It is a system of pillars - supports, which are located in a strictly determined order by calculation.
This type of foundation is advisable to use in the construction of relatively small light buildings without basements, which, as a rule, have no more than two floors, as well as various buildings for household needs and light frame-type structures.
If the following conditions exist on your site Not recommended To build a columnar foundation, it is better to choose another method of constructing the foundation of the building:
- The soil on the site is characterized by mobility in the horizontal plane. The influence of this factor can be eliminated by installing more powerful grillages (more on this below), but such work will increase the overall labor intensity of the process and raise the cost of materials.
- The construction of a house of massive construction is required: with walls made of reinforced concrete or brick.
- The presence of weak-bearing soils (clay, peat, water-saturated or subsidence rocks);
- There is a significant difference in height on the site allocated for construction, amounting to more than 2 meters.
The advantages of a columnar foundation include the relatively low labor intensity of its arrangement and the absence of the need for significant excavation work, which reduces the cost of construction work and materials. The cost of its construction compared to a strip one will be 30-50% less.
On life time The columnar foundation is influenced by the type of material used to make the supports, and on average it is:
- for wooden poles - depending on the type of wood, from 7 to 15 years without additional processing and from 10 to 30 years when using firing or special compounds;
- for pillars made of red brick - up to 40 years;
- rubble or concrete supports - 50-80 years;
- monolithic concrete pillars with reinforcing strapping - up to 150 years.
However, the given figures are quite arbitrary, since it is necessary to take into account many more factors that influence the durability of the columnar foundation. First of all, this is the quality of the materials used, the characteristics of the concrete and mortars used for masonry, and the correct waterproofing of the supports.
For example, it is quite difficult to process concrete pillars when constructing a foundation, so moisture-resistant concrete is used for their manufacture, and wooden supports are coated with special compounds.
Types of column foundation, materials and features
Depending on the base depth columnar foundations are divided into the following types:
- Non-buried- their depth is on average from 0.3 to 0.5 the depth of soil freezing in a given area.
- Shallow- these include the foundations of buildings laid at a depth equal to 0.5-0.7 freezing depth according to the standards.
- Recessed, the base of which descends to the level of soil freezing and below.
Columnar foundation supports are made from various materials. The choice of a certain type of material is influenced, first of all, by the weight of the building being constructed.
For pillars can be used:
- rubble stone or flagstone, having medium dimensions, and it is necessary to select material for supports of the same parameters;
- well fired red brick, since low quality material can quickly collapse;
- combination of concrete and rubble stone;
- monolithic reinforced concrete;
- reinforced concrete and concrete blocks; pipes made of asbestos cement or metal, filled with concrete mixture;
- hardwood.
To ensure the stability of the building and its long-term operation, the supports during the construction of the foundation must withstand significant loads, which is only possible with certain dimensions. The dimensions of each pillar, their depth, the number of pillars, locations, as well as the distance between adjacent pillars are calculated. It is definitely not worth using the “by eye” method in this case; it is better to use the help of professionals or specialized software tools.
According to the design, a columnar foundation is built monolithic (made of reinforced concrete), combined (pipes made of asbestos cement or iron, filled with mortar) or prefabricated from individual elements (brick, stone or ready-made blocks). In addition, a similar type of foundation is erected using ready-made pillars made of reinforced concrete or wood.
To the features monolithic columnar foundation include: the use of concrete as the main material; labor intensity due to compliance with the technology of pillar construction; the need to arrange formwork and use reinforcement; reliability, durability and structural strength.
Img by OakleyOriginals - flickr
Less labor-intensive and built using piece elements. This kind of foundation was widely used in the past, it is distinguished by the following parameters: a significant reduction in the time required for foundation construction; the need for waterproofing work. Brick foundation It is used quite rarely due to the complexity of construction and the ability of brick to absorb moisture, collapsing under its influence. Therefore, a combined option is often used, in which the lower part of the supports, located in the ground, is cast from monolithic concrete, and the upper part is built from brick. Concrete block foundation less susceptible to destruction under the influence of moisture, but absorbs it, therefore they require waterproofing measures. The masonry of blocks is carried out with the obligatory bandaging of the seams, and to increase strength, metal rods are installed in the voids and filled with mortar.
Features of a combined columnar foundation: reduction of foundation construction time; it is not necessary to strictly observe the depth of all supports, since this parameter is adjusted.
Img by Ashley Basil - flickr
Used as pillars, it resembles a pile pillar, but is characterized by a shallower depth.
Characteristic features of constructing a foundation from ready-made pillars: increasing construction speed; reduction in labor intensity of work. This technology is used supports made of wood or reinforced concrete.
Under wooden houses, especially those built using frame technology, you can install wood pillars coniferous or oak treated with a special anti-rotting compound.
In order to increase the stability of the supports and prevent their horizontal displacement, the upper ends of the pillars are connected to each other by metal beams, a channel or a monolithic structure made of reinforced concrete, called grillage. Depending on climatic conditions and terrain, its lower part may be buried in a trench, located at ground level, or have a gap between the soil and the surface of the foundation. To protect the walls from the adverse effects of soil and moisture, a plinth is built on a columnar foundation.
Technology (installation stages)
Before starting the construction of a columnar foundation, it is necessary to carry out calculations to select the material and determine the number of pillars and their installation locations, laying depth and other parameters.
To do this you will need the following data:
- characteristic features of the soil;
- building material;
- the depth of groundwater;
- soil freezing level;
- the magnitude of the frost heaving force;
- design features of the building (its height, type of floors, roofing material);
- the magnitude of the loads at each point.
