Grillage– the horizontal part of the pile-column foundation, connects individual piles (pillars) into a single structure. Its task is to evenly distribute and transfer the load from the walls to the piles and then to the ground, fixing the position of the piles and preventing them from further deviating from the vertical. The grillage itself does not lie on the ground and does not put pressure on the ground. This is its difference from a strip (strip-column) foundation. However, waterproofing is still needed.
Types of grillages
Prefabricated grillage
A prefabricated grillage, for example, made from steel beams (channels, I-beams, etc.) is usually welded. Its disadvantage is the difficulty of installing heavy beams on piles, the low strength of the connection of individual beams (the joints are weaker than the beams) and the high corrosion of unprotected metal located in a zone of high humidity (snow, humid ground layer of air) and the seam material. Convenient for short-term construction (country houses, verandas, gazebos) with a planned service life of a maximum of 10-20 years.
Prefabricated grillages can simply be laid on top of waterproofed pile heads and attached to them without grouting. In wooden houses, the role of the grillage is “entrusted” to the lower crown or lower trim.
Types of prefabricated grillages (image belongs to Fundex company)Prefabricated monolithic grillage
Prefabricated monolithic grillage is more often used in industrial construction and the construction of multi-story buildings. This is a kind of “constructor” from pre-cast parts with “locks” and keyed connections, which are monolithic during (or after) assembly. It is expensive, assembled on site using heavy equipment and requires high precision in piling installation. It is unprofitable for private housing construction.
Monolithic cast grillage
Monolithic-cast (hereinafter referred to as “monolithic”) reinforced concrete grillage is cast in the form of a beam (ribbon, closed perimeter, open contour) or monolithic slab. In any design option, the grillage connects the piles - being attached to them or including them in its thickness. The slab is usually high, the tape can be high, elevated, or recessed. A monolithic grillage is the most convenient option for low-rise construction.
Types of grillages according to tape position
Based on the position of the tape (and mounted formwork) relative to the ground surface, three types of grillage are distinguished:
- high
- elevated
- recessed
The most rational one is a high grillage, its lower plane is 10-15 cm or higher above the ground level. This is necessary so that in winter the soil, even rising along the piles, does not put pressure on the tape. Otherwise, when raising the grillage, the frozen soil will begin to pull out the piles or (more likely the latter) the grillage will be torn off from them.
Flaw This type of grillage for the Russian middle zone is an unsealed void between the ground and the lower floor. In fact, there is no insulating stationary air cushion under the floor, so it has to be additionally insulated, and the house cannot have a full basement. It is possible to provide shields that can be lowered for the winter, like centerboards, to cover the gaps between the grillage and the ground.
For areas with a subtropical climate and for wooden construction, on the contrary, such ventilation of the space under the floor is very convenient, as it helps reduce humidity in the house and cool the room in summer. This is how houses are built in Japan and China. In addition, with a high grillage tape, this is a convenient option for creating a small recessed ventilated space under the house for short-term summer storage of equipment, toys, and harvested crops.
Due to shading and ventilation, this space is quite cool in summer, and if made with a slope away from the house (especially going under the grillage), it will reliably protect from rain and dirt. To go under the house, you can make a small arch in the grillage between two piles and dig a staircase and a trench-corridor under the house, similar to a garage inspection pit, on the sides of which equipment is placed on the ground. Such access to the space under the house is convenient for periodically inspecting the grillage and lower ceiling and, if necessary, adjusting their condition. In villages, this is one of the favorite flight habitats for all kinds of living creatures such as chickens, dogs and cats, so the gap can be covered with a net.
Raised grillage
The raised grillage is arranged so that its base is level with the ground. 10-15 cm of soil is removed from under the formwork, so that the finished grillage hangs above the air cushion. This removes the gap where the wind blows and to some extent makes the air cushion motionless.
But since access to the space under the house in this case is almost impossible, it is necessary to protect the air cushion space with centerboards or simply plastic, etc., freely installed outside the grillage and reaching the bottom of the trench, from falling into this cavity of earth. Otherwise, the grillage will soon end up lying on the ground and winter heaving of the soil will begin to affect it.
It is also impossible to attach protective guards to the grillage - they must be independent, then the soil will be able to raise and lower them without affecting the grillage in any way.
Recessed grillage
A foundation with a recessed grillage is both the most popular and the least efficient. Along the perimeter of the building, directly along the projection line of its future walls, a shallow trench is dug, from the bottom of which the pile heads appear to be protruding. Then a formwork-gutter is made, its bottom is located below ground level, but there is also an air cushion under it (you can put the gutter on the bars or pour a temporary sand cushion). Such a foundation also requires protective centerboards and provides an almost motionless air cushion under the floor, which insulates the house.
Conclusion on the grillage
The grillage is often called a columnar-strip foundation because it looks similar to a strip foundation. This is an incorrect name, since there is a serious difference in design, purpose and properties. The strip of the strip foundation itself, with its entire surface, evenly transfers the full load to the ground, since its entire surface lies tightly on the ground. If it has pillars, then they are more likely needed to increase the lateral working surface and do not play a special role in transferring loads to the ground.
The meaning of the grillage- only the combination of piles working to transfer a point load to the ground, and the redistribution of the total load on them, while the pile itself does not transfer the load to the ground and never rests on it, since it is connected to the piles relatively weakly and during winter heaving of the soil from the piles it might just get torn off.
The grillage is used for relatively light 1-3 storey buildings, and in earthquake-prone areas only for very light and at the same time durable wooden, frame and vulture-panel houses.
Pile-grillage(or columnar-ribbon, both names are equivalent) the foundation is a structure consisting of pillars immersed in the soil and connecting them above the surface of the ground with reinforced concrete, wooden or metal tape. The peculiarity of this type of foundation is that they can be installed on any soil except rocky ones. SRF may vary in construction technology, material of manufacture and design features of piles.
Piles - types and features
According to the material of manufacture, reinforced concrete, wooden and metal piles are distinguished:
Wooden They are used mainly for the construction of buildings from the same material, often these are outbuildings, gazebos, bathhouses. For the construction of residential premises, more durable foundations are usually installed. Installation can be done either singly or in groups of 3-4 pillars in a bundle to increase strength and load-bearing capacity.
Metal piles can be driven or screwed, but the second option is more common. A screw pile post is a metal pipe, the immersed end of which is made in the form of a cone with a screw blade for screwing. The cone-shaped tip can be cast or welded. Cast piles are more reliable and durable, since they do not have a welded seam, the strength of which is reduced. The steel product must be treated with an anti-corrosion coating, and during the installation process the pipe cavity is filled with concrete. The service life of such a foundation can reach up to 400 years.
