Foundations - combined piled-raft

In private construction, as a rule, monolithic-tape type foundations are used. But in conditions of great depth of soil freezing, such an option is unreasonably expensive. This situation provides for deep laying of the foundation, and this significantly increases financial costs.

To reduce the cost of building a cottage foundation, the use of pile-grillage foundations is considered more profitable. The reliability and durability of this structure is not inferior to monolithic-strip foundations, but their financial benefits are obvious.

What is a pile-grillage foundation

From a constructive point of view, it represents reinforced concrete supports immersed in the ground below the freezing mark, connected to the tape with a reinforced concrete bundle. Such a structure evenly distributes the load of the entire structure to the ground.

The resulting point effects from the piles spread along the entire length of the base strip. There is no excess pressure in the walls in a certain place. Therefore, the masonry on this type of base in rare cases is destroyed or warped.

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Types of pile foundations

A steel channel or reinforced concrete is used as the main material for the pile foundation grillage. In most cases, preference is given to using a concrete structure with a reinforced frame. The version with a metal strap is usually used for small structures.

Regarding the type of supports used, pile-grillage foundations are divided into:

  • Screw;
  • Bored;
  • Jellied.

The principle of the first option is not much different from the foundations on screw piles, and implies the placement of a more powerful monolithic grillage on the supports. In this case, high strength steel screws with a large diameter and wall thickness are used.

In private construction, bored or cast piles are more often used with the use of the so-called fixed formwork. A feature of this technology is ease of implementation and lower financial costs.

Pros and cons

The significant pile depth provides good stability for the entire strip foundation above the ground surface. And their cost is several times less than a reinforced concrete structure of a similar height. If a bunch of support posts in the upper part is carried out using a metal grillage instead of a concrete tape, then you can count on more significant savings.

The main advantages of such a foundation include:

  • Erection on swampy ground and slopes;
  • Relative availability;
  • Minimum time spent on the construction process;
  • Good stability on moving ground.

The construction of a monolithic foundation on a site with a slope is problematic and expensive. The best option in this case is to use piles. Other options are too laborious and not attractive from a financial point of view.

The main difficulties arise when constructing formwork, the placement of which is provided by weight. The grillage part should rise 100 mm above the ground surface so that in conditions of strong heaving it does not "float" from the piles along with the building.

There are not many disadvantages in this design, but they still exist:

  • Difficulty in arranging a basement;
  • High costs for floor insulation.

The space under the building must be closed so that the wind does not blow out the heat. Facade panels or masonry work well for this purpose. Additional floor insulation in such a building is a necessary measure, so it is better to take this nuance into account in advance when drawing up a construction estimate.


Comparison of the advantages and disadvantages of the pile-grillage foundation shows that this type of foundation is significantly superior to other options. Such a base is the best option for private construction on soils with unstable characteristics or on slopes.

It is better to carry out all stages of construction work with the help of the construction company "Vitoslavitsa". The design itself is distinguished by its reliability, durability and simplicity of the device. Subject to all standards and with a high-quality implementation of each stage of the construction process, the pile-grillage foundation will last for many years.

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