we know interesting facts about pile-screw foundations and dispel several myths about this technology.

There are several opinions about pile-screw foundations. Some consider this option ideal for relatively light frame houses and log houses, while others criticize it, citing their own arguments. Let's together understand the myths that exist about foundations on screw piles.

Pile-screw foundation

Myth one: a pile-screw foundation is unreliable

In fact, there are reviews from homeowners that a house built on screw piles wobbles, sways, and the piles themselves begin to protrude. So, unreliability is not a myth at all, but the pure truth? Not really. If problems arise with a house built on a pile-screw foundation, it means the construction technology was violated! We wrote about what the optimal size of screw piles should be. In addition, the reasons for instability of the house may be:

• Insufficient depth of piles;
• The diameter of the piles is not large enough;
• Excessively deep pit;
• Small number of piles;
• Weak-bearing, too soft soil;
• Errors in calculating the load on piles.

If all technologies were followed, calculations were made accurately, and installation was carried out by professionals, there will be no problems with the pile-screw foundation! In this case, it will be possible to say for sure that the unreliability of such a foundation is a myth.

Myth two: a pile foundation can be erected in just a day

Of course, installing screw piles is much faster than pouring a concrete foundation. However, this is not to say that you can cope in just a day! This is not always the case. Firstly, professionals always carry out test drilling and test screwing. This is necessary to find out the characteristics of the soil.

It may be weak-bearing, too hard or rocky. The presence of stones in the soil will seriously complicate the screwing of screw piles, and in some areas the soil can be so strong that even metal will not withstand. In addition, sometimes it is impossible to use a drill and other special equipment on the site. In this case, the construction time for the foundation is also delayed.

Myth three: screw piles will rust within 10 years, the house will not last long

Experts say that a correctly selected screw pile will last at least 50 years. Service life depends on the following parameters:

• steel grades;
• metal thickness;
• quality of metal protection - painting, galvanizing, anodizing;
• soil aggressiveness.

In saline and acidic soils, metal rusts faster. In addition, special paint should be used to protect it and an anti-corrosion coating should be provided. You should not use cheap compounds.

Myth four: during installation, the blades of the pile may break off, causing it to sag

This can only happen in two cases - low-quality screw piles were initially selected and the installation technology was violated. If the soil is strong, rocky, and the installation was carried out harshly, then, of course, the blades can be broken. However, if you choose high-quality piles and do everything according to the rules, there will be no problems.

Myth five: you can install a pile-screw foundation only in the warm season

Not true! In winter, the soil, of course, freezes, but a small top layer can be removed using a chipper and you can easily install piles. Experts say that in winter it is often even easier to work, and no potato beds interfere with the plot.

Myth six: screw piles are a new technology, not yet proven by time

In fact, pile foundation construction has been known since ancient times. True, then the piles were driven into the ground. In 1833, Irish civil engineer Alexander Mitchell patented a device called the "screw pile". Unlike conventional piles, screw piles are screwed into the soil. Initially, such piles were used for the construction of piers and lighthouses, then the scope of application expanded significantly.

In Russia, screw piles have been known since the beginning of the last century, in particular, they were widely used in the field of military construction, in permafrost conditions. That is, we are not talking about any new product!

Research in the field of application of screw piles has been carried out more than once, including in the USSR, the advantages of this technology have been proven by specialists. True, screw piles began to be used in Russian low-rise residential construction later; previously they were considered the prerogative of the construction of industrial and military facilities.

Myth seven: all screw piles are the same, they differ only in price

Absolutely false. Piles differ not only in quality, size, metal thickness, and the presence of corrosion protection, but also in their scope of use. For example, there are piles created specifically for heaving, waterlogged or permafrost soils. In addition, they can be cast or welded. So you should choose based on your needs, preferably in consultation with specialists.

Myth eight: you can screw in screw piles without a pit

Professionals consider this a violation of installation technology, recommending that a small pit be made. This is due to the fact that the top layer of soil is usually the loosest, and the blades of the pile at the first stage loosen the soil until they reach denser layers. Often, without a pit it is completely impossible to screw in a bladed pile. In addition, concrete can be poured into the pit to strengthen the structure.

Myth nine: screw piles are ideal for building a house on a slope

Yes, this option occurs quite often. However, a house on a slope can also stand on other types of foundations; before choosing a foundation, it is important to conduct geological surveys. A pile foundation may be the simplest choice in this case, but it is by no means ideal.

Myth tenth: the floor of a house on a pile-screw foundation will be cold

This myth is connected with the fact that cold air will circulate under a house standing on stilts. However, if the floor is reliably insulated, the problem can be easily solved. And ventilation, by the way, will prevent the floors from starting to rot.published

If you have any questions on this topic, ask them to the experts and readers of our project.

The use of modern technologies in construction has made it possible to significantly reduce money and power costs. One of these technologies is the construction of a house on screw piles, which provide high reliability and strength to structures, regardless of the type of soil.

Houses on screw piles:

The important advantages of building a house on stilts include:

• Speed ​​of foundation construction (up to thirty piles can be installed per day);
• Low cost (the price of a pile foundation is 40-50% lower than a strip foundation);
• Durability (the service life of such a structure ranges from 100 to 150 years) is ensured by concreting the pile cavities and treating them with an anti-corrosion coating.

Technology for building a house on stilts in flooded areas

Foundation on stilts for a house– the best option if you want to build a reliable structure in the shortest possible time, regardless of the landscape. It is suitable for areas with various uneven areas, with the exception of rocky areas.

They can be installed in flooded areas (ponds, lakes and reservoirs), using long piles, and the structure is called a house on high piles. In such cases, the piles are driven to a sufficient depth until they are firmly planted in the ground. Their upper ends are cut to the required height above the water level and connected to each other with channels and reinforcing rods, which are secured with bolts. Thanks to the pile foundation, it became possible to build unique projects of private houses on stilts located on the banks of rivers and lakes.

Additional buildings on a pile foundation

Pile foundations are also used for the construction of additional buildings to existing buildings. These include bathhouses, outbuildings, verandas and other structures. The main advantage of such a foundation for the construction of additional buildings is that it does not require extensive excavation work and the use of heavy special equipment.