You can use special programs, seek the help of specialists, or do it yourself. In the latter case, the bearing capacity of the supports is checked, taking into account the type of soil. Why compare the maximum load of pillars on the soil with the permissible load, which depends on the strength of the soil. Based on the data obtained, a columnar foundation is erected in stages:
1. Carrying out preparatory work
First, the work site is cleared; if there is soil with a plant layer, it is removed, retreating at least 2-5 m from the perimeter of the planned foundation. Then, on clay soils, a cushion of sand and gravel is arranged, sandy and rocky soils are used without modification, and for peat and silty soils, an artificial base will be required. Finally, the site is leveled on a horizontal plane, for which the mounds are cut off and the holes are filled, guided by the level.
2. Marking the foundation
The axes of the house are marked on the site, the correctness of which is controlled by precise measurement and verification of compliance with the angles of 90⁰. It is also necessary to mark the bottom of the trench, at least in the corners of the building, and its depth must coincide with the design value. The location of each pillar is marked according to the drawings, and to control their height, pegs with a cord stretched between them are used. The use of special measuring instruments will ensure the accuracy of markings.
3. Excavation work
For a monolithic reinforced concrete foundation, rectangular holes are dug manually or using mechanized means. If the depth of the supports does not exceed 1 m, then the walls of the pits are not strengthened. Otherwise, a hole is dug with slopes and then reinforced with boards. To eliminate frost heaving of the soil, a cushion of gravel or its mixture with coarse sand is placed on the bottom. The cushion is spilled with water and compacted using a tamper, and then roofing felt or polyethylene is laid, which will prevent the poured concrete from drying out.
4. Construction of pillars
If the pillars are constructed from monolithic concrete, then at this stage formwork is installed from boards, plywood or particle boards, checking it for compliance with the vertical axis using a plumb line. When using metal or asbestos-cement pipes as pillars, they are placed 30-40 cm above the ground level. The construction of a columnar foundation made of blocks or bricks consists of laying a layer of waterproofing on the cushion, forming a backing material and performing masonry. Cement mortar is used to secure bricks or blocks together. Wooden poles are made from hardwood, and a cross is mounted underneath, which is sunk into concrete. Before installation, the wood is burned or treated with special protective antiseptics against rotting. Supports made of asbestos-cement or metal pipes are installed in pits on a prepared cushion, then concrete mixture is poured into them. To reinforce such pillars, ribbed reinforcement is used. It is not advisable to use rubble stone pillars in heaving soils, since during the operation of the house and the impact of load, the support may delaminate. To prevent such scenarios, the pillars are arranged in the shape of a trapezoid with an extension towards the bottom.
5. Installation of fittings
Reinforcement of pillars is carried out using metal rods installed in the vertical direction and horizontal wire jumpers. The rods must be placed in such a way that in the future it will be possible to connect the frame of the finished pillar and the grillage, that is, it is necessary to provide for the exit of the reinforcement above the surface of the support.
6. Pouring concrete mixture
Monolithic pillars are poured using a mixture of cement, gravel, sand and water, or ready-mixed concrete, having previously placed a waterproofing material, which is roofing felt, on the bottom of the formwork.
7. Grillage arrangement
To ensure the stability and rigidity of the columnar foundation, a grillage is constructed to connect the supports to each other. It can be made from a metal beam, channel, or in the form of a prefabricated or monolithic element.
8. Pickup device
When constructing a columnar foundation, in order to insulate the space under the floor and prevent snow, moisture and penetrating cold air, as well as debris or dust from entering it, a fence is installed. It is an enclosing wall and can be constructed from any materials, but brick or stone is most often used. The base of the screed is a concrete screed, which has no depth and is laid on a sand bed. Its construction will require formwork, as well as a frame made of metal rods to prevent possible ruptures of concrete due to soil movement. When laying materials for screeding on the screed, it is necessary to take care of the technical openings for connecting various utility communication networks.
Img by Yusoff Abdul Latiff - flickr
The technology for constructing a columnar foundation is not particularly complex and does not require significant excavation work, resulting in a reduction in the complexity of its installation. This base is the optimal choice for the construction of light structures, outbuildings and houses (usually made of wood) no higher than 2 floors. Choosing a foundation on pillars can significantly reduce the cost of materials and helps simplify the installation of utilities. In addition, the high speed of foundation construction makes it possible to begin building a house almost immediately, excluding the situation when the supports are made of monolithic concrete and it takes about 30 days to gain its strength. However, when building a columnar foundation with your own hands, some difficulties may arise. Firstly, the main problem is to correctly calculate the number of pillars and choose their depth. An error in calculating the load and assessing the bearing capacity of the soil can result in uneven subsidence of the foundation. This can be avoided if you entrust the work to specialists, and also by independently studying the technology for constructing this type of foundation.
At first glance, it may seem that building a columnar foundation for a house with your own hands is an almost impossible task. However, this statement is not true.
Features of a columnar foundation
First you need to understand the definition of a columnar foundation. To put it simply, it is a set of supports that bear the weight of the structure being built. The racks are installed in places of maximum load - these are the corner points of the building, wall connection points and spans longer than 2.5 meters.
The distance between the posts, as well as the shape of the posts, are calculated values that depend on a number of factors:
- type of racks;
- material of manufacture;
- building design;
- planned mass of the structure;
The standard distance is 1.5 - 2.5 m, the cross-sectional diameter for round supports is from 20 to 25 cm. The size for rectangular ones is from 25 by 25 to 40 by 40 cm. It is desirable that the ground part be at least 50 cm in height, length underground part depends on the depth of the backfill.
