Rising damp is one of the most misdiagnosed problems in UK housing – and misdiagnosis is expensive, because “treatment” is often sold for damp that is not rising damp at all. Here is what genuine rising damp looks like, what causes it, and how it is actually fixed.
What does rising damp look like?
- A tide mark – a horizontal stain or line of salts on the wall, typically up to about one metre from the floor, rarely higher.
- Blown or bubbling plaster and peeling paint in a band above the skirting.
- White fluffy salt deposits (hygroscopic salts drawn up from the ground).
- Damp, rotting or lifting skirting boards and damp floor timbers.
- Ground floor only – damp upstairs is never rising damp.
What causes rising damp?
Moisture from the ground travelling up through brickwork by capillary action, usually because the damp-proof course (DPC) has failed, is missing (common pre-1900), or has been bridged – by raised external ground levels, a paved patio above DPC line, render lapped over it, or debris in the cavity. Bridging is the most common cause we find, and it needs no chemical treatment at all – just removal of the bridge.
What looks like rising damp but isn’t
Condensation (mould in corners and on cold walls, worse in winter), penetrating damp (patches that follow rain, at any height), leaking gutters and plumbing. Most “rising damp” diagnosed by treatment companies falls into these categories – which is why an independent damp survey with no treatment products to sell is worth having before you spend anything.
How is rising damp fixed?
Depending on cause: lowering external ground levels, fixing the bridge, repairing or injecting a new DPC, then replastering with the right salt-resistant specification. Costs range from nothing (removing a bridge) to a few thousand pounds for injection and replastering – see our damp survey cost guide.
Think you have rising damp? Get an independent diagnosis first. Call 020 4579 8270 or book a damp survey anywhere in London.