How to build a foundation on screw piles. Installation and installation of pile foundation. How to deal with a screw foundation on your own
The screw foundation has been used in the military and industrial sphere for more than a hundred years; in private construction, this technology has been actively used not so long ago. The pile-screw foundation has established itself as a strong and versatile foundation that can cope with soils of "doubtful" stability.
What is a screw foundation
The screw foundation is much simpler than the traditional buried monolithic types of foundations, which involve earthworks and pouring concrete.
The foundation with the use of screw supports is one of the varieties of the pile foundation. There are some differences in the method of arrangement and the structural material used. The piles are made of reinforced concrete and driven into the ground with a pile driver or mounted in a ready-made pit. The screw support is made of galvanized pipe, and a drill is welded to the lower end.
This design allows without special efforts screw the pile into the ground. After the pile is installed, its cavity is filled with reinforcement and poured with concrete. Ultimately, the screw pile turns into a strong reinforced concrete pillar.
Screw supports are combined by horizontal ligation of a tile or beam type, the foundation base is formed from strip block or brick masonry.
The choice of grillage (monolithic strip foundation, metal, wooden or reinforced concrete beams) and its location relative to the soil depend on the type of building - multi-storey building or one-story building, and on the characteristics of the soil:
To protect piles from corrosion, technologies used in the construction of ships are used. This approach allows you to significantly increase the period of operation of the screw foundation. Manufacturers of screw piles indicate terms from 100 to 150 years. However, it is still impossible to confirm or deny the veracity of this information, since this technology has been actively used in our country for no more than 30 years.
Scope of the pile-screw foundation
Back in 1838, the English process engineer Alexander Mitchell proposed to simplify the labor-intensive driving of supports, replacing the process with a simpler and more comfortable screw pile driving. The idea was first tested in 1850 during the construction of a lighthouse in Delaware Bay, USA. This lighthouse still stands today, confirming the success of Mitchell's pioneering idea.
The idea of building a foundation on screw piles was "picked up" by the military. The foundation device made it possible to build a reliable foundation for a strategic object in a short time.
Subsequently, such a development began to be actively introduced into the construction of "peaceful" facilities:
The design of screw piles has been improved. And today, they are made of high-strength special steel, and some models are equipped with a special head with blades, which, when deepened, compacts the adjacent soil layers.
Screw foundation is the best option for building:
- areas with ditches and slopes;
- areas where driving piles is prohibited - not far from underground tunnels, metro, etc.;
- plots with increased level soil moisture;
- peat areas;
- areas with deep freezing of the soil;
- landscaped areas.
Advantages and disadvantages of the foundation on piles
Due to the design features, the installation and operation of a screw foundation has a number of advantages:
The construction of a screw foundation for a house will reduce the construction budget by 25-40% - a screw foundation is almost three times cheaper than a strip foundation
The screw foundation also has some disadvantages:
- If the level of soil freezing is not taken into account or the load on the piles is incorrectly calculated, then subsidence of the foundation is possible.
- Deformation of the foundation may be the result of a violation of the installation technology:
- the position of the piles during screwing was not fixed;
- installation of piles in dug pits;
- incorrect tying of piles;
- the piles were not screwed in, but hammered.
- It is impossible to equip a cellar in a house on a screw foundation.
- The need for insulation of the lower part of the structure.
- It is impossible to erect a really large, large-scale structure on screw piles.
- High-quality screw piles are not so easy to acquire.
It is better to buy screw piles not from intermediaries, but from manufacturers who have their own development and research departments where products are tested. Representatives of the company can monitor compliance with the technology during installation work
Types of pile-screw foundations
The design of the foundation on screw piles can be carried out in different ways - it depends on the design of the structure and the type of soil.
How to choose screw piles for the foundation
The bearing capacity of piles depends on the following parameters.
Pile diameter.
- 57 mm - piles for light fences;
- 76 mm - piles for fences made of wood, profiled sheet, for arranging the foundation for light household buildings (summer kitchens, gazebos, toilets, utility blocks); load bearing capacity piles - no more than 3 tons;
- 89 mm - installation of heavy and high fences, foundations for one-story frame houses and extensions to the house - terraces, verandas; pile bearing capacity - 3-5 tons;
- 108 mm - erection of the base for two-story frame houses, suitable for building houses made of light stone, wood and building outbuildings; bearing capacity - 5-7 tons.
Pile length depends on the type of soil in the area, the depth of screwing and freezing of the soil.
The occurrence of dense layers of soil can be determined independently. The garden drill must be slowly screwed into the ground, periodically pulling it out and checking for dense lumps of sand or clay. According to the length of the drill, you can calculate the depth of finding favorable soil for installing piles.
For the accuracy of the result, you can use the services of a specialized company that will perform test drilling and determine the required length of screw piles. The cost of such a service is about 1500 rubles.
The relief of the site also affects the length of the pile. For example, when overall length at home 6 meters and a height difference of 1 meter, three types of piles will be required: 2.5 meters for mounting the top row, 3 meters for installing the middle row and 3.5 meters for the bottom row of piles.
Advice. If the height difference is more than 0.5 meters, then it is better to take into account piles 0.5 meters longer than expected - usually, when installing a screw foundation in relief areas on the lower rows of piles, about 30 cm is not enough
Tip type. Typical types of piles are shown in the figure below.