The upper support points must be at the same level, which must be carefully checked after installing the racks and adjusted if necessary.
Disadvantages and advantages
Before you build a columnar foundation with your own hands for a frame house, you need to understand in which cases its use is suitable and in which it does not make sense, as well as its pros and cons.
Flaws:
- it is impossible to arrange the basement of the future house;
- cannot be used on floating or water-saturated soils
Advantages:
- quick drying and;
- minor costs;
- construction in any season;
- separate installation of each support;
- ease of installation;
- affordable replacement and repair.
Types of columnar foundations
There are different bases depending on the parameters, the cross-sectional shape of the supports, the materials and manufacturing processes of the pillars and the depth of the base. In cross-section, the racks are round, square, rectangular. It is possible to make supports in monolithic form from concrete, or in prefabricated form from bricks, blocks, rubble.
The classification according to the depth of the bookmark is as follows:
- for heaving soil, buried pillars are laid below the freezing point;
- for non-heaving and low-heaving soils with sand and gravel air embankment, use shallow racks with filling up to 70% of the soil freezing point;
- for non-buried for low-heaving or non-heaving soils using a dense sand cushion.
Base structure
In order to competently build a columnar foundation with your own hands for a frame house, it is important to clearly understand the structure and process of its construction.
Work with soil
- To begin work, it is necessary to prepare the site for the construction of the foundation.
- Complete removal of debris and removal of turf by approximately 15-20 cm.
- Leveling the ground surface.
- Marking the area with pegs according to the plan. The pegs are installed at the corner points of the future foundation, connected with a cord, after which the accuracy of the markings is checked along the perimeter.
- The installation points for the pillars are being marked.
- Digging holes.
Support arrangement
1. Brick supports . Some situations make it possible to make support posts from brick, which is advisable to do on stable soils and in places where groundwater is deep.
Laying is possible in two ways:
- laying on a sand bed;
- constructing a concrete shoe, then laying bricks on a hardened base.
The most commonly prepared supports are 25 by 25 cm (a row of 2 bricks). If you plan to build a large building, then you can lay 4 bricks - 38 by 38 cm with additional installation of reinforcement inside the pillar.
It is important to maintain an exclusively vertical position of the supports with regular checking with a plumb line or level.
2. Block . An alternative option is wall or shoe (cushion) rectangular concrete blocks measuring 20 by 20 by 40 cm. The latter should be mounted on top of a sand cushion at the base of the supports, the shape of the posts is trapezoidal. Most often they are erected as shallow or non-buried supports.
3. Monolithic . Such supports are made by pouring concrete mortar into pre-installed formwork, round or rectangular in cross-section, additionally reinforced with steel rods.
4. Rectangular supports . The formwork for such supports is constructed from plywood or edged boards. If construction takes place on stable ground, then the formwork is created naturally from the walls of the recesses. Before pouring the solution, it is necessary to cover the walls of the pit with waterproofing material.
When installing racks in loose soils, it is necessary to erect formwork along the entire height of the future pillar; recesses are dug in such a way that it can be installed and fixed without problems.
5. Round pillars . It is allowed to erect supports that are round in cross-section. For production, wells 20 - 25 cm in diameter are drilled. The construction technology coincides with the production of rectangular supports; instead of formwork, roofing felt, plastic or asbestos pipes are used.
In some cases, TISE technology is acceptable, when specialized drills with a plow are used for wells with expansion at the bottom in order to increase the support area.
6. Combined supports. In some cases, a do-it-yourself columnar foundation for a frame house is built not from one material, but from two. For example, first the buried part of the support is concreted, after which the above-ground part is erected, but using bricks.
Formwork
Before erecting the formwork for both installation options, it is necessary to create a cushion of a mixture of sand and gravel 30 - 50 cm high for shallow and non-recessed racks and 10 - 20 cm for recessed racks.
The formwork is mounted strictly vertically on the cushion, secured with stops. The inside walls are covered with waterproofing.
The supports can be of uniform thickness along the entire length or with a thickened bottom - a “shoe”. In this case, the width of the support pit must correspond to its dimensions. The “shoe” can be installed separately with the reinforcement released from it; after its hardening, the support formwork is installed on top.
Four ribbed reinforcing bars with a diameter of 10 - 12 mm make up the frame, connected by clamps 6 - 10 mm in diameter made of ribbed or smooth reinforcement. The distance between the reinforcement and the formwork is more than 3 mm, a similar gap from the cushion for the purpose of anti-corrosion protection of the metal. You can ensure distance using plastic stands, which will also prevent the reinforcement from moving.
When constructing supports with a “shoe,” the rods are installed before the formwork is mounted.
If a grillage is not planned, then the upper point of the end of the reinforcement is 5 - 6 cm down relative to the level of pouring the mortar. It is planned to install embedded studs with a diameter of 14 - 16 mm to connect the supports with the lower trim.
For foundations where the construction of a grillage is planned, the frame protrudes 15-25 cm above the pouring level in order to coordinate with the latter’s frame.
Next, a concrete solution is poured, either made independently or purchased from a brand no less. Portion pouring with tamping with a vibrator or other means. Removal of the formwork is permissible after final hardening.
