The foundation is the most important element of any structure: from a light garden gazebo to a capital multi-storey suburban mansion. This is the beginning of the construction and its foundation in a literal sense. The strength, durability and safety of building operation depend on how correctly selected, calculated and executed the foundation is. The question of what type of foundation to choose arises at the construction planning stage. The optimal solution in many cases is the decision to build a pillar foundation with your own hands: a step-by-step instruction on how to complete the work can give a complete picture of the principles of its construction and the intricacies of the arrangement process.
Advantages and disadvantages of the pillar foundation
Self-designed and equipped with their own hands pillar foundations for frame houses and buildings without basements that do not exert strong pressure on the ground, are simple to implement and relatively cheap.
Useful advice! The pillar foundation is the optimal solution for lightweight buildings, the volume weight of which does not exceed 1000 kg / m 3 ( frame houses , baths , utility units, garden houses, terraces, sheds, garages, summer kitchens, gazebos, etc.).
According to reviews, columnar foundations have a fairly impressive list of advantages:
They can be designed, calculated and built independently, without the involvement of special equipment and specialists.
They can be arranged on almost any soil (except those where heaving processes are possible or there are high groundwater).
They can be located in areas with noticeable differences in height (and even on hillsides).
Do not require preparatory work to level the landscape.
They can be erected as soon as possible (the maximum time for building a column foundation from scratch is 2 weeks).
Do not need complex and expensive waterproofing.
Strength and durability of the structure (the columnar foundation built with careful observance of the technology of work can last more than half a century).
Relative low total cost.
At the same time, there are only two drawbacks of columnar foundations:
Not intended for heavy brick buildings and multi-story buildings.
Excluded the creation of basements.
For foundations, the following materials may be used:
a natural stone;
pipes: asbestos or plastic.
The depth of the columnar foundation is determined by its design, technological parameters of the structure and geological characteristics of the soil in the construction site.
Useful advice! On sandy soil, in which groundwater is below 1 meter, a brick cottage can support a columnar foundation with a slab structure.
According to the depth of laying, columnar bases are divided into three main types:
Buried – with a depth below the level of soil freezing.
Shallow – with a depth of 40-70 cm from the ground.
Not deep – located on the surface of the earth in the complete absence of the underground part. At the same time, in the places where the columns are installed, the fertile layer is removed from the soil and the non-metallic material is added.
DIY pillar foundation: step-by-step instructions
For the construction of a columnar foundation with your own hands, a step-by-step instruction is needed as the most detailed and visual aid.
In general, the construction of the support-column foundation is a system of supports of the smallest possible cross section located at the points of concentration of the load: in the corners of the building, at the intersection of the walls, under load-bearing beams, piers, under the stove . To determine the number of free-standing columns, the distance between them is assumed to be 1.5–2.5 m. To connect the foundation supports in a single structure, a grillage is made between them.
The height of the posts above the zero mark is individual and depends on the design features of the grillage.
Calculation of the column foundation
The construction of the column foundation begins with the calculation. Most likely, for independent calculations, you will need a program such as “Foundation” or some other one that can be found on the Internet and downloaded for free. To work with such programs, you will need the following parameters:
Depth of foundation and its reinforcement.
The location of the future building.
The construction technology of the foundation with columnar supports also requires additional data:
The approximate weight of the building, including the weight of its intended interior and furnishings.
The total weight of the foundation itself.
Seasonal load (wind and snow cover).
Variety of soil and its properties.
The level of soil freezing and the average temperature in the winter season.
The level of groundwater occurrence taking into account its seasonal fluctuations.
As a result of the calculations, the following values will be obtained, necessary for the installation of a columnar foundation:
The minimum number of posts.
The cross-sectional area of the pillars and their sizes.
The value of the bearing capacity of the pillars.
Unshallow pillar foundation
A columnar, shallow foundation on supports located in increments of 1.5–2.5 m is used quite often. Such foundations can be erected on non-porous and slightly porous soils, despite the fact that the building (a wooden or panel house, a bathhouse, a hut, an extension or a summer kitchen) has a small area and, accordingly, a small weight. Moreover – if the construction is carried out on rocky, coarse-grained or not prone to shifts, this type of foundation can also be arranged under a fairly large area house made of logs or timber. It is also possible to erect a foundation on shallow 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, but 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 with dimensions of 20x20x40. The price of such a foundation, as well as the number of blocks necessary for its construction, can be calculated independently or using the “foundation” online calculator. You can also make a pillar foundation of brick with your own hands from a brick, but it must be borne in mind that it is unacceptable to use silicate or ceramic bricks with low frost resistance.
The construction of an unfilled pillar foundation from finished blocks can be divided into several main stages:
Marking up a future construction site, cleaning the soil, installing a drainage layer and waterproofing work.
Determining the location of the supports for the foundation (concrete blocks 20x20x40). At the same time, it is better to buy all materials in advance.
Preparation of places for supports. A sand cushion under each support.
Installation of supports, each of which consists of at least 4 blocks for the foundation 200x200x400. The price of the entire foundation, given the knowledge of this condition, is considered very easy. Supports (according to the instructions and photo) of the column foundation from blocks 20x20x40 with their own hands are laid out in two rows with a checkerboard pattern. For joints, a thick, undiluted cement mortar is used, the open part of the blocks should be finished with plaster.
Mandatory waterproofing of the foundation supports at the junction with the house with bituminous mastic, roofing material, roofing felt or glass insulation.
