Insulation of grillage. Construction of a pile foundation and its insulation from the outside How to insulate a grillage foundation

When doing the insulation of a pile foundation with your own hands, you should be guided by the current standards and rules.

As a rule, a pile foundation is installed on heaving soils. It is used in the construction of a cottage, a bathhouse, and other buildings on the estate.

In a climate zone with a sharp change of seasons, insulation of the pile-screw foundation is mandatory.

This severe necessity is dictated by concern for the comfort and health of the people living in the house.

The fact is that the distance from the floor to the ground forms a free space in which intense heat exchange occurs.

Construction of a pile foundation

It is necessary to create a foundation for a house on stilts when construction is carried out on heaving soils.

When installing a pile foundation, seasonal fluctuations in the soil and groundwater level do not affect the condition of the structure.

In order to give greater rigidity to the structure, the piles are connected to each other with special elements. This element is called a grillage.

The following can be used as a grillage:

metal beams;
wooden beam;
concrete or brick bulkheads.

It is the pile foundation of the grillage type, due to its versatility, that is used most often.

It is initially known that in a house built on a pile foundation, the floors can be cold, especially in winter.

Today, different methods can be used to insulate the floor.

One of them is to insulate the pile foundation from the outside. In this case, the base is installed, finished and decorated.

The volume of space that is formed between the lower floor level and the ground is used for household needs. At the bathhouse this space is not used.

The second method comes down to installing a “warm floor” in a living room with your own hands. Yes, labor costs in this case will be less. However, heating costs will increase significantly.

Insulation materials

When building a house or bathhouse with your own hands, each specialist is free to act according to his experience. No one doubts that thermal energy needs to be conserved and saved.

Disagreements arise at the stage when the question of what material to choose for insulation is decided.

Pile foundations (including bathhouses) can be insulated with expanded clay, expanded polystyrene or mineral wool. Insulation of the grillage should be carried out at the stage of arrangement of the pile foundation.

If mineral wool is chosen for these purposes, it must be reliably protected from moisture. On heaving soils this is one of the most important tasks.

Insulation technology

The procedure for insulating a grillage base includes several stages. Work should be performed in strict sequence.

All materials and tools must be prepared in advance.

Simultaneously with the thermal insulation of the foundation, the floor is insulated from the outside. The same thermal insulation material is used as insulation for the floor.

If there is a basement under the house, then the insulation is waterproofed especially carefully.

Waterproofing

The first step is to process all the joints of the grillage base.

If the foundation of a house or bathhouse is made of wood, it must be treated with antiseptic impregnation and a waterproofing solution.

There should not be a single open area where mold or insects can grow. In this case, all cracks and cracks in solid wood should be filled with waterproof putty.

An anti-corrosion compound is applied to the outside of the metal beams. For these purposes, bitumen mastic is used. Joints and joints must be handled with particular care.

Base installation

The heat-saving cladding is created in the form of a plinth. To do this, a brick wall is laid out and insulated with polystyrene foam.

Since the structure was erected on heaving soils, it is necessary to build a support that is attached to the piles. Thus, the decorative wall will be integral with the foundation.

The bulkhead can be mounted from timber or a metal profile. This design has less mass than a brick wall.

On the outside, it is finished with decorative panels that cover the heat-insulating material.

Attaching the insulation

When insulating the base with polystyrene foam, all joints between the plates must be filled with polyurethane foam. The insulation is applied from the ground up to the floor.

Laying should be done in such a way as to prevent access to it by small rodents. Expanded polystyrene sheets are glued to the wall surface using special glue.

If mineral wool is used, it must be reliably protected from the influence of atmospheric moisture. For these purposes, various rolled materials such as roofing felt or glassine are used.

Sheets of glass wool are tightly inserted into the pre-fixed sheathing.

Fastening finishing panels

When the thermal insulation of a pile foundation is performed with expanded polystyrene or mineral wool, the insulation must be protected from exposure to atmospheric agents.

And not only protect it, but also decorate it to match the overall background of the facade. For decorative finishing of the base, vinyl siding or PVC panels with a brick texture are used.

Many years of practice show that siding reliably protects the surface from the effects of atmospheric phenomena - rain, snow, wind, dew.

The technology for fastening siding is well established, and anyone can install the panels with their own hands.

Powder from the inside

For greater reliability, the insulated base can be sprinkled with soil from the inside around the perimeter. If possible, it is preferable to use expanded clay.

This bedding will reduce the ventilation of the underground volume.

To prevent air from stagnating, two ventilation holes must be installed on opposite walls of the basement.

It is necessary to install mosquito and mouse screens on these windows. They must be tightly closed for the winter.

Features of the procedure

Pile foundations are also used in cases where the construction budget is reduced to a minimum.

In this case, there is no need to insulate the floor for the bathhouse.

It is enough to insulate the base and leave it at that.

For a residential building, the insulation of the base and walls of the room under the floor with polystyrene foam must be of high quality.

As a result, the problem with cold floors and excessive energy consumption will be solved.

Plus, the house will have additional space for household needs.

Pile foundations are often used to save money. In order not to spend money on expensive and complex pouring of a strip base, you can concrete the piles and install a residential structure on them. The disadvantage is high thermal conductivity. Simply put, if you do not additionally insulate the pile foundation inside or outside, then there will be no heat in the house.

What is the best way to insulate a foundation on stilts?

When choosing the optimal insulation option, you must be guided by regulatory indicators and the possibility of using all acceptable options. At the same time, attention should not be diverted from the economic effect.

You can lay and insulate a strip foundation around the perimeter of a house on stilts. This will be a reliable option. The rooms will be warm and cozy, but the process will affect the cost of the work. As an option, a shallow tape is poured. Thus, you won’t have to spend money on complex work, and additional manipulations will protect your home from the cold.

