The use of piles in the construction of 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. However, if the pile foundation is correctly installed, you can get a completely reliable platform for the main structure of the building. Moreover, certain characteristics of the soil, in principle, allow only this method of foundation construction - for example, in frozen soil conditions.
Classifications of foundations on load-bearing piles
There are several signs by which foundations of this type are divided. The basic classification is considered to be based on piles:
- Drive-in. Concrete, metal, and evenwood - depending on the load requirements. The pile is driven into the ground to the required depth using special equipment. As a rule, plungers, hammers and vibrators are used to build a foundation on driven piles.
- Driven piles-shells. Modification of the previous rod, the difference of which is a reinforced concrete layer, which makes it possible to remove excess soil. The free niche after installation is filled with concrete.
- Screw piles. Such rods have cutting blades of one configuration or another. For the foundation on screw piles, wells are initially developed, into which steel rods are then twisted. A feature of this method is the possibility of manually installing piles, but only if we are talking about small volumes of construction using small-format rods.
- Stuffed piles. To install such elements, the soil is pre-compressed, and then concrete is poured into the wells. Deepening is done by 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 design - rectangular and square, hollow and monolithic, tee and I-beam. Foundations are also distinguished by the method of reinforcing the carrier system. For example, a one-piece supporting or composite structure can be created. Complex monolithic platforms are reinforced with metal and fiberglass rods if heavy pile loads 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 design of the base for construction is applied. There are the following options for its configurations:
- Strip foundation on piles - used in the capital construction of large houses. In fact, a combined option, which uses the installation of concrete supports around the perimeter of the building. The piles act as a bearing base, and the sand-cement tape acts as a base for the grillage.
- Single foundation base - involves the transfer of load from a small area element to the foundation. A point support structure is implemented according to the principle of load-bearing columns.
- Cluster foundation - provides load acceptance through several support elements that focus on the grillage under one of the structural parts of the object.
- Monolithic foundation - does not belong to the traditional slab base, but has common features with it in the sense that a systemic placement of supporting elements is created with minimal voids.
There are also differences in the level of execution of bearing supports. For example, a low foundation is placed directly above the soil surface, preventing the load from being transferred to the ground. This system involves the use of small-format rods that form a monolithic supporting base. For an elevated platform, more solid support elements are used. This may be a foundation on reinforced concrete piles, in which the grillage is closely aligned with the supporting structure. Can be included anda system of additional reinforcement with beams connecting the rods to each other.
Selection of materials
The main material will be piles. The most suitable bar type is determined, as well as additional selection options. The main characteristic of piles in terms of bearing capacity is the diameter. He will determine how much weight the structure can, in principle, support the foundation. Models with a thickness from 50 to 220 mm are available on the market. 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 of a large area, then it is better to focus on rods with a thickness of at least 200 mm.
When choosing screw piles for foundations, it is important to correctly determine the appropriate type of tip. It can be cast or welded. Cast tips (especially with a galvanized surface) are the best solution for a private house. Welded rods are more suitable for creating a supporting base for outbuildings, baths and massive engineering structures.
Not in every case, but when building a foundation on screw piles, concrete pouring may also be required. It is used both at the stage of creating a grillage, and when strengthening wells. For such purposes, it is better to use factory concrete grades B15, B20 or B25. You can also make a B15 solution with your own hands. Formwork and ancillary structures will require timber, marking tools, and associated mounting hardware.
Preparation of the site for the construction of the foundation
The territory is being marked according to previously prepared calculations of the foundation structure. By this time, the foundation configuration, pile placement points, well parameters, and reinforcement technique should be known. The working platform is cleared, a layer of vegetation, stones and all kinds of debris are removed from it. If it is planned to build a foundation of piles with strip formwork elements, then trench recesses up to 10-15 cm should be made along the construction lines. At the same stage, formwork contours are mounted for subsequent pouring with concrete. To avoid problems with the arrival of equipment, it is also necessary to 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 will not need special equipment, but at least you will need a partner. A drill with a diameter of 300 mm is used with an adjustable rod for wells with a depth of about 5 m. If we are talking about diameters of 500-600 mm, then you will have to arm yourself with an electrical modification of the drill. Without much effort, such a tool can provide niches up to 4 m deep. More complex drilling tasks will have to be performed using special equipment.