Grillage
You can install a grillage, you can do without its construction. This is a solid concrete structure that serves to ensure uniform load on the supports. The lower surface of a high grillage is located at a distance of 10 - 20 cm from the ground surface, a low one is laid on a sand and gravel cushion buried 15 - 10 cm into the ground.
Formwork for grillage
To install a hanging grillage, it is necessary to build a formwork. Two installation methods are allowed here: place the bottom at the level of the supports’ heads, or build it to its full length to the ground level, and then fill the space between the ground and the grillage with sand. The formwork must be closed with waterproofing.
The height of the formwork is important; its top should end flush with the level of pouring the concrete solution, or exceed it by 5 - 6 cm. The height of the grillage depends on its type and the type of cross-section of the supports: for a hanging one from 25 to 30 cm, for a low base 50 cm , and width from 25 to 40 cm.
Reinforcement
The frame is made up of 1 - 2 rows of longitudinally located reinforcement, which is connected by transverse rods or clamps. The connection is made with a soft wire. The gap between the frame and the formwork is at least 3 - 5 cm, the same rule applies to the upper surface of the grillage.
The reinforcement must be linked to the releases of the reinforcing cages of the supports. If the length of the support reinforcement outlets exceeds the height of the grillage, they must be bent at the highest points of the grillage surface at 90°.
Mortgages for vents are mounted at the stage of fastening the formwork along with studs to fix the lower trim. The diameter of the latter is 14 - 16 mm, and they are placed strictly parallel to the supports along the line of the bottom trim beam.
Concreting the grillage
Concrete is poured carefully, completely covering the reinforcement and without creating cavities. It is recommended to use tools for compacting the solution. At the end of the pouring process, it is necessary to level the top layer so that the surface is even over the entire area. The formwork can only be removed after the concrete has completely hardened.
Use of waterproofing
For those parts that are the above-ground component of the supports, waterproofing is necessary, since they are vulnerable to the influence of the environment and the weight of the building. In order to protect against external sources of moisture (rain, snow), wind, physical and chemical influences, you can use roofing felt or solutions designed for such tasks.
Conclusion
In general, it is obvious that a do-it-yourself columnar foundation for a frame house is a completely feasible task. In addition, installing such a foundation makes it possible to build a truly reliable foundation for the future home.
A durable and inexpensive columnar foundation is usually built under buildings whose walls can be called lightweight - and these are wooden and panel baths, framed and made of foam blocks. But it happens that a zero level of this type is also laid under a heavy brick bath - when a deep foundation is needed and the strip foundation in this case can ruin. After all, columnar ones cost at least one and a half times cheaper than the last option, which, in fact, are good.
For a usually light and small bathhouse, massive strip foundations are often akin to unnecessary luxury - but column foundations are much more suitable for such construction: both in price and in strength. Yes, the traditional structure of a columnar foundation does not require the presence of a basement - but the Russian steam room does not need one.
Budget column foundation with grillage
If you build a columnar foundation with your own hands, then the first thing you need to do is make an accurate calculation. For this purpose, it is necessary to calculate the mass of the bathhouse, and here it is important to take into account its snow load - in the Moscow region this is approximately 100 kg for each square meter of area. As well as the weight of the internal filling of the bathhouse: furniture, stove and people - that’s another 100 kg for the same meter.
By the way, if it is difficult to calculate the bearing capacity of the soil in a certain area, then it is better to proceed from this calculation: 0.5-0.6 kg per cm2. In fact, these are the parameters of a peat bog or an old drained swamp. In all other cases, things are much better.
Stage I. Making pits
The easiest way is to take a drill with a diameter of 25 cm and drill small holes in the ground - 15-20 cm. This will be the basis for making the lower part of the pillars. It must be reinforced with a fine mesh and filled with 200 grade sand concrete.
In the central part of the pit, you need to insert several rods of reinforcement so that they protrude no more than 10 cm from the pit. These can be old and unnecessary pieces of pipes, pieces of iron and debris.
And to prevent the cement lait from being absorbed into the soil, pieces of roofing felt or even ordinary plastic bags will help.
Stage II. Installation of pillars
A piece of asbestos-cement pipe with a diameter of 10 cm is taken, two reinforcing rods with a diameter of 1.2 cm are placed in it and the whole thing is placed on the “shoe”. You need to fill it with the same sand concrete, simultaneously compacting everything with another rod. On top is either a bolt or another piece of reinforcement.
Stage III. Second drilling
It takes about 4-5 days for the concrete to harden after the last steps. Next, you can begin the second drilling. To do this, you will need a drill - it makes a hole with a diameter of 30 cm and always below the calculated freezing depth. You need to quickly insert the resulting pillar into this opening so that it does not crumble. Its strength can reach up to 11 tons of load.
Stage IV. Construction of the grillage
The grillage for such a columnar foundation can be made from metal, concrete and even wood - here it’s up to you to choose what you like best. The only important thing is that the grillage itself hangs above the ground by more than 10 cm.
The main advantage of this type of foundation is that it is suitable for almost any bathhouse that is not very heavy - log, timber and frame. And it serves for a long time - at least a hundred years, and even when it stands in a swamp.
Solid support-column foundation
Of course, foundation pillars can be made of a variety of materials - concrete, brick or stone. But the most popular today for individual construction is affordable and practical reinforced concrete.
So, this is how a standard columnar foundation for a bathhouse is built:
Stage I. Site preparation
It all starts with cleaning the area - for this, the entire top layer of soil is cut off, right along with the plants. Its thickness is usually a little more than 30 cm, and it cannot be left under the foundation.