The first option is designed for installation on sandstones, permafrost soils, as well as dense loams with increased bearing capacity. The soil inside the pile does not compress, holding it both outside and inside. Pile parameters:
- wall thickness - 8-20 mm;
- pile length - 4-16 m;
- step between piles - 4 m;
- diameter - 219 and 325 mm;
- pile diameter with a "heel" - 300 and 400 mm;
- estimated price - from 4500 rubles / unit.
A pile for ordinary soils has a diameter with a "heel" of the order of 500 mm. Such piles are suitable for the construction of light non-residential buildings and fences. Pile parameters:
- wall thickness - 4-16 mm;
- pile length - 2.5-15 m;
- step between piles - 2.5 m;
- piles are produced in various diameters from 47 to 325 mm;
- estimated cost - from 2000 rubles / unit.
A pile with a wide heel is used on floating, heaving and loose soils. The propeller blades reach almost to the point of the tip, the number of revolutions is at least 2.
Pile parameters:
- wall thickness - 4-16 mm;
- pile length - 3-15 m;
- step between piles - 3 m;
- pile diameter - 159, 219 and 325 mm;
- estimated cost - from 3500 rubles / unit.
There are also more complex pile designs - with multi-turn turns, a built-in drainage system and additional blades. Such models are quite expensive, and the technology for their installation is more complicated. Therefore, these types of piles are practically not used in private construction.
Do-it-yourself screw foundation for a house
Design and calculation
First of all, it is necessary to conduct a qualitative analysis of the soil. It is better to entrust the study of the geology of the area to professionals - a company that builds houses on screw piles. Experts will calculate the bearing capacity of piles and the service life of the foundation in a particular area, determine the indicators of soil aggressiveness and issue an appropriate conclusion.
When determining the type and number of piles, the following indicators are taken into account:
- soil properties and type;
- groundwater levels and their seasonal fluctuations;
- the weight of the future structure with all the "stuffing";
- depth of soil freezing;
- margin for cutting piles during installation (about 20 cm).
The calculation of the screw foundation can also be made by companies selling piles. Very often they offer to pick up a "sole" for a future building for free.
When designing a screw foundation, it is necessary to take into account:
- The distance between the piles is no more than 2.5-3 meters.
- Each corner of the house should rest on a pile.
Stages of building a foundation
Screwing a pile is a rather laborious process, so it is better to enlist the support of two or three people.
For work, you can independently make a lever that will facilitate and speed up the screwing of piles into the ground. To do this, insert reinforcement (crowbar) with a diameter of 3 cm into the holes at the upper end of the screw pile. Put cuts of a square pipe on both sides of the crowbar. The optimal length of the sleeves of a homemade lever is 2.5-3 meters.
Phased installation of the screw foundation:
Screw foundation for the house: photo
The screw foundation is ready for further construction work.
Screw foundation for the house: video
- The vertical deviation of the pile should not exceed 2°.
- If the pile deviates significantly during screwing or “stumbles” into an obstacle, it must be dismantled and reinstalled in another place.
- A pile screwed at an angle cannot be built up.
- The depth of screwing the pile into the root soil is at least 600 mm.
- When adjusting the height, the pile must not be unscrewed. In the future, this will lead to subsidence of the foundation and, as a result, deformation of the building.
- The pile should go into the plane of dense soil by 600-800 mm.
- If a temporary structure is being constructed, then it is better not to concrete the piles, since the material can be used in the construction of another object.
Recently, the screw foundation has been actively used in Russia for the reconstruction of old buildings and the construction of new houses on problematic soils.
This page contains information about the pile-screw foundation: calculation of the foundation, materials for construction, we build a pile-screw foundation with our own hands, videos and prices are shown on the page. We will tell you where you can order a foundation in Moscow.
Pile-screw foundations- this is a type of foundations that is rapidly gaining popularity, which is characterized by high construction speed, economy and excellent performance. This is the best foundation for wooden houses, buildings made of foam concrete and gas silicate, as well as for small brick buildings.
The page discusses in detail the technology for calculating the pile-screw foundation, the features of its construction by one's own hands and the current prices for the construction of pile foundations when contacting the services of construction companies.
Fig 1.0: Construction of a frame house on a pile-screw foundation
Calculation of the pile-screw foundation
Correct calculation - necessary condition reliability and durability of the pile-screw foundation, therefore, its implementation must be approached with the utmost responsibility.
First you need to determine which type of pile is suitable for the type of soil on which you plan to start construction.
Figure 1.1: Piles with a widened foot
Figure 1.1 depicts piles intended for use in problematic soils - floating, loose and prone to heaving. They differ in a broadened heel, which helps to improve the fixation of the structure in the soil and increase its bearing capacity. The wall thickness in such piles can vary from 4 to 16 mm, length - 3-15 meters, diameter - 159-325 mm.
One pile with a wide heel, depending on the size, has a bearing capacity of 1-3.5 tons. They are placed with a step of 3 meters from each other. The estimated cost of the pile is around 3500 rubles.
Rice. 1.2: Standard screw piles
Figure 1.2 depicts piles used in ordinary soils. This is the best option in terms of price-performance ratio, which can be used for the construction of light houses made of wood or aerated concrete, one-story brick buildings and fences.
The length of such screw piles varies from 2.5 to 15 meters, diameter - from 47 to 325 mm, bearing capacity - from 0.7 to 2.5 tons. According to the requirements of SNiP, they must be placed in increments of 2.5 meters. The cost of one pile starts from two thousand rubles.
