What is a sub-base?
A compacted layer of crushed stone or aggregate laid beneath paving surfaces to distribute vehicle loads and provide structural support.
The sub-base is the crushed stone or aggregate layer installed directly on prepared ground before any paving material goes down. It sits between the soil and the finished surface (whether asphalt, concrete, or block paving), doing the critical work of spreading vehicle weight and preventing the paving above from cracking or rutting.
Without a proper sub-base, loads concentrate on weak spots in the ground, causing pavements to fail quickly. The layer typically consists of Type 1 or Type 2 aggregate (limestone, granite, or recycled materials) compacted to a specific density. The thickness depends on ground conditions and expected traffic, but Cheltenham contractors often lay 100-150mm for domestic driveways.
A well-prepared sub-base also manages water drainage, allowing moisture to move through rather than pooling beneath the surface. Poor drainage accelerates deterioration. Proper compaction is essential; loose material will settle unevenly, causing the paving surface above to crack or develop potholes. When paving contractors assess your driveway or path, they inspect existing ground conditions to determine the sub-base specification needed. Many common failures in older Cheltenham driveways trace back to inadequate sub-base work rather than faults in the top layer. Local paving providers can specify the right sub-base for your site's soil type and usage.