You can carry out construction on a pile foundation on your own, but before building a house on stilts you need to carry out certain engineering calculations, which only professionals can do.

The Ecofoundation company offers comprehensive services for the design and construction of foundations on screw piles. Our specialists will help you make accurate calculations of the pile field, in accordance with the chosen type of house, they will tell you which screw piles to buy (thickness, length), their quantity, connection method and other details necessary for the reliability and durability of the future structure.

Leave a request and receive a free estimate.

Until recently, pile foundations were almost never used in individual construction, with the exception of regions with difficult climates and soils. The pile foundation for a house gained its popularity simultaneously with frame construction technology. It was the companies that produce light-weight houses suitable for year-round living that first began to use them quite widely.

Example of a finished pile foundation

They were looking for a way to reduce construction costs without sacrificing quality, and the solution turned out to be replacing the traditional strip foundation with a pile foundation.

It is not always possible to directly support building foundation structures on the underlying soil layer. Depending on the conditions, the soil may be unsuitable for this, having low or insufficient bearing capacity, unstable nature of its occurrence, being located in the permafrost zone, etc.

In such cases, pile foundations are designed and installed, which makes it possible to transfer the load from the building to the underlying, stronger and denser layers of soil with predictable characteristics.

Project of a pile foundation on unstable ground

Pile foundations are widely used in construction, so a huge number of options have been developed that take into account almost any construction conditions and offer a variety of solutions, both taking into account technological capabilities and economic aspects.

Today, foundations on piles are one of the most popular in the private and commercial construction market. Since in terms of its price indicators it turns out to be much more profitable than classical solutions, and in terms of its technical characteristics and service life it even surpasses traditional foundations.

In most Russian regions, pile foundations are used for building houses on soft soils. These will be peat bogs and marshy soils. By the way, it will also be where the groundwater level is quite high.

Pile foundation installation diagram

A slab or shallow strip foundation will be ineffective on such land, since the top layer of soil simply cannot withstand the heavy load.

The design and construction of pile foundations is regulated not only by Building Codes and Rules, in particular SNiP 2.02.03-85, but also by other regulatory documents, which include, for example "Guide to the design of pile foundations". It sets out all the recommended solutions used for the construction of this type of foundation, defines the parameters of the necessary survey work, methods for performing design and types of calculation and design work carried out.

The issues of calculating piles based on bearing capacity, calculating pile foundations and foundations based on deformations, and general issues of designing pile foundations are considered.

Ready-made pile foundation project

The features of design in specific conditions, such as subsidence soils, swelling soils, undermined areas or seismic areas, are separately highlighted.

A pile foundation is a more complex system than just a set of piles, therefore, for qualified calculations of other elements, other materials recommended for use are also used, for example, “Manual for the design of reinforced concrete grillages for pile foundations.”

The use of normative literature allows us to ensure high quality of design work and informed adoption of economic decisions without compromising the safety and durability of buildings and structures.

This is what piles are used for. Vertical structures are lowered to a sufficient depth into the ground and transfer the load to denser layers of soil that are located below. The price of such a foundation is lower than that of classic types of foundations with excavation.

Also, installing a pile foundation will be the optimal solution in permafrost areas and where there are mobile soils.


It is also better to place a holiday house on the bank of a river or near a reservoir on a pile foundation. When using high-quality waterproofing, the structure will last much longer than other types of foundations.

Types of piles used

Pile foundations differ in several ways. A certain type is suitable for use in specific conditions. The cost of arranging the foundation, which includes the required building materials and the work of specialized equipment, also depends on this.

By materials used

Piles can be made from various materials. For foundations for various buildings and structures, piles made of wood, metal, concrete and reinforced concrete, as well as combined types of piles, are used.

The latter type is considered one of the most reliable, since different materials are subject to corrosion in different ways, and as a result, they retain their original appearance longer and perform basic functions.

By immersion method

The first and main difference between piles is the use of completely finished units that are lowered into the ground and piles that require fabrication on site.
The first type includes driven, drilled and screw piles. To the second -

bored and combined.

Driven and drilled piles are more often used in the construction of foundations in multi-story construction. They are very voluminous concrete or reinforced concrete beams. The price of the structures themselves is quite high, and their installation requires large construction equipment.

Renting special vehicles for individual construction will cost a pretty penny.

All piles are divided into two main types:

1. Post piles that penetrate soft and unstable layers of soil and ultimately rest on solid rock.
2. Piles that remain “hanging” in the ground. Such piles are used when hard rock is at an unattainable depth or simply does not exist, for example, in permafrost conditions, or in swamps and peat bogs.

In the first case, the entire load-bearing load transferred from the building to the foundation is transferred to the solid layers of rock, and the building, it turns out, has reliable support underneath it.

In the second case, a different principle applies. The load is distributed evenly across all piles, and the piles are held in the ground due to the frictional force between the surfaces of the pile and the ground. Both have proven themselves well and are used in construction on equal terms.

Read also

Constructions and foundation construction for a private house

Types of pile foundations

A pile foundation is a field of individual piles. Their number, the distance between the piles, the method of distribution and tying are calculated individually for each house project. On top, each pile may have a small platform or exposed reinforcement. This is necessary for subsequent installation of the harness.

Foundation on screw piles

Screw piles are the undisputed leader in the field of private construction. Most frame projects are based on a foundation on screw piles. The pile is a metal pipe, pointed at the bottom and with a welded helical blade.

In fact, this is nothing more than a large self-tapping screw, only without a head. Such a pile is simply screwed into the ground. For this, construction equipment can be used, or it is possible to equip a pile foundation with your own hands. One of the most budget and labor-intensive technologies.

Ready foundation on screw piles

Screw piles can be combined. If the classic screw pile is a hollow metal pipe, then the combined one involves filling the void with concrete or reinforced concrete mortar.
The advantages of a foundation on screw piles include its low cost, the possibility of installation without the use of heavy equipment, and use in permafrost conditions and on swampy soils.

The disadvantages of such a foundation are its fragility; according to reviews, it can last about 70 years. Another drawback is that a foundation on screw piles without a grillage can only support lightweight structures, such as wooden or frame houses. For stone, brick or block buildings, it is better to use other, more durable foundations.

