How do I dry out a room after a leak?

A leak that is stopped and mopped up looks dealt with. The real damage is in the water that has gone into plaster, under flooring and into the structure, and it shows up weeks later as mould, lifted floors and a smell that will not go.

Safety

Step by step

1. Make it electrically safe first.Turn off the power to the affected circuits before touching anything. Water and sockets, water in ceiling voids near light fittings, and wet extension leads are all genuine hazards.
2. Photograph everything before you start.For any insurance claim, this comes before the clearing up. Wide shots of each room and close-ups of damaged items and the source.
3. Get the standing water out quickly.Wet vacuum, mop, towels, a squeegee towards a door. Speed matters here more than thoroughness — every hour the water sits is more of it going into the structure.
4. Lift what is holding water.Carpet and underlay especially — underlay acts as a sponge and keeps the floor beneath wet for weeks. Lift it, take it outside, and decide about it later. Move furniture off wet floors immediately.
5. Open up the wet cavities.Remove skirting on the affected walls, lift a few floorboards, take kick-boards out of kitchen units. Water trapped behind them will not dry through the surface, and this is where the mould starts.
6. Use a dehumidifier with the room closed.This is the opposite of the instinct. A dehumidifier works by removing moisture from the room air so more evaporates from the structure — opening the windows just gives it the whole outdoors to dry.
7. Add fans to move air across wet surfaces.Air movement over a wet surface is what makes evaporation happen. Fans pointed at walls and floors, not into the middle of the room, and a dehumidifier to take that moisture out.
8. Use gentle heat, not high heat.Warm air holds more moisture, so mild warmth helps the dehumidifier. Blasting heat drives water deeper into materials and can crack plaster and warp timber.
9. Expect it to take days, not hours.Surfaces feel dry long before the structure is. A saturated wall takes days to weeks. Stopping when it feels dry is the classic error.
10. Check with a moisture meter rather than by feel.An inexpensive meter reads whether plaster and timber are genuinely dry. Compare with an unaffected wall in the same house for a baseline.
11. Treat surfaces before closing anything up.An anti-mould treatment on affected plaster and timber once dry, before replacing skirting or flooring. Sealing damp material in is how a smell becomes permanent.
12. Do not redecorate too soon.Paint or paper over damp plaster and it blisters, and the moisture is trapped behind it. Wait until the meter says dry, which is usually longer than the room looks.

Tips

• Hire a proper dehumidifier rather than buying a small domestic one for a serious leak. The capacity difference is large and hire is inexpensive for a fortnight.
• Keep a record of the drying — dates, readings, photographs. Insurers and, later, buyers both find that useful.
• A musty smell weeks later means something is still wet, usually under a floor or behind a unit. Chasing the smell is worth it.

Common mistakes

• Opening all the windows and leaving it — It ventilates the air but does very little for saturated structure. A closed room with a dehumidifier dries far faster.
• Putting the flooring back once the surface feels dry — The material underneath is still wet, and sealing it in produces mould and a permanent smell. Use a meter rather than a hand.

If it doesn't work

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