The article describes the features of solid slab foundations. The scope of their application, operational and design differences are discussed in great detail. The applied questions concerning the technology of construction of foundation slabs are brought to the fore.
This is a continuation of the series of articles on foundations, and we have already managed to publish a lot of interesting material. Therefore, we recommend:
- How to drain the site
- What type of foundation to choose
- Strip foundation. Part 1: types, soils, design, cost
- Strip foundation. Part 2: preparation, marking, earthwork, formwork, reinforcement
- Strip foundation. Part 3: concreting, final operations
- Strip foundation. Part 4: assembling concrete block structures
- Column foundation
- Pile foundation
A slab foundation, aka “solid”, aka “floating”, aka “Swedish, Scandinavian slab” is a solid slab located under the entire area of the building, buried in the ground, or laid on it. There are several design options for slabs – box-shaped, flat, ribbed, prefabricated from road concrete products, monolithic, with extensions at the corners, with or without reinforcement, insulated and cold … All of them have their own distinctive features and specific scope. For private suburban construction, in terms of economic and functional characteristics, flat monolithic reinforced concrete slabs with a thickness of 20 to 40 cm with insulation have proven themselves in the best way. We will talk about them further..
Why choose a slab foundation
In low-rise construction, which we are, in fact, interested in, this type of foundation, for many reasons, will be preferable to its competitors (both tape and pile structures). This is explained by the advantages, both of a purely technical and near-construction nature..
Strengths of solid foundations
Versatility in foundation geology.The floating structure can be correctly applied on all types of soils, including low-bearing, heaving, horizontally mobile, with a high level of groundwater, permafrost …
There are some restrictions on the relief – it is difficult to build such a foundation on a slope, most likely, piles will be preferable. However, there are American-proven technologies for erecting slabs on hillocks, which in their design (in the lower part of the site) have elements of high monolithic belts. Another “centaur” suitable for such places is a pile foundation with a low grillage in the form of a monolithic slab.
Good bearing capacity.This quality is due to the specific mechanics of interaction “house / slab / ground”. We’ll take a closer look at this point in the next chapter. In short – the slab has a large support area, so the pressure on the base soil is very low (from 0.1 kgf / cm2). Therefore, a stone house of two floors on a slab can be erected safely. They say that the elevator shaft of the Ostankino tower stands on a monolithic slab.
High spatial rigidity.It is due to the absence of seams and joints, the use of rigid reinforcement, massive structure and high material consumption. The slab foundation is perfect for houses with “inelastic” walls, which are very afraid of even the smallest (1-3 mm) movements of the supporting structure – brick, aerated concrete, cinder block, shell rock and other mineral materials.
In the presence of excessively heaving soils and a significant sensitivity of buildings to uneven deformations, it is recommended to build them on shallow and non-buried monolithic reinforced concrete slabs, under which pillows of non-heaving materials are arranged.