You can cover the piles with any building material and fill the underground space with expanded clay. The option is inexpensive, but not entirely effective and is suitable for places with low levels of moisture in the soil.

In fact, there are many options with which you can insulate a pile base and there is no point in listing each one. Over the years of using pile foundations in house construction, experts have developed their own “recipes” and suggest considering the following methods in this regard:

External insulation relative to the perimeter of the building. The method is in demand if the foundation piles do not rise too much above the ground. The process consists of erecting a frame along the base, insulating the basement space and external cladding.
External insulation on the floor. If the house is on “difficult” soil, this is the only option. Essentially, the floor is insulated without basement finishing and internal insulation of the foundation .
Combined insulation. In this option, the basement box is mounted externally, and insulation is also carried out in the basement.

On a note. The third option is preferable but a little more complicated. When implemented, high thermal insulation and reduced dependence of the house on the cold are guaranteed.

Scheme of insulation of the pile base.

First of all, waterproofing. This is the basis of any work related to reducing the temperature load on the building material and the entire house as a whole. The purpose of creating waterproofing is to prevent the formation of condensation on piles, grillages and places of contact of metal components with wood. In these cases, bitumen mastic is used. The composition is coated with all joints and foundation pillars.

Two ways to insulate a pile foundation

Of the technological options for insulation, two methods of protection can be considered:

Creating a brick plinth. An ideal option for reducing heat losses of a house in the base area. When choosing this method, a trench up to 50 mm deep is dug around the house and reinforced concrete is poured into it. After hardening, a wall of 1.5 bricks is laid out.
Panel plinth. If the heaving soil on site does not allow laying a shallow foundation, this option is used. To insulate the foundation on piles with a grillage and a conventional columnar foundation, in this case a frame is attached. This can be a wooden sheathing or a metal channel. The insulating layer is created by penoplex or other polymers, and the external decor is made of siding panels or other materials.

On a note. The second option is easier to implement, but has a slight drawback. It contains less thermal resistance. Brickwork will more reliably protect the underground space of a pile foundation from the cold.

Regardless of the choice, when installing an enclosing barrier, it is necessary to consider the ventilation of the underground space. In order for the waterproofing to cope with the manifestations of condensation faster, vents are created in the brick wall, covering them with a fine mesh to prevent rodents. In the panel version, a ventilation gap is left between the ground and the lining. It is also covered with fine mesh.

Insulation with brickwork.

Insulation of the basement level on brick and frame

Let's look at this process in more detail. By laying a brick wall or covering the pile foundation from the outside with a frame, it is necessary to additionally create a heat-insulating barrier. In both options, you can use penoplex or any other insulation under the foundation slab or protect the base from the outside . But as the best option, experts recommend using polymers because they are unpretentious in work, easy to cut and are not afraid of being in the vicinity of moisture.

If the base is brick, then after the masonry has dried, the outer side is plastered. This is necessary to close small gaps and create a flat surface on which the panels will be mounted. The work is carried out from the inside. Then the insulator panels are cut according to the dimensions of the wall.

The sheets are fixed from the inside. Installation is carried out using specialized glue or plastic dowels. To be safe, you can use both methods. It will be impossible to create maximum pressure on the panels during installation. To do this, after fixing, the joints are coated with an adhesive or foamed.

Important! The process of insulating joints is no less important than the installation of the insulator itself. Even small cracks that form “cold bridges” will create many problems in the future.

When insulating the frame base of a pile foundation, the panels are laid outside, covered with siding or profiled sheets. You can create two insulating layers: one from polymer, the second from panels for wall insulation . The latter are made from modern materials and incorporate the best qualities of insulation and decorative materials.

The only drawback of penoplex is its dependence on rodents. To protect the material from unfriendly actions from mice, outside and inside, it is covered with a mesh. For a better thermal preservation effect, you need to install the insulator in two layers or choose thicker panels.

The final touch to the insulation will be a layer of expanded clay. They create it from the inside (basement). It will protect the floors of the building from drafts, which are the main carriers of cold.

Insulation of the floor in a house on a pile basis

Creating a basement frame along the outer perimeter of the pile base will protect the housing from the manifestation of cold “walking” in the underground space. But the carrier of low temperatures is also the soil. Low temperatures in winter are transmitted through it to the underground space, so it is necessary to additionally insulate the floors .

Based on this type, the insulation is done from below. You can consider any options, but as additional protection for the foundation, underground lining will be more reliable.

Internal floor insulation.

The flooring is first covered with a vapor barrier. The sheets are glued overlapping and additionally the joints are fixed with masking tape. This process is especially important. It is aimed at preventing moisture from entering the flooring during temperature changes. Insulation panels are mounted on the insulation. It can also be penoplex or any other polymer.

If a house on a pile foundation is located high above the ground, then such insulation of the floor covering is simply necessary. The space under the structure and the driven supports create a lot of space accumulating cold air. And sometimes it happens that just creating a base is not enough. Insulating the floor in this case helps create the necessary temperature in the room.

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Method for eliminating the disadvantage of a pile foundation

The problem of a cold floor is solved by insulating the foundation in various ways.

The type of insulation is selected depending on the height of the foundation above the ground.

Design features and whether the “lower” space will be used for economic purposes.

There are several options to consider:

complete insulation;
external;
insulation of the floor under the house from the outside.

Complete

In this case, work is carried out to insulate the entire structure, both outside and inside:

External

This method is suitable for low-lying houses, when the size of the piles is small, and involves organizing a frame around the perimeter, starting from the line of the ground surface and to the edge of the building. Then decorative cladding and insulation are possible.

External floor insulation

If the house is significantly elevated relative to the ground and other options are impossible, so-called “partial insulation” is performed - from the outer, lower part of the building.

