Which ICPI-recommended base material provides drainage and load-bearing capacity beneath interlocking pavers?

Which ICPI-recommended base material provides drainage and load-bearing capacity beneath interlocking pavers?

• A. Poured concrete slab beneath pavers.
• B. A compactable granular base (base course) placed on a properly prepared sub-base.
• C. Crushed limestone subgrade with no base.
• D. Asphalt base layer.

Answer: (B)

The important idea is that the foundation under interlocking pavers must both carry loads and allow water to drain away. A compactable granular base (base course) placed on a properly prepared sub-base does exactly this: it distributes traffic loads evenly to the subgrade and provides permeability so water can move through the joints and base, reducing settlement and frost-related issues. A poured concrete slab beneath pavers, while strong, creates a rigid, mostly impermeable layer that can crack and transfer stresses directly to the pavers. That rigidity limits drainage and flexibility, leading to movement problems and failures in an interlocking system. A crushed limestone subgrade with no base lacks the structural thickness and drainage path needed to support loads and manage moisture, increasing the risk of settlement and pumping of fines. An asphalt base layer is not suitable as a sub-base for pavers because it can soften, deform with temperature changes, and impede drainage, compromising the stability and longevity of the paver system. So the recommended approach—a compactable granular base on a properly prepared sub-base—provides the necessary combination of load distribution and drainage that keeps interlocking pavers performing well.

The important idea is that the foundation under interlocking pavers must both carry loads and allow water to drain away. A compactable granular base (base course) placed on a properly prepared sub-base does exactly this: it distributes traffic loads evenly to the subgrade and provides permeability so water can move through the joints and base, reducing settlement and frost-related issues.

A poured concrete slab beneath pavers, while strong, creates a rigid, mostly impermeable layer that can crack and transfer stresses directly to the pavers. That rigidity limits drainage and flexibility, leading to movement problems and failures in an interlocking system.

A crushed limestone subgrade with no base lacks the structural thickness and drainage path needed to support loads and manage moisture, increasing the risk of settlement and pumping of fines.

An asphalt base layer is not suitable as a sub-base for pavers because it can soften, deform with temperature changes, and impede drainage, compromising the stability and longevity of the paver system.

So the recommended approach—a compactable granular base on a properly prepared sub-base—provides the necessary combination of load distribution and drainage that keeps interlocking pavers performing well.