Rice. 1.3: Hollow screw piles
Figure 1.3 you can see screw piles for compact soils, sandstones and permafrost. Such designs differ from other types in the absence of a tapering tip, they are hollow inside and at the same time have open ends. In the process of immersion, such piles are filled with a column of soil, which provides additional fixation.
Hollow piles, as a rule, are not subject to concreting. However, if it is necessary to give the pile foundation maximum bearing capacity, after immersion, the soil from the pile is removed by a bailer and concrete mortar is poured into the pipe. This technology makes it possible to build large brick buildings (3-5 floors) on pile-screw foundations even in marshy areas or permafrost.
Rice. 1.4: Hollow piles for permafrost soils
The wall thickness of hollow screw piles can be 8-20 mm, the diameter is either 219 or 325 mm. Length - 4-16 meters, carrying capacity up to 4.5 tons. The cost of one hollow pile starts from 4.5 thousand rubles.
If you plan to build on a pile-screw foundation wooden house, piles must be completed headroom. You can see it in image 1.2:
Rice. 1.5: Head for screw piles
The dimensions of the head are the same for all types of screw piles, only the size of the seat differs depending on their diameter.
Fig 1.7: Types of pile-screw foundation grillages
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Method for calculating the pile-screw foundation
The calculation of the pile-screw foundation for the construction of 1-2 storey wooden and brick houses is carried out according to the following algorithm:
- We determine the mass of individual elements of the future building;
- We calculate the load from precipitation (snow and wind) that will be applied to the building;
- We calculate the total load of the building on the pile-screw base;
- Based on the construction area and the standard distance between individual piles, we determine the number of required piles;
- By bearing capacity different types piles determine the appropriate size of piles;
- We draw up a drawing of a pile field based on the standard step between piles;
- Based on the standard size of the selected piles and the calculated load from the building, we determine the parameters of the grillage.
Fig 1.6: Pile-screw foundation with a metal grillage
How to determine the weight of individual parts of a structure?
This is done on the basis of the normative weight of the materials used in construction and the total area of \u200b\u200bthe building.
Walls:
- From a bar - 600 kg / m3;
- From brick - 600-1200 kg / m3 (depending on which brick is used - monolithic or hollow);
- From aerated concrete and foam block - 400-900 kg / m3;
- From frame panels (up to 150 mm thick) - 20-30 kg/m3.
Roof:
- From slate - 60-80 kg / m2;
- From tin or sheet steel - 20-30 kg / m2;
Interfloor floors:
- Wooden - 70-100 kg / m2;
- Basement - 100-150 kg / m2;
- From a monolithic concrete slab - 500 kg / m2;
- From a hollow concrete slab - 350 kg / m2.
The average indicator of household load on the foundation is 100 kg / m2.
How to determine the atmospheric load on a building?
- h is the total height of the building (from the bottom point to the ridge);
- S - building area.
The load from snow depends on the climatic conditions of a particular region. Here are the averaged data for different areas:
- Chernozem region and southern regions - 50 kg per m2;
- Middle band - 100 kg/m2;
- Latitude from Arkhangelsk to Novgorod - 150 kg/m2;
- North of Arkhangelsk - 200 kg/m2;
- Siberia - 350 kg/m2.
We determine the number, diameter and required length of piles
When calculating the actual number of piles, the area and weight of the building must be taken into account. The minimum step between piles on ordinary soils of medium latitude should be at least 1.7.
The maximum step is determined by the type of building:
- For log houses or houses made of timber and frame buildings - 3 meters;
- For buildings made of aerated concrete, cinder block and foam block - 2.5 meters;
- For brick buildings - 2 m.
If the step is less than the norm, the foundation will lead, since the soil will not be able to evenly distribute the load coming from the piles, if the norm is exceeded, there is a high risk of foundation settlement under the weight of the house.
It is also necessary to take into account that one pile must be installed at each corner of the house and at the intersections of the walls.
Fig 1.7: Log house on a pile-screw foundation
The required bearing capacity of piles is determined by dividing the total mass of the building and the load from precipitation by the number of piles. Knowing what bearing capacity piles should have, it becomes possible to choose the appropriate diameter of screw structures.
For building foundations one-story frame houses, as a rule, screw piles of the 89th are used diameter, for houses made of timber and foam concrete - the 108th, and for one-story brick buildings - the 133rd.
Pile length is determined based on the characteristics of the construction site - the type of soil, the depth of its freezing and the height differences at the construction site.
According to the requirements of SNiP, a geological study must be carried out for this, however, at home, you can use an ordinary garden drill (you need to drill until you start to remove dense lumps of yellowish clay from the hole).
Fig 1.8: Correct location piles in the soil
It is also necessary to take into account the height differences at the construction site. It is possible that in order to ensure the same height of the heads, it is necessary to use piles of different lengths.
Preparatory work, materials, tools
To perform the installation of a pile-screw foundation with your own hands, you will need the following tools:
- Scrap and cuttings of metal pipes (50 mm in diameter, 2.5 m long), which will be used as levers for screwing the pile;
- Hose and magnetic level;
- Garden drill for creating guide holes, its diameter must be less than the diameter of the screwed piles;
- Shovel and trolley for removal of soil from the construction site;
- Bulgarian for trimming piles;
- Roulette and marker;
- Welding for fastening a metal grillage or heads.
Of the materials, in addition to the screw piles themselves and the grillage, you will need a wear-resistant primer for metal. Priming of metal piles provides their protection from the aggressive effects of groundwater. If this point is neglected, over time, the bearing capacity of piles will greatly decrease.