Despite the fact that from the point of view of professionals, it is better to leave the ventilated part open, many owners of houses on a pile-screw foundation prefer to cover and insulate it using various available means.

Waterproofing device

If all measures for proper waterproofing are not carried out, the metal from which all structural elements are made may undergo corrosion. Wooden elements can be affected by fungi and rot.

Loss of characteristics of piles or wood can significantly affect the service life and durability of the building.

In order to secure the structure, one of the waterproofing materials is laid at the point of contact between the pile elements and grillages. For example, this could be a layer of roofing felt. It also needs to be placed on those edges of the grillage that meet the wall of the building.

Following this, the entire foundation is treated with waterproofing mastic, and the wooden parts are treated with an antiseptic.

After a week, after the solutions are completely absorbed, the next stage is insulation of the foundation.

Two ways to insulate the basement of a structure

brickwork walls;
preparing the frame for decorative paneling.

Brickwork

To begin with, a small trench is dug and a shallow foundation is formed: reinforced and poured. Actually, it is already additional insulation. Then, after drying, a small brick wall of the required height is laid on it. The masonry is done using half a brick.

Installation of frame for panels

Guides for fastening the panels are welded onto the pile structure, which are then glued or screwed. The panel joints at the corners are covered and flashings are installed.

Regardless of the insulation material chosen, it is recommended to make ventilation holes that should be made diagonally on the base. To prevent the entry of rats or other rodents, each of the openings must be closed with a grill.

This type of ventilation will prevent moisture from forming inside the space.

Insulation with polystyrene foam

High-density polystyrene foam (extruded) has good insulation and sound insulation properties and makes it possible to produce high-quality insulation of foundations on screw piles.

In addition, an inch and a quarter sheet of material does little to reduce the internal volume of the plinth.

Stage-by-stage execution of work

Before installing insulation sheets, a brick or concrete wall must be prepared: cleaned of dirt and dust, eliminate irregularities and cracks and treated with a primer (preferably deep penetration, GGP).
Installation of expanded polystyrene sheets is carried out using special adhesives or installation foam. The insulating elements are secured using special mounting dowels.
The space between the ends of the sheets must be insulated (spray foam, mineral wool, etc.). To achieve better thermal insulation properties, the sheets are attached in two layers.
A metal mesh is fixed over the insulation to protect against rodents.
Along the inner perimeter of the plinth (along the walls) a layer of expanded clay is filled.

Insulation with mineral wool

It is a heat-insulating material with good performance, non-flammable and non-toxic.

Stage-by-stage execution of work:

If the minislab has a high density, it can be fixed to the plinth with mounting dowels.
Waterproofing is installed from rolled materials (roofing felt, roofing felt, linochrome, etc.)

Floor insulation

When installing a screw pile foundation, it is necessary to provide for the production of a floor together with thermal insulation. If it is not available, it is necessary to insulate the outside of the building.

Stage-by-stage execution of work:

A vapor barrier layer is installed.
A layer of selected insulation is fixed (in accordance with the temperature conditions).
The next one is a waterproofing layer made of rolled materials.
The resulting structure must be protected from mechanical damage by an additional layer. The materials can be boards or sheet materials (plywood, chipboard and others).

Upon completion of the work, not only an insulated floor is obtained, but also a prepared ceiling for the utility basement.

Insulating a pile-screw foundation will solve the problem of cold floors, reduce energy consumption associated with heating and extend the life of the entire house.

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Insulation options for pile foundations

Modern compact equipment for installing screw piles allows fast and cheap arrange the foundation for a private house.

The desired type of finish and method of insulating the base depend on aesthetic preferences, the qualifications of the craftsmen and the financial capabilities of the owners.

Distributed two ways to insulate the foundation:

According to a separate shallow belt structure. It is laid out of brick or poured from concrete supported on the ground or its own shallow foundation. This method is ideal for regions with warm climates and sandy soil. The insulation is attached to the base according to the standard scheme.
On a metal sheathing, which is fixed on stilts. Installing a frame around the perimeter allows you not only to perform insulation, but also to effectively decorate the base of the house with siding, clinker panels or corrugated metal sheets.

The type of pile structure does not significantly affect the choice of insulation method; technical nuances are discussed in SNIPs 02/23/2003 “ Thermal protection of buildings».

Pile-screw foundation insulation technology

Features of the pile-screw foundation The problem is that it is almost impossible to insulate the piles. Therefore, a strip plinth made of brick or concrete blocks is erected along the perimeter of the foundation and the internal cavities are filled with soil or expanded clay mixed with sand. The bulk pillow is carefully compacted. The technology is quite simple, but requires physical effort.

In order to prevent the cold from creeping across the floor, additional thermal protection of the floor is provided. The design resembles layered cake and might look like this:

1 layer – subfloor;
2nd layer – moisture and windproofing substrate: Izospan, Yutavek, Tyvek or analogues;
3rd layer – mineral wool;
4th layer – vapor barrier membrane material;
5th layer – finishing floor.

Features of insulating a pile foundation from the outside on heaving soils

In cases where a building is being erected on heaving soils, the tape method of insulating the base is not suitable. The swelling process occurs unevenly, inclined cracks may appear on the masonry, so they use the second method. They arrange the sheathing, insulate it with polystyrene foam, and finish it with decorative trim.

Rules for insulating a pile-grillage foundation

The design of the pile-grillage foundation assumes only external thermal insulation. The side edges of the grillage serve as the walls of the basement floor, and they need insulation. Various methods are used:

Cover the side walls with a layer of bitumen or roofing felt. The resulting crust protects the base well from moisture.
Glue polymer materials (expanded polystyrene, foam) onto bitumen. The seams are sealed with polyurethane foam to avoid cold bridges.
Lay a layer of steel reinforced mesh. This provides protection from rodents and a ready-made base for finishing plaster.
A strip-type base or “warm masonry” is installed.