Read more about types, types and features technologies of pile foundations.
Reinforced concrete piles are made from reinforced concrete, at the enterprise (drived) or directly on site (rammed).
DIY pile-grillage foundation
Step 1 - Soil Study
The purpose of a geological study of a site is to determine the type of soil, its bearing capacity, degree of heaving, level of groundwater, etc. The choice of foundation and the features of its construction depend on these characteristics.
For a full analysis, you should contact specialists, since independently drawn conclusions may turn out to be erroneous, which will affect the quality of the foundation itself and the building as a whole. This is especially true for columnar foundations, since it is not possible to thoroughly check the soil layers, reaching the level of solid soil. To conduct research, you can contact a geodetic company or send soil samples to a laboratory.
If for some reason this is not possible, then the type of soil should be determined.
Types of soil and their characteristics.
- Sandy soil. It has good drainage properties, does not heave and compacts tightly. Foundations on such soils are easy to construct and durable.
- Fine sandy. It has increased buoyancy and a tendency to swell. It is not recommended to build foundations on such soils, but in the case of pile-grillage foundations, the main thing is to carry out installation work in accordance with all requirements.
- Clay. Clay soils are prone to severe swelling. To build a foundation, an anti-heaving cushion is required.
- Rocky and clastic soils. They are difficult to work with, but they have no equal in reliability. The rock does not freeze, is not subject to swelling and buoyancy. However, this is the only type of soil that is not suitable for the construction of pile foundations.
Step 2 - Carrying out calculations
Step 3 - Site Preparation
- Produced area cleaning.
- Determined location of the future foundation. It is important that the remaining buildings on the site are located at least 3 meters from the construction site. You should also choose an area free of tree rhizomes and stumps, as they make it difficult to drive the piles.
- The turf layer is removed under future construction, and the soil surface is leveled.
Step 4 - Marking
- To a cleared and level area from the drawings the layout is being transferred buildings - first, use pegs to mark the outer corners, then the intersections of the walls. Piles will subsequently be installed at these points.
- Then between the pegs the fishing line is stretched or twine, thereby denoting foundation installation line.
- Along the perimeter of the stretched twine there are marks places for installing additional piles. They should be located approximately 2 meters from each other.
It is important to make the markings accurate. Permissible deviation – 2 cm.
Step 5 - Installation of piles
Driving and screw piles are driven using the necessary equipment or devices.
Installation of bored piles consists of several stages:
- Held well drilling below soil freezing by at least 0.5 meters.
- If it is necessary to strengthen or drain the load-bearing soil layer, sand cushion is being installed.
- Into the well asbestos cement pipe is placed, the upper part of which should protrude above the surface to the height of the grillage. If this is a hanging option, then the length of the protrusion is about half a meter on a flat surface. If the landscape is sloping, then the length of the ground part varies.
- Then, using a level, it is made horizontal control And pipes are cut to the required level.
- After that the pile is being reinforced, most often using reinforcement with three or more (depending on the diameter of the piles) rods. For increasing strength, the vertical frame is pulled horizontal jumpers at a distance of approximately 0.5 meters.
- The fittings are located in such a way that it top part performed above fill level slightly lower than the height of the grillage.
- After this, using a gas pump or manually (in private construction) Concrete is poured inside the pipe. In some cases, concreting of piles is carried out along with pouring the grillage.
Step 6 — Arranging the formwork and pouring the grillage
Applicable only to poured reinforced concrete foundations.
- For installation of hanging type strapping under formwork a layer of sand is poured, the so-called sand cushion. It serves to maintain and stabilize the form for pouring concrete and raising the grillage above the ground.
- Formwork being constructed made of wooden boards and is a rectangular trench for subsequent pouring concrete, which connects all the piles of the structure with one tape. The formwork must be constructed in such a way that grillage tape was wider than the walls future the buildings by 5-10 cm.
- The formwork is being installed at a distance of 20 cm from the ground level for hanging grillages and 20-30 cm below the level for shallow ones.
- At erection of formwork, special attention is paid to its fixation. The immobility of the form for concreting is the key to a high-quality grillage tape and clear geometry of the structure. The fixing spacers should be located at a distance of approximately 0.8 meters from each other.
- Inside the formwork a reinforcing frame is placed which is necessary connect to the pile frame knitting wire. It is also important to make the correct bends of the reinforcing bars at turns - they must be made at right angles.
- Reinforcing frame should be located at least 3 cm from the walls and bottom of the formwork, so that when pouring it will be completely concreted.
- Horizontally located along the perimeter the rods are tied with tying wire for greater durability.
- Then it is produced pouring concrete form using a concrete pump.
- To distribute the mixture as evenly as possible, parallel to pouring, a deep vibrator is used. The principle is as follows: 1-2 people direct a stream of concrete into the formwork, and the third assistant distributes just arrived mixture using a vibrator.
- When the concrete will harden(usually it takes 2-3 weeks) the formwork is removed, A sand cushion is removed.
- IN hot dry weather, to avoid cracking, throughout the entire drying period grillage necessary moisten with water.
For self-preparing concrete mixture You will need to mix (proportions are indicated by weight):
- cement(M400) – 1 part;
- sand– 2.8 parts;
- aggregate(crushed stone) – 4.8 parts;
- water– is added in such quantity that the mixture turns out to be elastic and of medium viscosity.
From a mixture of ingredients in such proportions, concrete grade M200 is obtained.
The binding of metal piles is carried out using an I-beam or channel beam by welding. A wooden grillage is usually used for houses made of wood; in this case, a metal pin is placed in the pile post, with the help of which a transverse wooden beam is fastened.
Common mistakes
- Lack of space between the grillage and the ground. This happens if you don't delete it. sand cushion. In this case, the foundation will be be under pressure during soil freezing, which can lead to its deformation.
- Imprecise definition soil bearing capacity. Result - incorrect calculations, instability and immersion of the foundation into the ground.
- Insufficiently deep immersion of piles. If the piles are located at the freezing level, then in winter pressure on the poles may intensify to such an extent that supports Just will tear.
What determines the cost of SRF?
The price of a pile-grillage foundation is determined by a combination of several factors:
- Number of piles and them characteristics– material of manufacture, diameter, length.
- Difficulty level works For example, a foundation with a suspended grillage will cost less than one with a recessed grillage, since the latter option involves excavation.
- Installation method piles If screw piles can be installed independently, then for driven piles it is necessary attract equipment.
- Dimensions being built foundation.
- Quantity additional material– sand, cement, formwork, etc.