Before driving piles, the well should be insulated with roofing material. For this, casing pipes are made. In several layers, the pipe is wrapped with roofing felt, after which it is tied with wire. Direct installation of piles for the foundationcarried out either manually or with the use of lifting equipment. It is important that the diameter of the hole is 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, you can make a reinforcing cage based on three vertical rods with a thickness of 4-6 mm. They are fastened with crossbars and plunged with the girth of the pile.
Installation of the grillage
The most critical structural part of the foundation, which is responsible for coupling the foundation of the house and the bearing pile elements. The grillage is performed 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 connecting the pile heads with lintels and beams. A supporting frame is being formed, on the basis of which it will be possible to perform the upper part of the grillage.
If it is planned to create a foundation of piles with a monolithic grillage, then formwork should be performed over the entire area on a prepared reinforced basis. The height of the fill will be approximately 300 mm. The site is concreted with a laying of welded plates or thick metal rods with a diameter of 10-12 mm.
In the case of mounting a prefabricated grillage, the main attention should be paid to fixing reinforced concrete slabs to the pile frame. Usually, for this, a reinforcing bar is mounted (by welding or screwing) on the pile head, which will allow you to create a lock for laying a prefabricated beam. Slabs with a thickness of 200-300 mm will be laid in the beam system. Upon completion of the installation operationsthe structure is finished with concrete - the seams and joints are filled with mortar.
Pros of technology
The result is a fairly reliable foundation, which has both pluses and minuses. Benefits include:
- Minimizing earthworks saves both organizational and financial resources.
- You can do without cutting down trees, which allows you to preserve the original landscape of the territory.
- It is allowed to build houses on difficult landscapes and soils where it is impossible to use other types of foundations. For example, this applies to slopes, flooded and peaty soils.
- The extension of auxiliary buildings to the erected house is facilitated.
- High bearing capacity. Against the background of typical strip and monolithic foundations, a structure on metal piles may seem insufficiently strong. But this applies only to the assessment of resistance to static loads, which already involve minimal risks for the structure. But the resistance to dangerous dynamic loads in this case is much higher.
- Buildings on foundations made of piles practically do not shrink, which eliminates the need to "stand" the object after construction.
- Establishing the foundation of a house is possible at any time of the year. Unless the frozen ground in winter can complicate the work process, but in principle it does not exclude it.
- High speed laying the foundation. Installation activities are carried out in a few days.
Constechnology
The pile foundation method is quite attractive from many points of view, but it is far from perfect. His shortcomings testify to this:
- When building large private houses and cottages, one cannot do without the use of special equipment, which, by the way, is not always necessary for the construction of columnar and strip foundations.
- Clogging and, in principle, the development of 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 undergone corrosion or other factors of destruction.
Reviews of specialists about technology
Experts associate the spread of pile foundation technology with the versatility of the technology. In the design stages of small houses, she receives approvals in most cases, even in difficult future construction conditions.
Experts also highly appreciate the prospects of the technology, comparing its popularity with the growth in sales in the plastic window market. Practicality, affordable price and minimal labor resources are what houses on stilts under the foundation are famous for. But are such objects reliable during operation? According to many experts, the technology itself, when properly implemented by professionals, really allows you to builddurable and stable foundations. Another thing is that the pile rod market itself still contains a large share of low quality products. The same screw piles are often made from artisanal alloys. And this is not to mention the necessary external protection of metal surfaces with coatings, which should protect the rods in the ground for many years.
Conclusion
Faced with certain downsides to building a stilt house, it is likely that many will abandon this method in favor of more traditional foundation building techniques. For example, from the point of view of operational value, it can also be replaced by popular tape and column bases in different variations. What is the advantage of the foundation of a house on screw piles, if you do not take into account the advantages at the construction stage? There will indeed be few winning sides. This, in particular, the possibility of reconstruction of the bearing base and more efficient 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 movements and the need to equip the basement, without which the process of maintaining the house will be much more complicated.