Foundation on bored piles

Bored piles are a type of piles that are manufactured on site using concrete or reinforced concrete mortar and reinforcement. To begin with, wells are drilled on the construction field, marked according to the drawing. Vertical shafts are reinforced with reinforcement and then filled with mortar.

Depending on the type of soil on which the foundation is installed on bored piles, various casing materials can be used.

For example, in the case of loose and sandy soils, a special hollow pipe can be lowered into the shaft. The technology allows the wall to be insulated with roofing felt, roofing felt, or polyethylene film. Depending on the material used, after pouring the casing can be removed, or it can be left in the shaft, performing the function of waterproofing.

Installation of bored piles

Piles made according to the latest scheme, using casing and insulating materials, last longer than simple bored piles.

The advantages of such a foundation are ease of installation. One of the types of bored foundation is columnar. Such a foundation can be built without the use of special equipment. Dig or drill holes for the piles by hand, make your own mortar and fill the base.

Another advantage is the ability to place the house even in a place difficult to reach for equipment, almost right next to other buildings.

However, such a foundation will be short-lived and less strong. Without special waterproofing, cast-in-place piles are destroyed quite quickly. The disadvantages include the impossibility of their operation in regions where horizontal ground movements are observed.

Scheme for constructing a bored pile foundation

Types of harness used

The piles themselves are simply pillars or posts. In order for them to turn into a full-fledged foundation, it is necessary to tie the pile foundation. The pile-grillage foundation is superior in its characteristics to strip and monolithic slab foundations. It is considered more resistant to any soil movements. Depending on the weight of the structure, various solutions are used.

Piles-columns

The simplest type of pile is a column pile, which is used as a foundation for a fence or a light summer house. It will also be a continuation and basis of the structure, which will be mounted around the pile. In this case, no strapping is required.

Timber strapping

Most often used when arranging a pile-screw foundation for the construction of a light frame or log house.


In this case, the function of the grillage is performed by the 200th larch beam. If you are making a pile foundation with your own hands, then the timber should be laid on special platforms with which each pile is equipped, and securely fastened with bolts and ties. The junction points of two strapping elements are formed with a groove.

Metal harness

A grillage on a pile-screw foundation can be made of a profile, channel or corner. In this case, installation occurs using welding.

Fastening with bolts is also possible if the pile-grillage foundation initially provides for such a design. To do this, each pile must be equipped with a small platform with holes for two or four bolts, as well as the strapping included in the kit.

An example of tying a pile-grillage foundation

In this case, the pile field must be installed with the minimum permissible error, otherwise the arrangement of the grillage will become impossible.

Monolithic grillage

A pile-grillage foundation is a hybrid of a pile foundation and a classic strip or slab foundation. In cases where special structural rigidity is required, the following scheme is used: formwork is assembled on top of the piles and a monolithic grillage is made in the form of a slab or strip.

This design is best combined with bored piles. In this case, the reinforcing elements of each pile are brought up and become the basis of the grillage. In this case, additional reinforcement of the grillage is also necessary.

Stages of work when constructing pile foundations

Entrust it to specialists or build a pile foundation yourself - both options are possible. The work can be carried out either using construction equipment, or using an electric or manual hole drill, or even digging the shafts manually.

Land surveys

The construction of pile foundations occurs on fairly complex soils. To avoid design errors and calculate the settlement of a pile foundation, it is advisable to order land surveys. Several drilled information shafts and a detailed analysis by a specialist, which will be presented in the form of official documents - soil maps, will allow you to make an accurate calculation and determine the optimal depth of the shafts for the piles.

If you order a pile foundation without geological exploration, there is a risk of making piles of insufficient length.

Diagram of a pile foundation

The second problem that you may encounter is running into rock in one of the sections of the pile field, which will not allow you to screw in the piles to the required depth.

Design

The construction of pile foundations involves not only the process of physical work, but also includes a mandatory paperwork period. During the design of pile foundations, calculations are made that allow us to determine the size of the pile field, the depth of the shafts and their number, and the distance between the piles.

Lighter structures allow the piles to be placed in the foundation at a distance of 2.5 meters from each other. Calculation of the foundation for heavy structures and on difficult soil requires an increase in frequency - the distance can be reduced to 1 meter. Also, piles can be lowered into the ground not vertically, but at a certain angle, which strengthens the structure.

The problems of creating a strong and reliable foundation for capital buildings on very wet or regularly flooded soils have led to searches and experiments on the use of pile-screw foundations in private housing construction. Before this, buildings were built on stacked and cast supports.

As a result of numerous tests, in the middle of the 19th century, a technique for constructing pile-screw foundations emerged, making it possible to build houses in conditions where ordinary stone could not withstand more than one season.

What is the support of a pile-screw foundation?

The system of building buildings on a pile-screw foundation has been known for more than a thousand years, and all this time the widespread dissemination of successful technology has been hampered by the enormous labor intensity of installing piles. Today, more than half of light and medium-sized buildings are built on a pile-screw foundation.

The construction of a pile-screw foundation is somewhat different from the classical construction on piles, primarily due to the special design of the support. The basis of the foundation is a field or array of screw piles, and it is in them that the secret of popularity lies.

The screw pile can be divided into three main parts:

• Housing in the form of a pipe made of alloy or stainless steel, coated with a protective varnish;
• The head of the screw pile, to which the piping parts of the pile-screw foundation are attached;
• Blades or working auger mounted at the base of the support.

Important! All support parts for a screw-pile foundation are made from rolled stock and stamped units using conventional welding, which provides a simple technology for manufacturing a screw pile and the possibility of ongoing quality control of the connection of all its elements.

The design of a screw pile for the foundation is shown in the diagram.

The design of the screw-pile support is based on the main principle that ensures high quality foundations. This is the principle of screwing a support into the ground. At first glance, nothing significant; what difference does it make whether to hammer, wrap or cast a pile support? In a real situation there is a difference, and quite significant.

For example, reinforced concrete piles driven with a hammer or driven into the ground with a vibropress remain in a compressed, deformed state. According to experts, 15% of driven piles have problems after installation due to a large number of cracks and peeling of reinforcement. The picture is the same with cast bored piles; due to unfavorable conditions, the quality of the reinforced concrete is far from the design value. Therefore, driven or cast piles are often pushed out by heaving forces, which practically does not happen when assembling a house on a pile-screw foundation.

