Spot dry rot and know when to call a specialist

Learn to identify dry rot signs, test timber safely, and know exactly when a specialist survey is essential.

SDR-01Gather your kit and protect yourselfDry rot spores can irritate your lungs and trigger allergies, so wear an FFP3 mask and disposable gloves before poking about. Take a torch for dark spots like under floors, behind skirting, and in lofts. Open a window if you can, especially in a small room.

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SDR-02Look for the classic visual signsCheck for timber that has split into small cube-shaped pieces (cuboidal cracking) — this is dry rot's calling card. Look for pale grey fungal strands that spread across surfaces like cotton wool, or mushroom-like rust-red fruiting bodies, often with a strong musty smell. Also check for bulging or discoloured wallpaper and paint, which can hide rot underneath.

SDR-03Probe suspect timber with a bradawl or screwdriverPress a bradawl or flat screwdriver gently into skirting, floor joist ends, or window frames you're worried about. Sound timber resists the point; rotten timber crumbles, feels dry and spongy, or breaks apart into cubes. Do this in several spots, not just one, since rot spreads unevenly.

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SDR-04Check moisture levels with a meterPush the meter's pins into the timber and take a reading, then check the surrounding wall too. Dry rot (Serpula lacrymans) can keep growing even once the timber has dried out a little, unlike wet rot which needs ongoing damp. A high reading nearby usually points to a leak or damp source you'll need to fix as well.

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SDR-05Work out dry rot from wet rotWet rot stays where the damp is, makes timber feel wet and soft, and darkens the wood, but it doesn't spread into masonry. Dry rot is worse: it sends thick strands through mortar joints and brickwork even where there's no timber, and can produce flat, pancake-shaped rust-coloured fruiting bodies. If you're not sure which you've got, treat it as dry rot until a specialist tells you otherwise.

SDR-06Trace how far it has spreadFollow any strands along skirting boards, under floors, and into neighbouring rooms — dry rot can travel several metres through masonry looking for new timber to attack. Check adjoining rooms and any shared walls, since the fungus doesn't respect room boundaries. Note every location you find, even small patches.

SDR-07Know when to call a specialistIf you find fungal strands, fruiting bodies, or timber that crumbles under the bradawl, stop investigating further yourself and get a specialist in — a PCA (Property Care Association) member firm or a chartered surveyor experienced in timber decay. Don't attempt to cut out or treat dry rot yourself; it needs proper diagnosis of the moisture source and often removal of infected masonry, not just the timber. If structural timber like a joist or beam is affected, get a structural engineer to assess it before any repair work starts.

RULES

KNOW THE RULES

If load-bearing timber (joists, beams, lintels) needs replacing or repairing, the work may need Building Regulations sign-off under Part A (structural safety). Your specialist should tell you if building control needs notifying.

SDR-08Record your findings and tidy upPhotograph every affected area with today's date visible, and sketch a rough plan showing where you found problems — this saves the specialist time and helps you get an accurate quote. Bag up any debris from probing and seal it before binning it. Remove your gloves and mask carefully without touching your face, then wash your hands.

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