The use of piles in the foundation is often determined by the desire to optimize the design solution and overall savings. Indeed, the implementation of this technology for building the foundation of a house requires less financial and labor resources than in cases with traditional construction methods. Nevertheless, with the proper installation of the foundation from piles, you can get a completely reliable platform for the main structure of the building. Moreover, certain characteristics of the soil, in principle, allow only such a method of building the foundation - for example, in frozen soil.
Classification of foundation on supporting piles
There are several signs by which the foundations of this type are divided. The classification according to piles is considered basic:
- Clogged. Concrete, metal and even wood can be used as the material for the core of the rod, depending on the load requirements. The pile is driven into the ground to the required depth using special equipment. As a rule, for the construction of the foundation on driven piles, loaders, hammers and vibrocompressors are used.
- Hammered pile piles. Modification of the previous rod, the difference of which is a reinforced concrete layer, creating the ability to remove excess soil. The empty niche after installation is filled with concrete.
- Screw piles. Such rods have cutting blades of one or another configuration. Wells are initially developed for the foundation on screw piles, into which steel rods are then twisted. A feature of this method is the possibility of manual installation of piles, but only if it comes to small volumes of construction using small-format rods.
- Stacked piles. To install such elements, the soil is first crimped, and then concrete is poured into the wells. Deepening is carried out by means of a capstan.
In addition to piles, supports are often used. These are load-bearing elements made of metal or reinforced concrete, which differ in shape and construction - rectangular and square, hollow and monolithic, Tauri and I-beams. There are foundations and the method of reinforcing the supporting system. For example, an integral support or composite structure can be created. Complex monolithic platforms are reinforced with metal and fiberglass rods if large loads on piles are expected.
Foundation execution configurations
Depending on the severity of the object, the number of supporting elements and the architectural layout of the building, a certain foundation design for the construction is applied. The following options for its configurations are distinguished:
- Tile foundation on stilts - used in the capital construction of houses of large area. In fact, a combined version that uses the installation of concrete supports around the perimeter of the building. Piles act as the supporting base, and the sand-cement tape serves as the base for the grillage.
- Single foundation base - involves the transfer of load from an element of a small area to the base. A point support structure is implemented according to the principle of load-bearing columns.
- Bush foundation - provides load reception through several supporting elements that focus on the grillage under one of the structural parts of the object.
- Monolithic foundation - does not apply to the traditional slab base, but has common features with it in the sense that a systematic arrangement of supporting elements is created with minimal preservation of voids.
There are also differences in the level of performance of the bearing supports. For example, a low foundation is placed directly above the soil surface, not allowing to shift the load on the ground. This system involves the use of small-format rods forming a monolithic bearing base. For an elevated platform, more solid support elements are used. This may be the foundation on reinforced concrete piles, in which the grillage is closely interfaced with the supporting structure. The system of additional reinforcement with beams connecting the rods to each other may also be included.
Material selection
The main material will be piles. The most suitable rod type is determined, as well as additional selection parameters. The main characteristic of piles in terms of bearing capacity is diameter. He will determine how much the structure can in principle hold the foundation. Models are available in the market from 50 to 220 mm thick. If we are talking about building a small house, then the minimum diameter will be 100 mm, and if you plan to build a cottage with a large area - then it is better to focus on rods with a thickness of at least 200 mm.
In the selection of screw piles for the foundation, it is important to correctly determine the appropriate type of tip. It can be cast or welded. Cast tips (especially with galvanized surface) is the best solution for a private home. Welded rods are more suitable for creating a supporting base for farm buildings, saunas and massive engineering structures.
Not in each case, but when installing the foundation on screw piles, concrete pouring may be required. It is used both at the stage of creating a grillage, and in strengthening wells. For such purposes, it is better to use factory concrete grades B15, B20 or B25. You can also make a solution of B15 with your own hands. Formwork and ancillary structures will require wooden beams, marking tools, and associated mounting hardware.
Preparation of the site for the construction of the foundation
The territory is marked according to previously prepared calculations of the foundation design. At this point, the base configuration, piling points, well parameters and reinforcement techniques should be known. The working platform is cleared, a layer of vegetation, stones and all kinds of garbage are removed on it. If you plan to build a foundation of piles with elements of tape formwork, then along the lines of construction, trench recesses should be made up to 10-15 cm. At the same stage, formwork contours are mounted for subsequent pouring with concrete. In order not to cause problems with the arrival of equipment, you should also provide road routes to the immediate place of work.
Installation of piles for the foundation
The simplest way to deepen the bearing rod is with a hand drill. To implement this method, you don’t need a special technique, but at least you need a partner. A drill with a diameter of 300 mm with an adjustable rod for wells with a depth of about 5 m is used. If we are talking about diameters of 500-600 mm, then you will have to arm yourself with an electric modification of the drill. Without special efforts, such a tool can provide niches with a depth of up to 4 m. More complex drilling tasks will have to be carried out using special equipment.
