If you know how to build a columnar foundation with your own hands, you can safely start building any building on your country plot, from a small greenhouse or gazebo to a huge wooden house.
Columnar foundation - features and varieties
When it is planned to build a residential building made of wood, any economic building, bathhouse or garage, the question arises what type of foundation to choose for them. Anyone wants to spend less money on such an event and at the same time get a truly reliable foundation for future construction. The best option in this case is to arrange a columnar type foundation. It is the simplest to implement and relatively inexpensive.
The foundation we are interested in is suitable for another object that does not exert strong pressure on the ground and does not have basements.
It is not recommended to erect heavy concrete or brick structures on such a foundation.
The structure of this foundation is quite simple - a number of support pillars are placed on the ground in places where the main load will be directed upon completion of the construction of a house or other object. Such places include:
- piers;
- corners of the structure;
- sections of wall intersections;
- heavy load-bearing beams.
You can make a columnar foundation with your own hands from natural stone and wood, rubble concrete, brick, concrete, steel and asbestos pipes, bored piles. It can be prefabricated or monolithic. In the first case, the raw material for its construction is a “mixture” of stones, bricks and reinforced concrete blocks. The monolithic base is made of reinforced concrete, which provides increased foundation strength.
Columnar structures are also usually divided into two types, taking into account the degree of freezing of the ground on which it is installed and the type of soil itself. From this point of view, the foundation is:
- Shallow - the pillars are mounted into the ground at a depth of 0.4–0.7 m. Experts advise using such a foundation when constructing buildings on rocky or sandy soil.
- Recessed - the laying of supports is carried out to a depth that is 0.5–1 m below the freezing mark of the soil in a particular area. Pouring and installing such a foundation is recommended for watery and clayey soils, where there is always a danger of the foundation being washed away.
Note that a columnar foundation is built with your own hands using the same technology. Next we will look at how to make a columnar base yourself using various materials.
Preparing for arranging a columnar foundation - important tips
First you need to decide on the type of soil that is available on your site where you plan to construction work. After analyzing it, you can choose the type of base and installation depth of the support pillars (see above). For a light gazebo, it will be enough to deepen the foundation by 0.4–0.5 m and make it from wood or asbestos pipe products. But it's relatively big wooden house you will need to place it on a deeper (about 1 m) and powerful foundation, for example, made of concrete.
After this, you need to calculate the number of pillars that will go to construct the foundation. They must be present in the center and at all corners of any building (even if, in your opinion, it is very small). You will be guaranteed a truly reliable foundation for the building if you place pillars every 2 m (vertically and horizontally) of the structure. The height of the supports is usually taken 0.3–0.5 m above the soil level. It can be increased when there is a possibility large quantity precipitation and flooding.
Next, we begin to clean the area of land where the foundation is planned to be poured. We carry out these works as carefully as possible - we remove all unevenness in the ground, remove debris, add gravel to the clay soil. Then we create a point plan of the planned foundation and mark on it the locations of all the pillars.
You should also move 2 m away from the perimeter of the future building on four sides to mark the area from which you need to completely remove the surface earthen layer (20–30 centimeters). This is done to eliminate the danger of vegetation growing under the structure. And at the place chosen for construction, it is necessary to pour gravel or, after which you can begin to dig holes for installing the supports of the columnar foundation.
Formwork for the foundation - how to do it quickly and correctly?
The most common and economical is roofing felt formwork. This is what is most often installed on private farmsteads during the construction of various structures. It's done simply:
- We take a piece of roofing felt of the required length (we focus on the length of the post, and also add a little length to the scraps according to the level) and twist it in two layers into a tube. It is best to wind the material onto a template, for example, onto a metal pipe (its cross-section should be about 20 cm).
- We securely fasten the resulting twist with wide packing tape. Sometimes, before this, the roofing material blank is additionally wrapped with stretch film, which increases the amount of rigidity that the formwork will have.
- We take out the template from the resulting tube. In fact, the roofing felt formwork is ready!
Instead of roofing felt, you can use glassine. The sequence of operations in this case will be similar to that described above. Also, formwork is often made from wooden panels consisting of boards 15 cm wide and 4 cm thick. It turns out to be reliable and of high quality, but its cost, of course, is much higher than a structure made from roofing felt. Permanent formwork can be made of asbestos-cement or steel pipes. Their diameter should be 10–20 cm.
After this, we begin the process of strengthening the columnar base. For reinforcement, you need to use reinforcement with a diameter of 1.2–1.4 cm. It must be installed longitudinally. The function of horizontal jumpers will be performed by metal wire.
If the foundation is made with a grillage (special slabs or beams - the supports of the future building), about 20 cm of reinforcing bars are left above the pillars. With their help, after pouring the concrete mixture, you can easily connect the grillage to the columnar supports.
We make a columnar foundation from asbestos or steel pipes - you can do it!
In this case, permanent formwork made from pipe products of a suitable cross-section is required. The construction of such a foundation is recommended for any buildings, including wooden houses. For the work, you will need pipes with a cross-section of about 200 mm or more if the building is heavily loaded (several floors, large area).