There are three specific features of deepening the supports of a pile-screw foundation:

• The screw pile is screwed into the ground with minimal pressure on the body or tip, that is, after installation, the support of the screw-pile foundation is not weakened, does not become cracked, and is not in a complexly deformed state;
• The support is immersed to a given depth with an accuracy of several centimeters, as a result there is no risk of failure or not receiving the calculated load resistance from the weight of the building;
• If necessary, the screw support can be replaced with a similar one at minimal cost. It is enough to unscrew the housing and repeat the deepening.

It cannot be said that replacing the screw support of a pile-screw foundation is a simple and ordinary matter, but it is technically possible and is carried out under the guidance of specialists. It’s another matter if the foundation is driven out of reinforced concrete piles or bored pillars. In this case, failure of the pile can threaten the foundation with major problems.

The steel support of the pile-screw foundation is screwed into the ground carefully and securely. If we use an analogy, we can compare driven and screw supports with a screw and a nail - the difference in the ability to withstand axial load is about the same. Therefore, a pile-screw foundation is often called a geoscrew foundation.

Features of the screw pile device

Structurally, the supports of a screw-pile foundation are divided according to the type of screw tip and pipe, or pile body, therefore, two diameters are indicated in the marking of the pile: the first is the size of the pipe, the second is the diameter of the auger or tip in millimeters. For example, SV-89-250, the outer pipe size is 89 mm, the diameter described by the cutting edge of the blades is 250 mm.

Characteristics of the screw-pile support body

For the construction of private buildings, four main pipe sizes are used:

• 89 mm and 76 mm - a group for the construction of particularly light and lightweight buildings for the foundations of fences, gazebos, verandas and fences;
• 108 mm and 133 mm - group for the manufacture of foundations for medium and relatively heavy buildings. The first type includes country houses made of timber, frame-panel and panel construction. Heavy buildings include houses made of foam concrete and buildings made of rounded logs.

The most important characteristics of pile-screw foundation supports are the wall thickness and the corrosion resistance of the material. For piles made by the traditional welded method, the wall thickness rarely exceeds 5-6 mm, so the maximum load is no more than one ton. Welded piles are used for unimportant and unloaded objects. For full-fledged residential buildings made of gas and foam concrete, cast tubular buildings with a wall thickness of up to 12 mm are used. With a diameter of 108-133 mm, the weight of the body of the screw-pile support reaches almost 30 kg, but such a pile can easily withstand a load of 6 tons.

Augers and screw tips

When installed, the support body works only in torsion, then the blade tip ends up in an even more difficult loaded state. Therefore, the main type of failure of the supports of a pile-screw foundation is the destruction and separation of the blade. There may be several reasons, most often an undesigned mode of immersion of the pile or an impact with a solid obstacle, for example, stone or metal. 50% of the destruction of pile-screw supports is the poor quality of the weld. Instead of argon-arc welding, submerged arc welding or conventional manual welding with a consumable electrode is used; a metal with low weldability is used.

The danger of destruction of the screw tip of the pile is also due to the fact that almost the entire vertical load perceived by the pile-screw foundation under the influence of the weight of the building is transmitted to the ground through the blades of the piles. And this load is not always static; most often, an alternating force acts on the foundation due to the forces of heaving, wind, and redistribution of forces within the soil. Accidents and breaks of screw piles forced manufacturers to look for a way to strengthen the screw pile foundation.

The solution to the problem was found in changing technology. Modern heavy-class pile-screw supports with a pipe diameter of more than 100 mm are equipped with cast cutting augers. Moreover, to increase strength, the technology of vacuum remelting of relatively inexpensive structural steel St25 and subsequent casting into a ceramic shell was used.

Thanks to the improved technical process, an accurate part is obtained without defects and a single weld seam, with a blade thickness of 10-13 mm. For comparison, the thickness of a conventional welded blade is only 5 mm. The cast auger is seated on the pipe along a pre-machined belt, which ensures complete alignment of the axial pipe and tip. Why this is so important will become clear later when considering the features of installing a pile-screw foundation.

The result is a pile-screw support that can be screwed even into rocky soil, with a large amount of small stones, or even mixed with construction waste. At the same time, the service life of a screw-pile foundation, subject to installation rules, according to experts, can easily reach one hundred years, while welded piles rarely last more than 25 years. It is clear that a qualitative breakthrough in the manufacturing process of pile-screw supports has led to the appearance on the market of a huge number of low-quality fakes.

Carbon steel is subjected to thermal normalization and hardening in an emulsion, which ensures the hardness and wear resistance of the cutting edge, which is not and cannot be the case with fakes. Usually the fake is welded and clad with a casting coating. The cost of a reinforced pile-screw support of a factory-made brand is approximately 40% higher than for welded handicraft products, so there are many times more fakes on the market than original piles.

Advantages and disadvantages of pile-screw foundations

The widespread use of pile screw foundations in low-rise construction, especially on difficult soils with a lot of moisture and variable bearing capacity, has generated quite a lot of experience in its use, with all the disadvantages and obvious advantages.

What is good about a pile-screw foundation?

General statistics and reviews from owners show that the choice in favor of a pile-screw foundation for a private building, house or bathhouse was made based on the following considerations:

• A pile-screw foundation field can be installed in a couple of days, and in most cases even on your own, without the use of special equipment or labor-intensive excavation work;
• The use of pile supports allows you to begin the construction of frame-panel, timber or foam concrete buildings the very next day, without a month-long soaking period, as in the case of concrete foundations;
• The metal pile-screw foundation is not afraid of moisture and does not conduct moisture, therefore it is ideal for the construction of buildings made of wood, panels, SIP panels and foam materials.

In addition, the calculation of a foundation on pile-screw supports is simpler, and the result of loading is more predictable, since the strength characteristics and behavior of metal under load are well studied and much more predictable than reinforced strip concrete or reinforced concrete piles. Another plus is that replacing or repairing a metal pile is much easier than a concrete support.

