Sub Base For Concrete Slab

Then once the subbase is ready protect it until the concrete slab is placed see sidebar maintaining the slab support system.

Sub base for concrete slab.

Even if a concrete slab is being placed on top of a granite subgrade the lack of uniformity in the absence of a sub base will pose several problems. As a rule of thumb concrete slabs supporting lighter weights such as paths patios and shed bases will need to be 75 100mm thick while driveways and garages need to be at least 100mm thick. Parts of this article were contributed by previous articles written by boyd ringo bruce suprenant ward malish ronald lech and joe nasvik. Dig the area deep enough to accommodate the sub base 100mm and damp proof membrane dpm as well as the thickness of the concrete slab itself.

Subgrade and subbase are the foundation of a concrete slab and play critical role in its performance. According to the aci code the subgrade is a compacted and improved natural soil or brought infill whereas subbase is a layer of gravel placed on the top of the subgrade. For instance it is harder to obtain a proper grade and an optimal flat structure without a thoroughly prepared sub base. Other articles related to preparing the soil support system for a.

The entire subbase and base system should be at least 4 inches thick thicker if the engineer feels it is needed for proper support. A flat base course will also allow the slab to slide easily as it shrinks reducing restraint and the risk of cracks as the concrete contracts after placement drying shrinkage.