For small buildings with a bulk density of about 1000 kg / m 3, one of the best solutions is the foundation of pillars located in the ground at a certain depth. Talking about how to build a columnar foundation with your own hands, a step-by-step instruction is quite suitable even for a person who has basic construction skills.
To do this, you must carefully and correctly choose the materials, calculate and familiarize yourself with the construction technology in all details.
If you focus on the reviews of developers, the advantages of the column foundation are as follows:
- a large selection of varieties of materials to properly distribute the load;
- reasonable cost and low consumption of materials;
- low volume of construction;
- good adaptation to heavy loads.
For heavy buildings and with a high level of groundwater, the columnar foundation is not suitable.
How to calculate the foundation
With independent designing of the house, it is always known from what materials it will be built.
1. Determination of loads on the house. The weight of all parts of the building is easy to determine. Seasonal loads and the weight of the objects inside are added to them. It also takes into account the effect of grillage, usually made of reinforced concrete with a bulk density of 2400 kg / m 3 .
2. Assessment of the nature of the soil. Do-it-yourself pillar foundation for a house is usually built without laboratory studies of the composition and properties of the soil. The main indicator is its resistance, which is determined by the tables and is in the range of 1-6 kg / cm 2 . Its value depends on the composition and porosity of the soil.
3. The number of supports. The bearing capacity of the pillars depends on the area of the supporting surface. Bored piles are usually used. It is advisable that they have an extension (shoe) below. It is important to consider the composition of the concrete mix and reinforcement. The size of the step between the supports depends on the calculation and does not exceed 2.5 m. Their presence at all angles, in places where the walls adjoin, under the beams and in places of concentrated loads is mandatory.
Foundation material
You can choose many options for how to build a column foundation with your own hands. Materials can be very different, but they must be of high quality. They are as follows:
- a tree - for light houses, baths, saunas;
- red brick - for moderate homes;
- rubble stone - for buildings with heavier parts;
- reinforced concrete - for heavy buildings.
Column foundation with grillage. Step-by-step construction instructions
The construction of houses is not so complicated when all the work is divided into separate and interconnected steps, smoothly passing one into another. If you build a column foundation with your own hands, a step-by-step instruction should include all stages of work:
1. Preparation . The construction site is cleaned and a layer of black soil is removed under the base. If there is soil under it containing clay, it is necessary to backfill a layer of sand with gravel.
The site is aligned horizontally using the level. It provides a convenient access for vehicles with materials and mixers with concrete.
2. The layout of the house plan. First, the contours of the structure and the places under the pillars, which are located strictly along the axes, are noted. The corners of the foundation of the house must be straight. Checks the correct breakdown along the centerlines, as well as the lower mark of the trench for compliance with the design.
3. Digging holes under the pillars. The foundation is shallow (70-100 cm) and standard (from 100 cm). The first option is better for rocky and sandy soil. On a clay and wet area, the posts must be buried to a great depth. It is not necessary to dig holes: if possible, the posts are driven or screw piles are screwed. The most common and cheapest way is to drill wells and fill them with concrete.
4. Concreting. At the bottom of the pit, a pillow is laid out from a mixture of sand and gravel. Columns are concreted directly in the ground when it does not crumble. In all other cases, formwork is installed from the following materials:
- Boards with a width of not more than 155 mm, planed from the side of concrete.
- Finished metal shields.
- Pipes are ceramic, asbestos-cement or metal. Numerous reviews indicate the benefits of using pipes, especially on shear-prone and loose soil.
- Ruberoid rolled up and reinforced with wire or wire mesh on the outside.
Roll waterproofing is lined at the bottom with an overlap on the walls to prevent the flow of the solution through the slots of the formwork.
5. Installation of fittings. The posts are reinforced in the longitudinal direction with steel bars. They are installed vertically in the pit and are tied with clamps. Part of the reinforcement should protrude 15-30 cm above the foundation for further connection with the grillage.
6. Installation of poles. If the supports are made by laying concrete, it is fed in layers with a vibrator seal. No cavities should remain inside to increase strength. Concrete should not be too liquid or thick to further provide the necessary strength and prevent cracks. Prior to gaining the necessary strength, it is covered with a film and moistened.
When a column foundation is laid out of brick with their own hands, it is fastened with a cement mortar.
Deviation from the horizontal is allowed no more than 15 mm. Correcting distortions in the future will be difficult. When laying, there should not be any gaps.
After hardening, the supports are covered with mastic or bitumen for waterproofing. Coatings are applied in 2 layers with laying between them and outside of the roofing material strips.
Errors in laying the foundation
Developers who build homes on their own should not allow miscalculations with foundations that significantly affect the durability of buildings. In most cases, the errors are as follows:
- Uneven subsidence of the structure due to insufficient depth of the pillars or their different depths.
- Uneven load distribution on poles.
- Application for the construction of poor quality materials.
- Not assessed the composition and characteristics of the soil.
In order to be able to correctly build the column foundation with your own hands, step-by-step instructions must be fully followed during construction.
Making grillage
To equalize the load on the poles and prevent lateral displacement of the house, the instruction for creating a columnar foundation provides for linking the supports into a common monolithic structure using a grillage - horizontal fastening beams. It is equipped at a height above ground level.
For construction, timber, metal profiles or reinforced concrete are used. Particular attention is paid to the location of the grillage to the posts, since its reliability determines the stability of the entire building.
To erect a reinforced concrete base around the perimeter of the structure and at the locations of the bearing walls, a wooden formwork is fastened. Inside, a frame of reinforcement is installed, it is firmly connected with the protruding rods of the columns, and then the concrete mixture is laid. The grillage surface is leveled and covered with a film to dry.
When the concrete gains strength, they arrange waterproofing from above and proceed with the installation of ceilings and the erection of walls.
The full installation instructions for the columnar foundation also include waterproofing and pick-up operations.
Waterproofing grillage
On top of the grillage waterproofing is done. It is equipped in various ways, of which the following are most common:
- Bitumen is applied on top and roofing material is laid alternately with it.
- A cement mortar in a mixture with sand 1: 2 is laid out on the grillage. Then the roofing material is laid.
Pick-up device
The underfloor space is protected from atmospheric effects by arranging a blockage - a fence between the supports. It is made of wood, brick or stone. From the bottom, lay a screed of concrete, which serves as the base. To do this, first make a trench and fill the bottom with sand. For the screed, formwork is installed from the boards and the reinforcing frame. The connection of the fence with the supports is not done in order to avoid the appearance of cracks in it when the house is upset.
They try to make the base higher, thanks to which the structure looks attractive. It corresponds to the height of the supports.
Column foundation
The base of the pillars, combined with a monolithic concrete frame, combines all the advantages of both types of bases. When a column-strip foundation is being erected, the step-by-step instruction is followed the same as during construction with a grillage. Supports penetrate far into the depths, creating reliable protection against seasonal movements of the soil.
They are rigidly connected with a shallow ribbon base passing under the supporting walls of the structure. The entire structure is poured with concrete at the same time, as a result of which it becomes monolithic and durable. With the independent preparation of the mortar, concrete is laid in layers. The use of vibrators is mandatory in order to remove air bubbles from the mass as much as possible.
Conclusion
Various columnar foundation options are widely used in private housing construction. It is characterized by high reliability, speed of construction and minimal consumption of building materials.
Having basic skills, many developers can build a column foundation with their own hands. Step-by-step instructions will help to avoid mistakes and make the foundation reliable.