Preparatory work before starting work consists in clearing the construction site of vegetation and debris, after which all necessary tools and materials are delivered to the construction site.
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Fences on screw piles
In suburban construction, when installing fences summer cottages, forestries, farms and agricultural enterprises, laying a concrete foundation is usually not required. Pillars on screw piles are used as fence posts.
Do-it-yourself pile-screw foundation
The construction of a pile-screw foundation is carried out in the following sequence:
- The position of the piles is marked according to the design data. To mark the places of screwing the piles, reinforcing pegs or wooden bars are used, interconnected with twine. First of all, a "starting line" is created, which is one of the walls of the building, based on it, further marking is performed
Fig 1.9: Marking the place of screwing piles
- Next, the piles are primed in 2 layers, after the coating has dried, work begins on screwing them in. First of all, the installation of the corner pile is carried out at the highest point of the construction site, then - diagonal to it and the rest of the piles in the corners. A garden drill creates a guide hole at the place where the pile is screwed in, its depth should be half a meter less than the length of the pile.
Rice. 2.0
- A pile with a magnetic level fixed on it is placed in the well. Scrap is threaded into the holes on the pile, on the ends of which pipe trimmings are put on. Using a crowbar as a perpendicular lever, the pile is screwed, for this you need at least 2 people.
Figure 2.1: Screw pile screwing process
- After all the piles are immersed in the soil to the required depth, the trunks are trimmed. A hose level is used to determine the exact cutting height.
Rice. 2.2: Trimming the pile shaft with a grinder
- Concrete screw piles or not - it's up to you. If the diameter and length of the piles are chosen correctly, their bearing capacity will be enough even without concreting, in which case you will only incur unnecessary costs. If you still decide to concrete - to prepare a solution poured into the cavity of the pile, use cement of a class not lower than M300.
Rice. 2.3: Screw pile shaft concreting
- To create a grillage of a pile-screw foundation, I-beams or a channel can be used, in the construction of light frame houses - timber, for brick houses - a monolithic concrete grillage. If the grillage is metal, it must be primed to avoid corrosion in the future. The binding is carried out by welding the grillage to the pile shafts. To give the structure greater rigidity, reinforcing bars are welded to the junction of the grillage and piles.
Figure 2.4: Fastening the grillage from the channel to the shaft of the screw pile
Pile screw foundation video
For a better understanding of the technology of building a pile-screw foundation, check out the videos that explain the most important points construction.
Video #1- How to mark the places for screwing piles on a construction site
Video #2- We twist the screw piles with our own hands
Video #3- How to properly mark piles before cutting
Video #4- Features of the installation of a concrete grillage
Part 1
Part 2
Pile-screw foundation - prices
The cost of such a foundation depends on the number and size of piles used to create the foundation. For reference, here are the average prices for foundations of different sizes:
Foundation size | Number of piles | Cost (thousand rubles) |
Under a wooden bath 6 * 6 m. | 9 | 30 |
Under frame house 6*4 m. | 12 | 40 |
Under a log house 6 * 9 m. | 18 | 63 |
Under the house of foam blocks 6.5 * 6.5 m | 16 | 66 |
Under the brick house 8*8 m | 24 | 95 |
Pile-screw foundation reviews
We bring to your attention reviews of people with experience in self-construction of pile-screw foundations.
Oleg, 30 years old, Moscow:
"I recently completed the construction of a wooden bathhouse on a pile-screw foundation. All the work was done by myself, two friends helped. I can only say positive things about the foundation - it was not expensive, all the piles were twisted within two days. We were pleased with the pace of construction, because we had to wait for the concrete to harden strip foundation would take a very long time. I recommend!"
Dmitry, 35 years old, Zelenograd:
"I have been working in a company that has been building pile-screw foundations for 10 years already. They are ordered, as a rule, for light wooden and foam concrete houses, less often for brick ones. Among the advantages of such a foundation, I can single out the speed of arrangement and low cost. Among the disadvantages - the complexity of erecting with your own hands.If you want the pile-screw foundation to be reliable and durable, it is better to entrust its construction to specialists"
Reasons to contact us for a screw foundation
If, when reading this article, you have the impression that it is extremely difficult to equip a pile-screw foundation with your own hands, you are not far from the truth, in practice it is.
Firstly- direct construction should be preceded by detailed calculations, which can only be fully performed by specialists.
Secondly- how reliable the pile foundation will be, strongly depends on compliance with all the norms and rules of its construction technology, which, without proper experience, is simply impossible to take into account.
If you do not want to risk your money and time, and want to get a well-made screw pile foundation, contact construction company"Bogatyr".
We guarantee that:
- The foundation will be built in the shortest possible time - the mechanization of the workflow makes it possible to implement any project within several work shifts;
- Only high-quality materials will be used to create the foundation - we have been working with one manufacturer of piles for a long time, the quality of its products has been repeatedly tested in practice and does not raise any doubts;
- All calculations, from the analysis of the bearing capacity of the soil to the determination of the required pile size, will be carried out by the best designers.
"What about the prices?" - you ask? Our prices are more than reasonable. In Moscow and the region there is not a single construction company engaged in the construction of pile-screw foundations at prices lower than those offered by Bogatyr.
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The use of a foundation on screw piles in the shortest possible time and at a minimum of costs allows you to independently make a foundation for a bathhouse, a private house or a garage. Even a novice builder is able to handle the installation of piles in the form of steel screws. There are several types of such foundation supports with different bearing capacity; it is not difficult to select them for a specific building and soil.