Step-by-step instructions for building a foundation are as follows:
- We clear the site.
- We prepare cylindrical pits in which we install a reinforcement cage or pipes and fill them with earth, ensuring the fixation of the supports.
- We fill the pipe structures used with concrete solution to one third of their length. This procedure is mandatory; it creates the required hydraulic cushion for the base.
- We raise the pipes to a third of the height and pour the concrete mixture again, leaving about 15 cm of empty space at the top.
- We completely remove the pipes, and compact the concrete solution that remains in the hole and place a reinforced rod in its center.
- We are waiting for the concrete to harden.
The connection between the base and the erected walls of the structure is carried out using metal anchors. They should be attached to the lower wall beams and immersed in the 15 cm cavity left. You have made a reliable and durable foundation out of pipes. All that is required is to finally concrete the structure.
Construction of a foundation made of concrete blocks and wood - instructions
For frame private houses, various gazebos in suburban areas, saunas and outbuildings you can make the base from blocks. In this case, the support-column foundation is made with your own hands from concrete elements with geometric parameters of 20x20x40 cm.
The block base device includes the following stages:
- Site preparation.
- Digging holes, covering them with crushed stone and creating a sand cushion at the bottom.
- Installation (using cement-based mortar) of concrete blocks.
- Carrying out waterproofing measures (regular roofing felt is used, laid on the surface of concrete pillars).
- Plastering the surface of the blocks.
Block foundations cannot be constructed on horizontally moving soils, water-saturated and peaty soils. It is also undesirable to place overly massive buildings and structures on them.
You can also make a wooden foundation. But the service life of such a foundation will be objectively short. It can be increased by impregnating the wood with special antiseptic solutions. But even in this case, the foundation will last a maximum of a couple of decades.
For such a foundation, it would be correct to use coniferous wood or oak piles. The pillars are immersed in the soil by 0.5–1.5 m. The cross-section of the piles should be chosen larger - from 20 cm. Construction is carried out according to a simple scheme:
- We clear the area for laying the foundation.
- We dig holes. Their cross-section is taken to be 1.5 times the diameter of the wood supports used.
- We install wooden poles at the corners of the planned building, along its perimeter (every 2 meters) and at the points of intersection of the walls of the structure.
- Place a layer (15–20 cm) of sand on the bottom and compact it as thoroughly as possible.
- We carry out waterproofing of the lower part of the wooden supports (impregnation with oil, “wrapping” in 2-3 layers of roofing felt or ordinary roofing felt, which it is advisable to glue with bitumen-based mastic).
- We mount and align the pillars vertically (use a building level).
- We fill the voids between the pit and the pillar with broken bricks, large crushed stone and sand. These materials should be poured in layers and compacted constantly. The thickness of each layer is at least 10 cm.
- We level (now in height) the installed supports - we cut off their tops to achieve a completely horizontal plane. This procedure is easy to do if you stretch a cord over the posts.
- We apply roofing material or a special waterproofing film to the ends of the columnar supports.
Your wooden foundation is ready! Feel free to install a wooden structure on it.
Owners about the construction of a columnar foundation with their own hands land plots, private households, dacha cooperatives are thought of when you need to build a small and preferably light structure yourself - a bathhouse, a room for keeping poultry and animals, a veranda, an extension for equipment, a barn. Unlike a strip foundation, making a columnar foundation with your own hands is much easier, and one and a half to two times cheaper. This is especially true for heavy swampy, peaty and waterlogged soils, where sometimes only heavy equipment can cope with this difficult task. But a columnar foundation can be installed by one person with an assistant, quickly and efficiently, without special mechanisms, if he knows how to do it. Therefore the request is “ how to make a columnar one with your own hands step by step instructions » users choose quite often. Let us dwell on this issue.
Types and purpose of columnar foundation
Most often, a columnar foundation is installed for buildings made of wood. Experts do not recommend erecting heavy brick or stone structures on it; the foundation supports under the weight can become deformed and crack over time, which will lead to the destruction of the entire structure. Of course, there are special technologies used in permafrost areas, where the construction of a columnar foundation is the only way to build any structure, but this will require special equipment and knowledge.
Types of columnar foundations.
There are several main types of support-column foundations, united by the same type of construction, but different in the materials used in the construction process.
- Monolithic reinforced concrete structure is the strongest existing columnar foundation. It can be used for one or two-story residential wooden buildings.
- Brick columnar foundation is the most common, an example of this is buildings 100 and even 200 years ago. The main condition for its construction is high-quality baked brick. On this basis, it is also possible to build 1-2 storey wooden houses on dense soils, and the cross-section of the columns should not be less than 400x400mm.
- A block foundation has the same properties as a brick foundation. The only difference between them is the use of materials of different strengths. The most reliable are concrete blocks. The limitation for rubble stone blocks is the high mobility of soils in your area. If rubble material is available, it is better to pour a columnar foundation, a combined rubble-concrete foundation. Concrete, falling between the rubble stones, will secure them and make the structure monolithic and durable.