On average, 1 m 2 of grillage strip requires 350 kg of cement, 1000 kg of sand and crushed stone and 8 meters of reinforcement. The approximate cost of construction, taking into account the work, is from 2000 to 3000 rubles.
The price of some construction companies for the construction of a driven or bored foundation can reach 4,000 rubles.
In contact with
When solving problems of ensuring the stability of erected buildings, builders assign a serious role to the strength of the foundation. The construction of buildings is carried out on various types of foundations. For problematic soils, a column-pile foundation is preferable, consisting of individual supports that transfer the load to the soil. Reliable fixation of the heads of the supporting elements is ensured by the grillage. Many have heard this term, but not everyone has an idea about the purpose of the design, advantages and classification.
What is a grillage in construction
Among the various types of foundations, grillage is widely used. Grillage - what is it? This question is often asked by novice builders. Let's figure out what the grillage base of the building is. Experienced developers, when implementing, combine the upper parts of the supports with horizontally located beams. As a result, a single power circuit is created - a grillage, which has increased strength and rigidity. In the formed foundation, the load from the mass of the structure is carried by pile supports of the grillage structure.
The main purpose of the power harness:
- ensuring a fixed position of foundation supports;
- uniform distribution of loads transmitted by the building to the columns.
- formation of a reliable supporting surface for the construction of walls and partitions.
A similar structure, consisting of screw or reinforced concrete piles united by a horizontal belt, is widely used in the construction of one-story buildings on various types of soil, including soils with a high concentration of clay particles, sand and moisture.
The grillage base has a set of serious advantages:
- allows the construction of buildings on problematic soils;
- ensures the stability of buildings;
- does not require labor-intensive excavation activities;
- does not depend on the depth of the aquifers.
Along with its advantages, the pile-grillage foundation also has weaknesses:
- the complexity of the construction of the basement, the main dimensions and dimensions of which are related to the design of the grillage and the height of the protruding parts of the supports;
- the need to use special equipment to install the supporting elements of the foundation base into the ground.
When constructing pile foundations, in order to increase their load capacity, it is advisable to combine the protruding parts of the supports with a force belt. After all, the foundation is loaded with the weight of the roof, walls, ceiling, and household appliances. Estimates for the construction of a grillage base are always lower than for the construction of a strip foundation.
Depending on the type of foundation and the geological structure of the soil, the grillage may differ When understanding what a grillage is in construction, study its classification. The grillage foundation is classified according to the following criteria:
- location level;
- the material used for construction;
- design features.
Let us dwell in detail on the features of each type of grillage.
Types of grillage by location
When planning to build a grillage foundation for a frame house with your own hands, decide on the level of location relative to the zero mark.
The following options are possible:
- hanging foundation belt;
- towering grillage;
- shallow base.
Let's look at each variety.
Rising above ground level
A distinctive feature of a high grillage is the location of the bottom of the tie belt above the ground surface at a distance of 10–15 cm, which allows:
- build a raised grillage base on problematic soils;
- eliminate the influence of frost heaving forces in the soil;
- avoid the development of dampness by ventilating the space under the building;
- maintain the position of the foundation supports during movements of soil layers.
The raised grillage is the most common and involves the location of its sole at ground level There is another serious advantage of the rising power contour - a gravel-sand cushion for the foundation of a high structure is not required, since it is located above the zero level and does not contact the soil.
Design disadvantages:
- increased level of heat losses due to the penetration of cold air masses under the building’s foundation;
- the need for enhanced thermal insulation of the floor in contact with cold air;
- increased level of costs associated with the need to install protective shields of a decorative base along the contour of the building.
If you want to build a high grillage belt, figure out how to properly protect the lower part of the building and the floor from cold air currents.
Located at zero
The grillage base, located at the same level with the soil, is erected quite often. The binding belt is based on a sand-crushed stone cushion with a thickness of 15–20 cm. Backfilling is carried out after the soil has been removed under the lower plane of the grillage. The main feature of the design is the damping cushion.
Refers to this type if its sole coincides with the soil level mark She performs important tasks:
- prevents the negative impact of frost heaving of the soil;
- does not allow melt water and sediment to accumulate under the grillage base;
- seals the gap under the horizontal beam of the grillage.
To increase the strength characteristics of the structure and protect it from moisture, waterproofing is also performed. It’s easy to make a raised grillage with your own hands. Step-by-step instructions will help you cope with the task.
Buried in the soil
The power structure connecting the upper parts of the supports is located below the zero mark. The construction technology involves the following work:
- Preparation of a pit located between the support columns.
- Leveling the base of the trench.
- Adding a gravel bed.
- Installation of panel formwork.
- Assembly and installation of reinforcement grid.
- Pouring concrete solution.
They are concreted during the process of pouring the load-bearing frame. To increase the service life of a buried grillage, it is important to reliably protect it from the influence of precipitation. Figure out how to do it right. Concrete edging along the contour of the house, made with a slope, will ensure effective removal of moisture from the grillage foundation.
The main difference between this option is the location of the tape below ground level Classification of grillage according to the type of building material used
Let's consider what material a grillage can be made from. Various building materials are used to make grillage frames:
- concrete reinforced with reinforcing mesh;
- rolled metal of various sections;
- dried and processed wood;
- branded concrete without reinforcement.
The strength characteristics of the structure must correspond to the calculation of the pile grillage. Let us dwell on the features of using various materials.
Monolithic reinforced concrete grillage
In terms of performance characteristics, reinforced concrete structures are stronger than concrete ones.
The reinforced concrete grillage, thanks to its durable reinforcement grid, has the following advantages:
- increased load capacity;
- long period of operation;
- high level of reliability;
- sufficient rigidity;
- ability to withstand increased compressive loads.
For reinforcement, steel rods connected into a common frame, as well as ready-made spatial gratings, are used.
A monolithic grillage is a one-piece structure that is poured directly on the construction site Metal construction
A power belt made of rolled metal allows us to provide the required safety margin. The construction technology involves performing the following operations:
- Cutting blanks from channel or I-beam.
- Installation of profiled steel at the ends of columns.
- Welding individual beams into a common contour.
Apply a protective coating to improve corrosion resistance.
Wood grillage base
The strength of wood allows it to support the mass of light wooden or frame buildings. To ensure the durability of wooden beams:
- dry the material thoroughly;
- saturate the wood with antiseptics;
- waterproof the surface of the beams with roofing felt.
The service life depends on the quality of the material preparation.
