Any home should be built on a solid foundation. There are several types of foundations poured under buildings. At the same time, the most inexpensive variety of such designs is columnar. These foundations are quite reliable and durable. At the same time, they are poured by a relatively simple technology. To build such a foundation under the house is possible even for a person who does not have building skills.
Definition and purpose
The column foundation is a solid structure, which is a series of supports for the structure. The foundations of this type are usually built during the construction of houses of light type. That is, buildings with shield walls assembled from timber or foam blocks. In some cases, various small brick structures can also be built on columnar foundations. For example, such structures are often installed under the arbors. Depending on the material used, the supports of such foundations may have a round or square cross section.
The main load in such structures are pillars buried in the ground. In some cases, in addition to the construction of bases of this type, a grillage can also be poured. Sometimes the pillars of such foundations are made of brick or wood. But most often the supporting structures of this variety are poured all the same from concrete.
Pits under the pillars of such foundations are made using a drill. As formwork, roofing material or asbestos pipes are most often used. Of course, to increase the bearing capacity, the pillars of such a foundation are always additionally reinforced.
In addition to the grillage, one of the elements of such a base can also be pickup. This is the name of the structure that closes the gaps between the pillars. The fence is equipped in order to give the building a finished look and to prevent the penetration of cold air through the floor into the premises in winter.
Material selection
Columnar foundation is a construction, during the construction of which exclusively high-quality materials should be used. Cement for pouring such a foundation is chosen at least grade M400. The sand for the preparation of the solution is used exclusively large, preferably river. In addition to these materials, columnar foundations are being built using:
If necessary, the construction of grillage also use the following materials:
To connect the elements of the reinforcing cage of the columnar foundation, a special knitting wire is used. Pits under the pillars themselves during the construction of small suburban buildings are usually made using a garden drill with a diameter of 25 cm.
Regulations
The columnar foundation device is not too complicated. However, in the construction of such structures, it is certainly necessary to comply with certain rules. The supports of the bases of this type are usually installed at a distance of 1.5-2 m, but not more than 3 m from each other.
Pits under such foundations are supposed to be drilled below the depth of freezing of the soil. Otherwise, due to spring heaving, the entire structure may skew, resulting in cracks in the grillage and walls of the house.
The pillars of the base of this type are supposed to have:
at the corners of the box of the building;
under all the inner walls;
at the intersection of the walls.
Before starting pouring the bases of this type, it is also necessary to calculate the cross-section of the columns. The finished structure, of course, should easily support the weight of the buildings built on it.
The principle of calculating the column foundation
In order to determine the cross-sectional size of the supports of the base of this type, it is necessary to calculate first of all the load that the house will subsequently exert on the bearing soil. To do this, add up the weight of all materials used for the construction of the building. The pillar foundation for the frame house, of course, will not be so powerful. Unlike the bases for buildings with walls made of timber or foam blocks.
To the resulting amount should be added the mass of the columnar foundation itself. Also, when calculating the load, it is necessary to take into account the weight of those objects that will subsequently be in the house, as well as the people living in it.
Based on the obtained load indicator, the total cross section of the columns is further calculated. The following formula is used:
- S = 1.4 x P / Ro, where P is the weight of the building, Ro is the ground resistance.
When constructing a low-rise private building, the resulting figure is usually subsequently divided by 20-25. After all, it is precisely this diameter that pits dug by a garden drill have. The result is the required number of supports.
DIY pillar foundation: step-by-step instructions
The construction of such a foundation usually includes the following steps:
markup execution;
drilling pits under the pillars;
backfilling of a sand pillow;
installation of roofing formwork;
installation of fittings;
pouring concrete pillars.
When constructing frame and block houses, the grillage on the supports of such a foundation is usually not poured. His role in this case is most often performed by the lower harness or crown.
When using foam blocks or bricks for the construction of walls, concrete grillage is poured on the supports of the columnar foundation. Moreover, such a tape is necessarily reinforced with metal rods.
In some cases, a metal grillage can also be laid on the foundation supports to distribute the load from the walls. Most often, the posts are connected by a channel or an I-beam.
Pit Marking and Drilling
First of all, all rubbish is removed before pouring the columnar foundation for the house at the construction site. Next, markup is made using an inelastic cord, pegs and level. In order for the corners of the building to be as even as possible, when performing this operation, the methods of the Egyptian triangle or two curves are used. Of course, the location of all the pillars is also marked with pegs.
At the next stage, the upper sod layer of soil is cut off at the construction site. Then they start actually drilling holes under the supports. When choosing their depth, the height of the sand cushion is taken into account. At the final stage of drilling, the bottom of each pit is densely tamped and leveled.
Pillow device
Under the supports of the columnar foundation, sand must first be imposed. The pillow formed by this material is designed to absorb pillars during spring heaving and building movements during shrinkage. The thickness of such a layer under the supports, according to the standards, should not be less than 15 cm.
Arrange pillows under a columnar concrete foundation as follows:
5 cm sand layer is poured onto the compacted and leveled bottom of the pit;
Thoroughly spill it with water to seal;
pour the next 5 cm of sand and compact again;
pour another 5 cm of sand and pour it with water.
At the final stage, a sand cushion is covered with a piece of roofing material. This prevents water from being drawn from the lower layers of the concrete support.
Installation of formwork and installation of fittings
The metal frame of the pillars of such a foundation usually consists of 4 rods. With the help of a knitting wire and ring-shaped clamps, they are connected into a frame. Next, cubes (or special plastic coasters) of 5 cm thickness are placed in the pits. A frame is installed on them. This is necessary so that the metal reinforcement subsequently completely appears in the thickness of concrete and subsequently does not rust.
When erecting a columnar foundation under a wooden building, the length of the frame is chosen equal to the length of the supports themselves (minus 5 + 5 cm above and below). If it is planned to equip the grillage, the rods are brought out on top of the latter by 20 cm. Subsequently, this will make it possible to link the column reinforcement and the grillage.
Concrete pouring
Columnar foundation is a construction, the construction of which, of course, you need to strictly follow all the required technologies. Sand for the pillars of the foundation of a lightly loaded house must be sifted carefully before preparing the solution. In no case can you ignore this operation. Cement for kneading is supposed to be used exclusively fresh.
In prepared pits with reinforcement installed in them, formwork from roofing material is placed. For their manufacture, the material is simply rolled up.
The solution is prepared in the ratio of cement / sand as 1/3. Lime is not added to the mixture. This material may reduce the ability of pillars to resist soil moisture. To make the pillars strong, they are filled in one step. At the final stage, the mixture is pierced with rods to remove air bubbles.
How to make a columnar foundation: grill fill
This element is being built on approximately the same principle as the tape foundations of houses. That is, the concrete mixture is poured into the formwork with a metal frame pre-installed in it. The grillage reinforcement is connected to the rods of the posts using wire.
The bottom of the formwork under the tape is usually not stuffed. Instead, earth is poured under the walls of the mold from below. Filling is carried out with a solution also prepared in a proportion of 1/3.
Arrangement of pickup
Such a construction is often laid out of brick when erecting columnar foundations. In this case, they use conventional technology with dressing of stitches. Masonry for saving is done according to the “half brick” or “brick” method. For ventilation of the pillars in this clogging, small "vents" are left in several places.
Also, sometimes the supports of such a foundation of the house are closed with simply shields from boards. Of course, the wood is subsequently stained to extend its service life. In addition to boards and bricks, clogging the house can be equipped with sheet materials, for example:
- slate;
- moisture resistant plywood;
- siding;
- corrugated board;
- basement siding.
Under small structures, for example, arbors, pick-up is usually not collected.