If there is clay on the site, then you need to make additional gravel and sand backfill. Its thickness depends on the geological features of the soil.
Now all the unevenness in the landscape is removed, soil is poured into the holes and with the help of pegs and ropes you can begin marking for the future foundation.
Stage II. Foundation plan
Next, from the drawings to the land plot, you need to transfer the plan of the future bathhouse - where and what will happen. This can be done using standard materials, securing the axes and marking the main dimensions of the future foundation. How accurately everything is marked, the easier it will be to work later.
Stage III. Pit preparation
Pits for a reinforced concrete columnar foundation are dug either manually or using an excavator - which, of course, is both easier and more expensive. They will be located along the axes.
If the depth of the pit does not exceed a meter, its walls do not need to be strengthened. If it is more, you will have to dig with slopes and install fastenings from boards with special spacers.
The holes should be 30 cm greater than the calculated depth of the foundation - so that gravel and sand backfill can be used. The width is taken a little more than it will be - so that the formwork and spacers become free.
Stage IV. Installation of formwork
To make good formwork for a columnar foundation of a bathhouse, you will need planed boards up to 40 mm thick and 150 mm wide. Alternatively, you can use chipboard, metal sheets and moisture-resistant plywood instead of wood. The boards need to be placed against the concrete.
Stage V. Foundation reinforcement
Foundation pillars need to be reinforced in the longitudinal direction with A3 rods with a diameter of 12-14 mm. Horizontal jumpers need to be installed in increments of 20 cm - for this, wire with a diameter of 6 mm is quite suitable.
In order to then connect the pillars with a grillage through the reinforcement frame, it is necessary that the rods extend above the edge of the foundation by at least 10-15 cm. By the way, something more solid can also serve as a grillage - this is how a columnar-strip foundation is built, which has its own advantages, but, however, not always justified for a bath.
Stage VI. Pouring foundation pillars
Concrete must be poured into already installed pipes, which will then remain in the ground with the foundation.
It must be laid in layers - 20-30 cm, using hand vibrators for the convenience of the process. This will ensure the homogeneity of the mixture and remove all the air from the solution.
Stage V. Waterproofing a columnar foundation
The future foundation can be protected from moisture using the same materials as a strip foundation. These are cold and hot prepared mastics, adhesive membranes, roofing felt on bitumen - and all new and well-proven materials.
Stage VI. Construction of the grillage
A monolithic belt makes both a solid foundation and a columnar foundation made of blocks more rigid and stable. And it can be made from prefabricated reinforced concrete rand beams or immediately monolithic.
So, if a prefabricated belt is being made, then the jumpers need to be well connected to each other with scraps of reinforcement - by welding them with mounting loops. Next, the formwork and reinforcement cage are installed and everything is filled with M200 concrete.
As soon as the concrete hardens and becomes strong, and waterproofing is carried out, the sinuses of the pits can be filled with soil and the installation of floor slabs can begin.
By the way, in order to protect the underground space under such a bathhouse from snow and cold air, a fence is usually made between the pillars - a special wall, most often made of brick. There is no need to tie it to the pillars - after all, the bathhouse will still settle, and cracks may appear. And already in the intake itself technological holes are made for communications. Externally, all this is beautifully decorated with false panels and siding - that’s all.
The foundation is the most important element of any structure: from a light garden gazebo to a capital multi-story country mansion. This is the beginning of the building and its foundation in the literal sense. The strength, durability and operational safety of the building depend on how correctly the foundation is selected, calculated and executed. The question of what type of foundation to choose arises even at the construction planning stage. The optimal solution in many cases will be to build a columnar foundation with your own hands: step-by-step instructions for performing the work can give a complete understanding of the principles of its design and the intricacies of the arrangement process.
Advantages and disadvantages of a columnar foundation
Self-calculated and self-equipped columnar foundations for frame houses and buildings without basements that do not exert strong pressure on the ground are easy to implement and relatively cheap.
According to reviews, columnar foundations have a fairly impressive list of advantages:
At the same time, columnar foundations have only two disadvantages:
Types of columnar foundation
Before proceeding with the detailed design and calculation of a columnar foundation, you should decide on what site, what type and using what technology the building will be erected on it. The choice of material for the columnar foundations and the depth of their placement depend on these factors.
Materials for building the foundation
The following materials can be used for foundation foundations:
- reinforced concrete;
- rubble concrete;
- blocks;
- brick;
- a natural stone;
- tree;
- pipes: asbestos or plastic.
Foundation depth
The depth of a columnar foundation is determined by its design, technological parameters of the structure and geological characteristics of the soil in the building area.
Based on their depth, columnar foundations are divided into three main types:
To build a columnar foundation with your own hands, step-by-step instructions are needed as the most detailed and visual aid.
In general, the design of a support-column foundation is a system of supports of the minimum possible cross-section, located at points of load concentration: in the corners of the building, at the intersection of walls, under load-bearing beams, partitions, under the furnace. To determine the number of free-standing columns, the distance between them is taken to be 1.5–2.5 m. To connect the foundation supports into a single structure, a grillage is made between them.
The height of the pillars above the zero mark is individual and depends on the design features of the grillage.