- Wooden-post - used everywhere for light buildings. The main task of builders is to give the entire structure durability, for which long-term and reliable impregnation of wood immersed in the ground is carried out. Wooden supports are treated with antiseptic impregnations and bitumen mastics, after which a layer of roofing material is fixed to their surface. Most often, wooden posts with a diameter of 150-200 mm are used to build verandas and terraces.
- Asbestos columns are used for the construction of both light ones - diameter up to 150 mm, and heavier buildings - diameter 250-400 mm. It is possible to use such hollow structures for formwork, followed by pouring a concrete composition inside the pipe, strengthening it with reinforcing bars.
- Metal piles are an excellent way to erect a structure on rough and uneven terrain. Finished structures are screwed into the thickness of the earth until they reach dense and stable layers of soil. On an uneven area, it is possible to correct the terrain due to different lengths of the selected piles.
Construction of a columnar foundation with varying degrees of depth
To properly build a columnar foundation with your own hands, you need to calculate its depth in the ground. It depends on many factors, so the recommendations of specialists in your area should not be neglected. Ideally, you need to create a project that takes into account:
- Soil freezing depth;
- geological features of the site's relief;
- underground level groundwater;
- soil composition;
- climatic features of the area;
- weight of the building being erected.
There is a shallowly recessed option, when a depth of 650-700mm is sufficient for installing columns. Such a foundation is recommended for deep groundwater in sandy, rocky and shallow soils that are subject to minimal displacement.
The buried foundation is located at a depth of 1500-2000mm, and often lower. It is recommended to adhere to this depth in areas with deep soil freezing from 450-500mm or with high soil mobility in the construction region. The approximate distance between adjacent columns is 1000-2000mm.
Basic designs of columnar foundations
The construction of a columnar foundation usually does not cause any particular difficulties due to its fairly simple design. The photo shows several options for basic designs for installing a columnar foundation.
- The bottom layer in each of the structures is a sand cushion 100-200 mm thick, designed to remove moisture from the foundation area, which is also drainage.
- The next layer to be poured is concrete, 400-500mm thick, forming a concrete pad.
- Next, you should place the columnar support itself, reliably waterproofed and reinforced with reinforcing bars, to give strength and durability to the entire structure.
- As a rule, the columns are raised above the ground to a certain level to install a grillage or other connecting all the supports of the belt. It will not only tie the structure together, but will also evenly distribute the load between all erected supports.
The grillage for light buildings is usually made of wooden beams with a section of 150x200 or 200x200mm. In the absence of timber, it is possible to arrange a reinforced concrete, metal, brick, rubble-concrete grillage. It can lie directly on the ground, in the form of a strip foundation, or hover above it at various heights of 300-900mm, and sometimes higher. The disadvantage of a high grillage will be the impossibility of building a basement under the building, but residents of flooded areas will appreciate the advantage.
Do-it-yourself columnar foundation step-by-step instructions
1. Preparatory stage
Before building a columnar foundation, you need to select and clear a place, removing all household garbage, weeds, uprooting stumps and undergrowth. After which we proceed to remove the top layer of soil of at least 20 cm and an area exceeding the dimensions of the proposed structure by 2-3 meters.
The next work at the preparatory stage is to compare the topography of the site with filling in the resulting holes and cutting off the hillocks. To do this, use excess soil or a special sand and gravel composition.
Please note that it is not possible to pour a columnar foundation for the future. It is necessary to continue construction immediately after hardening, giving a load to the foundation. Otherwise, the flooded posts may come out of the ground after wintering in the ground.
2. Marking for supports
The most critical stage of work is transferring all calculated values from paper to the ground. First, the corner posts are marked out, the main axes of the future house are fixed, they will serve as a guide for drawing all the main lines for laying the foundation and maintaining the exact dimensions. After this, the location and size of all other foundation supports are determined.
Here you can watch a video with the correctly positioned foundation of a house.
3. Construction of a columnar foundation
This stage begins with the preparation of pits for the installation of supports. Holes can be dug manually, drilled with a hand drill, an excavator operator can be hired for these purposes, or any other in an accessible way. The depth of the pit must exceed the size of the installed support by the depth of the drainage sand cushion (15-20cm).
If the technological process requires formwork, then the width of the pits must be increased for its construction.
After preparing the hole, sand is poured into it and water is poured in to compact it. For reinforced concrete monolithic design, the sand is fixed with cement laitance, which helps maintain its optimal humidity.
For the precast foundation, everything is ready to go. For a monolithic one, it is necessary to make a reinforced frame. For pipes - carry out anti-corrosion treatment and impregnation before installing pipes in prepared pits. Asbestos pipes are immediately ready for use.
Photo of how to properly make a columnar foundation with your own hands.
After the preparatory work, concrete is poured directly, with periodic vibration, to get rid of voids and obtain a strong monolith. This will ensure high strength of the base and increase its service life.
For more uniform distribution load between all the supports of the house, a grillage or tying layer is created. It can be metal - a rand beam, reinforced concrete, or in the form of a strapping beam. This depends on the type and material of the future building erected on this foundation. Before starting its construction, all parts of the supports protruding above the surface are adjusted in height. The video can be viewed here.