Choosing a method of insulation pile-grillage foundation depends on the climatic and weather conditions of the region, soil structure, and the height of groundwater. Most often, to reduce heat loss, the optimal solution is used - they mix several methods into one. For example:

blind area device;
adding expanded clay filler;
the use of polymer insulation around the perimeter.

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Pile foundation design

Screw piles are chosen for light buildings or under difficult operating conditions. Bored piles save construction budgets. Low grillages are either immersed in the ground or start from its surface, protecting the floor of the lower floor from blowing. Hanging grillages are an unprotected underground, which developers who do not have practice or specialized education are trying to insulate.

When using a hanging grillage, it is impossible to make a floor on the ground. In 90% of cases, floors are used on joists, which can be insulated with basalt wool over the subfloor. The work is carried out from the inside and has nothing to do with the insulation of the pile foundation.

Why is it impossible to insulate a pile foundation?

Regardless of the type of thermal insulation material, each of them is designed to retain heat in the room. In the underground there is no pile foundation, no heaters, no warm air, so insulation is impossible in principle:

Warming cold air masses is literally money down the drain. However, excessive ventilation cools the floors from below, increasing the operating budget; storm and flood waters get under the building, and evaporation damages the structural frame of the house.

The problem is solved by the design of a false base, called a pick-up. It is made by laying half a brick or by lining a frame with basement siding attached to the pipes of a pile foundation. However, it is necessary to leave ventilation vents in it to ventilate the underground.

What needs to be insulated in a cottage on a pile foundation?

Having determined that the intake does not need to be thermally insulated, you need to pay attention to the communication input nodes. Water supply pipelines and drainage systems require insulation. Liquids have, although not high, a positive temperature, which must be preserved with several layers of insulation inside the foundation underground, underground until the freezing mark in the region.

Water supply pipeline entry point

The cold water pipe passes below the soil freezing mark, after which it rises to the base of the building and passes through the underground air to the floor. The insulation of this engineering system occurs in the following way:

In practice, the heating cable is used along the entire length of the pipeline, guaranteeing protection of communications from freezing.

Sewer outlet unit

Insulating the sewer system is simpler and cheaper than the previous case. The wastewater leaving the home has a high temperature and cannot freeze when passing through the basement underground. Therefore, underground they are protected with shells, and in the air they are wrapped in one layer of basalt or glass wool.

The gas line is not afraid of frost; there is no point in insulating it. The same applies to the power supply cable.

Slab grillage on piles - an exception to the rule

A pile foundation requires insulation in the only case - a monolithic slab grillage on the heads of SHS or bored piles. When choosing this technology, on a flat area without a difference in height, to save the construction budget and reduce labor costs, the slab is cast into formwork on the ground. The developer gets rid of the lower formwork panels (which are extremely difficult to dismantle later), while receiving loads from heaving forces that can tear the grillage slab away from the piles. In this case, the insulation technology looks like:

Stiffening ribs on the base of the slab grillage are not needed. Input of communications is carried out before the manufacture of the foundation pad. The blind area is insulated with polystyrene foam at the level of the base of the slab, protecting against lateral freezing. Communications do not need to be insulated, unlike other grillage foundations.

This technology is too expensive and is rarely used. The backings of prefabricated grillages (beams or I-beams) on screw piles, monolithic ones on bored piles do not need to be insulated. Waterproofing the facing material at ground level is sufficient.

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Features of a pile-screw foundation

The pile-screw foundation is suitable for lightweight buildings: frame, log and timber, made of SIP panels. Supports - steel piles - are installed under the walls at intervals of several meters. The support is a pipe with a sharp tip and a helical blade at the end. A screw pile resembles a screw both in shape and installation technology: it is literally screwed into the ground. It is advisable to connect the installed piles to each other with a metal corner at the top, this will prevent their possible displacement. Often, in order to save money, a corner is not installed; in this case, the piles are connected by a frame support board or the lower crown of the frame installed directly on them.

A properly constructed pile-screw foundation can withstand severe frosts; an unfinished and unused building can be safely left for the winter without insulation. The foundation is practically not subject to the forces of frost heaving: the screw blades lie below the freezing depth, and the treacherous heaving soil slides along the smooth pipes of the piles without causing any damage to the building.

A seasonal dacha “on screws” can be insulated without heat at all. You don’t have to close the base, just leave it open. But if the house is lived in year-round, you will need effective insulation of the pile foundation from the outside. Thermal insulation is needed in order to minimize heat loss through the floor of the first floor and thereby reduce heating costs. And also to prevent freezing of communications introduced into the house in the underground. It is necessary to take into account a number of features of the screw design:

Initial lack of vertical external perimeter fencing. It will have to be built.

Often, screw foundations are built on problematic heaving soils.

The presence of free space between the ground and the ceiling of the first floor.

As a rule, the soil under the house is wet.

Taking into account the above, there are three problems that you will have to deal with when insulating a pile foundation: humidity in the underground, heaving of the soil and its freezing:

How to remove excess moisture from the underground

It is possible to completely waterproof the soil under the house. But this is economically unjustified, since we are talking about cheap construction. You can, of course, lay plastic film on the ground, but this is a half-measure. The space limited around the perimeter under the ceiling of the first floor will inevitably receive moisture from the soil if the house is not built in an arid area.

The question inevitably arises of protecting the first floor ceiling structure from water. A vapor barrier for the ceiling is required, and it must be made from below, from the underground. Therefore, when building a screw foundation, it is worth choosing a pile height so that a person can move and work in the underground. Otherwise, you will have to install the lower vapor barrier while being above the frame, which is not very convenient. And if necessary, it will be impossible to repair or replace the insulation without opening the floor.

