A bored foundation with grillage is considered one of the most reliable and does not cost too much. This design can be built independently. Of course, one must have an idea of ββthe technology for performing such work. Previously, all necessary calculations should be made. Weβll talk about all this later in the article.
Is it worth arranging a bored foundation
The base for a house of this type is usually used on problem areas - marshy or on slopes. On ordinary soils, it will be cheaper and easier to put an ordinary strip foundation. On very unreliable grillages make a slab. In other cases, the tape is set as the last. Of course, the first option will cost more.
Pillar calculation
Of course, before embarking on the construction of such a structure as a pile bored foundation, you need to make all the necessary calculations. First of all, they are determined with the number of posts. This indicator directly depends on the weight of the house and is proportional to it. The second criterion that determines the number of required posts is, in fact, their diameter. The larger it is, the less need for piles. So, a pole with a diameter of 300 mm is able to withstand a load of 1700 kg. Such piles can be used for the construction of chopped, block or frame structures. Under heavy brick or flooded buildings, more powerful piles are installed - 500 mm each. They are capable of supporting weight as low as 5000 kg. The weight of the future home is the sum of all the materials necessary for its construction. Thus, it is not difficult to calculate the number of piles. Of course, the weight of the grillage will need to be added to the resulting figure.
With the right calculations, you get a solid foundation. Bored piles with grillage - the foundation is really durable. However, in order for it to turn out like this, you need, among other things, to correctly calculate the step between the posts. When choosing the distance between piles, one must take into account the fact that it should not exceed three of their diameters. That is, for example, the maximum distance between piles of 500 mm is one and a half meters.
Calculation of grillage
It is also easy to calculate the parameters of a tape of such a design as a pile bored foundation. Its width should be equal to the cross-section of the pillars. Also, when choosing this option, pay attention to the thickness of the walls. The width of the grillage should not be less than 1/3 less than them. The axis of the tape is laid so that it coincides with the axis of the wall. If the structure is light, the height of the grillage should be equal to its width or slightly larger. Such a tape is suitable for the foundations of frame and chopped houses. The height of the grillage for heavy buildings - brick or concrete - should not be less than 1.5 of its width.
Rebar calculation
Of course, a bored foundation with grillage should be reinforced with a metal frame. The heavier the building and the greater the step between the piles, the more reliable the fittings should be. The best option for the frame is a corrugated rod 12 mm. Material of a smaller diameter cannot be used for the foundation. According to SNiP, the metal in the tape should contain at least 0.1% of its total area. Reinforcement knitting is made with a special wire. Do not weld the frame for the foundation.
Foundation in the building project
So, the calculation of the bored foundation is done. Next is to draw his drawings. The project will need to include its plan (top view), as well as a sectional diagram. With such drawings, it is more difficult to make a mistake when building a house. In the project you also need to include a plate indicating all the materials necessary for pouring, their brand, characteristics and quantity.
Markup
So, all the calculations are done. It's time to start pouring. Previously, under the bored foundation with grillage, marking is done. In this case, the easiest way to use the method of "Egyptian" triangle. Previously, two corners of the future building are marked on the ground along a long wall. Then, using a rope with knots tied on it (at a distance of 3, 4 and 5 m), two other angles are found. The squareness is checked by the method of diagonals. Then the stakes are driven into the corners and the cord is pulled along the contour of the future foundation from the outside and from the inside. It is necessary to note the location of future pits.
Excavation
The foundation on bored piles must be arranged in compliance with certain rules. Pits under the pillars are drilled at all angles of the building, as well as at the intersection of walls inside it. The piling depth depends on the level of soil freezing. When building the base under the house with their own hands, experts recommend burying them at least 1.5-2 m. In this case, the levels of freezing and the location of groundwater will probably be passed. Work can be done with a garden drill. In the event that the soil on the site is swampy, sand should be poured on the bottom of the pit with a layer of at least 5 cm thick.
Installation of fixed formwork and fittings
So, the pits are ready. What next? Do-it-yourself bored foundation with grillage is usually done on pipes. On loose soils under pillars, metal products should be used. Cardboard pipes are also suitable for dense ones, but they must be impregnated with bituminous mastic or used machine oil. Their asbestos-cement variant is also often used. Above the surface of the earth, the formwork should rise at the same level in the plane. When pouring this type of foundation, you need to keep in mind that the grillage on the ground should not even lie on or touch it. The distance to its bottom from the surface of the sandy soil should be at least 5 cm, heaving - 10 cm.
As soon as the formwork is installed, reinforcing rods connected by metal clamps with a pitch of one meter are lowered into it. Above the level of piles, they should rise by 10-15 cm. This is necessary in order to subsequently make a bundle of column reinforcement with grillage reinforcement.
Pouring Pillars
The concrete mixture for bored piles is prepared from high grade cement (preferably M400) and coarse sifted sand without organic inclusions in a 1: 3 ratio. Having poured several buckets of the solution into the pipe, they pierce it and mix it with a stake or rod to remove voids. This is done until the formwork is completely filled. On sufficiently dense soils, reinforcing bars can be stuck directly into the mixture.
Screw piles
If desired, in our time, labor costs can be minimized as much as possible. If you do not want to spend time pouring concrete pillars, just buy ready-made metal screw piles. You can screw them into the ground without the use of special equipment. But, of course, several people should do the work. Usually two, having inserted crowbars into slots of a pile, screw it into the ground. The third person controls the level of its verticality. Of course, you can use a similar method only in not too stony areas.
Grillage device
They continue to build such a structure as a bored foundation with a grill, constructed with its own hands, by filling the tape. Under it, you can make a formwork with a bottom. But since the grillage in such foundations is usually not located too high above the ground, you can do simpler. Under its bottom, sand is simply poured and leveled on top so that a platform is obtained along the entire length of the future tape of sufficient width. On the resulting "bottom" should definitely put a strip of roofing material. Otherwise, water from the solution will be drawn in by the sand. A regular formwork is installed on the sides.
At the next stage, a footing of 5 cm thickness is poured. Once it grasps, you can proceed with the installation of the reinforcing cage. It needs to be connected with rods sticking out of piles. Next, concrete is laid in the formwork. When pouring the tape, as well as piles, it should be pierced from time to time with a stake or a shovel.
The final stage
So, you poured the bored foundation with a grillage. The technology of its construction, as you can see, is quite simple. However, in order to get the highest quality foundation for the house, you need to do something else.
After a couple of days, the formwork is removed from the tape. Sand is best left for at least a week. Over the next fourteen days, the foundation will need to be moistened with water from time to time so that surface cracks do not appear on it. The base under the house must stand for at least a month. It is during this period that concrete gains sufficient strength.
Before proceeding with the masonry or assembly of the walls, the tape must be waterproofed with two layers of roofing felt, glued with bitumen mastic.
As you can see, pouring such a structure as a bored foundation with grillage is technically a simple matter. The main thing is to comply with all recommendations and use quality materials. In this case, the foundation will turn out to be reliable, and the building itself will stand on it for more than a decade.