Some experts note the good adaptability of a pile-screw foundation to uneven loads, when, along with vertical pressure from the weight of the building, a horizontal component appears. Buried to the design depth, a thin metal pipe with a wide tip at the base has the ability to deviate from the vertical axis, even if it is filled with concrete. Just a few degrees, but this is enough so that any load on the pile-screw foundation is distributed more or less evenly across all supports.

For concrete structures, this situation is more dangerous; part of the supports of a pile-screw foundation could be squeezed out by heaving forces, while some elements remain in an overloaded state, for example, when using a timber grillage.

The main fear of all pile foundations is the forces of soil heaving at low temperatures. There are many myths among developers about how a screw pile can be torn off by expanding ice. In fact, the strength of a steel pipe is strong enough to be broken by ice. The tensile strength of ST25 is 400-500 MPa, which is several orders of magnitude less than the specific load created by ice.

Moreover, with strong compression, part of the ice and soil turns into a semi-liquid state, so the mess of ice and soil slides more along the surface of the pile-screw support than pushes it out. If the insulation of a screw pile foundation is carried out according to all the rules, the tip rests on warmer deeper layers, then there is no reason to worry about heaving of the soil around the steel pipes.

Of course, a screw pile foundation has its pros and cons, so it would be wrong not to mention the disadvantages of using tubular screw piles.

Disadvantages of the design of pile-screw supports

The main negative aspect of using metal pile-screw supports is their high price. The price for an ordinary screw with a diameter of 89 -108 mm is 900 rubles, screw piles made from a tubing pipe with a cast tip will cost 1,500 rubles, and those made from stainless steel - all 4,000 rubles. The costs of manufacturing a pile-screw foundation from geoscrews and a field from bored piles will be approximately the same. And if the project includes the use of cast pipes, then the pile foundation will turn out to be even more expensive than a conventional shallow foundation.

In addition to cost, the list of disadvantages of a pile-screw foundation includes:

• Intensive destruction of metal in a corrosive environment;
• The need for a precisely dosed force for screwing in and settling the pile-screw support;
• The high thermal conductivity of metal requires solving the question of how to insulate a pile-screw foundation.

The most important of these problems is the anti-corrosion protection of metal located in soil with a high content of moisture and active substances. This is a long-standing problem with all underground steel communications. For more than a century of their use, attempts have been made to make pile-screw supports from cast iron, forged metal, alloy and stainless alloys, to use zinc and aluminum coatings, protective paints and varnishes, but the problem is considered unsolved.

For your information! If houses on a pile-screw foundation are located closer than 50-70 m to transformer substations or high-voltage transmission systems or power generating installations, then metal piles cannot be used, since the screw supports will be quickly destroyed by electrochemical corrosion and stray currents.

Insufficiently effective resistance to corrosion processes is inherent in the nature of pile-screw supports. Even when a metal surface is oxidized or galvanized, not to mention paint and varnish coatings, the metal still rusts in a humid environment. The only question is the rate of rusting. In addition, when screwing in the screw supports, the surface of the pipe and the tip slides relative to the soil masses, as a result of which sand, fine gravel and stones tear off the protective coating, even zinc and oxide film, like an abrasive.

The only coating that has shown good results is considered to be a two-layer protective film made of aluminum with an oxidized surface, but the cost of applying such protection is comparable to the price of the pile-screw supports themselves. If the problem of corrosion protection is solved in the near future, then pile-screw foundations with cast tips in low-rise housing construction will completely replace concrete.

Calculation of foundations on metal piles

The use of a foundation on pile-screw supports requires, at a minimum, thoughtful planning, calculations and geological testing. Even if a preliminary examination of the soil surface and a study of the outcrops of layers in the lowlands closest to the site do not give reason to doubt the bearing capacity of the soil, it will still be necessary to check the bearing capacity of the layers at a given depth.

Planning the foundation layout

The design development of a pile-screw foundation usually begins with a soil test. Knowing the maximum freezing depth in a given area, it is necessary to drill at least 3 equidistant points on the site. Once a sample is obtained, a soil composition specialist can evaluate its load-bearing capacity.

• Single piles - used to support canopies and canopies over the entrance to the house;
• Linear or row arrangement, used for arranging pile-screw foundations for terraces, verandas or extensions to the house;
• Location of pile-screw supports around the perimeter and under the load-bearing walls of the building;
• Pile field. In this case, almost the entire sole or base of the building is evenly filled with screw piles.

In order to pre-select the arrangement of screw supports, you can use a rough estimate of the load-bearing capacity of piles; an ordinary support of 76 or 89 mm can withstand up to 2 tons of load, heavier pipes of 108 mm and 133 mm can withstand 2800-6000 kg.

Calculation of the number of support points

To perform a more accurate calculation of a pile-screw foundation, you will first need to calculate the weight of the building, taking into account all the structural elements, the internal contents of furniture, household appliances, and even the weight of the snow cover on the roof. The resulting value is multiplied by the safety factor, since any pile-screw foundation is always built with a margin of bearing capacity.

The resulting weight is divided by the load value for a specific screw pile size. As a result, it turns out that a pile-screw foundation requires from 30 to 50 piles. Next, the installation points for the piles are marked on the foundation drawing so that the average distance between the supports is 2.5-3 m. If the number of points is too large, then you need to choose a screw pile design with a higher load-bearing capacity.

At the last stage, it is necessary to perform a verification calculation of the pile-screw foundation based on the bearing capacity of the soil. For each variant of the soil mixture, the maximum loads or the specific static pressure that the soil can withstand have long been determined. Since the size of the screw pile, namely the diameter of the tip, is already known from the results of the preliminary calculation, it remains to multiply the area of ​​the auger blades of one support by their number. The total weight of the house is divided by the resulting surface area of ​​the base of the screw piles and compared with the specific pressure that the soil can withstand.

To logically complete the calculation, you will need to select the option of tying the heads of the screw piles. For small frame buildings, timber is used to tie a pile-screw foundation. Heavier buildings made of foam concrete require the installation of a channel or I-beam. To tie the channel to the screw support, concrete is poured into the pipe and an embedded anchor pin is installed. When assembling horizontal crossbars, you have to spend a lot of effort in order to accurately hit the mounting holes on three studs at the same time on a six-meter run.

