundations where the soil is highly compressible. Even worse for architects and developers of territories with changing soil properties.
The type of substrate also determines the preferred options for the base under the house. The contact space is calculated based on the resulting load and the predicted response from the ground.
Varieties
In domestic low-rise construction, a much smaller range of foundation options is used than in the industrial sector. That is why it is possible and necessary to study each type most closely in order to prevent errors from occurring. Along with tapes and slabs of monolithic design, glass-type bases were also widely in demand. The name is not accidental - an excessive load is taken by a point structure, then this force is distributed exactly where the pressure can be very large. Under large buildings of low height, it is precisely the "glasses" that are mounted in many cases.
Important: do not take the name of this foundation literally. In geometric terms, it most of all resembles steps in the form of trapezoids, the tops of which are narrower compared to the base.
It should be noted that glasses should not be placed under low-rise buildings in principle.
They are preferably placed under:
- bridges thrown over water bodies;
- crossings and crossings over railroad tracks;
- underground garages, parking lots;
- single-tier storage, sports, entertainment and commercial establishments;
- workshops and ancillary facilities at energy enterprises.
Glass foundations are formed strictly within the framework of the terms of reference and GOSTs, there can be no amateur initiative here in principle. Determining the properties of soil and material, drawing up a picture of geological layers is carried out through thorough tests. For each specific case, design institutes develop special series of glass foundations, the features of which are fixed as strictly as possible.
The key components are:
- the slab, which plays the role of a support, is installed on a pillow of sand and gravel that occupies the bottom of the pit;
- Column;
- podkolonnik, it is he who looks most like a glass;
- a concrete pillar that holds the support beams under the walls.
A heavy reinforced "glass" is made point-shaped, and therefore the load on the ground is minimal. The speed of work impresses even those who are quite familiar with construction. Moreover, the need for special machines when lifting heavy parts does not adversely affect the timing of the work. The low severity of contact with the ground allows you to minimize the absorption of water. Under buildings of considerable size, the “glass” is very good, but under a private house it does not justify itself.
A glass foundation cannot be made if the surface is not properly cleaned to a perfectly even state. It is forbidden to lay the slab above 1 m. In the process of work, the geometry is constantly monitored using levels and levels. After delivery to the construction site, the glasses are cleaned of any debris, they are lifted and installed using a crane. You need to work slowly, carefully checking the provisions of the risks.
A mesh of thread will help to connect the individual elements. The excavated soil cannot be taken out, it will be useful for backfilling the pit to the top of the mounted block. Next, they put the support beams on the glasses themselves or on the posts.
The use of wedges under the columns of industrial buildings is strictly mandatory. In private and individual construction, the "floating" type of foundation has a certain significance.
Of course, there should not be any liquid in it or around it. On the contrary, the structure being created is a rigid, reinforced concrete slab, located under the entire volume of the future house. "Swimming" is reduced to the adaptation of the support to the emerging loads. Such a solution almost does not change under the action of soil movements, unlike metal pipes (piles), they are not deformed by cold heaving forces. In most cases, 25-30 cm thick slabs are used, under which there is a layer of sand and gravel of comparable sizes.
A serious problem with any floating bases is the significant consumption of building materials. It is impossible to pour a slab where the area has at least a slope different from the measurement error. And even in the most favorable cases, it is not possible to organize a basement or basement. The requirements for communications are becoming more stringent, their wiring and planning become a filigree art. Moreover, if mistakes are made with the infrastructure, the complexity and cost of correcting them is unacceptably high.
materials
Much when choosing the type of foundation and its optimal organization depends on the type of building materials used at the top. Thus, a brick wall is heavier than a comparable (or even slightly larger) wooden structure, so you will need to create a strong, stable base under it. A building with a deep foundation is recognized by most experts as the most reliable and stable, but the complexity of preparing such an element makes it acceptable only for a large brick house.
In addition to concrete strips, piles of three types are often mounted:
- bored;
- screw;
- clogged.