4. Waterproofing works
Groundwater and flood waters cause great harm to the foundations being built and the houses on their foundation. Therefore, it is not enough to make a columnar foundation correctly - you need to reliably waterproof it, making sure to include a grillage. To protect the supports, special bitumen compounds are often used, and to insulate the walls of the building, a layer of roofing material fixed to bitumen mastic and adhesive membranes are laid between the grillage and them. Such work is carried out carefully; the humidity regime in the constructed room depends on it. After which, all the resulting voids around the supports are filled with soil, or better yet, with a sand and gravel mixture. Such work is carried out in several stages, with diligent compaction of the laid layer.
5. Pickup
Buildings built on columnar foundations often do not have a basement. Therefore, the distance from the surface of the earth to the bottom of the building requires additional cladding. This is a kind of basement of the building and a lot depends on its arrangement:
- Floor temperature;
- No drafts from under the floors;
- Protection against moisture and dust getting into the underground.
Before complete cladding, provision should be made for ventilation ducts and the laying of utilities - water supply network, sewerage system.
The backyard, after its arrangement, is decorated with brick, stone, facing tiles, decorative plaster– there are no restrictions in this process.
Before starting the construction of the fence, it is required to make a screed with a thickness of 180-220mm, it will act as a support for the walls of the building. The height of the fence-base depends on the height of the grillage and the length of the support pillars protruding above the ground. It is better to leave at least 300-400 mm for such, which is, firstly, aesthetically pleasing, but also practical. In areas with floods and high groundwater levels, the height of the intake can reach impressive sizes and this is economically justified. In addition, a house hovering above the ground at a great height looks quite impressive, despite its design, color and materials used in its construction.
Conclusion
We looked at the main stages of the work and learned in more detail how to properly make a columnar foundation with your own hands. But it’s still better to entrust the design of such a foundation and the entire structure to specialists, especially if you plan to build more than just a shed or toilet on summer cottage, and 1-2 storey house for the whole family to stay. Such expenses will pay off over time, when the house will stand for decades and will be left as an inheritance to children and grandchildren. For this work, specialists use special software, and today their cost has become more affordable and accessible.
In the family of point-support foundations, the columnar structure looks like the black sheep. Unlike pile-screw schemes or options on bored piles, a columnar foundation cannot ensure the stability of a building on a slope or on decrepit peat soil. Even the most desperate amateur house-builders do not try to install columnar structures on a swamp or heaving foundation.
How to install a columnar foundation
But in fact, the columnar version has two remarkable features. Building a columnar foundation with your own hands is accessible even to beginners in construction, and the cost is approximately half the estimate for a shallow-depth tape. If you have a need to build a hut on a sandy area, near a pine forest or on hard calcareous soils, the easiest way to solve the problem of arranging the foundation is in one of the following ways:
From the above list, the first two options will require the use of construction equipment and handling equipment; for a brick scheme, the skill of a mason is required. The last method from the list above requires only time and a little patience in working with your own hands and following the recommendations of the practical guide.
Important! A cast columnar foundation can be safely called universal; if there is drainage and drainage on the site, it can be installed even on small slopes without the need to work with a grader to level the horizon on the site plan.
In fact, a columnar foundation is the best option for building a small summer kitchen, gazebo or bathhouse on a country plot with your own hands. For large and heavy buildings, a columnar foundation is weak and dangerous.
How to make a columnar foundation with your own hands quickly and easily
Casting concrete columnar structures will require lengthy and rather messy mixing work cement mortar, installation and strengthening of post formwork, leveling and cleaning of working surfaces. You can take a simpler route and buy ready-made blocks with a length of 40 cm and a cross-section of 20x20 cm. A foam concrete block of the structural grade D1200 or heavy expanded clay concrete grades are best suited.
For heavier versions of the house, granite blocks can be made. For this purpose, blocks are cast on manual machine for pressing cinder blocks filled with heavy rock. Such a block will be able to withstand a load of 300-400 kg, which corresponds to the weight of the walls of a log house. If you have experience working with your own hands with laying stone with cement mortar, then you can build 6-8 columnar supports in half a work shift.
In addition to standard rectangular blocks, massive hollow blocks in the form of a truncated pyramid with a reinforcing frame are cast on the machine. A pin or threaded rod is placed in the upper base of the pyramidal columnar support, which allows you to tie the installed pillars with a wooden beam or steel profile. It is enough to compact and fill the horizontal platform in order to install a finished foundation field of columnar supports along stretched cords.
Do-it-yourself columnar foundation step-by-step instructions
Casting foundation supports from cement is no more difficult than working with a shallow-depth tape, but the volume of concrete and earthworks is three times less. Most of the time is spent on the first columnar support, made with your own hands. From practice, it turns out that the next two columnar supports take the same amount of time as the previous one. The entire technology for arranging a columnar foundation comes down to five simple operations:
- Preparation of the cushion and pit at the site of marking the columnar support;
- Assembling the formwork to be poured with concrete;
- Installing reinforcement into the formwork and pouring concrete into the form;
- Assembling and tying the foundation.
Advice! To make a foundation field, it will take at least three days and three to four sets of split formwork. If we assume that one columnar support will require three days to cure the concrete, then in a week you can make a columnar foundation of 8 supports with your own hands.