Before diving the piles, it is necessary to isolate the well with roofing material. Casing pipes are made for this. In several layers, the pipe is wrapped with roofing material, after which it is tied with wire. Direct installation of piles for the foundation is also carried out either manually or with the use of lifting special equipment. It is important that the diameter of the well be slightly larger than the thickness of the rod. Expansion of the hole in the ground is required for subsequent reinforcement with concrete and reinforcement of the structure. For example, it is possible to make a reinforcing cage based on three vertical rods with a thickness of 4-6 mm. They are fastened with cross members and plunged with a girth of piles.
Mounting grillage
The most responsible structural part of the foundation, which is responsible for coupling the base of the house and the bearing pile elements. The grillage is made either as a monolithic concrete platform, or on the basis of prefabricated elements - for example, reinforced concrete slabs with a beam fastening system. In both cases, work begins with the connection of the pile heads with jumpers and beams. The supporting frame is formed, on the basis of which it will be possible to perform the upper part of the grillage.
If you plan to create a foundation from piles with a monolithic grillage, then on a prepared reinforced base, formwork should be performed over the entire area. The fill height will be approximately 300 mm. The site is concreted with a bookmark with welded plates or thick metal rods with a diameter of 10-12 mm.
In the case of mounting a precast grillage, the main attention should be paid to fixing reinforced concrete slabs to the pile frame. Usually, for this purpose, a reinforcing rod is mounted on the pile head (by welding or screw method), which will create a lock for laying the precast beam. Slabs 200-300 mm thick will be laid in the beam system. Upon completion of installation operations, the structure is finished with concrete - the joints and joints are filled with a solution.
Technology advantages
The result is a fairly reliable foundation, which has both pluses and minuses. Among the advantages, the following points can be distinguished:
- Minimization of earthworks allows saving on both organizational and financial resources.
- You can do without cutting down trees, which allows you to save the pristine landscape of the territory.
- Allowed the construction of houses on complex landscapes and soils, where it is impossible to use other types of foundations. For example, this applies to slopes, waterlogged and peat soils.
- The extension of auxiliary buildings to the erected house is facilitated.
- High bearing capacity. Against the background of typical strip and monolithic foundations, the construction on metal piles may not seem strong enough. But this only concerns the assessment of resistance to static loads, which already assume minimal risks for the construction. But the resistance to dangerous dynamic loads in this case is much higher.
- Buildings on the foundations of piles practically do not shrink, which eliminates the need for "standing" of the object after construction.
- The foundation of the house is possible at any time of the year. Unless frozen ground in winter can complicate the work process, but in principle it does not exclude it.
- High foundation laying speed. Installation activities are carried out in a few days.
Cons of technology
The pile method of foundation construction is quite attractive from many points of view, but it is far from perfect. This is evidenced by its shortcomings:
- During the construction of large private houses and cottages, you can not do without the use of special equipment, which, by the way, is not always necessary in the construction of columnar and strip foundations.
- Plugging and, in principle, developing wells to a depth of several meters negatively affects nearby buildings. Especially the use of special equipment can give tangible vibrations with longitudinal vibrations in the ground.
- The location of piles under the foundation excludes the possibility of building basements and other underground facilities.
- After several years of operation, it may be necessary to replace piles that have corroded or other fracture factors.
Technology Reviews
The experts associate the spread of the technology of installing pile bearing foundations with the universality of technology. At the design stages of small houses, it receives tolerances in most cases, even in difficult conditions of future construction.
Experts also highly appreciate the prospects of the technology, comparing its popularity with the growth in sales in the plastic window market. Practicality, reasonable price and minimal labor resources are what stilt houses are known for under the foundation. But are such objects reliable during operation? According to many experts, the technology itself, when properly implemented by professionals, really allows you to build long-lasting and stable foundations. Another thing is that the pile shaft market itself still contains a considerable share of low-quality products. The same screw piles are often made of artisanal alloys. And this is not to mention the necessary external protection of metal surfaces with coatings that should protect the rods in the ground for many years.
Conclusion
Faced with certain negative nuances of building a house on stilts, it is likely that many will abandon this method in favor of more traditional technologies for building the foundation. For example, from the point of view of operational value, it can also be replaced by popular tape and columnar foundations in different variations. What does the foundation of a house on screw piles win from them, if you do not take into account the advantages at the construction stage? There will really be few winning sides. This, in particular, is the possibility of reconstruction of the carrier base and more effective floor insulation. But, on the other hand, it is important to keep in mind the negative impact on the pile structure in the conditions of soil shifts and the need to equip the basement, without which the process of maintaining the house will be significantly complicated.