Even without special geological and geophysical studies, it is obvious that the properties of the soil in different places are not the same. Its composition and mechanical parameters directly affect the choice of the optimal and acceptable type of material.
It is also worth taking into account the freezing zone, the characteristics of the above-ground structure, the climate, groundwater, and the funds available to the developer.
- reinforced concrete;
- asbestos pipes;
- metal constructions.
But wood, even especially durable and processed according to all the rules of protection, cannot be recognized as a completely effective solution. In most cases, independent developers choose reinforced concrete because this material is versatile and suitable for all known types of soil. It can be prepared using cement, sand of various fractions, gravel and reinforcing bars. The installation of steel strips is done in the formwork, after they are connected, a mortar is poured inside.
By changing the proportions of its components, consistency and adding special additives, you can flexibly adjust the properties of the finished casting.
When building a building on solid soil composed of rocks, natural stone and light grades of rubble concrete can be used for laying the foundation. The same materials are recommended for use on most soils that are not subject to winter heaving. But it should be noted that compliance with the work methodology becomes critical. The irregularity of the contours of natural stones makes it difficult for them to be densely and uniformly laid out. It is very difficult to correct the detected shortcomings; for this, it is almost always necessary to call lifting equipment.
Therefore, plain concrete is much more often chosen (even without reinforcing reinforcing inserts). In addition to cement, polymers of a special composition and a combination of silica and lime are sometimes used as a binder for the production of concrete. But the latter type, which makes it possible to make silicate concrete, shows itself very poorly where the soil is abundantly saturated with moisture or is subject to freezing to a great depth.
Instead of pouring with your own hands, the installation of ready-made blocks is allowed, but this is a less accurate and reliable method. Semi-finished products of industrial production are needed for pole and strip foundations.
Much attention should, of course, be paid to the sand. In addition to being part of the concrete solution, it is "noted" in one more role - the underlying pillow. Such linings are recommended to be created if the rocks at the bottom are loose and cannot bear the resulting load on their own. Both cases, when sand is used in the construction of the foundation, require mainly its quarry variety with a large fraction. As reinforcement, special rods are used, the geometry of which is designed for perfect adhesion to the concrete mass.
The tree is used in the form of supports, in formwork structures. The cheapness and availability of this material do not allow, unfortunately, to ignore its main problem, that is, a short period of operation. When choosing a natural stone, you should carefully consider not only its characteristics and cost, but also transportation costs. Quarry stone is cheaper and more practical than granite or sandstone, it can be obtained without excessive costs. Expanded clay is traditionally used to insulate foundations, but it makes sense to think about other, more modern and practical insulating materials.
Peculiarities
The device of a particular foundation to a very large extent depends on the type to which it belongs. Low-rise private buildings are characterized by the whole range of classical foundations and their combinations with each other. The slabs are invariably cast only inside the formwork, they cannot be used on a steep slope and on subsiding ground. The assembly of pillars from concrete racks and glasses does not exhaust all possible options; it is quite possible to cast the solution into the formwork of a tubular or shield form. Such formwork is distinguished by a particularly wide lower part, but its bearing capacity is less than that of piles.
The strip base can be assembled from FBS foundation blocks, laid out of rubble, decorated with bricks or poured into the formwork.
If the soil is prone to heaving, the tape requires:
- drainage works;
- backfilling of non-metallic materials;
- thermal protection of the most problematic parts of the structure.
As for piles, each of their subspecies has its own specifics. So, bored execution performs well in areas with difficult terrain or with weak soil. But at the same time, the lack of waterproofing makes it impossible to use such supports at an average and high level of soil water. Screw props have no technological restrictions, however, it is recommended to use them only under wooden buildings.
All pile and pillar foundations are supposed to be equipped with a grillage, it can be made in various ways, but in any case it is designed to become a support for the walls and increase spatial rigidity. Under the stairs located in the house, emergency power generators, stoves, capital fireplaces, and so on, it is required to organize autonomous foundations.
When an extension is being built, it is advisable to give preference to solutions on piles and on poles. Regardless of whether these or any other types of foundations are chosen, it is very important to leave a technological gap between the main and secondary foundations.
