What rising damp is
Rising damp happens when ground moisture soaks up through the bottom of a wall because the damp proof course has failed, was never there, or has been bridged. It shows as a tide mark up to around a metre high, white salt deposits, crumbling plaster and lifting skirting boards, mainly on ground floor walls.
Check for bridging first
Many "rising damp" walls are actually bridged. That means something lets moisture bypass a working damp proof course:
- Garden soil, patios or paths built up above the damp proof course
- Render or plaster carried down past the damp proof course
- Rubble in the cavity
- Blocked or covered air bricks under a suspended floor
Fixing these is often far cheaper than injecting a new damp proof course.
How we treat genuine rising damp
- Remove skirting and salt contaminated plaster, usually to around a metre high
- Install a chemical damp proof course by drilling and injecting a cream into the mortar line
- Let the wall start drying out
- Replaster with a salt resistant renovating plaster, or a breathable lime system on older solid walls
- Refit skirting and treat any mould in the room
Price
Rising damp treatment with replastering often costs £1,200 to £3,500 for a typical London terrace wall, depending on length, height of damage and plaster type. Bridging fixes can cost a few hundred pounds. You get a fixed written quote after a survey. No VAT added.