Subbase / foundation course A subbase, also called a foundation course, is the compacted layer of granular material placed beneath concrete or asphalt pavement. It distributes loads and provides stable support.
A properly constructed subbase helps prevent settlement, cracking, and uneven pavement by creating a firm foundation for the finished surface. The material is placed in layers and compacted to achieve the required density before paving begins. Good drainage within the subbase also improves long-term pavement performance.
Frequently Asked Questions About Subbase / foundation course
What is a subbase?
The compacted layer of granular material placed beneath concrete or asphalt pavement, which distributes loads and provides stable support.
Why is the subbase important?
Most premature sidewalk failures trace back to the base, not the concrete. A firm, uniform subbase prevents settlement, cracking and rocking slabs.
How is it built?
Material is placed in layers and compacted to the required density before paving begins.
Does drainage matter in the subbase?
Yes. A free-draining base prevents water from saturating and softening the support layer, which is a major cause of freeze-thaw damage.