For your information: the truss systems of roofing blocks must also be autonomous. The pole system is attractive due to its exceptional simplicity and the ability to perform almost all work without assistants. The column is supposed to be poured in one go.
The constituent structures of the foundation, assembled from pillars, are:
- slabs 0.3 m thick;
- reinforced concrete racks;
- reinforcing vertical frame;
- grillage from various materials.
With all the advantages, the pillar option will not cope with the load from heavy walls. It will work poorly on wet soil, on soil prone to subsidence and creep. It is not recommended to use this approach where there are steep slopes. But heaving is not too dangerous, a typical set of measures to prevent it is enough.
Poles are better than piles in the sense that they provide additional formwork and waterproofing after construction is completed.
Private developers highly value strip foundations with low depth. It is much more difficult to equip them than any pillars. For reinforcement, frames are used, the junction points of which are reinforced with anchors. To make the outer layer of concrete last longer, linings and side rings are used.
Additional cover is provided by:
- waterproofing layer;
- insulation materials on the outer edge;
- blind area (preventing swelling);
- non-metallic materials (for the same purpose);
- backfilling of the trench sinuses (so that the tape does not pull out to the surface).
It is necessary to deepen the tape only if there are basement floors. In any case, it is not used on sagging and wet soils. If construction is carried out on a slope, stepped concreting often helps out, but even it does not allow you to confidently mount heavy walls. The undoubted advantage of the tape is the convenience of working with utility entry points and the absence of prohibitions on the height of the house. Floors can be built on the ground, it is also possible to install ceilings on beams. In the most difficult cases, when tape, poles and piles are ineffective, it is recommended to use slabs.
It should be noted that even this very reliable technology has objective limits. If the soil has low resistance, the slab base may sag. Under the action of heaving forces arising on the overhanging slope, the block can move to the side. The floating slab has an identical perimeter thickness and requires a significant consumption of building materials.
Ribbed option allows you to reduce the thickness of the central area; there are also solutions with built-in underfloor heating and with a built-in cellar blank.
Regardless of the option used, all foundations must be air vented. The underground continuously accumulates moisture evaporating from the ground. Water vapor is very dangerous for any building structure, for any finishing material. Increased attention should be paid to wooden buildings and all kinds of houses in areas where radon accumulation is likely. The absence of soil freezing causes moisture to seep into the underground even in winter.
If you do not take care of the air, the water will collect and freeze on various parts of the foundation, on the reverse side of the floors of the first floors. SNiP provides that even in ideal cases, the total area of ventilation ducts should be at least 0.25% of the basement or technical underground space. And when work is carried out in areas with an increased level of radon concentration, this figure is increased by 2-3 times. Additionally, it is worth considering that equipping air vents is less than 0.05 sq. m just doesn't make sense. Their limiting value is 0.85 sq. m, since if this size is exceeded, the structure will have to be carefully reinforced.
What form to make products - the owners of the houses themselves decide. Most often, a rectangle is chosen, such a configuration is not only simple, but also the most aesthetic in appearance. But the location of the holes on the outside should be uniform in area. It is possible to exclude the formation of "bags" that do not have ventilation, if the vents are not removed from the corners by more than 90 cm (measurements are made along the inner edges). The most effective solution is the symmetrical arrangement of an even number of holes.
How high to put the vents is determined according to the height of the first floor above the ground. But their lowest point should not be closer to the ground than 20-30 cm. If you do not follow this rule, you may encounter an underground bay in the spring and autumn months.
Important: when the house is equipped with internal load-bearing walls, ventilation should be done for each underground space. If the calculation results in an unnecessarily large number of holes that could weaken the foundation structure, this problem should be circumvented by increasing the size of the individual channel.
In addition to ventilation, the rational arrangement of the foundation also implies backfilling. Houses of permanent residence, heated year-round, do not allow freezing of the underlying soils. Therefore, under such buildings, it is allowed to use any type of backfill, even from clay. Projects in which it is planned to carry out the overlap along the beams are recommended to be covered from the inside with clay as the cheapest material. Sand will have to be used under floating floors in the form of a layer of at least 100 mm.
