Find the cause of a damp patch on a ceiling

Work through loft, bathroom and outside checks in order to find what's really causing a ceiling damp patch.

DP-01Gather your tools and note what's above the patchGet a torch, a moisture meter (or use the back of your hand), a notepad or phone camera, and a stepladder. Work out what's directly above the patch: loft space, a roof, a bathroom, a flat above, or a valley between two roof slopes. This tells you where to look first.

1 each · Torch

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1 each · Moisture meter

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1 each · Stepladder

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DP-02Photograph and measure the patch before you touch anythingTake a photo with something for scale, like a tape measure, and write down today's date. Note the shape, colour and whether the edges are sharp or feathered. This record matters because damp patches change size with weather, and you need to know if it's growing.

1 each · Tape measure

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DP-03Check if it's an old stain or an active leakPress the patch gently with a finger. Soft, spongy or genuinely wet plaster means an active leak right now. A dry, hard, flaky or brownish ring with no give usually means an old leak that's already been fixed, or ongoing condensation. This decides how urgently you need to trace the source.

1 pair · Disposable gloves

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DP-04Check the loft if there's roof space abovePut the stepladder under the loft hatch, take your torch, and look for wet insulation, dark tide marks on the underside of the roof felt, or daylight showing through where there shouldn't be any. Damp insulation directly above the patch points to a roof leak, not a pipe.

RULES

KNOW THE RULES

If the loft hatch, boarding or pipe lagging looks like old textured material or has a rough, spray-on finish, don't disturb it. Materials fitted before 2000 can contain asbestos. Get it checked before you touch it (Control of Asbestos Regulations 2012).

DP-05Check for a bathroom, kitchen or flat aboveIf there's a bathroom or kitchen directly above, ask someone to run the bath, shower and taps for a few minutes and flush the toilet, while you watch the ceiling and any exposed pipework below. A drip that starts as soon as water runs points to a leaking pipe, waste or shower seal, not the weather.

1 each · Torch

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DP-06Rule out condensationCheck nearby windows for condensation, look for black mould spots rather than a single stain, and check if the extractor fan in the room above (if it's a bathroom) actually works. Condensation patches tend to be near cold spots like corners, above cold water pipes, or under a cold roof with poor insulation, and they get worse in winter.

DP-07Map the damp with a moisture meterPress the meter's pins lightly into the plaster at several points around the patch and just beyond it. The highest reading usually marks the point closest to the source, which helps you trace it back to a specific pipe, joint or roof detail rather than guessing at the whole ceiling.

1 each · Moisture meter

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DP-08Check the outside of the buildingLook at the roof, guttering and any wall above the patch's outside face. Check for missing or slipped tiles, cracked flashing around chimneys or roof windows, blocked or overflowing gutters, and cracked render or pointing on the wall. A patch that gets worse only after heavy rain usually has an outside cause.

DP-09Write up what you found and decide next stepsCompare your notes: is it active or old, roof-related or plumbing-related, weather-linked or condensation? A pipe leak or roof leak needs a plumber or roofer. Condensation needs better ventilation and heating, not a repair to the ceiling. Keep your photos and notes, they're useful if you need to call in a tradesperson.

1 each · Notebook

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DP-10Tidy upFold away the stepladder, wipe down the moisture meter pins, and put your tools away. Leave the loft hatch and any covers exactly as you found them. Do not paint over or fill the patch yet, wait until the actual cause is fixed, or it will just come back.

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