To remove excess moisture, ventilation holes will have to be made in the outer fencing of the foundation. Vents should be located on all four sides of the building; for a large house, preferably two on each side, closer to the corners of the building.

The hole should be covered with a grate to prevent rodents and wasps from entering the subfloor. Regarding the size of the holes: SNiP recommends taking the total area of all holes in the basement equal to 1/400 of the total floor area of the first floor of the house. For example, for a house 8x8 m, eight vents with a diameter of 8 cm each will be required. Underfloor ventilation will be even better if you move the exhaust duct from there to the roof.

The air temperature in the underground in winter will be positive, but it will definitely not be hot there. This must be taken into account when installing the ceiling of the first floor; the insulation layer must be sufficient, at least 15 cm. It is imperative to insulate the water supply inputs and the sewerage outlet.

How to avoid deformations from the heaving effects of soil

Heaving soil (clay, loam) increases in volume when it freezes; in winter its level rises. Jammed gates and rickety fences are the result of this very process. When installing an external vertical fence and insulating the base of a pile-screw foundation, it is unlikely that we will bury it below the freezing depth of the soil. As a rule, the fence is lowered just below ground level. But in cold weather, the heaving soil will rise and begin to put pressure on the foundation fence. The result will be deformation.

In order not to repair the basement fence every spring, the heaving soil underneath should be replaced with non-heaving soil: remove the clay and pour coarse river sand into the trench. For the central regions of Russia, it is enough to replace it to a depth of 60 cm. It would also not be superfluous to lay a damper strip of foam plastic or other non-rotting material that can compress under load in the ground between the soil and the outer fence.

How to prevent soil freezing under the foundation

Having made vertical insulation of the foundation from screw piles only to the ground level, we still will not achieve proper thermal insulation of the building. Wet winter soil is an excellent conductor of cold; frost will inevitably “make its way” horizontally under the house. The soil under the vertical fence will freeze, bypassing the insulated but not buried wall below. Freezing of the soil under the foundation can be prevented by installing a so-called “insulated blind area”. Under the covering of the blind area (concrete, tiles, gravel, lawn) at a depth of 10-30 cm, it is necessary to lay a layer of thermal insulation horizontally. Extruded polystyrene foam is best suited for these purposes. It is necessary to ensure that the vertical and horizontal thermal insulation are connected, without leaving a cold bridge for cold penetration into the subfloor.

How and how to close the basement of a house with a pile-screw foundation

The thermal insulation material needs to be placed somewhere; it needs a base. First of all, it is necessary to close the underground. The type of insulation of a foundation on screw piles is determined primarily by the design of the outer fencing of the base. How to close a screw pile foundation?

Basement fencing with brickwork

You may come across a recommendation to make a fencing for a screw foundation from brick or rubble. Some developers do just that. However, you need to understand that it will not be possible (more precisely, it is irrational) to provide a sufficiently reliable support for a brick wall and the strength of the structure is not guaranteed.

If the soil is heaving, in the place where the wall rests it should be removed to a depth of at least 80 cm, replacing it with sand. And to support the masonry, monolith a reinforced mini-foundation with a cross-section of at least 20x20 cm. Between the concrete and the brick, as well as the wooden support beam of the house frame and the brick, it is necessary to lay a layer of rolled waterproofing. The insulation will have to be placed on the inside of the subfloor during the laying process. If the subfloor is high enough, it makes sense to make a manhole into it, then the insulation can be laid even after the construction of the brick structure is completed.

We do not consider the solution with a brick base to be rational. Having built the foundation and house using the cheapest and “fastest” technology, it is illogical to then get involved in lengthy and rather expensive work with stone fencing. It’s easier to build a lightweight subfloor fencing using a frame.

Base fencing with light lining on the frame

How and from what to make a frame on screw piles?

You can make a frame from metal - it is more reliable, more durable, but more complex and expensive. It is easier and more convenient to use a corner; with a pile pitch of 2 m, a 40x40 mm profile is sufficient. Having placed the corners horizontally with the shelf down, support them with wooden blocks, to which it will be easy to attach the sheathing. How to connect metal parts, by welding or hardware, is a matter of taste and availability of equipment. For fire safety purposes, welding work should be carried out before installing wooden structures on supports.

It is easier and cheaper to make a wooden frame, from bars or boards. The wood must be pre-antiseptic, because the underground is humid. It is better to fasten the bars to steel pipes not with self-tapping screws, but with long bolts or ties. You will have to drill a recess in the wood under the bolt heads to place the fastener flush-mounted.

Having built the frame, we will get a more or less solid base for attaching the sheathing and laying the insulation of the base. Any sheet material that is not afraid of moisture and is not very heavy can be used as cladding. Flat asbestos cement sheets are very strong, durable and relatively inexpensive. Plastic siding designed for covering the base looks great. Even a “fence” metal profile and ordinary galvanized sheet steel will do.

How and how to insulate a pile-screw foundation

How to choose insulation? First of all, it must be moisture resistant. Hydrophobic synthetic materials are well suited: polystyrene foam, EPS, polyethylene foam, etc. Of the mineral insulation materials, only foam glass is suitable, mineral (basalt and glass) wool - in no case. No organic-based thermal insulation materials are suitable. The final choice of thermal insulation material depends on where it is located.

How to insulate a pile foundation along a frame, where to place the insulation? It is clear that from inside the underground, but there are options here too:

Placing a thermal insulation layer behind the sheathing frame

At first glance, the easiest way is to first fasten the base sheathing directly to the frame, and then lay the insulation behind the frame. It is behind the frame, and not between its elements. So that there are no cold bridges. But in this case, the question arises about its reliable fixation. You can, of course, attach sheets of thermal insulation to the back of the frame. But it will be inconvenient to carry out such installation with a low base. Access from the reverse side is difficult, but you need to secure the fixing elements and fill the cracks with construction foam.