Calculation of a columnar foundation
The construction of a columnar foundation begins with calculations. Most likely, to perform the calculations yourself, you will need a program like “Foundation” or some other that can be found on the Internet and downloaded for free. To work with such programs you will need the following parameters:
The technology for constructing a foundation with columnar supports also requires additional data:
As a result of the calculations made, the following values required for installing a columnar foundation will be obtained:
Columnar non-buried foundation
A columnar, non-buried foundation on supports spaced at intervals of 1.5-2.5 m is used quite often. Such foundations can be erected on non-heaving and slightly heaving soils, despite the fact that the building (wooden or panel house, bathhouse, outbuilding, outbuilding or summer kitchen) has a small area and, accordingly, light weight. Moreover, if construction is carried out on rocky, coarse-grained or non-moving soil, this type of foundation can be installed under a fairly large house made of logs or timber. It is also possible to build a foundation on non-buried supports, provided that the influence of heaving forces on the structure is reduced. To do this, the soil under the supports is replaced with a sand cushion.
As a material for pillars, it is possible to use concrete, rubble concrete, sand concrete or concrete blocks for the foundation, the sizes and prices of which are very diverse. However, most often they take foundation blocks measuring 20x20x40. The price of such a foundation, as well as the number of blocks required for its construction, can be calculated independently or using an online “foundation” calculator. You can also make a columnar foundation from brick with your own hands, but it must be taken into account that the use of silicate or ceramic bricks with low frost resistance is unacceptable.
Work on the construction of a non-buried columnar foundation from ready-made blocks can be divided into several main stages:
When building a foundation using 20x20x40 blocks with your own hands, video clips and step-by-step instructions will help you understand the technology of work, understand the process and more accurately estimate financial costs.
Shallow columnar foundation
A shallow foundation is one of the most popular types of columnar foundation. The funds and effort that its device requires are minimal, and the range of applications for frame-type buildings is very wide.
As a basis for a frame house or a light bathhouse, a columnar foundation is often made using pipes as formwork for the concrete mixture. Since the reinforced concrete pillar will take the entire load, the material of the pipes does not matter much: both plastic and asbestos pipes, usually used for installing sewer networks, are suitable.
The diameter of the pipes depends on the load. For light buildings such as gazebos or extensions, 10 cm is enough; for log buildings, pipes of 25-30 cm are needed. The amount of concrete is ultimately determined by the diameter of the pipe. For 10 m of a pipe 10 cm in diameter, you will need 0.1 m3 of concrete, a 20 cm pipe will require 0.5 cubic meters, and a 30 cm pipe will require 1 cubic meter. The calculation was made taking into account the concrete base pad.
The scheme for carrying out work on constructing a columnar foundation from asbestos pipes with your own hands (a video of the process can be found on the Internet) is generally as follows:
- preparation of the construction site - removing debris, removing foreign objects, removing turf and leveling. Marking the perimeter of the future building, corners, internal walls and their intersections. Places for installing foundation supports are marked with pegs;
- Then, holes are made in the ground using a hand-held post drill. The depth of the well should be 20 cm greater than calculated: for the installation of a sand cushion;
- installation of a sand cushion with mandatory compaction and spilling of sand with water. After the final absorption of water, pieces of roofing material should be laid on the bottom in order to prevent moisture from the concrete mixture from escaping into the sand;
- installation of pipes in wells with a height reserve of at least 10 cm. Leveling pipes and securing them in wells using wooden blocks. If groundwater is close to the ground, the pipes must be coated with bitumen mastic to the ground level for waterproofing;
- then the base of the pipe, 40-50 cm deep, is filled with a thoroughly mixed concrete-gravel mixture (1 part cement and 2 parts sand, diluted with water to form a batter, combined with 2 parts fine gravel). Immediately after pouring, the pipe is raised to a height of 15-20 cm and left in this position until the cement has completely hardened. This is necessary to create a foundation that resists pushing out during soil heaving;
- after the concrete has hardened, the pipe should be waterproofed from the outside with roofing material and the well should be filled with sand, gradually poured and compacted;
- Reinforcement is placed inside the pipes, after which the remaining part of the pipe is poured with concrete;
- after the concrete has completely hardened - 2-3 weeks later - construction work continues. It should be added that it would be useful to waterproof the foundation with polymer or bitumen solutions.
Using the same scheme, it is possible to install a columnar foundation made of plastic pipes with your own hands. Videos and photos will help you navigate the intricacies of the work process, which is generally simple.
Columnar foundation with grillage
The grillage is a system of rand beams and strapping beams. It rigidly fixes the foundation, preventing it from moving in the horizontal plane or overturning the entire structure. In the presence of a grillage, the load from the structure is distributed evenly across all installed columnar supports, resulting in increased stability and resistance to destruction.
To facilitate understanding of the process, the necessary work is outlined in stages.
Preparation and installation of supports:
- In any case, the initial stage of preparation for the construction of the foundation is the arrangement of the construction site. After removing debris, etc. the turf and top layer of soil are removed along the perimeter of the future foundation;
- for supports it is necessary to dig holes 20 cm deep than the freezing level of the soil. The width of the pit should be 40 cm greater than the width of the wall, since 20 cm are added on each side for formwork and spacers;
- at the bottom of each pit, a 20 cm high cushion of sand-crushed stone mixture, spilled with water and well compacted, is made. The cushion is lined with roofing felt or polyethylene so that moisture from the concrete poured into the pit does not go into the ground;
- boxes for formwork are assembled from boards 20 mm thick;
- It is recommended to thoroughly moisten the formwork installed in the pits to prevent the absorption of moisture from the cement mortar and facilitate removal;
- After installing the formwork, a frame made of reinforcement is placed in the pits. The frame is assembled separately, from a rod 10-14 mm in diameter. The length of the rods is selected in such a way that when the concrete hardens, their ends protrude 30-40 cm above the ground level;
- the concrete mixture is poured continuously, in layers of 20-30 cm, leveling with a vibrator to avoid the formation of air bubbles;
- the formwork is removed after 3-4 days, the surface of the supports is treated with any suitable waterproofing mixture and the remaining part of the pit is covered with sand. Before backfilling, it is also possible to insulate the foundation with extruded polystyrene foam.