Concrete grillage
The sequence of actions for arranging a grillage foundation made of concrete is similar to the construction of a reinforced concrete belt. The main difference is the concreting of the load-bearing frame without reinforcement cages. The susceptibility of concrete to tensile forces and bending moments limits the range of use of a concrete grillage.
Structural types of foundation with grillage
The classification provides for the division of grillages into types depending on the design. Possible options:
- prefabricated structure. Consists of profiles welded together. The service life is limited to two decades due to insufficient rigidity. The prefabricated version is used for temporary buildings;
- one-piece grillage. It is formed from concrete mortar reinforced with a reinforcement cage. Ensures the stability of low-rise buildings on problematic soils;
- combined version of the grillage base. Includes factory-fabricated components. They are assembled into a single load-bearing frame and concreted. The design is used in industrial construction.
The choice of the optimal option is determined by the requirements of the project.
The grillage is a loaded part of the foundation that increases the rigidity of the structure. The classification allows you to select the required type of tie belt depending on the structural features and soil characteristics. When deciding on the grillage design, listen to the opinions of professionals.
Do-it-yourself pile-grillage foundations are most in demand among owners of suburban areas. In dense settlements, it is impossible to use heavy special equipment (hammers, pile drivers) for driving driven piles with a design length of more than 10 m or for light buildings. Renting this equipment is expensive, so short suspended bored piles with a monolithic grillage are used.
Due to the variety of construction technologies and materials used for pile-grillage foundations, there is a special terminology:
- base - a layer that absorbs vertical loads and lies below the freezing mark;
- pile - a vertical structure made in the soil or immersed in it;
- pile field - a group of piles for one structure, building;
- grillage - a monolithic or beam structure along the heads of piles (slab, lattice, frame or beam);
- low grillage – buried in the soil or located at the ground level;
- high (hanging) grillage – raised above ground level;
- bearing capacity of a pile is the sum of soil resistances on the side surfaces and under its lower end.
Based on material, bored piles are classified as follows:
- composite - reinforced concrete inside steel or polymer permanent formwork (large diameter pipe);
- rubble concrete - in the lower part of the pile stones are sunk into concrete (maximum size 15 cm, strength not lower than the design grade of concrete), the upper part (0.5 - 0.7 m) is filled with clean concrete, reinforcement is usually along the entire length (except for backfill);
- reinforced concrete - the pile is poured entirely from concrete with reinforcement along the entire length (usually not stressed);
- concrete - reinforcement only in the upper part for piping with a grillage.
The pile shaft can be manufactured in several ways, even using the same materials. For example, if a hole in the ground with a reinforcement cage placed inside is filled with concrete, the pile will be shellless.
Scheme of a pile with expansion - TISE.
If the pile reaches the bearing layer, is poured into a polymer or metal pipe, which does not carry loads and remains in the well for the entire period of operation (non-removable), acting as waterproofing, a pile with a shell is obtained.
If the temporary formwork is removed after pouring, the pile is called a temporary shell, the method is a vertically moved VPT pipe. If the formwork remains inside the well and performs load-bearing functions, the pile is called a pipe-concrete pile.
To increase the load-bearing capacity, the base of the pile can be widened with a monolithic base. The base is drilled out with a special tool, an explosion or concrete piles. In a general grillage, the head of a bored pile can have a sliding mate or a rigid embedment into a monolith.
If, during geological exploration of the site, the occurrence of a bearing layer deeper than 3 m is revealed, bored piles-racks will cost an individual developer more than a screw foundation SVF or a floating slab. In this case, suspended piles are more effective, the bearing capacity of which depends on the density and porosity of the soil. If the frictional forces on the side surfaces are not enough, other foundation options should be considered.
Unlike a strip foundation, the depth of the grillage does not depend in any way on the characteristics of the soil:
- the tape rests on the ground with its sole, there are lateral shear loads from heaving forces;
- The grillage does not rest on the ground, it is created solely for tying piles, distributing loads, and supporting wall materials (especially important for foam blocks and bricks).
After pouring the monolithic grillage, an air layer is created between the soil and its base to compensate for heaving forces. In low grillages, it is protected on the sides with sheet materials to prevent the soil from shedding and filling this space with heaving soil.
Taking into account the above, a monolithic grillage along the heads of bored piles is effective in the following cases:
- lightweight buildings - budget savings of 30 - 50% in comparison with a slab, strip foundation for log houses, half-timbered, frame, panel (SIP technology), panel cottages;
- complex terrain - slopes with a height difference of more than 1.5 m in the building area;
- high groundwater level - piles can be poured into the shell with a slight rise in water or by temporarily pumping it out of the well;
- swamp, coastal zone - excavation work for other types of foundations is impossible.
Piles are economically effective in individual construction only at a depth of 3–5 m, which is usually sufficient for lightweight structures. With normal geology on flat areas, piles reduce the construction budget of brick and concrete buildings by half. Only in this case does the foundation comply with the requirements of SP 24.1333, which regulate the design of pile foundations.
Step-by-step instructions using the example of a monolithic grillage on bored piles
To build a foundation of this type, an individual developer needs to determine the main dimensions of the elements: cross-section of the grillage (height, width), depth of the well, parameters of the reinforced belt, type of formwork. After which, the amount of building materials is calculated. For convenience, below are step-by-step instructions describing the key points.
Geological surveys, calculation of parameters
Unlike screw piles, for which it is often enough to test screw in a building spot in several places to determine the depth of the bearing layer, this will require full-fledged geological surveys. According to SP 24.1333, this will require a set of operations:
- soil testing with static loads;
- pessiometry, dynamic and static probing;
- laboratory analysis of groundwater, soils from different layers during drilling 3 m below the design level.
In addition, specialists will take into account the impact of piles on nearby buildings and the environment. The result of the research is a geological section in which the thickness of each layer of the layers of different rocks present in the building area is visible. This allows you to select from the corresponding SP tables the standard values of the bearing capacity of clay, sand, and loam to calculate the bearing capacity of the pile.
For example, for soil conditions of 2 m refractory loam, 1 m hard loam, on top of wet sand, there are several options for drilled piles:
- A – the depth of the piles is more than 3 m (passing through loam with the base resting on the sand), diameter 0.5 m;
- B – depth 3 m, diameter 0.4 m;
- B – depth 2 m, diameter 0.5 m.
For reinforcement, rods of 10–12 mm of periodic section are used. The clamps are bent from 6–8 mm of smooth reinforcement. For tying, it is better to use annealed wire. The pitch of the horizontal clamps is 30 - 60 cm, the rods should protrude 30 - 40 cm above the heads. After stripping, they are bent at right angles parallel to the axes of the walls and connected to the lower belt of the grillage.
