The technology of bored piles with grillage is often used in private construction. Installation and manufacture are especially necessary during construction on soft soils. A bored foundation will also be able to help out with a high groundwater level. But in this case, for the duration of the construction work, it will be necessary to provide for measures to reduce water. Otherwise, drilling wells under the foundations will become impossible.
Features
The technology provides for the presence of free-standing supports and a connecting element - grillage. The depth of piling depends on the geological conditions on the site and the design features of the building. Drilling wells over a long distance allows you to increase the contact area of the building's support with the ground. Due to this, friction increases. Such foundations are able to withstand heavy loads.
The device of bored piles has one serious drawback: all supports work separately. This option increases the likelihood of uneven precipitation, which is dangerous for almost all types of buildings. To prevent the destruction of walls, provide a reinforced concrete tape grillage. Its reinforcement allows you to well perceive bending loads and combine all the supports in one foundation. Manufacturing technology grillage may be different depending on geological conditions.
Benefits
Drilling wells and installing piles in them allows you to achieve several positive results at once:
- High bearing capacity. A bored foundation with a grillage under a brick house perfectly copes with its task. The base accepts loads well even from a massive building. A mandatory condition is waterproofing between the tape element and the walls of the building. Thus, it is possible to protect materials of different properties from destruction.
- Drilling wells and filling the foundation does not have a devastating effect on neighboring buildings. It is possible to carry out construction work even close to existing buildings.
- Installation is possible under difficult geological conditions. Reinforced concrete supports are also suitable for the location of existing utilities in the ground.
- The technology is simple and involves minimal labor costs for soil development. Drilling wells avoids the need to tear out a pit or trenches.
- The foundation on bored piles is made at a construction site. There is no need for heavy equipment or special devices. To increase the speed of work often hire a concrete pump.
A pile foundation with a monolithic grillage is made in several stages.
Getting Started
Before you make a grill foundation with your own hands, it is necessary to carry out geological research and design the supporting part of the building. You can order full-fledged research, but it will cost quite expensive. When constructing a private house, you can determine the soil indicators yourself. To do this, pit holes (pits) or drill wells are used. The soil is developed to a depth of 50 cm lower than the projected elevation of the base of the foundation. Knowing the type and characteristics of the soil, it will be possible to accurately calculate the pitch and reinforcement of piles and grillage. Without excess stock. And this in turn will reduce the overall cost of the foundation.
The result of this stage should be known:
- types of soil on the site;
- groundwater location level;
- water saturation of the soil.
The moisture content of the soil and the level of moisture will determine which waterproofing is necessary for the foundation:
Based on the data obtained, a foundation is designed. The process here is to select the following characteristics:
- piling depth;
- their cross section;
- distance between piles;
- cross section of grillage;
- reinforcing piles and grillage.
Better if the work is done by an experienced designer. With the independent appointment of the mark of laying and other characteristics, it is necessary to carefully study the information on the topic and regulatory documentation.
Spend two calculations:
- Calculation of piles. Reinforced concrete elements are designed for compressive loads. Due to the fact that concrete works well for such efforts, powerful reinforcement is not required. The calculation assigns the depth of the supports, section and step.
- Calculation of grillage. The tape element is calculated as a multi-span beam. But it is important to consider working conditions: the tape lies on the ground or hangs in the air. When carrying out calculations, it is necessary to assign a section and reinforcement.
At the design stage, it is necessary not only to assign reinforcement, but also the concrete class. Different materials often use different materials:
- for piles, concrete of class B15 – B20 will be sufficient;
- for grillage it is necessary to use material not lower than class B20.
Here is an example of a calculated foundation with selected sections of reinforcement and concrete class.
After selecting all the parameters of the foundation, you can begin to manufacture them.
Land marking
A pile foundation with a monolithic grillage begins to be built with the removal of the location of the supports on the ground. First, remove the fertile soil layer. In order that the marking does not interfere with earthwork, it is necessary to make a castoff.
The cast is usually made of wood. To install it you will need racks and jumpers. Set the element around the perimeter of the building at a certain distance. It is important that you can drill wells without obstacles.
Nails are hammered into the boards, to which a cord denoting the axis of the building will be tied. During the construction of the cast, it is important to control the perpendicularity and parallelism of the lines. It is recommended that you study the triangle method that builders often use.
After the markup is completed, you can proceed to the next steps.
Well drilling, reinforcement and piling
It is important to note that the pile-grill foundation for a wooden house and the pile-grill foundation for aerated concrete, for example, are built almost the same. The differences are only in the following characteristics:
- pitch of piles;
- their cross section;
- reinforcement of supports and grillage;
- cross section of grillage.
The technology of construction does not have significant differences. A pile-grill foundation for a wooden house will be less powerful than for a brick or concrete. This is because less massive materials for walls and floors are used in construction. All loads must be considered in advance in the calculation.
Drilling wells for filling is carried out according to the markup described at the last stage. Depth of laying should be assigned earlier by calculation.
Formwork and reinforcement are installed in the drilled well. The work is performed by the indentation method. After the drilling depth has been reached, the loose soil must be removed from the bottom of the well. The supporting part of the base is rammed, after which a pillow of coarse or medium sand is laid. The thickness of the cushion is assigned from 30 to 50 cm. It should be taken into account when the depth of laying and the mark of drilling are assigned.
Having installed reinforcement, you can begin to pour concrete mixture. For convenience and increasing the speed of work, it is recommended to rent a concrete pump. If the laying depth is small (as well as the scope of work), concrete can be laid manually.
Do-it-yourself bored foundation (each support) should be poured in one go. This is the only way to ensure the integrity of the element.
Ribbon grillage
The grill grouting technology is a bit more complicated than piling. This is due to the design features. Work on its manufacture includes the following steps:
- formwork installation;
- installation of reinforcing cages;
- pouring concrete, preferably at a time;
- vertical waterproofing;
- horizontal waterproofing.
The marking of the grillage may be different.
When lying on a site of coarse soil or sand of medium and large fractions, you can rely tape grillage directly on the ground.
When lying on a site of heaving soils (clay, loam, sandy loam), a damping layer will have to be provided. It will not allow the soil to damage the grillage during frost heaving. The elevation mark in this case is assigned 10-15 cm above the surface of the earth.
To provide clearance, you can use a sand cushion, which, after solidification, is removed from under the structure. Polystyrene is also used, it is not necessary to remove it after completion of work. When selecting a mortgage, data obtained at the stage of geological research are used.
Do-it-yourself bored foundation needs such protection as waterproofing. Vertical will protect concrete grillage from negative environmental influences. This type of waterproofing is usually made of plastering materials.
Horizontal waterproofing is necessary to separate materials with different characteristics. In this case, the tape grillage is covered with several layers of rolled materials. Waterproofing helps prevent mold and mildew from touching materials of different properties. Waterproofing is necessary when laying brick walls on concrete, as well as laying walls made of wood and light concrete.
Pile grillage foundation with your own hands will last a long time, but for this you need to correctly select the materials, observe the technology. An important element in ensuring durability is waterproofing. It is especially important to correctly make a tape grillage, which will connect all the supports in a single system.