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Wet Rot In Skirting Boards
Skirting board that is soft, dark and crumbling, often with paint lifting and a musty smell at floor level.
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What's happening?
Wet rot is fungal decay in timber that is genuinely wet — typically above about twenty per cent moisture content — and its defining characteristic is that it stays where the water is and stops when the timber dries. In a skirting board it is nearly always the messenger rather than the message: skirtings sit against the wall base and on the floor, so they are the first timber to register that the masonry behind them is wet. That makes them useful. Soft skirting on one wall points at that wall; soft skirting on several points at the floor. What matters is not replacing the board but finding what wet it, because a new skirting nailed onto damp masonry decays exactly as the last one did.
What usually causes it?
- Rising damp in the wall behind, keeping the back of the skirting permanently wet
- A bridged damp proof course from a raised external path or a floor screed laid over the barrier
- A slow plumbing leak — a radiator valve, a waste pipe or a heating pipe under the floor
- Penetrating damp at the base of an external wall from splashback or a defective gully
- A solid floor with no damp proof membrane, or a membrane not joined to the wall's damp proof course
- A blocked or bridged suspended floor void with no through ventilation, so the void stays humid
- Condensation running down a cold external wall onto the skirting day after day
Is it dangerous?
Wet rot in a skirting is not structural, but it is a warning about what else is in that wall and floor. The timbers that matter are the ones you cannot see — joist ends built into the wall, floor plates, staircase strings and door linings — and they are in the same moisture conditions as the skirting that failed. There is also the dry rot question: wet rot stays in wet timber, while dry rot can spread through masonry into timber that is dry, so telling the two apart changes the size of the job considerably.
Can I fix it myself?
Probing with a screwdriver to find how far the softness runs, and lifting a section of skirting to look at the wall and floor behind it, are both genuinely useful and low-risk. What is worth avoiding is the obvious sequence of replacing the board and redecorating: it hides the moisture, and the new timber and new paint fail on the same timetable. If a floorboard near it is also soft, stop and get the floor looked at before walking on it.
When should you call a damp proofer?
Call a damp proofer when the skirting is soft over any length, when the wall behind it is damp, or when the softness extends into a door lining or the floor. Call promptly if you can see white or grey strands, sheets of growth or fruiting bodies, because that is a dry rot question rather than a wet rot one. Where a leak is the likely source, that is plumbing work, and it comes first.
What will the damp proofer actually do?
- Remove affected skirting to expose and assess the wall base and the floor edge
- Identify the moisture source — rising damp, bridging, a leak, floor construction or void ventilation
- Confirm the decay type, separating wet rot from dry rot, since the treatment and extent differ
- Inspect concealed timbers in the same conditions: joist ends, plates, linings and staircase strings
- Remove decayed timber, cure the moisture source, and reinstate with treated timber isolated from damp masonry
- Restore through ventilation to a suspended floor void where it has been blocked
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