The foundation is the base of any capital structure, the strength and integrity of the structure built on it depends on the quality of its arrangement. In cases where the natural properties of the soil do not allow the use of the usual form of support, a pile structure is used. Before starting any construction, it is important to know how to build a pile foundation properly. Step-by-step instructions, general description of the process will help you with this.
The main purpose and types of pile foundation
The pile foundation is used in the construction of industrial and residential facilities, it can be used in the construction of multi-storey buildings, even on soft soils. Such a foundation can significantly reduce the process of building basements or completely exclude these construction works from the cost estimate. The main reasons for the construction of the pile foundation are as follows:
- weak topsoil. Such soils may contain humus, peat admixture, sand, clay. The presence of a large amount of water in the soil makes it a quicksand. Such natural conditions create the need to transfer the load of the structure to more dense and deeper soils;
- increased soil density. Applying a pile foundation can reduce the amount of land work. Preparation costs will also be reduced: digging a pit, hiring a truck, removing dug up soil, filling it up, purchasing concrete, and more.
The pile foundation has several varieties: pile-grillage, pile-screw, pile-tape. Each type has advantages and disadvantages, consider them in more detail.
Pile-grillage foundation: pros and cons
The use of pile-grillage foundations has both positive and negative sides. The advantages of such a foundation:
- allows you to build on virtually any type of soil;
- increased stability;
- increased bearing capacity (allows you to hold roofs and walls with a rather large specific gravity);
- profitability (no need to use the finished solution, you can make it yourself);
- the solidity of the base makes it possible to precipitate the entire structure in case of soil shrinkage;
- does not require special preparation of the construction site (cost reduction by reducing labor-intensive work);
- providing natural ventilation of the entire lower plane of the structure (humidity decreases, condensate is eliminated);
- safety (the risk of flooding in case of floods is reduced);
- speed of construction;
- high speed construction.
Important! The construction of the foundation on piles requires accuracy in the calculations and compliance with construction technology. When overloading the support tonnage, there is a great risk of building destruction in the future.
Disadvantages of the pile-grillage foundation:
- the impossibility of erecting a pile-grillage foundation on rocky soils;
- the complexity of installing the base with horizontal displacement of the soil;
- quite high price of pile-grillage foundation, which far exceeds the cost of other options;
- the impossibility of building a basement or basement (a similar type of foundation is used exclusively for lightweight and medium-weight structures);
- accuracy of calculations (errors in the calculation will lead to deformation of the supports and the formation of cracks in the house). To order the calculation of the pile-grillage foundation from specialists is not cheap. Consequently, the total price of the work will increase significantly.
Pile-screw foundation: pros and cons
This technology has been known since the last century, so its pros and cons have long been studied. Benefits:
- low price of pile-screw foundation, which is several times cheaper than monolithic or tiled;
- high speed of construction (there is no need to level the soil or dig trenches);
- minimal disturbance of soil structure;
- lack of vibration (the ability to build buildings near architectural monuments, monuments, centuries-old trees);
- recommended for installation on swampy soil, the banks of water bodies (ideal choice for the construction of a berth);
- complete independence from weather conditions;
- repeated use of the design;
- installation work is carried out at minimal cost (physical, technical).
Disadvantages of pile-screw foundation:
- supports are highly susceptible to corrosion (iron alloys are used for manufacturing);
- structural weakness;
- the inability to use the space under the house (it is strictly forbidden to build a basement or basement).
Pile and strip foundation: pros and cons
A fairly common type of foundation, which also has its own specific features. Advantages of the pile and strip foundation:
- can be erected on plots with complex land relief;
- profitability (the minimum amount of equipment and human resources involved in the construction);
- ability to withstand weak shocks and shifts of soil;
- piles can be made independently, using only improvised material;
- speed of construction.
The disadvantages of the pile and strip foundation:
- the need for detailed geodetic measurements;
- individual calculation of the length, thickness and depth of each pile;
- the inability to create a basement;
- obligatory work to warm the underground;
- It is used exclusively for the construction of low buildings (maximum three floors).
How to build a pile foundation: step-by-step instructions
Currently, the cost of any construction work has increased significantly. Therefore, many owners solve the problem of building the foundation on their own and with all sorts of improvised means. Let us consider in detail the main points of the construction of three types of pile foundation.
The main rules for the construction of a pile-grill foundation
This kind of foundation has a characteristic construction of a concrete base. A beam is fixed in it, which is poured out of concrete and reinforced with reinforced elements. This is a single system consisting of supports (piles) and grillage.
The support function is performed by pillars of rounded or rectangular shape. Pillars are immersed at a specially calculated depth. It is on them that the entire weight component of the building is held. The grillage is a monolith uniting all installed piles.
The pile-grillage foundation can be built on its own, because there is no need to remove the soil. In order to drive the supports into the ground, special pressing devices are used. After the final installation of piles, they are cut at the same level. Then carry out a general connection grillage, which provides a uniform load on each individual support.
A photo of the pile-grillage foundation will show it much better than any detailed description. Often, the basis of the supports are metal pipes hollow from the inside. This makes them lighter than other types of piles. They are easier to hammer to a considerable depth. To increase stability, concrete is poured inside.
Important! The grillage in this case serves as a reliable and rigid foundation for the next stage of construction – masonry walls.
Rostverk can be performed in two ways:
- Assemble from reinforced concrete elements.
- Pour monolithic tape.
