Damp and waterproofing of ground slabs
The waterproofing of ground slabs against rising damp should be ensured by land drains and correct soil layering and by using the right types of insulation below the floor.If this cannot be done, or if the structure is defective in this respect, the floor may be damp-proofed from the inside as well. Application of a bitumen coating, which was common practice in the past, cannot be considered to provide damp-proofing, and therefore in exacting conditions it is always safer to use bitumen membrane materials. By using a continuous bitumen membrane it is also often possible to avoid the stale smell of damp concrete and soil in problem structures. If structural movement or cracking of a structure is anticipated, the bitumen membrane type should be chosen with a view to the extent of the movement, and a sufficiently resilient membrane specified. It is recommended to cast a top slab over the membrane.
TL2 class elastomer bitumen membranes are recommended for the most demanding projects: Foundation Wall and Radon Membrane or K-MS 170/3000 membrane. The Super Underlay Sheet (TL3) with self-adhesive edges is also a good alternative. A lighter solution is to use K-EL 60/2200 TL4 waterproofing felt, which is sufficient in many applications.
If damp is only a slight problem, the concrete slab may be brushed with K-80 and K-70 bitumen solutions. In this case DPC (Damp Proof Course) strips are recommend under any timber members (timber floor joists or wall cill plates).
In refurbishment projects a problematic damp basement floor may also be renewed by installing Katepal Dimple Sheets over the old floor and casting a new slab on top.