Service
Rising damp treatment in North Somerset
A new damp-proof course is the right fix for genuine rising damp, and the wrong fix for everything else. We confirm the diagnosis with proper testing before we quote.
What rising damp actually is
Rising damp is ground water moving upward through the base of a wall by capillary action, because the original damp-proof course is missing, has been bridged, or has broken down. It carries dissolved ground salts (nitrates and chlorides) that stay in the plaster after the water evaporates, which is why treated walls still read damp until the old plaster is removed.
Typical signs of the real thing:
- A horizontal tide mark, usually up to about 1 metre, no higher
- Blown, bubbling or salt-crusted plaster along the affected run
- Skirting boards and timber grounds decaying from the back
- Damp that doesn’t change much with the weather or the seasons
What gets mistaken for it
Before we ever recommend a chemical DPC we rule out the cheaper, more common causes:
- External ground, path or flowerbed raised above the internal floor / existing DPC
- Render, debris or a solid floor screed bridging the DPC
- Leaking gully, downpipe or waste pipe at the base of the wall
- Condensation and poor ventilation at low level behind furniture
Our survey uses moisture readings taken at several heights up the wall, if the profile doesn’t show moisture decreasing with height, it isn’t rising damp, and a new DPC would be a waste of your money.
The treatment, where it’s needed
- Damp-proof course injection. A silane/siloxane cream injected into the mortar bed to form a new water-repellent barrier.
- Removal of contaminated plaster. Typically to around 300mm above the highest sign of damale, back to the brick.
- Replastering. A salt-retardant render system, or a breathable lime plaster on older solid-walled properties that need to breathe.
- Drying and redecoration. We tell you how long to wait and which paints and finishes to use so you don’t seal moisture in.
Left untreated, the moisture that comes with rising damp will eventually reach floor timbers and joist ends, at which point you’re also looking at wet rot repair.
Where we treat rising damp treatment
Common questions
Is rising damp really as common as I've been told?
No. Genuine rising damp exists but it’s over-diagnosed. Far more “rising damp” call-outs turn out to be a leaking downpipe, bridged cavity, high external ground level or condensation. We confirm it with readings before recommending a new DPC. Our guide to the signs of rising damp goes through the checks.
How is a chemical DPC installed?
A line of holes is drilled into the mortar bed near the base of the wall and a silane/siloxane cream is injected. It diffuses into the masonry and cures to form a water-repellent band. Contaminated plaster is then removed and replaced with a salt-retardant or lime system.
How long before the wall dries out?
Roughly a month per 25mm of wall thickness after treatment and replastering, so a 9-inch solid wall can take six months or more to reach equilibrium. Redecoration should wait until then.
Do you treat rising damp in my area?
Yes, across Weston-super-Mare, Portishead, Clevedon, Nailsea, Cheddar, Burnham-on-Sea and the surrounding North Somerset towns and villages. See areas covered.
Think you have rising damp trouble?
Call or request a callback and we'll arrange a proper look at the problem.