The optimal option for arranging the base of a columnar block
The most serious problem with columnar foundations is not the weak load-bearing capacity of the supports, but their tendency to tip over when the lateral component of the load increases. Strong winds and uneven subsidence of the foundation, when some supports sink into the ground, while others are torn off by beams from the cushion, lead to tilting and overturning of the foundation pillars, as in the photo.
Therefore, when preparing a cushion for a columnar foundation, it is necessary to pay attention to the presence of reinforcement in the form of a backfill of gravel and soil. For columnar supports installed on the surface or in a slight recess, it is recommended to strengthen the base by expanding the support spot or use fungal types of pillars. In the latter case, the foundation structure can be made in the form of two independent elements: in the form of a round concrete platform, buried 10-15 cm into the ground, and a vertical support of a round or rectangular cross-section, connected to the platform by one reinforcement cage.
In any case, to install the supports of a columnar foundation, you will need to dig a pit to a depth of immersion plus 20 cm of sand and gravel cushion and 20-25 cm of a layer of large rubble or crushed stone material. The filling mass is placed on the bottom of the pit in layers of no more than 10 cm, with compaction of each layer using a hand or electric tool.
It is clear that for the manufacture of supports, formwork boxes of exactly the same size are most often used. This makes it possible to obtain columnar foundation supports of the same height, but only under one condition - if the crushed stone cushion in all pits has the same height. Therefore, it would be correct to do the following:
- Dig the required number of mini-pits for the foundation supports, trim and level the walls so that the soil and fertile layer do not fall on the gravel bed;
- Hammer a reinforcement rod into the center of the bottom of the pit of the future column, align it with the stretched foundation marking cords;
- Pour the gravel-sand mixture onto the pillow using a compactor. The compaction of the cushion must be done with the utmost care, the main thing is to prevent the centering rod from moving or deflecting. We constantly check the height of the pillow by the distance from the cord to the backfill plane using a clogged piece of reinforcement.
Installation of formwork and reinforcing frame
To obtain a homogeneous, defect-free concrete casting, you will need to make collapsible, reusable formwork of a box-shaped or tubular structure. The inner surface of such a box is covered with plastic film, or materials with a laminated surface are used. Thus, a support with smooth and even walls is obtained. In addition, the internal coating of the formwork significantly reduces the swelling of the wooden structure and helps maintain the original shape of the foundation pillars.
Before installing the formwork, it is recommended to tighten the dimensional cords, which can be used to align and fix the wooden frame of the form with a minimum error. In addition to the horizontal supports of the walls, it will be necessary to install additional fixing wedges to prevent the formwork from floating under the influence of concrete pressure on the lower part of the wooden form.
At the next stage, a reinforcing frame is installed inside the wooden form, welded from 4 or 6 rods with a diameter of 8-10 mm, photo. Like formwork, the reinforcement is aligned inside the form and fixed in a vertical position, after which you can proceed to pouring the concrete mixture inside the support.
Leveling and pouring concrete
Filling the formwork with concrete must be done as carefully as possible to prevent displacement of the installed support elements. Long foundation columns are poured in several portions, with each layer being “punched” inside the support using a vibrator or manual tamper for 10-15 minutes. In total, it will take 35-40 minutes to fill out one support form. 2-4 studs are embedded in the concrete surface of the upper part of the post, allowing the strapping beam to be subsequently secured to the concrete surface of the support. The poured formwork is covered with a plastic bag to reduce moisture loss and prevent the foundation concrete from being washed away by rainwater.
Important! If you have made the formwork boxes high, but not rigid and strong enough, especially in the central or bottom part, then a situation may arise where the concrete mass crushes and expands the lower part of the foundation form.
The result is not a rectangular shape of the support, but a barrel-shaped one. Everything would be fine, but the volume of the form increases, and the level of concrete drops, which means the height of the foundation column will decrease. Therefore, the formwork has to be poured several millimeters higher than the calculated one. After about a couple of hours, the surface can be sprinkled with damp sand to reduce cracking and shrinkage of the foundation columns.
After the concrete mass has set, the formwork is disassembled and removed, after which that part of the support surface that will be under the soil layer must be treated with waterproofing bitumen coating. After 7-8 hours, the space around the columnar base can be covered with layers of a mixture of gravel, expanded clay and sand.
Conclusion
No matter how hard you try, a columnar base does not have a perfectly flat and horizontal top surface. After about a couple of days, until the concrete reaches the design strength, the plane of each support must be trimmed horizontally and vertically with a grinder or grinder. Before tying the columnar foundation supports, treat them with mastic and lay roll waterproofing. Next, you can lay a wooden beam and tie it to the supports of the columnar foundation, but the construction of walls and further construction is permitted no earlier than a month later.
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;
- 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 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 necessary 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 required for its construction are minimal, and the range of applications for frame-type buildings is very wide.
As a basis for 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 uncomplicated.
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, make a water-spilled and well-compacted cushion of sand-crushed stone mixture 20 cm high. 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 consists of 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.
