For small buildings with a volumetric weight of about 1000 kg/m3 one of the best solutions is a foundation of pillars located in the ground at a certain depth. A step-by-step instruction telling about how to build a columnar foundation with your own hands is quite suitable even for a person who owns elementary construction skills.
To do this, you need to carefully and correctly select materials, calculate and familiarize yourself with the construction technology in all details.
Based on developer reviews, the advantages of a columnar foundation are as follows:
- large selection of materials to properly distribute the load;
- affordable cost and low consumption of materials;
- low construction volume;
- good adaptation to heavy loads.
For heavy buildings and high groundwater levels, a columnar foundation is not suitable.
How to calculate the foundation
When designing a house on your own, you always know what materials it will be built from.
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 influence of the grillage, usually made of reinforced concrete with a bulk density of 2400 kg/m3.
2. Assessment of the nature of the soil. A do-it-yourself columnar foundation for a house is usually erected 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/cm2. Its value depends on the composition and porosity of the soil.
3. Number of supports. The bearing capacity of the pillars depends on the area of \u200b\u200bthe supporting surface. Usually bored piles are used. It is desirable that they have an extension (shoe) at the bottom. It is important to consider the composition of the concrete mix and reinforcement. The step between the supports depends on the calculation and does not exceed 2.5 m. They must be present at all corners, at the junction of walls, under beams and in places of concentrated loads.
You can choose many options for how to build a columnar foundation with your own hands. Materials can be very different, but they must be of high quality. They are as follows:
- wood - for light houses, baths, saunas;
- red brick - for medium-sized houses;
- rubble stone - for buildings with weighted parts;
- reinforced concrete - for heavy buildings.
Pillar foundation with grillage. Step-by-step construction instructions
Building houses is not so difficult when all the work is divided into separate and interconnected steps that smoothly flow into one another. If a columnar foundation is being built with your own hands, the step-by-step instructions should include all stages of work:
1. Training. The construction site is cleared and a layer of black soil is removed under the base. If there is soil containing clay under it, it is necessary to backfill a layer of sand with gravel.
The site is leveled with a level. It provides convenient access for vehicles with materials and mixers with concrete.
2. House plan layout. First, mark the contours of the building and places under the pillars, which are located strictly along the axes. The corners of the foundation of the house must be straight. The correctness of the breakdown along the center lines is checked, as well as the lower mark of the trench for compliance with the design one.
3. Digging holes for poles. The foundation is shallow (70-100 cm) and standard (from 100 cm). The first option is better suited for rocky and sandy soil. In a clayey and wet area, the pillars must be buried to a great depth. It is not necessary to dig holes: if possible, poles are driven in or screw piles are screwed in. 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 from a mixture of sand and gravel. The pillars are concreted directly into the ground when it does not crumble. In all other cases, formwork is installed from the following materials:
- Boards up to 155 mm wide, planed on the concrete side.
- Finished metal shields.
- Ceramic, asbestos-cement or metal pipes. Numerous reviews speak of the benefits of using pipes, especially in shear-prone and loose soil.
- Roofing material rolled up and reinforced with wire or reinforcing mesh on the outside.
Rolled waterproofing is lined at the bottom with an overlap on the walls to prevent the solution from flowing out through the cracks of the formwork.
5. Fittings installation. The pillars are reinforced in the longitudinal direction with steel bars. They are installed vertically in the pit and tied with clamps. Part of the reinforcement should protrude 15-30 cm above the foundation for further connection with the grillage.
6. Pillar installation. If the supports are made by laying concrete, it is fed in layers with compaction by a vibrator. There should be no cavities inside to increase strength. Concrete should not be too liquid or thick in order to further provide the necessary strength and prevent cracks. Before gaining the necessary strength, it is covered with a film and moistened.
When laying out a columnar foundation of brick with your own hands, it is fastened with cement mortar.
Deviation from the horizontal is allowed no more than 15mm. Correcting distortions in the future will be difficult. When laying, no gaps should remain.
After hardening, the supports are covered with mastic or bitumen for waterproofing. Coatings are applied in 2 layers with laying between them and outside the strips of roofing material.
Mistakes in laying the foundation
Builders who build houses on their own should not make miscalculations with foundations that significantly affect the durability of buildings. In most cases, the errors are as follows:
- Uneven subsidence of the building due to the insufficient depth of the pillars or their different depths.
- Uneven load distribution on poles.
- Using poor quality materials for construction.
- Soil composition and characteristics not assessed.
In order to properly build a columnar foundation with your own hands, the step-by-step instructions must be fully followed during construction.
To equalize the load on the pillars and prevent the transverse displacement of the house, the instruction for creating a columnar foundation provides for tying the supports into a common monolithic structure using a grillage - horizontal fastening beams. It is equipped at a height from the ground level.
For construction, timber, metal profiles or reinforced concrete are used. Particular attention is paid to the place where the grillage is attached to the posts, since its reliability determines the stability of the entire building.
For the construction of a reinforced concrete base around the perimeter of the structure and at the location of the load-bearing walls, a wooden formwork is fixed. Inside, a frame of reinforcement is installed, firmly connected to the protruding rods of the pillars, and then the concrete mixture is laid. The surface of the grillage is leveled and covered with a film from drying out.
When the concrete gains strength, they arrange waterproofing from above and proceed with the installation of ceilings and walls.
Full instructions for installing a columnar foundation also includes operations for arranging waterproofing and picking.
Waterproofing is done on top of the grillage. It is equipped in different ways, of which the following are the most common:
- Bitumen is applied on top and ruberoid is laid interspersed with it.
- Cement mortar mixed with sand 1:2 is laid out on the grillage. Then roofing material is laid.
Underground space is protected from atmospheric action by the arrangement of a fence - a fence between the supports. It is made of wood, brick or stone. From below, a concrete screed is laid out, which serves as the base. To do this, first make a trench and fill the bottom with sand. For the screed, formwork from boards and a reinforcing cage are installed. The connection of the pick-up with the supports is not done in order to avoid the appearance of cracks in it during the draft of the house.
They try to make the plinth higher, which makes the building look attractive. It corresponds to the height of the supports.
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 instructions are the same as for the construction with a grillage. The supports penetrate far into the depths, creating reliable protection against seasonal ground movements.
They are rigidly connected with a tape shallow base, passing under the load-bearing walls of the building. The entire structure is poured with concrete at the same time, as a result of which it becomes monolithic and durable. With self-preparation of the solution, the concrete is laid in layers. The use of vibrators is mandatory in order to remove air bubbles from the mass as much as possible.
Various options for columnar foundations 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 columnar foundation with their own hands. Step-by-step instructions will help you avoid mistakes and make the base reliable.