For instance it is harder to obtain a proper grade and an optimal flat structure without a thoroughly prepared sub base.
Sub base for concrete slab.
Other articles related to preparing the soil support system for a.
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.
Then once the subbase is ready protect it until the concrete slab is placed see sidebar maintaining the slab support system.
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.
Parts of this article were contributed by previous articles written by boyd ringo bruce suprenant ward malish ronald lech and joe nasvik.
Both subgrade and subbase shall be constructed.
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.
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.
The recommended gravel base for a concrete driveway.
Subgrade and subbase are the foundation of a concrete slab and play critical role in its performance.