And, most likely, the thermal insulation will not fit in the locations of the steel piles or its layer will be thinner. These are the disadvantages of this method. Pros: you can use any insulation, in particular inexpensive and easy-to-cut polystyrene foam of the lowest density. Due to the low price, you can increase its thickness. And screw piles can be additionally thermally insulated on three sides from the inside of the subfloor.

Installation of insulation in front of the sheathing frame

Another option for insulating a pile foundation is to first attach the insulation to the frame, and then the sheathing on top of it. The advantage of this method is the ease of work. With due diligence, the fixation of the insulation will be as reliable as possible. It is easy to seal all existing cracks with construction foam.
If you attach a fine-mesh steel mesh to the frame before installing the thermal insulation sheets, the thermal insulation will be reliably protected from rodents, even if they penetrate into the underground. You will have to use a fairly rigid material as insulation; extruded polystyrene foam (EPS) is ideal. Sheet sheathing is fixed over the insulation sheets.

But EPS can be finished in other ways. The first, cheap option: plaster with a thin layer of facade plaster over a polymer mesh. The second method is more expensive, but for many it is more beautiful and definitely more prestigious: lining the thermal insulation slabs with light facade tiles that imitate brick.

We talked only about the most accessible methods of thermal insulation of the foundation subfloor on screw piles. There are other methods, for example, covering with double thermally insulated finishing panels or constructing a basement wall from polystyrene blocks of the “Warm House” system. But, regardless of what technical solutions for the construction and arrangement of your own home you decide to use, we recommend that you consult with specialists on all important issues before starting construction work.

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Why insulate a pile foundation?

In areas with problem soil, where there are areas with floating layers of soil, the optimal solution for building a house would be a pile-screw foundation. It will provide reliability in places with high groundwater levels, in contrast to strip monolithic or prefabricated foundations.

The pile-beam structure and dynamic loads are not afraid. It is very durable and resistant to soil heaving. It is also not afraid of the destructive effects of groundwater, since the screw piles are made of anti-corrosion steel.

Another advantage of this type of foundation is its relatively low cost, as well as the speed and ease of construction. Installation of one pile foundation by a team of experienced specialists will take only one working day.

But, despite a number of positive qualities, the pile-screw foundation has a number of negative features. The house, built on stilts, does not have a basement, and also has poor thermal insulation parameters.

There is a space between the floor and the ground that is easily blown through. This is precisely why precious heat leaves the house very quickly. This is especially noticeable with the onset of cold weather. Radiators don't do their job because warm air always rises and the floors remain cold.

To solve this problem, you need to think about it at the stage of designing a house - thermal insulation. Insulation of a pile-screw foundation occurs at the stage of working with a grillage in order to completely isolate it from external air flows. Finished houses can also be insulated, but it will not be as effective as thermal insulation during the construction stage.

Also, for high-quality and effective insulation of a pile-screw foundation, it is necessary to install a false base. It should prevent wind and precipitation from entering the free space between the soil and the house.

Materials for foundation insulation

When insulating a pile-screw foundation, it is necessary to pay attention to the false base and grillage. These elements come into contact with the surface of the house and, when frozen, can transfer low temperatures to it. The screw piles themselves, immersed in the ground, do not need to be insulated.

When insulating a false base, it is necessary to select a material that is not afraid of water and retains its thermal insulation properties even in a damp state. After all, a large amount of moisture comes from the ground, which means that the insulation will be in a very humid environment. It must also be resistant to various salts and minerals found in the soil. It is better to use high-density sheet materials or a liquid heat-insulating mixture when insulating a pile-screw foundation.

The most popular materials for insulating a pile-screw foundation are:

Styrofoam;
liquid penoizol;
foam glass blocks;
extruded polystyrene foam or polystyrene foam.

Penoplex and foam plastic have the same thermal conductivity and also do not allow vapor to pass through. Penoizol also has similar thermal conductivity, but allows moisture to pass through. It is better not to use mineral wool and basalt insulation, as they are not very convenient for installation.

Do-it-yourself insulation of a pile-screw foundation

You should start insulating the foundation only after the grillage of the house has been waterproofed. Waterproofing membranes are perfect for this. The most budget-friendly option may be roofing felt or similar bitumen-based materials.

For the manual construction and insulation of a false base, the following tools are required:

welding machine;
trowel, spatula, hammer, tape measure, knife;
low speed drill or screwdriver;
concrete mixer.

The false base of a pile-screw foundation does not bear any load, since its main task is to isolate the free space under the house from external factors.
The first option is to build a brick wall under the grillage. Its thickness should be half a brick. The second option is to cover the free space with decorative panels that are attached to the grillage.

Creating a brick plinth

This option is more labor-intensive, but the effort will not be in vain. Since the brick base is as reliable as possible and has greater durability, while the decorative alternative is easily damaged.

Before erecting and insulating the basement, it is necessary to dig a trench around the house under the grillage. The depth of the trench should be 20-30 centimeters, and the width should be slightly larger than the brick.

The trench should be filled with concrete mixture and allowed to harden. This will be a kind of foundation on which the brick plinth will be laid. Due to the shallow depth of concrete, reinforcement with a reinforcement diameter of 10-12 mm should be used.

After the concrete has completely set and hardened, you can begin to build the walls of the brick plinth. It should be laid in small sections 1-2 meters long. This is necessary in order to simplify the insulation on the surface of the base.

To secure the material chosen for insulation, you will need specialized adhesive compositions that should not contain organic solvents.

After insulating the base, you need to cover the brick wall with a decorative cap. There is a huge selection of materials to suit everyone’s preferences. You can also use plaster.