What is a pile-screw foundation?
According to the constructive device, a screw pile is an iron pipe hollow inside, at the lower cone-shaped end of which drill blades are welded for screwing it into the ground. After immersion in the ground, these supporting pillars are connected with a grillage or the lower rows of a log house. As a result, each of the supports takes on part of the load from the building, distributing it throughout the pile field.
This is what the base looks like
The blade at the end of the tip from below, on the one hand, simplifies screwing the pipe into dense soil layers, and on the other hand, it plays the role of a holding anchor. In some cases, if necessary, such a support is simply twisted out of the ground and used in a new place for a new pile foundation. The main thing is that it does not rust by this time, being in the ground.
Types of screw foundation
According to the configuration and purpose of the blades, there are:
Wide-bladed - a typical variant with one blade in 1–1.5 passes.
Multi-blade - with several blades.
Narrow-bladed - with a tip in the form of a screw for 5-8 turns of the screw.
Various types depending on the soil
The first option is designed for light buildings and stable soils. The second type of screw piles is used when it is necessary to improve the bearing capacity of the support with compensation for its vertical movements, as well as for high and heavy cottages of 2-3 floors in terms of total weight.
The third variety is for foundations on soils with an abundance of stones. For permafrost conditions, it is also recommended to take a narrow-bladed analogue, only having not a pointed end, but an open cut with teeth along the perimeters.
The pile tip can be cast (VSL) or welded (SVS). The first one costs more. However, it is more durable and able to withstand heavy loads than the fatty counterpart. If the soils at the construction site are dense or the foundation needs to be made for a large house, then it is better to spend money and take it with a cast tip.
Pros and cons of foundation on piles
Benefits of using these bases include:
Durability and high bearing capacity - such piles withstand seasonal heaving without problems and serve 50–80 years;
Profitability - costs 20-30% cheaper than other options;
Lack of construction debris and large volumes of excavation;
High speed of construction - for an independent foundation of screw piles, two to three days are enough;
Ability to create on almost any type of soil;
Ease of implementation - do-it-yourself slab or strip foundation is much more difficult to do;
A large number of modifications of tips and heads;
Possibility of reuse;
The absence of seasonality of work as such - you can screw in screw supports even in winter, if only the soil allows it.
There are also disadvantages to the screw foundation, but they are much smaller and only worth mentioning:
The impossibility of arranging below under the floor ground floor or basement;
Additional costs for warming the house from below.
Considering the pros and cons, it is clearly seen that the advantages greatly prevail over the disadvantages. However, there is one big "BUT".
Electromechanical corrosion
The screw support must be made in accordance with standards and from high-quality steel. And after it, it is also mandatory to check in the Quality Control Department with the help of ultrasound or X-ray. The main problems for developers who have opted for a pile-screw foundation usually arise precisely because of defective materials.
Installation of a pile-screw base
The technology for arranging the foundation with your own hands from screw piles is as follows:
Control screwing is carried out to determine the strength of soils.
Calculations are carried out with the preparation of a plan for the placement of supports.
The area is marked.
The installation of supporting piles is carried out with their subsequent trimming according to the level.
Concrete is being poured inside the support.
The created pile field is tied up.
For each type and modification of a pile in the form of a screw, its bearing capacity is indicated in the passport. Both the size and configuration of the blades, as well as the wall thickness and barrel length, play a role here. Depending on the GWL, the depth of freezing and the composition of the soil, the layout of the pile field is calculated in each case separately.
When designing, it is also necessary to take into account the mass of the entire future structure, under which the foundation is laid on screw piles. Moreover, the calculation should include the weight of not only walls and ceilings, but also roofing and loads from snow with wind. After all, ondulin or membrane roofing weighs obviously less than slate or tiles. And all this must be foreseen in advance.
The stage of project preparation is best entrusted to a specialist. If you plan to make a screw foundation with your own hands, then the calculations should be carried out on the basis of SP 24.13330. Or you will have to install supports in larger quantities with a margin, increasing the construction estimate.
Step by step photo instruction
Marking the first support of the foundation according to the landmarks of the site
Markup shouldn't be a problem. You just need to mark on the site places for supports in accordance with the project. The main thing during construction is the strict vertical of the pillars screwed into the ground.
We dig a "pit" 20-30 cm deep for the first support
Insert into pit
We twist with the help of special levers (steel pipes)
To simplify the positioning of pile supports when they are immersed in the ground, you can use a drill or a shovel to dig a small pit half a meter deep. Further, the supports are screwed into the soil with a crowbar acting as a lever, a powerful electric drill with a gearbox or automotive special equipment. This is done in increments of 1-3 meters.
When the pile is strong enough, we hang the magnetic level and adjust the last part of the screwing according to the level - we level it with weight
The first is screwed exactly on the level
We mark the second - angular on the same side of the first
We dig a pit, put the second support, level it and check the distance from the first
When installing and screwing them in, it is extremely important to ensure that the supports do not go to the side. This immediately reduces the ability of the column to withstand the design loads. It is better to unscrew such piles and do it all over again. At the same time, it is strictly forbidden to put them on a new one in the same place. It will be necessary to shift this “screw” a little to the side.