Private owners most often prefer to work with timber. Firstly, laying timber frames with a cross-section of 100x150 mm on welded support platforms is much easier than working with a heavy and rigid I-beam or channel. Secondly, strengthening a pile-screw foundation with timber frame is completed in a couple of hours, whereas with metal it is necessary to spend at least two days cutting and lifting the channel with a jack.

Installation of screw piles

The process of constructing a pile screw foundation always begins with cleaning the construction site, you need to free it from debris and the top layer of fertile soil. In essence, they carry out planning and leveling of the territory. Soil with a high organic content, grass and roots are removed until the lower layer of loam is exposed.

If there is a slope on the future base of the screw-pile foundation, then it is better to carry out the marking process using a level and a laser level; this simplifies the work, since it will be necessary to ensure the same depth of the screw piles, and at the same time there should be a sufficient margin of height for the pipe with the head to cut supports in one horizontal plane.

Pile driving technology

The most critical stage in the construction of a pile-screw foundation is screwing in the screw supports. In theory, you can install the supports of a pile-screw foundation with your own hands. The maximum tip size that can be manually driven into the soil is 300mm. Larger sizes can only be deepened using a tractor or automotive machine. But even for a pile with a 30 cm auger, you will need to weld a reinforced head and use levers 2.5-3 m long.

The main difficulty when screwing in a pile-screw support is that it is necessary to maintain a strictly vertical position of the screw. If we take into account that the torque on the gate can reach several hundred kilograms, it becomes clear that it is not so easy to maintain the vertical line even with a team of two or three people. Especially if the tip is not welded to the pipe coaxially. Most often, such screw structures break before the calculated penetration point is reached.

Therefore, the installation of a pile-screw foundation must be carried out by at least four workers. One pair rotates the gate, the second controls the position of the support in two perpendicular planes.

To make the hard work easier, before deepening, smaller diameter channels are punched with a motor drill to a depth of 120-150 cm. After part of the soil is removed, it is much easier to screw the screw support into the ground, and this does not affect the load-bearing capacity of the pipe. If the soil is too dry, then a small amount of water with clay is poured into the cavity. This way you can reduce the force on the gate by at least half.

When screwing in a pile foundation using a machine, it is necessary to control the rotation force, and after installation it is customary to check the load-bearing capacity of the screw support.

After all the screw supports have been installed, the plane of the future piping is marked using a level, the line is transferred to the pipes, after which the heads are cut off, the internal cavity is filled with concrete and anchor fasteners are laid. If the height of the pipes of a pile-screw foundation exceeds 50 cm, diagonal spacers or struts are welded between the columns.

Finishing operations on a pile-screw foundation

At the final stage of construction, they move on to insulating and finishing the base of the pile-screw foundation. The lower crown of the wall, as a rule, turns out to be raised above the ground to a height of 30-70 cm, so the surface of the soil under the building without insulation of the base of the pile-screw foundation easily freezes. In addition to the fact that precious heat is lost, the soil rising due to heaving peels off the protective coating on the surface of the pile-screw supports. Therefore, before closing the base in a pile-screw foundation, the piles need to be insulated; you can fill the soil around the supports with expanded clay or lay polystyrene foam slabs. The insulation layer must be covered with sand or fine gravel screenings.

There may be several options for finishing the base of a pile-screw foundation. The simplest is to install a sheathing of boards and timber and line the basement space with siding panels, waterproof plywood or similar materials. The panels should not reach 7-10 cm to the ground level. The gap is necessary to avoid the decorative cladding being torn off by the soil rising in winter.

To prevent rodents, snow and rainwater from entering through the gap, the lower edge is covered with a composite blind area. It is best to use sand or gravel backfill over extruded polypropylene slabs laid on the ground, followed by paving with paving slabs. Monolithic options for the blind area of ​​a pile-screw foundation made of concrete or asphalt are rarely used, since soil heaving leads to the formation of numerous cracks and pinholes.

Conclusion

In the totality of the information considered, it may seem that the disadvantages of a pile-screw foundation make the use of screw metal supports advisable only for auxiliary construction, all kinds of gazebos and canopies. But heavy pile-screw supports are widely used for arranging foundations in climatic zones where the freezing depth reaches 1.8-2 m. In this case, a pile-screw foundation is cheaper and more reliable than a strip foundation, and even more so a slab foundation. The only significant drawback remains the impossibility of building a full-fledged basement.

With a limited construction budget, a pile-screw foundation (SVF) is a rational choice for a prudent owner. If you have time and energy, you can make a screw foundation with your own hands; to do this, you need to immerse the piles to a layer with bearing capacity. The technology does not depend on the weather; a cottage or garden house is guaranteed to be built in the same season, since there is no need to wait for the concrete elements of the base to gain strength.

In comparison with all known technologies, a do-it-yourself screw foundation is the most economical foundation for any above-ground structures. The advantages of SVF are:

• construction in difficult conditions - hilly, swampy terrain, coastal zone, dense buildings, presence of trees on the site, passage of third-party communications;
• minimum budget - almost complete absence of concrete, earthworks, formwork, waiting for concrete structures to gain strength, rental of special equipment;
• variability of construction technologies - a screw foundation is suitable for log houses, brick, panel buildings, panel buildings, half-timbered frame buildings, house grounding loops, fences, MAF;
• maximum number of storeys - three-story buildings with an attic permitted in individual construction are allowed;
• high resource - with normal anti-corrosion treatment, the service life of screw piles is 75 - 100 years.

Please note that grounding is a separate structure, and not connecting the grounding wire to the body of the foundation pile field. Piles for the grounding loop should not have protective coatings that do not conduct current.

The only drawback of SHS is its unsuitability for projects with a basement/basement floor. Manual installation of screw piles is not only acceptable, but also recommended by experts. When immersing these structures with special equipment, it is more difficult to control the tightening force when reaching the bearing layers.

Step-by-step foundation technology on screw piles

Thanks to a fairly simple design, if you have the necessary tools and equipment (welding machine, gas cutter), screw foundations can be made at home. Installation is carried out using the following technology:

• control screwing;
• design;
• marking;
• production of guide wells;
• SHS dive;
• trimming the level of pipes rising above the ground;
• pouring concrete;
• installation of heads;
• tying the pile field with a grillage;
• input of communications.