Creating a plinth with decorative panels

A much simpler way to construct and insulate a false base, as opposed to constructing a brick partition, is to install decorative panels. If you approach this issue seriously and competently, this method will provide durable and reliable insulation of a pile-screw foundation.

First, you should start choosing a supporting structure on which the decorative panel of the false base and the material chosen for insulation will actually be installed.

The distance between the guide profiles depends on the height of the free space between the floor of the house and the ground. Usually two or three longitudinal profile frames are sufficient.

A wooden beam will also do a good job as a frame, but it must be treated with an antiseptic or mastic in advance. The main thing is to protect the tree from rotting and insects.

Next, the frame cavities are filled with insulation. Foam plastic, penoplex or any other insulation. Do not forget about the thickness of the slabs if penoplex is used for insulation. If it extends beyond the grillage, it will greatly complicate the installation of decorative panels.

After installing the thermal insulation material, a decorative fence should be installed on the grillage of the building using an adhesive mixture. The size of the decorative panels is also an important aspect. To ensure reliable fixation, it is necessary that the lower part goes into the ground to a depth of about 5 centimeters, and the upper part fits tightly to the grillage. In the place where the lower part of the panel contacts the ground, you need to dig a small ditch 10-15 centimeters deep and fill it with expanded clay.

Expanded clay filler has low thermal conductivity, which will eliminate the possibility of the structure freezing at subzero temperatures. Consequently, this will also help reduce heat loss from the floor of the building.

The choice of this false base option for a pile-screw foundation with vapor barrier materials (penoplex) implies the presence of natural ventilation. It is needed to prevent moisture from accumulating in the internal space. Because of it, condensation will settle on the inside of the floor of the house, which can negatively affect the wooden structure. In order to allow air to circulate freely, you need to make special holes for ventilation. With the onset of cold weather, the holes should be closed with a plug or any heat-insulating material.

The energy saving problems that developers face are related not only to the insulation of walls and ceilings. Insulation of the foundation strip or basement walls should be considered equally responsibly. A “cold” grillage cools down the walls and ceiling of the first floor, creating uncomfortable living conditions and leading to heat losses. Residents are especially concerned if the floor on the first floor is cold. The floor surface is the only element of the enclosing structure of the house with which a person is constantly in contact, stepping on it with a booted or bare foot. To create comfortable conditions, the difference in the surface of the floor should be less than the air temperature in the room by no more than 2°C. Structurally, the insulation of the grillage is linked to the design and insulation scheme of the walls and ceilings. The desire to protect the underground from rodents can also affect the insulation and finishing of the basement of the building.

Insulation of the grillage of a columnar-strip foundation can be carried out by developers according to various schemes (Figure 167). It should only be taken into account that the greatest insulation effect can be created by installing an insulating layer on the side walls of the grillage. From the outside, the grillage can be insulated with polystyrene foam, penoizol, polyurethane foam, polyethylene foam and other insulation materials, protected from the outside by plinth finishing panels (decorative plastic panels, siding, DSP panels, asbestos cement sheets...).

Figure 167. Insulation of grillage:
A – with wooden ceiling; B – with concrete floor; B – walls and grillage with external insulation; G – with a concrete floor on a sand backfill;
1 – grillage; 2 – wall; 3 – insulation; 4 – blind area; 5 – wooden floor; 6 – floor; 7 – logs; 8 – foundation support; 9 – plate-wall; 10 – backfilling of soil; 11 – sand backfill; 12 – polyethylene foam; 13 – concrete floor; 14 – tin box; 15 – reinforced concrete floor slab; 16 – exterior trim panel

The grillage can be insulated from the inside with the same insulation materials. This can be done according to the traditional scheme for insulating the subfloors of log houses, in the form of backfilling with soil. But in such a case, the gap under the tape should be closed with any sheet material (Figure 167, a).

If the beams of the first floor are wooden, then protection from rodents can be carried out both from the outside of the grillage (protecting the gap under the grillage with a blind area) and from the underground side (protecting the insulation with a tin casing (Figure 167, c).

If the floor of the first floor is a concrete slab cast on a sand bedding, then thermal insulation can be made in the form of rigid polystyrene foam slabs or rolled foam insulating material (polyethylene foam, polyurethane foam...) (Figure 167, d).

Developer, don't forget!

Before starting the construction of walls, you should arrange a place for supplying utilities to the house. This can be done before the construction of the foundation begins or after, before installing the lower floor. Developers who put off this work until later are faced with certain difficulties. It can be extremely difficult to install a ring or dig trenches for supplying water and draining sewage under the lower floor of a house.

Insulation of the foundation is necessary solely to reduce heaving forces or comfortable operation of the underground floor. Pile foundations that fall below the freezing mark are not afraid of heaving forces. In principle, there cannot be a basement floor in these structures. The underground of the pile foundation is not heated, the ground freezes completely. Therefore, there is nothing to insulate here.

Statistics show that in 5% of cases, the underground of cottages located on areas with a serious difference in elevation is used as a workshop or utility room. In this case, a heating device is installed here, and the fence is insulated using ventilated facade technology.

However, in the absence of an insulated floor, heating costs are enormous and high-quality ventilation is necessary. Otherwise, evaporation from the soil will lead to the destruction of the floors of the first floor and other structures of the building’s load-bearing frame. For the same reason, storing lumber underground is not recommended.

Pile foundation design

Why is it impossible to insulate a pile foundation?

What needs to be insulated in a cottage on a pile foundation?

Water supply pipeline entry point

In practice, the heating cable is used along the entire length of the pipeline, guaranteeing protection of communications from freezing.

Sewer outlet unit

The gas line is not afraid of frost; there is no point in insulating it. The same applies to the power supply cable.

