Construction companies today offer many design solutions for laying an inexpensive and at that time reliable foundation. Compromise options are usually a hybrid of two traditional methods of building a carrier base. This concept fully applies to the pile-grillage foundation, which was originally focused on light wooden structures, but as it improved, it began to be used for concrete structures as well.
Technology overview
The house is arranged on a monolithic platform (grillage), which, in turn, is based on load-bearing piles. Accordingly, in the process of work, it will be necessary to create wells and carefully calculate the load-bearing structure that will distribute the load from the building frame. Contains this base and elements of the strip foundation.
It is recommended to pay special attention to the trench, according tothe lines of which the piles will be installed. The configuration of their placement can be checkerboard, dense, single or striped. For example, it is recommended to lay a pile-grillage foundation for aerated concrete according to a two-lane scheme, in which the bearing supports are installed in two rows. For a bathhouse or a sennik, it is quite possible to confine oneself to an infrequent arrangement of single piles, and industrial buildings and two-story cottages are erected on a grillage held by a dense group of supports integrated in a checkerboard pattern.
Which piles are used?
All types of traditional driven and screw piles are used, but it should be taken into account that the support must allow immersion in a rammed concrete tunnel or casing pipe. In terms of the choice of materials, the pile-grillage foundation technology practically does not impose restrictions - depending on the load, wood, metal, concrete, and even composites can be used. But more often metal piles are used due to their practicality, durability and reliability.
It is important to take into account further possibilities for pairing the supporting elements with the same grillage and casing. Wire bonding, reinforcement and welding technologies can be used. It is recommended to use steel combinations for a monolithic pile-grillage foundation, since on a small construction site reinforced concrete allows you to take heavy loads from the frame without additional reinforcement.
Preparing the construction site
To begin with, it is worth highlightingtypes of soils on which, in principle, the construction of a pile-grillage bearing base is allowed. As a rule, these are weak and unstable soils that are in a fluid-plastic state and are prone to swelling. This applies to quicksand, loam, forest and vegetation cover, the dynamics of which does not allow the installation of permanent tape and monolithic structures.
How is problem soil prepared? The top fertile layer is completely removed along with the turf and roots. Next, the marking of the territory is carried out, on which the pile-grillage foundation with trenches will be arranged. Stakes should mark the points of placement of load-bearing partitions and the contours of the floors. A rope is pulled between them strictly according to the level.
Installation of bored piles
A trench is being dug along the perimeter of the location of the partitions of the future frame. In depth, it can also correspond to a tape structure, but in principle, the pile-grillage foundation is shallow, so 50 cm will be enough. Moreover, in the trench, work will be carried out to install the pile, and this will require additional space.
The bored support elements are set to a depth of about 150-200 cm. At the bottom, a pillow 20-30 cm thick is arranged on the basis of sand and gravel. Then a reinforcing frame is installed, the walls of the well are covered with roofing material, and the casing pipe is immersed in the niche itself. To increase the durability of the pile-grillagefoundation for a house, sometimes borehole blasting techniques are also used to expand the lower part of the planting, which is then poured with concrete mortar. You need to fill the entire niche of the casing pipe.
Installation of screw piles
This technique is suitable for light and small buildings - for example, aerated concrete or wood. The supporting elements are immersed by 50-70 cm. From the point of view of device technology, manual creation of a well is the main advantage of a screw pile-grillage foundation. With your own hands, using a drill, you can drill a hole of the desired depth without connecting special equipment. To do this, insert a pile into the prepared recess, and attach a lever to its upper part. Further, during the rotation of the support, a small well up to 100 cm will be formed. But this operation must be done with a partner who will ensure control of the verticality of the drill string.
The configuration of the location of the piles must also be maintained horizontally - that is, the placement on the same line. After installing the columns, it is also necessary to fill the niches with concrete mortar. Problems when using a screw pile-grillage foundation can arise on permafrost soil. Such soils are advantageous for their density, which also increases the reliability of the fit of the bearing elements. However, difficulties may arise due to the fact that after the destruction of the ice structure during drilling, its subsequent restoration will disrupt the position of the pile relative to the vertical. Therefore, for some time after drilling,securely fix the piles in the cement mortar with special props.
The device grillage and strapping
When the supports gain sufficient strength, you can proceed with the installation of the upper carrier platform. Formwork is carried out along the previously created trench, the bottom of which must be provided with a sand cushion with a thick layer of geotextile-based insulator. Then a reinforcing frame is formed from metal rods 8-10 mm thick. After that, the pillars are poured under the pile-grillage foundation strictly at the level of the trench. When the screed hardens, you can disassemble the formwork and start installing the grillage.
At this stage, different approaches can also be used, but the most reliable option would be to install a metal structure based on I-beams and a channel. Trimming the elements of the required size is done with a grinder at a 45-degree angle. Butt joints are fastened with double welding and additionally twisted with bolts. Such a grillage can be used for suburban residential buildings made of brick or stone, and for lightweight buildings, the design on wooden beams is also suitable.
Advantages of Technology
Practically all the strengths of using this type of foundation come down to optimizing the construction process. This is expressed in a reduction in the cost of work and materials, sometimes in the abandonment of special equipment and a reduction in construction time. More importantly, weather conditions do not affect the devicepile-grillage foundation. The pros and cons in terms of technical and operational qualities also deserve attention. Of course, there is no question of comparison in terms of strength with monolithic platforms and a tape base, but the flexibility of the design allows you to safely build a grillage on piles, regardless of the characteristics of the terrain.
Flaws of technology
As already noted, the strength of such a foundation is not the strongest side, which imposes restrictions on its use for many capital buildings. In individual construction, a significant drawback of this technology is the complete exclusion of the construction of basement floors with basements. Also, despite some ease of the workflow, the pile-grillage foundation for the house requires a rigorous calculation in the installation of load-bearing elements. Errors in this case are much more significant than in the construction of the same monolithic foundation. For example, shrinkage with an insufficiently stable position of piles can even lead to the destruction of the building.
Conclusion
In the process of developing projects for private houses, architects often face the problem of combining several conflicting construction parameters. For example, the task may be to build a functional, inexpensive and reliable house with a full range of protective insulating properties of the frame. As a result, a decrease in the cost of the project leads to the abandonment of a number of technological solutions,used, including at the foundation stage. I must say that the foundation as such to a large extent determines the future technical and operational qualities of the building.
The optimal solution in such situations is just the pile-grillage foundation, the pros and cons of which can be adjusted during construction. For example, the lack of capacity of the carrier base can be made up for at the stage of creating the first floor in the frame of the house. On the other hand, the functional tasks of the grillage can be enhanced - the metal platform, in particular, is supplemented with insulators. At the same time, the unconditional advantages of the foundation in the form of financial savings and high construction speed will remain.