Pouring and waterproofing
The formwork for the grillage begins to assemble from below.
Due to the large volumes of concrete work, a pile-grillage foundation is usually poured in stages. First, the mixture is placed in pile formwork and compacted with an in-depth vibrator or reinforcing bars to remove air. The grillage formwork is installed after the piles have gained at least 50% strength (3 – 5 days after pouring). The technology looks like:
- deck installation - only for a hanging grillage, holes are cut in the shield according to the size of the piles, it is put on the heads, supported by H-shaped posts along the entire length;
- installation of side panels - attached to the deck, propped up with bars or pins, the top side should be 5 - 7 cm higher than the design mark;
- reinforcement - two belts of 10-16 mm bars of periodic cross-section reinforcement, fastened with 6-8 mm clamps, bend at the corners, at the junction of the walls.
Grillage reinforcement.
Filling occurs according to standard technology with laying and vibration compaction of the mixture. The entire formwork must be filled in one go. Caring for concrete consists of protecting it from waterlogging (covering it with a film from rain), drying out (sand or sawdust on the top edge of the grillage with periodic moistening in the first three days).
This is done after stripping the grillage in several ways:
- impregnation with penetrating compounds (the service life is similar to concrete structures, no repairs are required);
- coating with bitumen mastics (resource 15 – 30 years, budget option);
- gluing with roll materials (lifespan of glass hydroisol is 30 - 50 years, the need to seal joints, use 2 - 3 layers).
Preferable impregnation waterproofing or a set of measures according to the last two options (coating + gluing).
Blind area and storm drain
For any foundation, regardless of its design, a blind area is required that has a 4–7 degree slope from the building outward. This structural element allows rain and melt water to be drained away from concrete structures under a monolithic low grillage and under a high grillage. To prevent runoff from destroying the soil adjacent to the blind area (usually the fertile layer), stormwater inlets (receive water from the roof drain) and trays that transport liquid to a separate underground reservoir are integrated into its outer perimeter.
To reduce the heaving forces under the monolithic grillage, which exert pull-out loads on the piles, at a depth of 40–70 cm. To do this, extruded XPS polystyrene foam is laid at the bottom of the trench. The width of the blind area should be 5–10 cm larger than the projections of the roof slopes, so that when the roof gutters overflow, the water does not destroy the fertile layer.
The standards SP 71.13330 of 2011 recommend a blind area width of 0.7 - 1 m for sandy, clayey soils, respectively, with a tight connection to the backfill (false base) of the pile-grillage foundation. It is made of waterproof material:
- concrete screed 5 cm thick in the thinnest areas;
- paving slabs/paving stones;
- rubber or PVC tiles;
- composite decking.
A budget option is a blind area made from dry asphalt concrete mixtures, used for repairing roadways and lining garden paths. It is compacted with a tamper, does not require heating or melting, and increases strength over time.
Following the recommendations given, even an individual developer without special education will be able to produce a pile foundation with a monolithic grillage with a minimum budget without errors. When properly calculated, the service life of underground structures is not inferior to other types of foundations, maintaining high maintainability and the possibility of increasing the usable area during operation.
Advice! If you need contractors, there is a very convenient service for selecting them. Just send in the form below a detailed description of the work that needs to be performed and you will receive proposals with prices from construction teams and companies by email. You can see reviews about each of them and photographs with examples of work. It's FREE and there's no obligation.
Any structure needs a reliable, high-quality, well-designed and equipped foundation. Today, a grillage foundation on piles is very popular, which has economic benefits compared to a traditional strip foundation. A special feature of the design is the horizontal lintel connecting the piles. Grillage: what it is and what its main purpose is, is described in detail in the article.
It is necessary to begin to consider this issue with a definition: what is a foundation grillage. The internal building element is a horizontal concrete, steel or wooden lintel that connects the disparate elements of a columnar or pile foundation with each other, resulting in the creation of a flat platform for installation of the flashing crown. The grillage takes the load from the load-bearing structures of the building and evenly distributes it to the supports, which transmit the load to the ground.
This design is not inferior in its rigidity and strength to a traditional strip foundation, but the price of a grillage foundation will be much lower, which is associated with less labor and labor intensity.
The foundation structure is created using frame technology, where pillars or piles are tied together to form a strong foundation. A foundation with a grillage is constructed on clay, peat, loess-like, loamy, heaving and silty soils. The construction of a house can be carried out in areas with ornate terrain or on slopes.
Types of grillage and what types it has
The ergonomics, durability and aesthetics of the building depend on the type of grillage that is laid on a columnar or pile foundation. It can be slab, tape and glass.
Depending on the location of the grillage relative to the subgrade, the following types of structures are distinguished:
- increased;
- high;
- recessed
The jumper design can be:
- monolithic;
- prefabricated monolithic;
- national team.
Depending on the material of manufacture, grillages are distinguished:
- metal;
- wooden;
- concrete;
- reinforced concrete.
Types of element and the main task of the grillage
The main purpose of the grillage is to absorb the load from the load-bearing elements of the building and distribute it evenly on the foundation. The most common and economically justified is a pile foundation.
A slab grillage on piles in the form of large-format reinforced concrete slabs is installed with significant dimensions of the building along its perimeter. This grillage is placed on a standard pie consisting of:
- sand and gravel cushion in the form of two layers of 10 cm each with vibration compaction;
- ring drainage located at the level of the grillage base;
- concrete preparation in the form of a screed without reinforcement;
- waterproofing.
Strip foundations on piles can be monolithic or prefabricated. The first option is used for bored piles. This is due to the fact that the materials have the same linear expansion and technical characteristics. It is also easier to wall up the heads with protruding reinforcement in the body of the grillage.
Prefabricated strip grillage is used in wood construction technology. Wooden beams are laid on the heads and joined into half a tree. This allows you to reduce construction costs and begin construction of the structure the very next day after laying the foundation.
A prefabricated strip grillage can be made in the form of reinforced concrete beams adjacent to the pile cap. This design is used primarily for screw piles tied with I-beams or channels.
When installing reinforced concrete bored piles with a grillage, a glass type of structure can be used. The grillage is represented by a kneecap mounted on a pole, a multiple of 15 cm in height and 30 cm in width. Each glass must be supported by four piles. This type of base is used when installing columns. Most often used in agricultural and industrial construction.
What is a grillage: element design
A monolithic grillage is the most successful solution for low-rise construction. The element is represented by a solid closed-type structure made of reinforced concrete or concrete. It is poured during construction, in the form of a monolithic slab or beam (ribbon). In the first option, the design connects all the piles into a single system that covers the entire area of the building. The tape grillage connects the piles in series and is installed only under the load-bearing elements of the building.