Grillage arrangement:
There are two options for installing the grillage: laying it on the ground or raising it above its surface. The advantage of the second method is the elimination of the effects of heaving forces:
Cost of work on installing a columnar foundation
The total cost of a columnar foundation is the sum of the cost of materials and the cost of the work itself. In most cases, it is significantly lower than the cost of other types of foundations, since almost all types of columnar foundations can be built with your own hands. Videos and photos, instructions and guides found on the Internet are also usually cheap or free.
You can calculate the cost of most types of columnar foundations yourself using special online calculators or programs. Many of them are quite easy to find on the Internet, free and have an intuitive interface.
The foundation is the support of the entire house; the durability of the entire building depends on its design and strength. When choosing the type of foundation for country houses, our compatriots play it safe and lay a strip foundation. You can easily verify this by taking a tour of the gardens. But such measures are completely unnecessary. For light buildings, such as wooden, frame, frame-panel houses, a column-type foundation is more suitable. In addition, indications for its use are soils supersaturated with moisture, sandy soils, peat, swampy soils and those where frost heaving forces can push out or damage the strip foundation. You can build a columnar foundation with your own hands in an extremely short time, without involving heavy equipment and a team of workers.
A columnar foundation consists of pillars - supports buried in the ground and protruding outward. The top level of the pillars must be the same. A grillage is installed on top of the pillars to connect the supports and distribute the load evenly. The pillars must be placed at each corner of the building, as well as at the intersection of walls and in places where the maximum load is applied.
The material for the pillars can be wood, brick, concrete, concrete blocks, asbestos-cement or metal pipes, as well as rubble stone.
Wooden pillars Today they are used extremely rarely, as they are short-lived. But under light wooden buildings or terraces it is quite acceptable to install a columnar foundation made of wooden posts. The diameter of such pillars should be 0.15 - 0.2 m. Before deepening, they must be treated with special preparations and impregnations that prevent rotting and prevent combustion. Bitumen mastics can be used as a waterproofing material.
Iron ore brick, fired in a kiln, is used for shallow or non-buried columnar foundations. The width of the pillar must be at least 0.38 m.
Concrete reinforced pillars are the most common and reliable option for a columnar foundation. They can be either monolithic or constructed from ready-made concrete blocks. The width of the pillars should be 0.4 m.
Asbestos-cement or metal pipes are used for arranging pillars as permanent formwork, since reinforcement is inserted inside them and concrete is poured.
Depth columnar foundation is calculated depending on the structure of the soil, the level of groundwater and the level of soil freezing. A foundation buried 0.4 m into the soil is considered shallow. Recessed - immersed 0.15 - 0.5 m below the freezing level.
Very often, a columnar foundation is installed in areas where the soil freezes 1.5 - 2 meters deep, since the construction of a strip foundation in this case is simply unprofitable. The lower level of the column is buried 15 - 25 cm below the soil freezing level.
The distance between the pillars can be from 1 to 2.5 m, but spacing more than 3 m is not recommended.
As grillage you can use a strong beam. If the structure is wooden, then it will act as a mortgage crown. But monolithic concrete grillage poured into wooden formwork is gaining more and more popularity.
The grillage of a columnar foundation can be high (above 35 - 75 cm above ground level) and low (lying on the ground).
A very important design feature of columnar foundations is that it is impossible to install a basement in the house. Sometimes, to enclose the space between the pillars, a fence is formed, which is smoothed out of brick or stone, but is not connected to the foundation pillars, so as not to disrupt its integrity in case of movement. It is very important to arrange ventilation in the enclosure to ventilate the underground space. But collection is not always done. In frequently flooded areas, columnar foundations are erected to a high height above ground level, which can range from 1 to 2 m. In this case, the house remains completely “hanging” in the air on pillars.
Columnar foundation: drawing, calculation and diagram
Before starting any work related to the construction of the foundation, it is imperative to stock up on design documentation. It is better to entrust the creation of this documentation for the house to special architectural companies.
The columnar foundation diagram looks something like this:
The first step is to calculate the columnar foundation to determine the number of pillars, their material, laying depth, arrangement locations, width, and more. Calculations will require soil characteristics, groundwater level, frost heaving forces, soil freezing level, building material, its height and number of storeys, type of floors, roofing material, loads at each key point of the building, and more. For independent calculations, there are corresponding online calculators on the Internet for calculating columnar foundations.
All dimensions obtained for a columnar foundation are entered into the design documentation, where all characteristics, material and much more are indicated.
DIY columnar strip foundation
Recently, the so-called lightweight foundation for modern one- and two-story cottages has become popular, which consists of pillars buried below the freezing level of the soil, and a non-buried strip foundation connecting these pillars. It won’t be easy to make such a foundation yourself; it’s better to call friends for help and order a ready-mixed concrete mixer to make the structure durable.
Excavation
Before making a columnar foundation, it is necessary to prepare the site for construction. To do this, remove excess soil and eliminate unevenness. If the top soil is clayey, you will have to remove most of it and fill it with sand.