Significant volumes of construction work make it quite justified to backfill with soil from the building site, taken out of the trenches. Only the upper part can be covered with sand to fill the footing. In areas with high standing groundwater, crushed stone is used. If the aquifer lies relatively deep, it is allowed to save using sand.
For your information - the organization of external clay castles described in the building codes of outdated editions is now prohibited.
Compaction of the backfilled soil is mandatory every 0.2 m. The presence of large stones in the backfill (over 0.25 m in size) is unacceptable. Drainage, if necessary, is formed in the form of longitudinal channels connected to a single circuit, standing around the entire perimeter of the building. It is necessary to cover the foundation with non-metallic materials at different depths. So, with occasional heating of the house, 0.2 m of sand is enough next to the inner walls.
If there is no heating, and the soil can freeze by 100 cm, it is required to form a sinus of 200 mm, saturated with inert materials. But when the freezing depth reaches 2 m, you will have to put 50 cm of the protective layer.
Important: it is customary to count this backfill depth from planning marks, most often from the blind area. It cannot exceed ¾ of the deepening of the soles of the tapes. Only when forming floors along the lags is it allowed not to compact the filled materials, in all other cases this is extremely important.
Under the screed, it is always necessary to compact the backfill to a level of 0.95 m. It is necessary to finish the rammer, whether in manual or mechanized mode, after it is impossible to leave a mark on the ground. Irrigation of sand, loam and sandy loam is impractical; this can lead to excessive saturation of soil horizons with water. Heavy soil can be moistened up to no more than 23%, and light sandy loam up to a maximum of 14%. In any case, it is unacceptable to mount the screed before the soil is completely dry.
Footing should be used under all monolithic foundations.
Its role is threefold:
- reducing the height of the protective layers;
- exclusion of a breakthrough of cement laitance into the lower layers;
- covering the waterproofing of the base of the foundation.
The soil, located along the outer edges of the foundation, is not protected from the cold. This means that it will swell, and inhomogeneously throughout the volume, and there will be a force pulling the concrete base up. There are three main options for solving this problem, one of which is just backfilling. You can also insulate the blind area, forming a tape 0.6-1.2 m wide around the entire house. Another way is to create a sliding-collapsible thermal insulation.
Its essence lies in the fact that rigidly dense extruded polystyrene foam is attached to the outer walls. Further, the plinth, fixed in the ground, is covered with a pair of layers of polyethylene. PSB-25 sheets are mounted, they must be placed strictly vertically and tightly pressed against the wall. Sand powder can hold these sheets, so additional fastening is not required. The heaving forces invariably crumple the polystyrene, but its rise over the flattened film layer does not compromise a key level of thermal protection.
Returning to the sole under the foundation, it is worth noting that most often it is twice the width of the base itself. In order to rely on the entire length of the sole could stably, the so-called footing is equipped (other functions of which have already been discussed). In industrialized countries, this support structure is prescribed by all building standards and technological regulations. Double rechecking of all distances between milestones placed by surveyors helps to eliminate errors. Only then are all the installation lines shown using cords.
Crushed stone footing allows you to save on construction work. The thickness of the created layer cannot be less than 200 mm. But the problem may be related to the low rigidity of the formed substrate. Therefore, it makes no sense to fill rubble under the foundations of serious, responsible buildings. But under utility blocks, sheds, such a decision fully justifies itself.
The concrete preparatory layer is widely used under slabs and tapes. In addition to the increased bearing capacity, this is also due to the convenience of organizing these types of foundations on rigid underlying surfaces. This advantage is especially important in the winter months, when soil characteristics deteriorate sharply.
According to standard rules, preliminary concreting is carried out strictly with solutions from M-350 and above.
How to choose?