The grillage, securely fixed to the piles and incorporating them into its thickness, connects the base elements. A monolithic strip grillage can be raised, high or recessed. It is arranged under unfavorable geological soil conditions. The implementation of such a grillage is distinguished by high technical and operational characteristics. However, the design has increased labor intensity, high cost of work and requires the creation of dense reinforcement.
The prefabricated grillage is represented by a structure made of steel beams connected to each other by welding. I-beams and beams are used as connecting elements. The structure can also be made of wooden beams. This option is used mainly for the construction of non-permanent structures and industrial buildings. The structure is mounted and secured to the pile heads, which does not require subsequent embedding.
Helpful advice! It is not advisable to use a prefabricated grillage for the construction of a private house, since this is associated with a very labor-intensive and costly process.
The prefabricated type also has its disadvantages. First of all, the installation process is very labor-intensive, which is associated with the significant weight of the metal elements. In some places of the grillage, areas with low strength may form, which is associated with the low rigidity of the welded joints. Due to the formation of corrosion or rotting of wood, the structure is short-lived, which is limited to 1020 years of operation.
An intermediate solution between the two previous options is a monolithic prefabricated grillage. A prefabricated structure consists of prefabricated parts that are laid on piles and connected to each other with a key joint. This is done during construction. Then the entire structure is monolithic.
Optimal grillage location
The most rational solution from the point of view of the integrity of the structure and the stability of its operation in the event of various deformations is considered to be the installation of a high or hanging grillage on bored piles. It is installed above the ground level at least 10 cm. If the distance is less, there is a possibility of damage to the integrity of the grillage and the nodes connecting it to the piles, which will lead to the tearing out of the latter.
The main disadvantage of this design is the lack of sealing of the space between the lower part of the grillage and the ground. Due to the fact that free access of cold air is created, heat loss in the house increases. The problem can be solved by installing panels or additional insulation of the floor of the house.
Helpful advice! It is advisable to choose this type of grillage for a subtropical climate, also when constructing wooden structures.
The base of the raised grillage is located at the ground level, on which a gravel or sand cushion 10-15 cm thick is laid, for which a layer of soil is removed. This layer helps reduce soil moisture under the building and freely filter water. This option eliminates the formation of a blown area between the ground and the ceiling.
A recessed strip foundation on bored piles is the most popular option, but at the same time the most irrational. To create it, a shallow trench is dug along the perimeter of the future building. Next, the piles are installed so that their heads protrude from the bottom of the trench. A sand cushion is installed. After this, a formwork trough is made, the bottom of which is located below ground level. Next, a concrete grillage is created.
Helpful advice! Despite the fact that a windproof space is formed under the recessed grillage, centerboards can be installed as additional insulation, which will take the load from heaving soil during frosts.
What material is the grillage made of?
Reinforced concrete grillage is characterized by increased strength, reliability, stability, rigidity, load-bearing capacity and durability. This is the most common option. The structure contains reinforcement, which increases the strength characteristics of the grillage, taking on part of the load. Reinforcement can be performed by creating a full-fledged spatial frame or laying individual rods.
Important! When forming a reinforced concrete grillage, a sufficient protective layer for the reinforcement must be provided.
The production of a concrete grillage is identical to the previous option. The difference is the lack of reinforcement. The entire load is absorbed by a concrete structure that covers the pile heads to a height of at least 10 cm. This option is less strong and durable. Concrete grillage is used in the construction of one-story buildings.
The production of a metal grillage is carried out from rolled profiles, represented by I-beams and channels. The result is a strong and rigid structure. But due to possible corrosion of the metal, especially in places of welded joints, the metal grillage is short-lived. It is used for the construction of one-story buildings.
Characteristics of a pile foundation with a grillage
A pile foundation is a structure in which the load on the ground from a structure is transmitted through piles, which are represented by pillars or beams partially or completely buried in the ground. For a rigid and reliable connection of the upper parts of the piles, a grillage is installed. It is rational to use this type of foundation when constructing buildings on water-saturated soft soils, on slopes with a steep slope, in areas where the depth of soil freezing exceeds 2 m, and also if the weight of the future structure exceeds 350 tons.
Related article:
Drainage system around the house: drainage device for the foundation of a residential building
Drainage device to protect the foundation part of the building, the specificity of this procedure, the technology for creating a structure with your own hands.
Piles are metal, wood or concrete pointed, long or heeled rods of round or square cross-section. They are immersed in the ground in finished form or made directly into the soil. In its finished form, the pile has a sharp end on one side, with which, with the help of special construction equipment, it is immersed into the thickness of the soil, passing through moving layers, and rests on solid soil. When making piles, holes are drilled in the ground, which are subsequently reinforced and filled with concrete.
Types of pile foundations with grillage
Depending on the method of immersion into the ground, a pile foundation can be driven, driven or screwed. The first option is represented by concrete or reinforced concrete structures. To create them, the reinforcement is prestressed, which increases the crack resistance of the foundation. To install piles in the thickness of the earth, it is necessary to drill the required number of holes of a given diameter and depth. A casing metal or concrete pipe is inserted into each of them. The reinforcement is lowered into it and the entire cavity is filled with concrete.
The design can be made with a closed or open lower end. The main advantage of this type of pile foundation is its high load-bearing capacity, simple technology, reduced cost of work, which is associated with minimal labor costs, and the absence of negative impacts and vibrations on surrounding structures.
The second option involves driving ready-made reinforced concrete piles into the ground. As special equipment, pile drivers, vibratory hammers and hydraulic pile-pressing units can be used, the choice of which depends on the characteristics of the soil, the features and depth of driving piles. This type of foundation is used in permafrost zones. The driving elements can be round, square or trapezoidal. To increase reliability and load-bearing characteristics, piles can be equipped with additional support rings.
Screw grillage foundation: what is it?
A foundation with a grillage on screw piles is one of the new options. The design has good performance characteristics and can be installed on any type of soil. The pile is represented by a hollow pipe, a sharp tip and one or more blades. The tip can be welded or cast.
For each type of soil, a certain type of screw piles is used. For stone areas, narrow-bladed screw piles are used, which have especially strong welded tips and double blades, which ensure reliable adhesion to the ground and prevent the pile from skewing. For thawed and waterlogged soils, piles with a sharp cast tip and medium-sized blades are used, which guarantees easy penetration of the element into the soil without loosening it.
For permafrost soils, piles with small blades are used, which facilitates the rapid introduction of the element into the soil without the risk of distortion. The tip of the pile has a special cutter made of especially strong alloy steel. Such elements are highly expensive.