When the support has risen to the desired distance, we twist it in the same way as the first
Similarly, by slopes, we adjust the distance between the pillars
After observing the distances - we twist the third
In the same way, we mark and twist the fourth, observing the dimensions along the diagonal and side
We stretch the twine around the entire perimeter and mark intermediate supports with a marker on the twine
We install each support in the pits according to the marks and level and ram it with earth
After spinning all the pillars, we mark the same marks with a hydraulic level
We cut all the supports according to the level with a grinder
We fill the pile with cement-sand mortar up to 10 cm of the level to the end
We fill the rest with ready-made dry cement-sand mixture
After the piles are installed in their place, they are cut at the right level from the ground. Then these supports, of which the considered version of the foundation consists, are recommended to be poured from the inside with concrete. This allows you to protect the metal from corrosion and further strengthens the entire pile helical field.
On top of each installed pole, a head is welded in the form of a square steel plate measuring about 25 x 25 cm. And at the end, all welds are treated with protective compounds. Further on this pile foundation, you can already lay the grillage or immediately the crowns of the log house.
So that the wind does not walk under the house and does not cool it down, the pillars must be closed with an outer lining around the entire perimeter of the building. For this, corrugated board is perfect either. But you can also use facing bricks. All at the choice of the owner of the cottage.
Application of the foundation on screw piles
For the construction of a screw foundation made of iron piles, a team of 5–7 people often takes one day. At the same time, it is not necessary to wait for precipitation or setting of concrete. Such a base is completely ready for the further construction of the building. This is a strip or monolithic foundation with a slab that must withstand at least 20–30 days. With screw supports, the stage of arranging supports under the house takes much less time.
House from SIP-Panels
If you managed to buy a wonderful plot at a surprisingly low price, do not rush to rejoice - it is quite possible that the groundwater on the purchased plot comes close to the surface, or you got heaving soil. These factors can lead to the fact that the construction of the foundation will take much more money than expected. In addition, you still need to choose the right type of foundation so that uneven settlement of the house does not occur in the spring.
What is a pile-screw foundation
The best option in such cases is a foundation on screw piles, suitable for any terrain and for any "problem" soils.
The pile screw foundation has been successfully used in construction since 1850, when the first lighthouse on piles was built in the United States. The fact that the lighthouse is still standing today confirms the high strength of the screw foundation and explains why this technology has gained such popularity around the world in a relatively short time.
Installation of the foundation on screw piles is possible on any terrain
The peculiarity of the screw pile is that this steel pipe has a pointed tip with a thread and blades or a combined thread for screwing into the ground. The most expensive are screw piles equipped with blades, but they also compact the soil better due to their design. There is no specific standard for screw piles. They are solid and hollow, of various diameters and lengths, with a cap in the upper part of the tube of a rectangular, round or U-shaped shape.
Video about the foundation on screw piles
Installation of the foundation on screw piles is possible on any terrain: on uneven or flooded areas, on slopes, on peat soils, on well-groomed lawns without the risk of harming the lawn, next to large trees. Thus, there is no need to carry out any preliminary work on clearing the site and leveling it, and there is no need to disturb the natural relief.
Benefits of a screw foundation :
- there is no need for earthworks;
- no need to provide access roads for equipment;
- installation can be carried out in winter;
- three people are enough to build the foundation;
- all foundation works take from one to three days;
- you can always easily attach a new structure to a house built on stilts.
All foundation works take from one to three days
Piles can be screwed into the ground, both with the help of special equipment, and manually - the pillars make their own way in the soil to a given depth. If necessary, the screw foundation can be quickly dismantled (if the hollow pillars are not filled with concrete) and moved to another location. Thanks to the listed advantages, the foundation on screw piles invariably deserves the best reviews and is successfully used in industrial and private construction.
How to deal with a screw foundation on your own
Screw piles under the foundation must cut into solid layers of soil that lie lower than the soil freezes through, in which case the pillars will not be subjected to the force of heaving of the soil. To correctly determine at what depth a stable layer of soil is, it is best to contact a specialist. In addition, for the correct calculation of the future foundation, you will need to take into account the weight of the future structure, seasonal fluctuations in groundwater, soil type, wind load and climatic features of your region. It's not easy to figure this out on your own.
The number of piles is determined depending on the dimensions of the building under construction. The pillars will need to be evenly distributed under the base of the building with the same pitch, not forgetting about the nodes of the internal walls and about the corners. The length of the ground part is usually about half a meter, the visible part of the piles can be hidden behind a false plinth or left open.
The number of piles is determined depending on the dimensions of the building under construction
The construction of the screw foundation is carried out as follows:
- markings are applied to the site with pegs exactly in the places where the piles will be located;
- piles are twisted using a special rod manually, while using a level, their even position is checked;
- the installed piles are aligned to one level with a laser level, the longest pillars are cut by a grinder;
- concrete is poured into the cavity of the pipes in order to protect the internal surfaces of the piles from corrosion;
- outside, the ground parts of the pillars are recommended to be coated with an anti-corrosion compound;
- a metal frame is welded to the supports and painted in two layers with protective paint.
Video about the screw foundation
Insulation of the foundation on screw piles is not required, since this type of foundation is ventilated. High supports protect the house from the cold that comes from the ground. You can insulate the grillage, but keep in mind that improper thermal insulation will lead to dampness, which will negatively affect the entire structure. To make the house warmer, it is better to pay attention to the insulation of the floor, and not the screw foundation.
If you come across reviews about the pile screw foundation that are not too positive, this means that some mistakes were made during the construction of the foundation (pits for the pillars were dug out, the position of the pile was not controlled during twisting, the pipes were not protected from corrosion, etc.) . But even if, due to improper installation, the building sank a little, it is always possible to repair the foundation with screw piles, replacing the sagging pillars with new ones. The ability to quickly repair is another great advantage of a screw foundation.