No matter how carefully the footing, drainage, if the type of the main foundation is chosen incorrectly, all these works and structures will be almost useless. When the construction site is composed of easily moving wet clay or dusty sand, prone to deep freezing, you should not choose a strip foundation. As soon as spring comes, frost heaving will be replaced by lowering. This will inevitably lead to the occurrence of cracks and even faults. Worst of all, even an immediate repair in accordance with all the rules using adequate tools and materials will already be powerless.
But if there are no such problems with soils, the tape has a clear advantage - accelerated installation even without the help of professionals. Therefore, it is it that is recommended to be considered primarily for a residential building, courtyard buildings and baths. A monolithic strip foundation made of concrete can last up to 150 years, and at the same time everyone can mount it, without even spending money on renting powerful construction machines. The cost of the tape is very high, and it is not possible to mount it during the cold months.
Problematic soils, which are quite common, especially in areas of new development, are easy to "win" using a slab. The speed of its installation with the same level of preparation is the same as that of the strip base. Slab substrates are confidently poured in 1-2 months on their own. More precisely, pouring is faster, but it takes a lot of time for the mixture to solidify. During the ascent and descent, the buildings on the slab move evenly, and this eliminates the danger of their destruction.
The monolithic structure can be mounted both on the surface and with some depth; The benefits are largely offset by the increased costs.
The solution to the problem of complex soil is also possible due to piles. The bored type is mounted exclusively with the help of special equipment, and it is very diverse - it will require concrete pumping systems, forklifts, and drilling machines. If you plan to equip a clay castle around the pile supports, it will have to be supplied with special pumps. Of course, the use of a whole fleet of machines and the involvement of several professionals noticeably increases the cost of construction work.
If the goal is to reduce costs and labor intensity, screw structures can be used.
Calculations
The drawing of the foundation is prepared only after all the necessary calculations, calculations of linear and strength parameters have been completed. Remote images are prescribed separately, the general scales are from 1: 100 to 1: 400. To make it easier to transfer the scheme to the terrain, use axial markings. You should definitely note in the documentation the gap from the extreme to the center axes. Another indispensable element of any well-thought-out scheme is the grid of coordinates.
During the calculations, parameters such as:
- the degree of penetration into the soil;
- section geometry;
- belt support width;
- diameter and internal thickness of piles.
Importantly, according to the results of well-conducted calculations, it becomes clear which types and brands of building materials should be used in a particular case. Experienced developers always lay down a certain reserve for all indicators related to strength and stability. Even if it is not used immediately, it will at least help correct errors, offset the consequences of increasing loads over time, and delay critical wear of the structure.
The drawing should show what type of footing is used and how it is organized. No less significant is the demonstration of entry points for engineering systems and a description of their technical capabilities.
Sections should show:
- external contours of support blocks;
- blind area (for external walls);
- means of protection against water;
- the size of the ledges, if the foundation or its parts are mounted non-uniformly in height.
Tape bases are drawn with the indication of levels, it is possible to increase the visibility of such marks by making marks with a turn away from a specific section. For the zero mark on any foundation scheme, they take the plane of the floors of the first floor. Additionally, they demonstrate the soil surface, the line of the base of the foundation and sections. The point of the section of the tape on the main plan is marked with broken strokes and arrows showing the direction. To perform sections, scales 1: 20, 1: 25 and 1: 50 are chosen.
Professional builders, when preparing drawings, add to them a general specification of all parts under the zero mark, a load table, mounting plans for prefabricated supports and a list of additional notes. Piles are placed under the outer walls around the entire perimeter, and the internal load-bearing walls are placed on supports. The gap from one support to another, in whichever direction the count is taken, can be a maximum of 3 m.
If it is planned to create a grillage, a separate scheme of such a design is created. Together with it, specifications or explanatory notes on materials are prepared.
The height of the foundation increases if it is planned to form a base. Accurate information about its value can be gleaned from building codes and regulations. In any case, the base should rise 100 mm above the calculated level of the maximum predicted snow mass. Tapes, even in those places where there is no or very little snow, should have a height of 0.3 m. The distance to the sewer is reflected in the transverse street profile, it is coordinated with the placement of other underground infrastructure.