One of the popular foundations small houses and outbuildings - columnar. It is attractive due to its low cost, ease of execution and the fact that even a person who is not particularly experienced in construction can build it with his own hands. Another good thing about a columnar foundation is that it can be designed to fit most buildings and conditions.
Device and types
A columnar foundation consists of a number of support pillars that transfer the load from the building to the ground. The pillars can have a rectangular or round cross-section and can be made from:
- monolithic reinforced concrete;
- bricks (solid ceramic, well-fired);
- concrete (made of heavy concrete grade no lower than B15) and reinforced concrete blocks;
- rubble and rubble concrete.
The most reliable ones are made of monolithic reinforced concrete. They can be used on soils prone to heaving with high groundwater levels. All the rest consist of elements held together with concrete mortar and are inferior in strength to a monolith. They are recommended for use on normal soils.
The pillars must be placed in the corners of the building, at the junction of walls and piers. If the distance between the supports exceeds 3 m, additional ones are installed. The installation step is on average 1.5-2.5 m. The heavier the building stands, the smaller the step, but there is no point in installing more often than 1 m: the foundation will be too expensive.
Types of grillage
To ensure that the load from the building is transferred evenly to the pillars, they are connected by a transverse beam - a grillage or shallow tape. This eliminates one of the main disadvantages of columnar foundations - possible uneven shrinkage of the supports.
When constructing wooden houses or frame frames, a large-section wooden beam is often used as a grillage; sometimes metal is used - a large-section profiled pipe or T-/I-beams. To connect beams and frames during the construction of pillars, studs, special fastening elements are placed in them, or reinforcement is released. The shape of the mortgages is selected based on the planned grillage type.
For heavy houses, a concrete beam is made. It can be composite - from ready-made reinforced concrete beams, or it can be monolithic. Although composite ones are easier to implement (buy, install, connect), a monolithic one is cheaper and even more reliable. Therefore, a monolithic grillage is used more often. It is more suitable for houses made of brick and other heavy materials.
When making a columnar foundation with a monolithic grillage, the reinforcement of the pillars is done with an outlet of at least 70 cm. These outlets are then connected to the reinforcement of the grillage frame.
Extensions and their foundations
If there are lighter extensions to the house—a porch, a veranda, a driveway—the foundations are made separate and incoherent. This means that they make their own outline for the house, and their own for the porch. And they should have no points of contact with each other. Since the grillages (beams running along the top of the supports) are located nearby, a damping layer is laid between them. For example, roofing felt in two layers, cardboard from mineral wool and other similar materials.
This is necessary since the weight of these elements is very different, and the magnitude of the load on the foundation is correspondingly different. If you make it coherent, a large difference will cause distortion, and possibly the destruction of the building.
How to close the gaps between the pillars
When installing a columnar foundation, the building turns out to be raised above the ground and there is a draft under the subfloor. This is good for maintaining normal wood moisture, but bad for heating: the floor becomes too cold. One more thing: all kinds of living creatures like to live under the house. Both homely and not so... For these reasons, they try to close the space between the pillars. You can do this in two ways:
- collection device - stone or brickwork between pillars;
- by attaching pieces of sheet material or finishing materials.
It’s easier, of course, to attach sheet material. It is then cut off in such a way that it does not rest on the ground. The remaining gap will be useful for ventilation and heaving compensation.
They do the removal if they plan to make an insulated blind area around the house. At the same time, it is installed so that it does not support the grillage or bottom trim- make them level with the outer edge of the pillars (they must be at least 10 cm wider than the wall).
It is advisable to prepare the base for the pick-up: dig a trench at least 20-30 cm deep, pour and compact a layer of sand, and crushed stone on top of it, which is also compacted. Then a decorative wall is placed on this compacted base.
On normal soils, small light buildings with an area of no more than 30 square meters - such as a barn, gazebo and other similar buildings - can be built on a lightweight foundation. It is called support-columnar. Typically this is one or more concrete blocks laid on a sand and gravel bed.
The planning of the pillars is the same: at angles, at the junction of walls and intermediate ones, if necessary. With this type, it is important to compact the cushion well, thereby increasing the load-bearing capacity of the soil. And one more point: do not use this type of base on loose or clayey water-saturated soils. Even under or. He will be completely unreliable.
What is the difference between a pile and columnar foundation?
If you look at a columnar foundation from round pillars and pile, at first glance there is no difference. But it is there. These are the soils on which they are placed and the depth to which they are buried. Pile foundations They are placed on soils with weak bearing capacity and their task is to pass through unstable soils and transfer the load from the house to denser layers. Columnar ones are placed on soils with normal bearing capacity and their depth is determined by the type of soil, climatic zone and groundwater level. Structurally, they are similar, but their tasks are different, as well as their scope of application.
What is soil heaving and how does it affect the choice of foundation?
The most difficult soils for construction are clayey soils. They do not drain water well, and it accumulates in small cavities. When frozen, it significantly increases the volume of the soil. As the soil increases in volume, it puts pressure on everything in it, including the foundation. This phenomenon is called heaving (the soil swells), and soils in which they are clearly expressed are heaving.