Slab grillage on piles - an exception to the rule

In some cases, pile foundations have an advantage over columnar, strip and slab foundations. This is especially true when soils freeze to a significant depth, in wetlands, in areas with a high layer of loose soil, as well as when there are large slopes and differences in height of construction sites. Savings due to the choice of pile technology can reach 50% or more. However, developers need to plan an additional budget for insulation of the pile foundation. The problems solved by thermal insulation and methods of its construction are described in this article.

For low-rise construction, solid reinforced concrete piles, steel screw piles and bored concrete piles are most suitable. Regardless of the design of the piles, the method of their installation and the grillage installation technology, this type of foundation has a number of disadvantages.

Disadvantages of a pile foundation:

A pile foundation that is not insulated during the cold season can lead to big problems

Cold underground. Increased heat loss through the floor in winter.
If the grillage is made of reinforced concrete, then a powerful cold accumulator is created. If there are interruptions in heating, it takes a very long time (up to several days) to restore the normal microclimate in such a room.
Danger of freezing of utilities laid under the floor.
Pushing out piles caught in the freezing zone. Piles are a conductor of cold. If anti-frost measures are not taken, metal and concrete supports can cause local heaving.
Uneven shrinkage under the weight of the house when individual piles fall into areas of low soil density.
From an aesthetic point of view, a conventional pile foundation is a purely utilitarian design solution that requires decoration.
The emptiness under the house, blown by the winds, quickly becomes littered and periodically requires time to restore order under home.

Why are individual piles pushed out, leading to a situation where the plane of the grillage is disrupted? One of the common reasons is uneven soil moisture: it is stronger around the perimeter and corners than in the center. This, in turn, leads to uneven freezing depth. In addition, specific expansion during heaving also depends on the percentage of humidity.

4 of the 7 problems listed in the list are directly related to exposure to cold and can be solved with the help of a competent thermal insulation device.

Insulation of a foundation made according to a pile scheme with a reinforced concrete grillage

This or that decision on thermal insulation is made depending on the height of the base. Small heights make it expedient to arrange floors on the ground. In this case, the principle of insulation is the same as in the uv scheme.

The grillage, like the MZLF, takes the load only from the walls. The floor slab is cast over a layer of polystyrene boards. The slabs are laid out on a compacted sand bed. Under the pillow there is a main layer of backfill consisting of anti-capillary crushed stone.

External perimeter insulation consists of vertical cladding of the base and insulated scaffolding. There are no original engineering solutions unique to houses on pile foundations here. Everything is done according to the principle of eliminating cold bridges. There should be no gaps or breaks between the insulating layers of the wall, plinth and scaffold. In this case, overlap connections are preferable to butt contacts.

To cover the base with insulation and finishing, it is necessary to form a sheathing. For this purpose, piles are tied. The strapping can consist of rolled metal and wooden moldings. The idea that this measure is an additional factor in increasing the rigidity of the pile foundation has no real basis. Sometimes, instead of cladding with EPS, half-brick masonry is used on the sheathing. But they try to rest it from below not on the blind area, but on the channel, which is welded to the bottom of the piles.

The version with a high base differs in that the floor slab rests not on the ground, but on a grillage. In this case, it is acceptable to perform both external and internal insulation of the slab. In any case, it makes sense to exclude the cold bridge from the ceiling to the piles through the grillage. For this purpose, a thermal break in the horizontal plane is used. It can be done by installing EPS between the grillage and the belt of additional foundation blocks on which the ceiling directly rests.

Insulation of a pile foundation with a wooden beam floor

When designing a house on a foundation made of metal screw piles, in most cases they try to minimize the load on the ground. To do this, use a beam ceiling made of special wooden beams. How to insulate a foundation on screw piles if wooden structures are used at the base of the floor? Firstly, for thermal insulation of the ceiling, a structural “cellular” relief formed by beams and joists is used. Secondly, in order to reduce the impact of condensation on the beams, the insulation of the base is carried out according to a different scheme than when using concrete floors.

Flush with the bottom of the beams, a beam with an approximate cross-section of 50×50 is attached along them. This molding is the support for the “subfloor” - boards on which sheet waterproofing and the first layer of insulation are laid. The most commonly used is mineral wool. Logs are attached on top of the beams perpendicular to them. A second layer of thermal insulation is laid between the joists.

When arranging horizontal insulation of the base, they try to maintain a ventilated gap between the cladding and the scaffold. This is done in order to increase the service life of wooden beam floors.

Yes, this measure reduces the energy efficiency of the house, but the only alternative to it is the use of vents. It is allowed to keep the vents closed during frosts. Sheet waterproofing, located between the sheathing and horizontal insulation, extends below the cladding and is bent in such a way as to direct precipitation runoff to the blind area.

Choosing the finishing finish for an insulated base

From a technological point of view, it is permissible to use all types of cladding and finishing coatings. This can be plaster, decorative clinker, and various types of linings. Some EPS collections are produced with a finished coating already applied, which reduces costs and speeds up work.

Insulation of pile foundations with decorative EPS boards

If we talk about the aesthetic side, then when using imitation of any materials, you should think about naturalness. For example, is it worth using clinker bricks as cladding for the basement of a house made of wooden beams?

If we turn to tradition, then during the times of mass wooden house construction, a stone base was much more often used. Today, when building cottages made of timber on a screw foundation, it is much more logical to use special slabs made of EPS that imitate masonry.

Conclusion

How to achieve maximum energy saving and reliability of construction, insulate a pile foundation, and even achieve the maximum possible lifespan of the house? To do this, you should first perform a complete design of the house and foundation before construction, and not “solve problems as they arise.” When using any standard design solution for thermal insulation, be guided by two basic principles: eliminating cold bridges and ensuring acceptable operating conditions for the specific materials used.