The construction of any building begins with the foundation. It is very important to choose its type correctly, since the estimate for this type of work can reach 30% of the cost of the entire object. In addition, everything is complicated by the fact that during operation, access to these structures is limited, and inspection or repair becomes a rather costly undertaking. The article will focus on the device pile screw foundation.
Foundation types
The most commonly used structures are of three types:
- tape;
- slab;
- pile.
Piles allow significant savings compared to others and can perform their functions on soils with poor characteristics. They, in turn, are divided into:
- bored, made of monolithic reinforced concrete directly on the construction site;
- driven, installed in the design position using a special installation;
- screw, metal piles, immersed in the ground by screwing.
Driven piles were used quite often a couple of decades ago. If construction was going on in the area of a kilometer, one could hear strong pops that arose during the impact of a heavy load on a pile. This method has limited application, for example, it cannot be used in dense building conditions, since the work will have a destructive effect on neighboring buildings. They are also not suitable for a small building.
For the construction of individual houses, it is rational to use bored or screw piles. In the first case, it is necessary to install a reinforcing cage in the casing pipe and pour everything with concrete. A screw foundation is much easier to mount and in most cases cheaper.
What are screw piles
- This type is a long metal pipe with a screw at the end. The pipe has rather thick walls. The propeller blades allow the foundation to swirl into the ground and catch on there. In this case, the screw prevents the structure from being pulled out of the ground and preventing the building from moving.
- During installation, the pile is rotated with pressure. In this case, you can use special installations or physical force. The more often the blades are placed, the better the traction will be.
- The diameter of the pipes is usually in the range of 90-140 mm, the wall thickness is taken at least 4 mm. If there is a need to install products with a diameter of more than 140 mm, they must be made to order.
Types of screw piles
There are two varieties depending on the type of construction:
- cast tip;
- weld tip.
Piles with a cast tip
- Such piles are a one-piece structure consisting of a pipe and a screw tip. They are made in special shapes according to standard sizes. They are more expensive, but due to the integrity of the structure, they have increased strength and long term services. The cast structure is completely made of steel, which provides the foundation with high reliability. This pile screw foundation receives only positive feedback.
Piles with a welded tip
- This is a metal pipe, pointed at the bottom. Blades are welded onto the sharp end, which are made by cutting metal. The tip is treated with anti-corrosion compounds.
- The diameter of the pipe used may vary. This method of manufacture allows the use of products of sufficiently large diameter. There are several types of blades:
- single blades;
- double blades.
- The double screw prevents misalignment and ensures maximum structural stability.
Scope of pile screw foundation
Foundations are selected based on the geology of the site. Soil features that force the use of screw piles are as follows:
- weak soils (bulk, marshy);
- high groundwater level;
- swampiness of the territory;
- location of the construction site in the water;
- a large degree of uneven terrain.
In all these cases, the use of a concrete foundation is undesirable, since it will not be able to provide a reliable foundation for the house. In addition, serious waterproofing will be required to protect the material from moisture penetration, since concrete is still a more porous material than steel.
Screw piles become an ideal solution for such types of construction as:
- low-rise individual housing construction;
- small buildings requiring short construction times;
- strengthening of slopes and slopes;
- towers for power lines;
- supports for lampposts and billboards.
Products can be used in the construction of a private house from timber, logs or frame housing construction.
Advantages and disadvantages of a pile screw foundation
Screw piles are now quite widely used in the construction of private houses, but before choosing a house on a pile screw foundation, it is necessary to study their positive and negative sides. The pluses include:
- strength due to the use of steel as a raw material;
- durability, the service life of such a base can reach 150 years, subject to the manufacturing and installation technology;
- low cost of the product itself and its installation;
- simplicity and high speed of installation;
- the ability to use on terrain with difficult terrain, for example, on slopes;
- ensuring reliable operation on poor soils, such as sedimentary rocks, swampy areas;
- possibility of reuse if necessary.
Simplicity and speed of installation are possible due to the fact that:
- lack of preliminary development of the soil (digging trenches or pits);
- there is no need for complex special equipment;
- the simplicity of the technology does not require special skills and knowledge;
- unlike concrete foundations, it is not required to wait 4 weeks until the structure is ready.
All these positive characteristics allowed screw piles to become widespread, but do not forget about the negative aspects. Especially if you can prevent their consequences in time.
Pile screw foundation video
Pile screw foundation cons:
- corrosion of metal;
- limited bearing capacity;
- the inability to install close to the walls of an existing building;
- the impossibility of arranging the basement in the house.
Corrosion can be avoided by treating the material with special compounds. With individual construction, there are no large loads on the foundation, so the second point does not become significant. With an impressive list of advantages and a small number of shortcomings, which are rather features of operation and are completely preventable, screw piles become an excellent support option for a private house.
Pile screw foundation calculations
Basically, calculations are made to determine the diameter, length and pitch of the piles. These values are influenced by the type of soil and the weight of the structures of the future house.
- Soil type can be determined using geological surveys. With individual construction, they do it easier: a hole is dug, about 50 cm deep, and the soil is analyzed. If layers with sufficient strength have already begun at this depth, a pile length of about 2.5 m can be used.
- If on the site there are lenses of poor soil, quicksand, or it was not possible to reach a layer of soil with good characteristics, it is better to take a length with a margin to prevent possible problems. On rather poor grounds, the required length can reach 3-4 m.