Heaving forces are applied both from below, trying to push the pillar out, and from the sides, trying to move the support to the side. It is for this reason that in clayey - heaving - soils it is better to make the pillars monolithic with reinforcement.
Also, to prevent the pillars from being pushed upward, the lower part is made wider. This area is called the heel and is usually twice the size of the pillar itself, and its height is equal to 1/3 of the cross-section of the pillar. For example, under a 40 cm pillar they make a heel 80*80 cm, 13 cm high or so.
The seams between blocks/bricks/stones in prefabricated columns are not always able to withstand lateral loads, therefore, to reduce the influence of heaving forces on prefabricated columnar foundations, they are made with beveled walls. This increases their reliability in heaving soils. On normal soils, the pillars are stacked with even walls.
Scope of application
As already mentioned, a columnar foundation is also called a pillar foundation or on pillars) behaves normally on soils with normal bearing capacity. They are not used on loose sand, peat bogs and other unstable foundations. Its main features are that it is impossible to organize a basement and a ventilated gap between the ground level and the subfloor. They also need to be kept in mind when choosing.
They are suitable for the following cases:
At the same time, there are a number of situations (except for weak soils) when it is not recommended to use foundations on pillars:
- with a large difference in height on the building site - more than 2 m;
- in complex geology with possible displacement of layers.
In other cases they can be used.
Laying depth
The main criterion for choosing foundation parameters is ensuring its integrity. Therefore, when planning, they always include a safety margin of about 20-40%. It compensates (to some extent) for unforeseen changes in conditions (groundwater levels, unexpectedly low winter temperatures) or loads. This is especially evident when planning foundations: the laying depth is taken with a margin and the bearing capacity is usually underestimated. This is understandable: adding something to an already finished foundation is either a very expensive or unrealistic idea.
The greatest safety margin is laid on heaving soils: it is impossible to calculate their manifestation, so they try to make it as reliable as possible. To do this, for private houses, foundations are buried below the freezing depth of the soil. You will find out the average data for your region, and add about 15-25 cm to this figure. This is how you get the depth of the foundation. For example, in the region the soil freezes to 1.5 m, which means the foundation depth is 1.65-1.75 m.
As you understand, if you make prefabricated pillars - from brick, rubble, blocks - you will have to dig a decent size hole under each one. The bottom must be 20 cm below the laying depth to make backfill. Also, the pit should be considerably wider - you will have to work in it, folding the supports. This is another reason why monolithic pillars are made: holes are drilled under them, gravel or sand is poured onto the bottom and formwork is inserted (most often pipes of the required diameter). Inside of which a reinforcing element is installed - a frame made of reinforcement or a metal pipe.
This rule works for heavy buildings. But columnar foundations are rarely made for them. They are placed mainly under light buildings: wooden or outbuildings. If a basement is not planned for such a building, it is more advisable to make a shallow foundation (laying depth from 0.5 to 0.7 freezing level) or shallow (from 0.3 to 0.5 freezing depth).
An example of a non-buried columnar foundation with a freezing depth of 1.2 m (1/3 of 120 cm is 40 cm)
With this choice, heaving forces will act on the pillars, but since their area is smaller than that of the tape, the impact will not be as strong. These impacts are successfully compensated by the construction of a frame or wooden house. Moreover, additional measures are being taken to reduce the impact of heaving forces:
- at the bottom of the hole under the post they make a gravel cushion, which takes on part of the load;
- make the side surfaces smooth and additionally lubricate them with grease, bitumen mastic, epoxy resin etc.
- make insulated
As a result, in most cases, the owners do not even notice that the foundation is heaving. Some supports rose slightly, the grillage and trim compensated for them. After the ground thawed, everything returned to its place.
In soils that drain water well, the columnar foundation is made shallow or not buried. It is only important to select the correct area of the columns in order to evenly transfer the load.
Pole sizes
Eat minimum dimensions pillar foundation supports. They depend on the materials:
- Monolithic reinforced concrete 30 cm.
- Burnt brick pillars - 38 cm;
- Rubble, concrete blocks and rubble concrete - 40 cm;
- Stonework - 60 cm.
But at the same time, the size of the pillar should be 10 cm larger than the width of the wall. For normal operation of the foundation, it is necessary that the wall lies in the middle of the support and protrudes at least 5 cm on the sides.
Construction stages
As usual, everything starts with cleaning the site and marking it. The turf is removed from the entire site and the fertile layer is removed. He is not considered to be load-bearing and is taken out. At the same time, leveling is done - the mounds are cut off, holes and depressions are filled and compacted. The horizontal position is controlled using a two- to three-meter board with a building level installed on it.
Marking
Along the perimeter of the building, cast-offs are installed - pillars or pillars with nailed slats - benches. They are placed at a distance of about a meter from the perimeter of the future house. Using cords stretched between them, the perimeter and width of future pillars are indicated.
How to mark a foundation
When setting, make sure that the angles are strictly 90°, and measure the diagonals of the rectangles. They must be equal. At the intersection of the stretched cords, a perpendicular is lowered down (using a plumb line), marking the dimensions of the pillars on the ground.