To plan the work time, it is enough to measure the pitch of the propeller blades. With each rotation, the pile will sink to this depth, allowing the time of each cycle to be calculated. For example, with a step of 5 cm, 40 circles will be required to screw in the SWS to a depth of 2 m. A professional team installs 15 - 25 SWS per shift, creating a field for a cottage with an area of ​​100 m².

Calculation of a pile-screw foundation

The technology has been sufficiently developed in all regions of the Russian Federation; to calculate the SVF, you can use the SP from 2011, number 24. 13330 for pile foundations. The main calculations are:

• the bearing capacity of the formation at the immersion depth of the pile blade; the bearing capacity of one pile is calculated from this parameter;
• quantity - SHS pitch on straight sections, positioning at the junction of walls, laying piles under individual structures (boiler/furnace, porch/internal staircase, emergency generator/pumping equipment.

In order not to order expensive geological surveys of the site, in 75% of cases a trial screw-in is used, which allows one to calculate the data necessary for the project:

• depth of the bearing layer (necessarily below the freezing level of the region);
• soil composition (presence of large stones, gravel, limestone in different layers);
• GWL level (very conditional).

The main characteristics of piles are indicated by manufacturers. For example, the dimensions of the SHS are selected based on the type of structure for which a foundation is needed:

• berth/pier – pipe 89 – 108 mm, wall 3 – 4 mm, screw 20 – 25 cm;
• reinforcement of bases – pipe 89 – 108 mm, wall 3 – 4 mm, blade 20 – 25 cm;
• retaining wall – 54 – 89 pipe (2 – 3 mm wall), screw 15 – 20 cm;
• MAF, gazebos, fences - 54 - 76 mm pipe with a wall of 2 - 3 mm, propeller blade 15 - 20 cm;
• combination with tape MZLF – pipe 108 – 168 mm, wall 4 – 8 mm, blade 25 – 40 cm;
• block, brick cottage - wall 6 - 10 mm, body diameter 168 - 270 mm, blades 40 - 80 cm;
• panel, half-timbered, panel, frame, log house - 89 - 114 mm pipe with 3 - 5 mm wall, 20 - 30 cm blade.

Thus, after calculating the prefabricated loads (operational + wind + structural + snow), the figure is divided by the load-bearing capacity of the pile to calculate the required number of SHS.

Preparation and marking of the site

Due to the lack of planning and excavation work, marking the construction site is simplified as much as possible. It is enough to bring the axes of walls, partitions and additional heavy equipment (boiler, ladder, pump, etc.) to the area. To do this, pegs are installed slightly further from the corners of the house along which the cords are stretched. Instead, you can use a more complex design of two stakes with a horizontal jumper, which allows you to install two cords along the outer dimensions of the pile.

Driving piles

Step-by-step instructions for screwing in SHS, regardless of the type of blades, tip, groundwater level, and other factors, are as follows:

• production of pits - guide holes are created to a depth of 0.5 - 0.7 m using a manual or motorized drill, they allow precise positioning of piles, facilitate the entry of the blade into the ground, the diameter of the leader hole should be slightly less than the size of the SHS blade;
• immersion of the pile - a crowbar is inserted into the holes inside the pipe body, tubular levers are put on it, two workers move them in a circle, creating a torque, the third controls the vertical of the shaft with a bubble level, with a sharp increase in tightening force (necessarily below the freezing mark) the work stops;

There is a technology for mechanical immersion of SHS without the use of special equipment, which slightly increases the construction budget:

• a torque amplification device (reducer) is put on the upper end of the SHS;
• an electric drill is installed on it (power from 1.5 kW);
• the structure is installed in a vertical position above the guide well;
• the drill is connected to the electrical network.

The torque amplifier device is a gearbox with a gear ratio of 1/60. Instead of levers, an electric tool drive is used; the operation can be performed by two workers.

Alignment of SHS in the horizontal plane

The pile field must be tied with a grillage in the form of concrete, metal or wooden beams located on the heads. To do this, the pipes protruding from the ground must be brought back to normal. The leveling technology looks like:

• single level mark - use a level, theodolite or laser plane builder, level;
• trimming - the body of the pipe is cut with an angle grinder according to the markings.

At this point, the construction of the pile field is considered complete when using a monolithic or metal grillage. If a frame, log, panel or panel house is being erected, it is necessary to mount heads on which timber or calibrated logs can rest. The head has several modifications:

• square – 10 x 10 – 30 x 30 cm plate welded to the pile;
• reinforced - the size is similar to the previous case, the plate is welded to a pipe, the internal size of which is equal to the outer diameter of the pile, there are 4 stiffeners (kerchiefs);
• U-shaped - the internal dimension between the shelves is 17 cm for laying timber 15 x 15 cm.

This element is put on the SHS body and attached to it by welding (less often with bolts). The holes in the plate allow you to fix the wooden beams of the grillage to obtain a single spatial structure.

Pouring concrete

The pile, even with a hermetically welded head, is covered with moisture from the inside. To prevent this phenomenon, special protection is used - filling the pile body with concrete after immersion to the design depth. Several technologies are usually used:

• dry mix - packaged sand concrete M 300, which, upon contact with condensate, is independently cemented inside the product;
• ready-mixed concrete - classic pouring through a funnel, the technology has a significant drawback - the presence of voids and cavities inside the mixture;
• sand concrete – grades M 300 – M 400, due to the absence of coarse filler, there are practically no voids in the concrete;

In addition, concrete injections make it possible to increase the spatial rigidity of the structure, which is important for thin-walled piles.

Tying piles with a grillage

On straight sections, the recommended height of the grillage base from the ground is 0.5 - 0.7 m. This is the optimal size for placing ventilation ducts in the fence. Without it, the floors of the lower floor will be a source of heat loss; in the absence of natural ventilation, the power frame will quickly become unusable. For each type of grillage there are installation features.

