A bored foundation with a grillage is considered one of the most reliable and not too expensive. Such a structure can be built independently. Of course, you need to have an idea about the technology for performing such work. All necessary calculations must be made beforehand. We'll talk about all this later in the article.
Is it worth it to arrange a bored foundation
The base for a house of this type is usually used in problem areas - marshy or on slopes. On ordinary soils, it will be cheaper and easier to install a conventional strip foundation. On very unreliable, the grillage is made slab. In other cases, the tape is set as the last one. Of course, the first option will cost more.
Calculation of pillars
Of course, before proceeding with the construction of such a structure as a piled bored foundation, you need to make all the necessary calculations. First of all, they are determined with the number of columns. This indicator directly depends on the weight of the house andproportional to him. The second criterion that determines the number of required pillars is, in fact, their diameter. The larger it is, the less piles will be needed. 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, cobbled or frame buildings. Under heavy brick or flood buildings, more powerful piles are installed - 500 mm each. They are able to withstand a weight of already 5000 kg. The weight of the future house is made up of the mass 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 correct calculations, you will get a reliable foundation. Bored piles with a grillage - the foundation is really durable. However, in order for it to turn out like this, you also need to correctly calculate the step between the pillars. When choosing the distance between piles, it must be taken into account 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 piled 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 them by more than 1/3. The axis of the tape is laid in such a way that it coincides with the axis of the wall. If the structure is light, the height of the grillage shouldbe equal to its width or slightly more. Such a tape is suitable for the foundations of frame and log houses. The height of the grillage for heavy buildings - brick or concrete - should not be less than 1.5 times its width.
Calculation of reinforcement
Of course, a bored foundation with a grillage must be reinforced with a metal frame. The heavier the building and the greater the pitch between the piles, the more reliable the reinforcement should be. The best option for the frame is a corrugated rod 12 mm. Material of smaller diameter for the foundation cannot be used. According to SNiP, the metal in the tape must contain at least 0.1% of its total area. Reinforcement is knitted with a special wire. It is impossible to weld the frame for the foundation.
Foundation in building design
So, the calculation of the bored foundation is completed. Next is to draw his drawings. The project will need to include its plan (top view), as well as a sectional diagram. In the presence of such drawings, it is more difficult to make a mistake when building a house. The project also needs to include a plate indicating all the materials necessary for pouring, their brand, characteristics and quantity.
Performing markup
So, all the calculations are done. It's time to start filling. Previously, under the bored foundation with a grillage, markings are made. In this case, the easiest way is to use the "Egyptian" triangle method. Previously, two corners of the future building are marked on the ground along the longwall. Then, using a rope with knots tied on it (at a distance of 3, 4 and 5 m), two other corners are found. Squareness is checked by the diagonal method. Then 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. You also need to mark the locations of future holes.
Earthworks
The foundation on bored piles must be arranged in compliance with certain rules. Holes for poles are drilled at all corners of the building, as well as at the intersection of the walls inside it. The depth of the piles depends on the level of soil freezing. When building a foundation for a house with their own hands, experts recommend deepening them by at least 1.5-2 m. In this case, the levels of freezing and the location of groundwater will most likely be passed. The work can be done with a garden drill. In the event that the soil in the area is swampy, sand should be poured into the bottom of the pits with a layer of at least 5 cm thick.
Installation of fixed formwork and reinforcement
So, the holes are ready. What's next? A do-it-yourself bored foundation with a grillage is usually done on pipes. On loose soils, metal products should be used under the pillars. For dense ones, cardboard pipes are also suitable, but without fail impregnated with bituminous mastic or used engine oil. Their asbestos-cement version is also often used. Above the ground, the formwork should rise at the same level in the plane. When pouring this type of foundation, it must be borne in mind that the grillage should not lie on the ground or even touch it. The distance to its bottom from the surface of the sandsoil should be at least 5 cm, heaving - 10 cm.
As soon as the formwork is installed, reinforcing bars are lowered into it, connected with metal clamps in increments of one meter. Above the level of the piles, they should rise by 10-15 cm. This is necessary in order to subsequently make a bunch of pillar reinforcement with grillage reinforcement.
Filling pillars
Concrete mixture for bored piles is prepared from high-grade cement (preferably M400) and coarse sifted sand without organic inclusions in a ratio of 1:3. After pouring several buckets of mortar into the pipe, it is pierced and mixed 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 don't want to spend time pouring concrete into the posts, 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 must do the work. Usually, two people, having inserted crowbars into the slots of the pile, screw it into the ground. The third person controls the level of its verticality. Of course, this method can only be used on areas that are not too rocky.
Rollage device
They continue the construction of such a structure as a bored foundation with a grillage, with their own handsconstructed by pouring the tape. Under it, you can make a formwork with a bottom. But since the grillage in such foundations is usually not too high above the ground, you can do it easier. Sand is simply poured under its bottom and leveled from above so that a platform is obtained along the entire length of the future tape of sufficient width. On the resulting "bottom" it is necessary to put a strip of roofing material. Otherwise, the water from the solution will be drawn into the sand. Regular formwork is installed on the sides.
At the next stage, a footing 5 cm thick is poured. As soon as it seizes, you can proceed with the installation of the reinforcing cage. It must be connected with rods sticking out of the piles. Next, concrete is poured into the formwork. When pouring, the tape, as well as piles, should be pierced from time to time with a stake or shovel.
Final stage
So, you have poured a 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 base under 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 foundation under the house should stand for at least a month. It is during this period that concrete gains sufficient strength.
Before you start laying or assembling walls, you need to tapewaterproof with two layers of roofing material, gluing them with bituminous mastic.
As you can see, pouring such a structure as a bored foundation with a grillage is technically a simple matter. The main thing is to follow all the recommendations and use high-quality materials. In this case, the foundation will turn out to be reliable, and the building itself will stand on it for decades.