In order to lay communications as correctly as possible, one should not forget about convenience considerations when laying out, inspecting and repairing networks. It is also recommended to take into account the need to protect adjacent pipelines, to separate cables from each other. Another consideration is maintaining the safety of foundations and underground facilities, ensuring the tightness of water supply networks.
Pressure pipelines should be located 5 m from the base of the house, and non-pressure pipelines should be at least 3 m. If you have to cross the water and sewer lines, the sewer should be placed lower.
Construction stages
Do-it-yourself construction of a private house at the stage of foundation work breaks up, in turn, into a number of phases.
First of all, it turns out the type of suitable technology, which starts from:
- general condition of soils;
- frost lines;
- standing heights of ground liquids.
When working, special reference publications are used, but it is much more correct to do a full-fledged geological study. Regardless of the technical nuances, any step-by-step instruction provides for the installation of waterproofing and water drainage. Monolithic foundations are placed by pouring concrete mortar into the formwork.
Tapes are created by digging trenches, while their manufacture is divided into the following stages:
- clearing and compaction of the bottom of the pit;
- erection of a sand or gravel cushion;
- installation of hydraulic protection;
- checking the verticality of the walls;
- placement of reinforcing cages and filling the formwork with concrete;
- formwork removal and external waterproofing.
Build a columnar foundation will have to be different. The soil is taken to a depth of 100 to 300 mm, removing mounds, filling the pits with soil. Horizontal lines are checked with building levels. Pillars are placed at the intersections of the walls, these marks are used to dig holes and install formwork. Then comes the turn of laying vertical reinforcement and pouring concrete into the formwork.
The poles that have gained mechanical strength are covered with a strapping. If small houses and outbuildings are being built, wooden support poles can be used. But it needs to be prepared through the use of antiseptic mixtures.
The formation of monolithic bases also has its own characteristics. The first step in the work is a site carefully prepared and cleared of dirt. It is possible to determine whether equipment is needed for work by the magnitude of the construction work. It is correct to make a pit of the same depth as the foundation line. The base of the trenches is supposed to be compacted, covered with sand and rammed, achieving the elimination of the slightest voids. A thin layer of concrete is poured over the sand mass, into which reinforcement is introduced and waterproofing is applied. On dry days, the surface is doused with water, and when precipitation falls, it is covered.
Pile foundations are represented by various types; residential buildings on terrain with difficult terrain should be placed on screw piles. The diameter is calculated from the resulting load. In selected places, stakes are driven in, the basting is used to obtain recesses. Screw supports are screwed in using pipe segments or a specialized tool.
It is imperative to check whether the above-ground fragments of piles coincide with each other, if necessary, excess metal or concrete is cut off.
It is recommended to make a strip foundation from concrete compositions of category B22.5. To get them, take 1 share of M-200 cement, 2 parts of coarse sand and 2.5 shares of gravel. Steel rods with a cross section of 0.8-1.2 cm should be used as reinforcement for it. The installation of a shallow tape is recommended for the construction of one-story houses on stable soils. A prerequisite for success is the location of the support above the freezing line of the earth.
To align all the lines, you need to use a laser level; special attention is paid to the verification of corners, the deviation in them is even worse than in the geometry of straight sections of the walls. Under the bath and the utility block, it is impossible to make a foundation with a width of less than 250 mm; on heaving soils (silty) and on sandy masses, the minimum value is 500 mm. If a full-fledged house is being built on one floor, these parameters are 400 and 800 mm. The embedded part is designed to connect blocks for the foundation, but flights of stairs, wall panels, floor structures can also be attached to it. Any type of mass-produced rolled metal can be used as embedded parts.
There are special technological methods that allow you to build a foundation on a site with a high water level. First of all, a drainage system should be built, which only allows you to avoid damage to building structures, their subsidence. Piles or precast concrete also protect against water, but using them is very expensive and difficult. Particular attention should be paid to the base and the nuances of its execution. A reinforced concrete wall is optimally combined with piles, and with a tape - a continuation of the outer surface of the foundation itself.
See the following video for the technology of creating a concrete slab foundation.