Monolithic grillage

The technology is the most complex and is more expensive than other options, but it is the only one possible for brick cottages on difficult terrain, in the coastal strip and in swamps. Installation of a monolithic grillage using technology:

• formwork assembly - the bottom panels are put on the pipes, supported by jumpers attached to two pegs, the side panels are attached to the bottom, connected to each other by spacers and ties;
• reinforcement - two belts of periodic cross-section rods (12 - 16 mm corrugated) are connected to horizontal and vertical 6 mm jumpers or clamps;
• connection with piles - holes are burned or drilled in the pipes into which additional reinforcement is inserted, connected with tying wire to the reinforced belts of the structure;
• pouring - the formwork is filled with concrete mixture to the design level, compacted with reinforcement bars or deep-seated vibrators.

All types of masonry for the walls of a brick house and any other construction technologies are allowed on a monolithic grillage.

Wooden grillage

The technology for constructing wooden houses facilitates the task of the developer, who needs to connect the pile field with long elements to ensure the spatial rigidity of the house. The lower crowns of the log house (calibrated logs) and the framing of the “frame” are a ready-made grillage.

The manufacturing technology looks like:

• installation of flat heads - necessary to increase the area of ​​the supporting surface;
• laying beams - beams, logs are joined into half a tree, attached to the heads with self-tapping screws, bolts or nails.

This is the fastest grillage device, however, the technology is unsuitable for brickwork and high-rise projects. The height of the building cannot exceed one floor with an attic.

Metal grillage

If the height of the log house or “frame” exceeds the standard floor, the wooden grillage may not withstand prefabricated loads. It is not economically profitable to pour monolithic beams for wooden buildings; you can use a grillage made of rolled metal. The technology looks like:

• laying pieces of channel with shelves down, wall up on SHS pipes or I-beams on the bottom shelf in exactly the same way;
• joining grillage elements, tack welding in several places;
• double welding of each joint.

A metal grillage is suitable for one-story brick buildings only if the pitch of the pile field is reduced to 1 - 1.5 m. This is due to the large structural mass of the material - for example, the channel begins to bend under its own weight already in 3 m spans.

Insertion of engineering systems into a building on screw piles

Most often, SHS pipes protrude slightly above the ground surface. This makes it difficult to lay out communications in an underground 0.5 - 1 m high. Therefore, it makes more sense to introduce life support systems at the foundation stage. Later, for this you will have to open up the subfloor and carry out excavation work in a confined space. For normal operation of the building it is necessary to provide:

• plumbing - in a frozen underground, pipes must be insulated, both in the ground to the freezing mark and above its surface with polystyrene shells or mineral wool (2 - 3 layers) and a heating cable, respectively;
• sewerage - wastewater enters the external sewer circuit warm, so it is enough to wrap air pipes with one layer of basalt wool, underground pipelines with polystyrene foam shell to a depth of 1–1.5 m;
• grounding of the house - SHS of minimum diameter can be used in the form of a triangular circuit immersed at the 2 m mark, tied with thick wire or tires made of a metal strip, while the piles should not have a protective coating that does not allow current to pass through;
• power supply cable - sometimes an underground input is used, always in a protective casing.

After wiring the engineering systems, you can install a fence. If the project includes brick walls, a false plinth is made at the façade finishing stage. Because in this case there is a high probability of damage to the facing materials by random stone or mortar.

Climbing on screw piles

There is no full-fledged base in the pile foundations; a fence is made to protect against blowing and penetration of precipitation into the underground. Several technologies can be used to build a false plinth:

• frame system - a beam or galvanized profile is attached to the piles, the lattice is sheathed with basement siding, corrugated sheets, panels;
• masonry - ceramic, clay brick, rubble stone.

The intake is complemented by a blind area for drainage of storm and flood runoff. The facing materials of these structures must be waterproofed. To do this you need:

• install frame sheathing;
• fix the roofing material vertically on it;
• run it under a horizontal blind area;
• install siding and paving slabs.

Natural ventilation of the underground is carried out due to the vents left in the false base, the total area of ​​which should be equal to 1/400 of the surface of the intake. There is no need to insulate the structure, since there is no heating inside the underground.

Resource of screw piles

To increase the service life of SHS, anti-corrosion treatment of each product is necessary in accordance with GOST R 9.905, 9.908, 5272. Manufacturers use the following anti-corrosion technologies:

• cold galvanizing - peels off almost completely even when the pile is immersed due to abrasives contained in the ground;
• hot galvanized – lasts a little longer, does not provide the declared 75-year service life;
• powder coating – lasts 30 – 50 years after installation, is destroyed by walking currents in the ground;
• painting with bituminous compounds – protects against groundwater, regardless of the height of the groundwater level, ensures a 50 – 70 year service life

• primer VL 05 + cold galvanizing (enamel IR 02) + fiberglass – service life 300 – 400 years in extreme conditions, no electrochemical corrosion;
• IR02 or Zinga Metall enamel + polyurethane or epoxy two-component enamel - created to protect oil pipelines (overhead, underground), have a 50-100 year lifespan;
• primer VL 05 + polyurethane enamel Hempel, Masco - standard level of protection for the bottoms of icebreakers, submarines, fuel tanks, 30 - 70 year life.

Even when purchasing SHS with a factory-made anti-corrosion layer, it is necessary to coat the piles with the specified compounds for reliability.

Purpose of screw piles

The first pile structures with screw tips in the Russian Federation began to be used exclusively for the needs of the army in the middle of the 19th century. They could be used for temporary structures or in difficult operating conditions. The declared resource was 100 - 180 years, which modern manufacturers cannot boast of. Currently, SHS and other modifications of piles are used for:

• building a house in a swamp, slope, in dense buildings, forest zones, on soils with high groundwater level, low bearing capacity;
• budget construction of fences, MAF, gazebos, outbuildings;
• strengthening strip and slab foundations;
• production of engineering systems, for example, grounding of a house, water intake wells.

The height of the SHS is practically unlimited - when the lower element with the auger blades is immersed to ground level, the next piece or several can be welded to the pipe to ensure that layers with load-bearing properties are achieved. For installation, three people or one specialist with a powerful electric drive with a gearbox are enough.

This step-by-step instruction is suitable for installing screw piles under a building constructed using any technology from different wall materials. Recommendations will help you avoid mistakes and increase the service life of your home.