Useful advice! Sometimes (for example, in the case of a columnar foundation for a bath), supports can also be wooden – from the butt parts of oak or pine with a diameter of 20-30 cm, impregnated with tar or used oils. To increase stability, the supports are immersed in a 10-15 cm layer of concrete mortar poured into a previously opened pit.
When making a foundation of 20x20x40 blocks with your own hands, video clips and step-by-step instructions will help to understand the technology of work, to delve into the process and more accurately assess financial costs.
Shallow pillar foundation
Shallow foundation is one of the most popular varieties of pillar foundation. The means and efforts that his device requires are minimal, and the range of applications for frame-type buildings is very wide.
As a basis for a frame house or light bath, a columnar foundation is often made using pipes as formwork for concrete mix. Since the reinforced concrete pillar will bear the entire burden, the material of the pipes does not really matter: both plastic and asbestos pipes, usually used for sewer networks, are suitable.
The diameter of the pipes depends on the load. 10 cm is enough for light buildings such as arbors or extensions, 25-30 cm pipes are needed for log buildings. The amount of concrete in the end is determined precisely by the diameter of the pipe. For 10 m of pipe, 10 cm in diameter will need 0.1 m 3 of concrete, a pipe of 20 cm will require 0.5 cubic meters, and 30 cm will require 1 cubic meter. The calculation is made taking into account the concrete cushion of the base.
The scheme of work on the installation of a pillar foundation of asbestos pipes with your own hands in general is as follows:
preparation of the construction site – garbage collection, removal of foreign objects, removal of turf and leveling. Marking the perimeter of the future building, corners, internal walls and their intersections. The installation sites of the foundation supports are marked with pegs;
then make a hole in the ground with a manual drill for poles. The depth of the well should be 20 cm more than calculated: for the installation of a sand cushion;
sand cushion device with mandatory tamping and pouring sand with water. After the final absorption of water, pieces of roofing material should be laid to the bottom in order to prevent moisture from entering the sand from the concrete mixture;
installation of pipes in wells with a margin of at least 10 cm in height. Alignment of pipes by level and fixing them in wells using wooden bars. With a close occurrence of groundwater, the pipes must be coated with bitumen mastic to the ground level for waterproofing;
then the base of the pipe is poured 40-50 cm into a carefully mixed concrete-gravel mixture (1 part of cement and 2 parts of sand diluted with water to the state of batter are combined with 2 parts of fine gravel). Immediately after pouring, the pipe is raised to a height of 15-20 cm and left in this position until the cement hardens completely. This is necessary to create a base that protects against ejection during heaving;
after the concrete has solidified, the pipe should be waterproofed from the outside with a roofing material and the well should be filled with sand with gradual pouring and ramming;
Useful advice! During work, periodically check the pipe installation using a level.
fittings are placed inside the pipes, after which the remainder of the pipe is poured with concrete;
after the final hardening of concrete – after 2-3 weeks – continue construction work. It should be added that it will be useful to waterproof the foundation with polymer or bitumen solutions.
According to the same scheme, installation of a column foundation from plastic pipes is possible. Videos and photos will help you navigate the intricacies of the workflow, generally uncomplicated.
Pillar foundation with grillage
The grillage is a system of random beams and strapping beams. It firmly fixes the foundation, excluding its horizontal displacement or overturning of the entire structure. If there is a grillage, the load from the structure is distributed evenly over all installed columnar supports, as a result of which stability and resistance to fracture are increased.
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 garbage, etc. along the perimeter of the future foundation, sod and topsoil are removed;
for supports it is necessary to dig holes 20 cm deeper than the level of soil freezing. 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 struts;
at the bottom of each pit, a well-compacted pillow is made of a sand-gravel mixture of 20 cm high. The pillow is lined with ruberoid or polyethylene so that the moisture from the concrete poured into the pit does not go into the ground;
formwork boxes are assembled from 20 mm thick boards;
Useful advice! If the walls of the pits do not fall off and are dry, it is possible to simply lay them with polyethylene and dispense with the formwork.
It is recommended that the formwork installed in the pits be thoroughly moistened to prevent absorption of moisture from the cement mortar and to facilitate removal;
after installing the formwork in the pits place the frame of the reinforcement. The frame is assembled separately, from a bar 10-14 mm in diameter. The length of the rods is selected so that the solidification of the concrete ends stick out above the ground by 30-40 cm;
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.
There are two options for mounting the grillage: laying it on the ground or lifting it above its surface. The advantage of the second method is the elimination of the effects of heaving forces:
Installation of formwork. The formwork is installed continuous around the perimeter of the foundation.
Filling the bottom of the formwork with sand and lining it with polyethylene.
Assembly and installation of reinforcing cage from a bar with a diameter of 12-14 mm.
Simultaneous pouring grillage concrete with the removal of air from the solution with a vibrator.
Removing formwork after setting concrete and removing sand from the grillage.
The cost of works on the installation of a pillar foundation
The total cost of the column foundation is the sum of the cost of materials and the cost of the actual work. In most cases, it is significantly lower than the cost of foundations of other types, since almost all types of columnar foundations can be built with their own hands. Videos and photos, instructions and manuals found on the Internet are also usually cheap or free.
The calculation of the cost of most types of columnar foundation can be done independently using special online calculators or programs. Many of them are quite easily found on the Internet, are free and have an intuitive interface.