- For private construction, piles with a diameter of 108 mm are most often used. The calculation of the pile pitch depends on their required number. Here there is a need to collect loads from home.
- In order to calculate all the loads, it is necessary to determine the materials used, the dimensions of the building and the main dimensions of the load-bearing elements. The load is calculated based on:
- floors together with the floor structure;
- walls with decoration;
- partitions;
- roofs, taking into account the roofing;
- snow cover, which depends on the area of construction;
- furniture and equipment, for residential buildings 150 kg per square meter of the total building area is accepted.
- To find these values, you need to calculate the planned volume and multiply it by the density of the materials used. To ensure the margin, it is allowed not to subtract window and door openings from the volume of the walls. The found value is multiplied by 20-30%, which will provide a safety margin for the load.
- Depending on the characteristics of the base, a screw pile with a diameter of 108 mm can withstand from 4 to 9 tons. The number obtained in the collection of loads is divided by the value of the bearing capacity (in case of doubt about the characteristics of the soil, it is better to take the minimum value) and find the required number of products for the foundation of the house. Further, this amount is evenly distributed around the perimeter of the building.
Pile screw foundation technology
Screwing piles can be carried out with special equipment or manually. Regardless of the method chosen, the base is first prepared. Preparation works are carried out in the following order:
- choice of starting point;
- removal of the location of piles on the ground;
- twine marking.
The work is carried out with great care, the dimensions must match to the millimeter. Otherwise, there will be problems with the grillage device and the normal distribution of loads.
Screwing with special equipment
- Such work is best left to professionals. The installation process is carried out using a heavy-duty machine equipped with a special installation. First, the equipment is brought to a predetermined position and fixed with outriggers, after which the accuracy of the location is checked and the screwing process begins. The machine moves to the next position. The method allows you to complete the work in the shortest possible time.
Screwing by hand
When building a foundation on your own, it is difficult to rent special equipment and master it, so the most competent solution would be to use physical strength. Screwing piles with your own hands requires the following tools:
- shovel for leveling the surface;
- building level to maintain the accuracy of work;
- measuring tape;
- scrap metal with two pipes with a diameter of 50 mm as a lever for screwing;
- hammer or small sledgehammer;
- garden drill;
- grinder for cutting the top of the pile;
- gloves and overalls.
A garden drill is used with a smaller diameter than the selected piles.
Stages of work
- Drilling holes with a smaller diameter than piles using a garden drill. The depth must be shorter than the length of the pile. The hole in this case serves as a guide and ensures the accuracy of the installation. Screwing starts from the corners;
- installing a pile in a hole, attaching a level to it and threading a crowbar that will serve as a lever;
- the screwing process is carried out under constant control of the vertical. That's what the level is for. Several people put pressure on the levers, but unevenly, so the pipe can move away from the design position;
- as they go deeper into the ground, pipes are put on the scrap, thereby increasing the lever arm, which allows you to apply less effort;
- after screwing in one corner, go to the other;
- after completing the work at the corners and checking the accuracy of the installation, they proceed to screwing the intermediate pipes;
- cutting metal pipes to obtain one level;
- device for trimming piles grillage.
The grillage for this type of foundation depends on the material of the house and can be made of:
- timber;
- glued board;
- metal corner;
- metal channel;
- tee beam;
- in a house made of timber or logs, the first row of wall fencing can become the strapping.
The arrangement of the grillage is necessary for the coordinated work of individual piles. Thanks to the strapping, even if one of the pipes fails, the house will continue to stand firmly.
- The pile will not enter the ground strictly vertically, it will need to be constantly leveled and returned to the design position, therefore it is better that at least three people carry out the work: two act on the lever and one checks the accuracy. To prevent it from shifting, special devices are sometimes used to fix it.
- If, as the pile is screwed, an obstacle or a layer of dense soil is found in the path of the pile, the penetration depth and location are analyzed. If it is not located at the corners of the house and it turned out to enter it into the ground for a meter or more, it is allowed to simply cut off the top and leave everything as it is. With a depth of less than a meter, there is the possibility of warping the house. At the corners, the piles must be installed to their full length, as these are the most critical areas.
- The final stage of installation may be concreting. It will provide additional reliability, but this process is optional in the case of screw foundations.
The cost of a pile screw foundation
- The total price of a pile screw foundation depends on the dimensions of the building. The most common piles of 108 diameters can be purchased at a price of 1900-3000 rubles. per set depending on the required length. The cost of installing such a pile is approximately 2000 rubles. When installing with your own hands, you will need to add the price of tools to the total cost. It turns out that for screwing one pile you will have to pay from 1900 to 5000 rubles, depending on the installation method.
- You also need to consider the cost of the grillage, if any. For example, we can give the price of a turnkey pile foundation for a house measuring 6 by 6 m. good performance soil, it will be less than 30,000 rubles. If the question is how much does a pile screw foundation cost, then for example, we can give a calculation for a building measuring 10 by 10 m, in this case it will be from 70,000 rubles, a pile field of 12 by 12 m will cost about the same.
Screw piles are an excellent solution for the construction of light private houses, they will allow you to get a reliable and solid foundation for a small building in the shortest possible time at low cost. The ability to choose the design and installation method gives them another advantage over other types of foundations. However, it is important to remember that such supports are not suitable for a heavy brick or stone house, since their bearing capacity is insufficient to withstand such loads.