Options for the location of piles and their types
Piles can be hanging or in the form of racks. In the first option, the load on the surrounding soil is transmitted through friction against the side walls. Such piles are characterized by a developed lateral surface along the entire length with many protrusions, which ensures good load-bearing capacity of the structure. This type is used for soils with a high groundwater level or having a thick layer of weak soil, under which there is a stronger one, but it is still not able to support the rack pile.
Rack piles transfer the load from the structure directly to the strong soil, which is located under the weak layer. The elements are characterized by a smooth surface to which the soil does not cling. The most important criterion for this type of pile is a wide base, which can bear more than 80% of the total load.
Helpful advice! For multi-storey and durable buildings, it is advisable to choose TISE rack piles, which have a significant widening in the lower part of the element, which eliminates further settlement.
Piles in the ground can be located in one of the following ways:
- single;
- tape;
- stripes;
- in the form of a bush;
- field.
The first method is selected for a free-standing support. Depending on the terrain, the pile can be installed inclined. The tape method involves placing piles along the entire perimeter of the structure. For the construction of massive multi-story structures, piles are installed in several rows in the form of strips.
Cluster placement involves installing elements under load-bearing walls and objects with heavy loads. This method is used for the construction of canopies and structures with a large number of columns that hold the roof. For large buildings, piles are installed in a checkerboard pattern.
The choice of pile placement method depends on the construction project. Elements should be located in corners and at the intersections of piers. The optimal distance between piles in a grillage is 2–3 m.
Pros and cons of a pile-grillage foundation
When choosing a foundation for a future structure, it is necessary to study the pros and cons of a pile foundation with a grillage. This design has excellent stability and high load-bearing capacity. This is especially important for building houses on soils that are prone to movement. This type of foundation is often found in seismically active areas, where the foundation will remain motionless during small earthquakes.
Important! Classic piles can withstand loads of up to several tons.
It is advisable to choose a pile-grillage foundation for the construction of structures on soils with a complex structure, especially in mountainous areas, which are characterized by a small layer of loose soil. Manufacturers produce piles of various lengths, which allows you to build foundations on slopes, as well as create curved objects. A pile-grillage foundation is an ideal foundation for the construction of a building from any material.
Due to the fact that the grillage is not in contact with the ground, the possibility of flooding of the structure with groundwater and rodents and various insects entering the house is eliminated. To erect a pile foundation with a grillage, there is no need for preliminary cleaning and leveling of the construction site, which reduces the labor intensity and cost of work. You can build the foundation yourself without using powerful construction equipment, which is especially important in densely built areas or on small plots of land.
However, this design has its drawbacks. When designing this type of foundation, accurate calculations should be performed with the assistance of a specialist. Here you should take into account the length, diameter, weight, number of piles and their exact location.
Important! Pile foundations are not recommended for use for heavy, massive structures, even by increasing the diameter of the pile elements.
Another disadvantage is the labor-intensive repair of the foundation, which will require the construction of retaining walls or the installation of additional piles. The construction of a pile foundation with a grillage eliminates the need for a basement and requires additional insulation of the lower part of the building.
Calculation of pile-grillage foundation
Calculating a pile-grillage foundation is a serious and responsible undertaking. This process is best left to a specialist in this field. To perform the calculation, it is necessary to collect information about the territory for construction: geological structure and physical properties of the soil, hydrogeological and physical-geographical conditions of the area. You can obtain all the necessary information from your local geological exploration service by placing an order in advance.
Based on the data obtained, calculations of the parameters of the selected foundation are performed. The load on the foundation with a grillage is calculated based on the total mass of the structure. Next, the depth of the supports is calculated. Based on the bearing capacity of the foundation and the magnitude of the load, the minimum total area of the supports is determined. Next, the type, diameter and number of piles are selected, which are distributed over the area of the building, according to the selected layout. Next, the dimensions of the grillage are determined by calculation.
Helpful advice! To calculate a pile foundation with a grillage, you can use online calculators or the services of specialists from construction companies.
The calculation of the pile foundation grillage is carried out on the basis of SNiP II-B.1–62. It should be taken into account that the width of the structure should be 10–20 cm thicker than the wall of the building, and the height should be approximately equal to the width. The final stage is the selection of building materials.
Installation of a pile-strip foundation with your own hands
Constructing a grillage on a columnar or pile foundation with your own hands is a feasible and feasible task. It is advisable to choose the first option for the construction of small structures without constant load, such as country houses and gazebos. Pile foundations are the most popular solution for the construction of buildings intended for permanent use.
It is advisable to construct a pile-grillage foundation with your own hands in late spring, early summer or early autumn. The first step is to prepare the site by clearing it of debris and vegetation.
Helpful advice! It is recommended to treat the area for future construction with chemicals, which will prevent the growth of vegetation.
Next, the territory is marked based on the project, indicating the location of the piles. If screw piles are used, they should be screwed in without first creating holes. To do this, you can use a pipe or a crowbar, which must be inserted into the head of the support. For screw piles, it is more convenient to make a metal or wooden grillage. It is advisable to install a concrete lintel only under a future house made of stone, which requires high rigidity of the base.
Important! The piles must be positioned strictly perpendicular to the ground.
If you are installing bored piles, you will not be able to install them yourself. To create holes in the ground, you need to use special equipment. Bored piles can be made in two ways. The first option involves placing formwork in the form of a metal pipe of the required diameter in each drilled hole. The internal space is reinforced and filled with concrete. The second option eliminates the installation of formwork.
To construct a pile foundation with a grillage, class B7.5-B15 concrete is used, which is the optimal solution for small buildings. For large buildings, concrete of class up to B25 can be used. It is not advisable to use a more durable building material for private housing construction. This is not economically justified, since the safety factor of the material exceeds the load from the building. Reinforcement with a diameter of 12-16 mm of class A400 is placed in each hole.
Laying a pile foundation with a monolithic grillage
For the work you will need the following tools and materials:
- bayonet and picking shovel;
- stakes;
- rope;
- wooden boards or chipboard sheets for formwork;
- set of steel screw piles;
- fittings for reinforcing piles and grillage;
- metal pipes;
- concrete solution;
- plumb line;
- level or hydraulic level;
- roulette;
- specialty chemicals;
- foam boards;
- sand;
- crushed stone;
- bitumen mastic.
