Hard Surfacing Against a Damp Foundation: The Correct Layering System

You're in Scotland, converting a damp grass area against the house to slabs and stone. A plumber suggested the lawn might be driving moisture into the walls. You've dug to the pipe depth. Need the correct build-up: gravel, sand, weed barrier, slab mortar.

The Right Stack (Bottom to Top)

1. French drain at foundation base, daylighting to soakaway.
2. Crushed angular gravel (Type 1 MOT or similar) over the drain.
3. Geotextile fabric (woven, not weed barrier) over gravel.
4. Sharp sand / cement dry mix (4:1 or 6:1) as bedding layer.
5. Slabs laid on the dry mix, tapped level.
6. Same dry mix brushed into joints.

Key Points

• Slope the entire assembly 1:60 away from the house.
• Keep the top of the slab below the DPC (damp proof course) by at least 150mm (6").
• Don't use building sand—it washes out. Sharp sand + cement locks up.

This system drains water away before it reaches the wall. The grass wasn't the cause—it was the symptom of poor drainage.