This way you can make them all the same, and also monitor the height when setting up the formwork for monolithic pillars or when laying prefabricated ones.
Digging holes for poles
Under prefabricated foundations, holes are dug manually or using an excavator. If the depth required is up to 1 m and the soil is not loose, you can dig them with straight walls. If the depth is greater or there are signs of crumbling, the slopes are made inclined.
When they have reached the design depth of the foundation, they dig another 20-30 cm lower. The bottom is leveled, its dimensions should be 10-20 cm larger than the planned dimensions of the heel or pillar.
Easier with round posts. Wells are drilled under them using a manual or automated drill. If you plan to expand at the bottom - the heel, you can either make the hole wider - according to the size of the heel, or use a drill with a folding blade. It is called a TISE drill. The additional blade opens after the set depth has been reached.
Installation of sand and gravel cushion
A layer of crushed stone of about 10-15 cm is poured onto the bottom and compacted well. Coarse sand is poured onto compacted crushed stone. It is spilled and compacted. The total layer of sand and gravel cushion must be such as to reach the specified depth of the foundation.
In the case of round posts, the cushion is made in the same way, compaction is done whenever possible. Take a long pole, which is used to compact the bedding.
Heel device
If the pillars are made prefabricated - from blocks, bricks, rubble, it is easier to make the heel from a ready-made concrete block. Place a block-pillow on the sand, leveled. It has a trapezoidal cross-section, which is convenient.
Two types of heel - monolithic from concrete block
For monolithic ones, it makes sense to make a half-shelf from a monolith. The formwork is placed according to the specified dimensions (twice the cross-section of the column and at least 1/3 of the cross-section in height). The reinforcement is laid in two tiers. Use a rod with a diameter of 12-14 mm. Also, reinforcement is installed in the heel, which will then go to the pole. The result is a single reinforced concrete structure.
Construction of pillars
If we are talking about a monolithic pillar, then formwork is installed and reinforcement is installed inside. The formwork for square pillars is made from boards; for round ones, you can use plastic pipes of a suitable diameter. There is an economical formwork option - rolled roofing material of the required length. It is twisted into a pipe of the required diameter, screwed onto the standard. After making two or three layers, secure with tape. The result is a reliable formwork that, even in the part protruding above the ground, normally holds the mortar.
For reinforcement, three to four reinforcement rods of class A III with a diameter of 12-14 mm are usually used (for square ones, 4 are required, for round ones, 3 are possible). They are connected to each other into a single structure by transverse dressings installed every 20-25 cm. They can be made from smooth class A I reinforcement, with a diameter of 6-8 mm. It is better to knit the frame rather than weld it - higher strength.
Please note that there must be a distance of at least 50 mm from the edge of the formwork to the reinforcement bar. It is necessary to prevent the metal from rusting. The photo below is an example of incorrect reinforcement: the reinforcement is close to the formwork. It will quickly rust and the pole may break.
If pillars are made of brick, then it must be graded at least 100, solid, well-burnt. If there is a high groundwater level in the area, brick pillars will not work: they will quickly collapse. The mortar for laying brick pillars is made with Portland cement no lower than M 300, and preferably 400 or 500. There are several mortar options:
- 1 part cement, 3 sand;
- 1 cement, 2 lime paste, 10 sand;
- 1 part cement, 1 part clay adze, 10 parts sand.
The masonry is carried out with bandaging, carefully checking the verticality. Even small deviations can then lead to the destruction of the foundation, and maybe even the building.
When laying a rubble columnar foundation, the stones chosen are flat with smooth edges. When laying, the vertical load should be transferred to the entire plane of the stone, and not to its individual sections. The stones are also placed with a bandage, placing the largest fragments in the corners, filling the gaps with smaller ones.
The thickness of the stones should not be more than 30 cm. They are laid on the mortar, fitting tightly to each other. The gaps are filled with crushed stone, compacting it well. To increase strength, such pillars can be reinforced both vertically and horizontally. Horizontal reinforcement is done every 25-40 cm, rods of at least 6 mm in diameter are inserted vertically, you can use reinforcing mesh from wire of the same diameter.
Important: the pillars must all be driven to the same level. To do this, during construction or pouring, constantly beat off the vertical plane: cutting off the tops is long and difficult.
Grillage arrangement
As mentioned earlier, when pouring monolithic pillars, embedded parts are installed at the tops:
- pins for tying wooden or metal strapping to beams;
- reinforcement outlets of at least 70 cm in length for connection with the reinforcement frame of the monolithic grillage.
The strapping device is discussed in the description. You can read about the design of a monolithic grillage in the article Everything is the same, right down to the calculation of the load-bearing capacity.
Waterproofing
To prevent moisture from suction from the soil between the foundation/grillage and the frame or the first row of masonry, a layer of waterproofing is required. You can use coating (the most common is bitumen mastic) or roll or a combination of both.
There is no point in insulating the pillars. For concrete pillars, the presence of moisture is not a minus, just as for rubble ones. And it is better to install brick ones on dry soils. It may be worth impregnating their surface with some kind of deep penetration impregnation, which significantly reduces hygroscopicity. The only problem is that they are expensive.