The construction of a pile foundation with a monolithic grillage is carried out according to the following algorithm:
- cleaning and leveling the base;
- drilling holes in designated locations of the required depth and size for piles;
- compacting the soil and creating a cushion of medium or coarse sand 30-50 cm thick at the bottom of the holes;
- installation of screw or bored piles according to the work technology;
- preparing a sand cushion for a monolithic grillage;
- formwork installation;
- a frame made of reinforcement is lowered into the pit, consisting of at least 4 rods, the length of which is selected taking into account the height of the strapping;
- performing concrete pouring;
- creation of wooden formwork for a monolithic grillage;
- after the concrete has hardened, the reinforcement frame for the grillage is assembled;
- installation of formwork for strapping;
- concreting the grillage;
- removing the formwork after the concrete has gained the required strength;
- performing waterproofing.
Helpful advice! If an underground space is formed, it is better to cover it with a decorative base or fence.
The grillage is reinforced using rods of class A400, which can be joined into a frame by welding or tied using binding wire. The second option is more labor-intensive, but reliable. When laying the frame, you should leave a distance from the rod to the formwork of at least 3 cm - to create a protective layer of concrete, which will prevent the formation of corrosion.
Helpful advice! At the corners of the building, reinforcement bars must be tied with wire.
Creation of a monolithic foundation grillage on piles
Before installing the grillage, a layer of waterproofing should be laid on the piles. This is necessary in order to eliminate the possibility of the soles of the elements getting wet. Roofing felt, polyethylene films or membranes can be used as a waterproofing material. If a cushion of fine gravel is provided under the base of the grillage, which may compromise the integrity of the waterproofing layer, a concrete footing should be provided.
The next stage is the installation of formwork for the foundation on concrete piles. To do this, markings are carried out in increments of 0.5-0.8 m with driving in pegs with a cross-section of 5x5 cm along the entire perimeter of the building. Next, horizontal wooden boards are laid, in which holes for the piles are pre-cut.
Vertical formwork elements are installed and nailed to horizontal boards. For formwork, it is recommended to use durable wooden boards or chipboard sheets. The inside of the prefabricated formwork should be covered with plastic film. The dimensions of the formwork must exceed the height of the future grillage by at least 5 cm.
Helpful advice! In the case of a low grillage, you can use permanent formwork, which will subsequently become additional thermal insulation for the walls of the premises.
Grillage reinforcement: step-by-step instructions
The next step in constructing a pile foundation grillage is the creation of a reinforcement frame, which must subsequently be completely recessed into concrete on all sides. To do this, it is necessary to lay wooden blocks of any width on the bottom of the formwork in the transverse direction, but with the same thickness of 30-50 mm. The bottom row of reinforcement bars is laid on them, which must be tied together so as to ensure the same distance between the rods.
The upper chord of the reinforcement cage must be suspended from the transverse beams that connect the formwork posts. Then you should tie the lower and upper belts together.
For reinforcement of monolithic tape, class A400 reinforcement is usually used. The number of rods is calculated based on the ratio of the cross-sectional area of the horizontal lintel to the sum of the cross-sections of all rods, which is 1000:1. The following calculation procedure is performed:
- it is necessary to multiply the width by the height of the grillage, dividing the result by 1000;
- the resulting value must be divided by the cross-sectional area of one rod.
The result obtained is the minimum number of bars required for reinforcement.
Helpful advice! The distance between rows of reinforcement should not exceed 150 mm.
Installation of additional elements and concreting the grillage
Before pouring concrete on a horizontal lintel, special pipes should be laid through which utilities will pass, such as water supply, heating, sewerage and communications. Ventilation holes should also be provided in the base.
Important! This stage should not be neglected, since then the integrity of the grillage will have to be compromised.
To create a monolithic grillage, it is recommended to use concrete grades M300 and M500. When filling the formwork with concrete mixture, you should use a vibrating machine that can shake the concrete to eliminate the possibility of cavities, which will increase the strength characteristics of the concrete.
Two hours after pouring the concrete, it is recommended to cover it with film. If it is hot outside, it is periodically necessary to remove the film and moisten the concrete with water so that cracks do not form on its surface. Complete hardening of the structure will not occur earlier than in a week, which depends on the ambient temperature.
If the outside temperature reaches 20 degrees, the formwork can be removed after 4 days, since the concrete base will gain more than half its strength. If the temperature does not rise above 10 degrees, the formwork does not need to be touched for 14 days. When the air temperature is below 10 degrees. it is necessary to provide additional heating and organize insulation of the foundation. After the concrete has completely hardened, you can begin to create a waterproofing layer using bitumen mastic.
Construction of a columnar foundation with a grillage
The construction of the foundation for future construction is carried out according to the following algorithm:
- clearing the area of vegetation followed by treatment with chemicals;
- marking the site based on the project;
- creating holes for future pillars;
- compacting soil at the bottom of the pit;
- creating a sand cushion at least 15 cm high;
- laying geotextiles;
- backfilling with crushed stone;
- performing formwork for each pit;
- covering the formwork system with polyethylene;
- creating a frame for reinforcing piles;
- forming pillars by pouring concrete into holes;
- treating the surface of the pillars with bitumen mastic;
- installation of formwork between reinforced concrete pillars to create a grillage, the height of which should exceed the height of the future structure by 5-10 cm;
- sand cushion device;
- concreting the grillage with structural reinforcement;
- creation of hydro- and thermal insulation.
The main mistakes when constructing a pile-grillage foundation
The first mistake that can significantly affect the reliability and rigidity of the structure is incorrect calculation of the load on the base of the building. Here it is very important to take into account the peculiarities of the type of soil of the area where construction will be carried out.
The next mistake is considered to be small depth or incorrect installation of piles. Free space may form in the soil under the piles, which will cause shrinkage of the foundation. This will undoubtedly lead to a decrease in the air gap under the grillage, which can cause the pile to break in the winter. To eliminate this possibility, piles should be installed below the freezing depth of the soil.
In practice, there are cases where the design does not provide for the creation of an air gap under the grillage. This is especially dangerous in the winter, when the frozen ground expands significantly in different directions, including vertically. This will lead to the formation of excess pressure on the bottom of the grillage, which may cause damage or breakage. To eliminate this, care should be taken to organize an insulating layer in the form of polystyrene foam boards, which will also act as artificial shock absorption.
An equally important point is the creation of a reliable connection between the grillage and the piles. If there is no reliable fixation, this can lead to horizontal displacement of the pillars. As a result, they will not be affected by the design load from the structure, which may sag in this place.
A grillage foundation for a house or other structure is the most popular and economically viable option in modern construction. It is characterized by versatility, increased strength and reliability. A well-made grillage, in accordance with regulatory requirements, is the key to a durable structure.
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