To build the foundation with your own hands, it is better to choose the second method – a monolithic grillage. This will greatly facilitate the task of pouring concrete. Installation of weighty reinforced concrete blocks will require additional labor and equipment. The sequence of actions is as follows:
- Provide a small space between the ground and the lower border of the grillage. This will help protect the entire structure from swelling;
- mark the future location of piles;
- drill wells and install piles;
- formwork should be laid on top;
- Reinforcing frame is mounted inside the formwork. It must be completely immersed in concrete mortar. To do this, place small bars under the lowest rods;
- the protruding rods from the support must be connected to the grillage reinforcing cage. This will provide the base with greater reliability and strength;
- then the grillage can be poured with concrete. Concreting is done in layers to avoid the appearance of air pockets.
To correctly choose the type of foundation , you need to proceed from the approximate weight of the future home. The pile-grillage foundation has rather high restrictions on the load, therefore, it is suitable as a base for buildings made of aerated concrete , panel and frame houses . It is not recommended to use this type of foundation for high-rise buildings because of the low resistance to overturning loads arising on moving soils. The best option is the use of a pile-grill foundation for aerated concrete.
Useful advice! The width of the grillage should slightly exceed the width of the walls of the future structure. This will add sustainability to the building.
Example of calculating a pile foundation with grillage
The total number of piles and their pitch is calculated for the construction of a one-story building with a size of 7×7 m.
The approximate weight of consumables (roof, timber, cladding, etc.) is 25,000 kg.
Payload: 7x7x150 (accepted value for residential premises) = 7350 kg.
Snow load: 7x7x180 (constant) = 8820 kg.
Calculation of the total mass of the load on the foundation: 25000 + 7350 + 8820 = 41170 kg.
This value must be multiplied by a safety factor of 1.1. We get 45287 kg.
Now it remains to divide the resulting value by the size of the load per one pile (for example, a screw): 45287/2000 = 22.6435. After rounding, we get 23. Such a number of supports you will need. Installation step – 1.2 m.
The main rules for the construction of a pile-strip foundation
If the site on which you decide to build a house has a complex terrain, then it is more advisable for you to use a pile-strip foundation. It consists of a tape (grillage) and piles. The technology for erecting this type of foundation is not particularly difficult, therefore, it can be done with your own hands. To complete this work, observe the following rules:
- make markup. To do this, drive the rods in the corners of the future structure and pull the cord between them;
- determine the location of the piles;
- dig a pit under the tape;
- drill holes for piles at its bottom;
- install asbestos cement pipes in dug holes, filling them with about 30 cm of sand;
- equip thorough waterproofing of piles with roofing material;
- install several metal rods in each pipe. The rods should rise above the soil surface by 20 cm;
- fill each pipe with concrete, avoiding the appearance of air pockets;
- after the concrete has hardened, install the tape. For this, the bottom of the structure is laid out with 5 cm thick bars. Then, a special mesh is installed. Grid elements reliably connect with reinforcing elements of supports;
- formwork is installed (wooden panels, which are strengthened by struts and struts). The formwork should slightly exceed the height of the future base ;
- concreting. Concrete needs to be poured with periodic tamping, without leaving empty places.
Useful advice! To give additional reliability to the walls of the formwork, fix them with stakes driven into the ground (from the outside and inside). The tops of the stakes should be firmly tied with wire.
Pile screw calculator
According to reviews, the pile-screw foundation is best used for the construction of residential and non-residential premises on moist soils.
We calculate the number of piles required using an example. Initial data:
- pile diameter – 40 cm;
- the estimated mass of the house is 80 tons;
- bearing capacity of soil – 5 kg / cm2.
Fsv = (πd2 / 4) × R .
The load on one pile: 3.14 (constant value) x 1600 (diameter squared) = 5024.
Divide the obtained value by 4 (constant number) and multiply by the value of the soil bearing capacity: 5025/4 x 5 = 6280.
The required number of piles: 80t / 6280 = 12.738. Round the resulting value.
You need 13 piles.
Remember that for the proper construction of the pile foundation, the calculation of the number of piles is a necessity. Erroneous calculations will lead to cracks in the house and the gradual destruction of its walls.
The basic rules for the construction of a screw foundation
To build a house without a basement and basement, you should opt for a screw foundation. It is a pile that is screwed into the ground like screws. Not recommended for hard rock primers. How to properly install screw piles for the foundation with your own hands – the video clip will show more clearly. Such video material can be easily found on the Internet. The construction process consists of the following steps:
- determine the number of necessary supports and the magnitude of the load on them. Calculation of the load of screw piles for the foundation is done according to the formula: house area x (40 + 15xB), where B is the height of the facade of the building;
- make markings on the land using stakes and a cord;
- we drill holes for piles. Their diameter should be slightly smaller than the diameter of the pile blades;
- install supports;
- excessive length of piles is removed with a grinder;
- a steel platform is welded to the trimmed edge of the support. A metal channel is mounted on it.
Useful advice! Be sure to use the level to observe strict vertical installation. If the support is not level, the foundation will not withstand the load.
How to make a pile-screw foundation with grillage
The grillage is that part of the foundation that rises above the surface of the soil. It is designed to distribute the load on the pile structure. For the manufacture of grillages, reinforced concrete or metal beams are used, which combine the piles into a single structure. To properly build a grillage, the following sequence must be observed:
- formwork is being built;
- fittings fit. It is carefully strengthened to avoid possible displacement;
- concrete is poured. Make sure that there is no leakage outside the formwork;
- concrete is discharged from the air. You need to do this with a regular pin;
- ready grillage give time to harden. To do this, it is covered with plastic wrap. During the week, it is necessary to periodically remove the polyethylene and water the structure;
- then the formwork is removed. The grillage is checked for size and shape.
To build a strong and reliable house, you need to qualitatively equip its base. Before starting construction, carefully read the basic principles of building a bookmark and the basic installation rules. Observing all the necessary technologies, you will perfectly cope with the independent construction of the foundation.