Next, you need to mark the area. Using construction thread, we mark the site according to the attached drawing. We stretch the thread in two lines parallel to each other, with a distance equal to the thickness of the future strip foundation. We control the angle of intersection of the threads and the angles of the future structure; they should be equal to 90 °. We mark the places of intersection and junction of walls, as well as the corners of the building, places with the greatest load.
Throughout the marked area, we remove 30 - 40 cm of soil where the strip foundation will be. We make the width 7 - 10 cm larger so that there is room for the formwork.
According to the drawing of the columnar foundation, using a hand drill we make holes where the pillars will be. The diameter of the hand drill is 150 mm, 200, 250, 400 mm. If the depth of the pillars does not exceed 1 m, then additional fixation of the walls from crumbling is not necessary. If the depth is greater, then you will have to form supports from boards so that the soil does not crumble.
We fill the bottom of the wells with sand, a layer of 10 cm.
For the last time, we check the location of the wells along the axes and the evenness of the future foundation.
Arrangement of pillars
We will use concrete to construct the pillars, but to waterproof it, we will use a little trick.
From roofing felt, twisted in two layers, we form a pipe of the required diameter. We glue the connections with tape, and also tape the pipe around the circumference. We insert the structure into the well until it touches the ground.
We knit and weld a reinforcing frame from a reinforcing rod 10 - 14 mm in diameter and 6 mm wire. We insert it into the well. The top of the rods should protrude from the well by at least 15 - 25 cm.
We begin to fill the pillars with concrete. To do this, first pour 20 - 25 cm inside the well and lift the roofing felt pipe so that the concrete below spreads and forms a base. Then we fill the hole completely with concrete, forming a pillar. Using an electric deep vibrator, we shake the concrete so that there are no air bubbles or voids left in it.
While the concrete in the pillars dries, let's work on the strip foundation.
Arrangement of a lightweight strip foundation
We weld and knit a frame from reinforcing rod and wire to reinforce the strip foundation. Be sure to weld it and screw it to the rods sticking out of the pillars.
The rods will be located along the foundation strip, and the wire will be reinforced in the transverse direction, forming horizontal jumpers.
We install the formwork for the strip foundation. To do this, we use boards 10 - 15 cm wide and 4 cm thick. Instead of boards, you can take chipboard, plywood or iron sheets. When the formwork is knocked down, we lay waterproofing material inside. It is best to use modern membranes or polyethylene film, which will also be needed to ensure that concrete does not spill out of the formwork through the cracks.
We fill the strip foundation with concrete. For simplicity, it is better to order a mixer machine to fill such a large space. We also shake the concrete with a vibrator. When the concrete gains its strength, after 20 - 28 days, the formwork can be removed and all the necessary work on waterproofing the foundation can be carried out. Then we fill the remaining trenches with soil.
For more information about how such a strip-column foundation is made, video:
Important! Many experts are extremely negative towards columnar-strip foundations, insisting that the foundation should be either columnar or strip. Only in this case will it fully perform its functions and not interfere with movements in the ground. Despite this, many construction companies continue to equip a combined foundation. So it's up to you to choose.
DIY columnar foundation
For comparison, let’s consider the option of arranging a purely columnar foundation with a high grillage. Its arrangement is advisable for light buildings on sandy soils.
Excavation
We mark the site, as in the first option. Then we remove fertile soil from the site by 15 - 25 cm. In the corners and places where walls intersect, we drill wells 0.6 m deep. Better yet, we dig square-shaped pits in the place of future pillars by hand.
We pour a 10-15 cm layer of concrete at the bottom of each pit under the pillars. It will serve as a cushion for us. When the concrete has dried, you can begin to form the support pillars.
Construction of a columnar foundation
For the pillars we will use iron ore brick, carefully baked in a kiln. We lay out a support pillar with brickwork, 38 cm wide and 35 - 45 cm high above ground level. The bricks can be placed in a closed loop, leaving free space inside. Inside the empty space we form a reinforcement frame, tie at least 1 - 3 rods and insert them. Then fill it with concrete.
We check that the pillars are at the same level. Once the concrete has dried, the pillars can be waterproofed.
We fill the trenches with soil. We arrange a grillage on top of the pillars. It can be done using wooden rand beams. The edges of the beams must necessarily rest on the pillars and be connected to each other with a tongue-and-groove joint.
The grillage can be made of concrete. Then it is necessary to install formwork from wooden boards, weld a frame made of reinforcement inside and fill everything with concrete.
The columnar foundation technology allows the pillars to be made from asbestos-cement pipes. They are lowered into the well, then concrete is poured inside. Raise the pipe so that the concrete spreads, and then add concrete further, not reaching 10 - 15 cm from the top of the pipe. When the mortgage crowns of the house are connected to the foundation, they will need to be secured to the pipes using anchors and corner joints.
The construction of a columnar foundation allows you to significantly save on materials and a team of workers, since all work can be completed independently in a matter of days. Such a foundation can be safely built for wooden houses, bathhouses, technical buildings, terraces, verandas, gazebos, garages and other buildings whose weight is not enough to load the strip foundation. By the way, if you built a columnar foundation in the fall, it is not advisable to leave it unloaded for the winter. Therefore, concrete slabs are installed on top or they try to build the entire building before the onset of frost. Otherwise, during the winter, the forces of frost heaving may push the pillars out of the ground, and their location will no longer be even. It will be easier to dig them up and make a new foundation than to correct the consequences.
Do-it-yourself columnar foundation: video instructions