My ceiling has been soaked — will it dry out or does it need replacing?
What to do in the first hour, how to tell plasterboard that will recover from plasterboard that will not, and the tests that decide between drying out, patching and taking the ceiling down.
- Difficulty
- intermediate
- Time
- 1 hr
- Read
- 5 min
- Safety
- warning
Short answer
Stop the water, isolate the lighting circuit, and drain a bulge deliberately with a small hole at its lowest point into a bucket rather than letting it burst. Once it is dry, judge it: plasterboard that is still firm, flat and holding its screws usually recovers; board that is soft, sagging, stained through or has lost its paper face has to come out.
Plasterboard is gypsum with paper on both faces, and both parts respond badly to prolonged wetting — the core softens and loses strength, and the paper delaminates. Brief wetting from a one-off overflow often does no lasting harm. Sustained wetting from a leak that ran for days almost always does. The distinction is not how it looks while it is wet; it is how it behaves once it is dry.
Safety
What you'll need
- A bucket and a screwdriver or a small drill bit
- Dust sheets and towels
- A dehumidifier or fans (optional)
- A torch
- Access to the consumer unit
Step by step
- Stop the water at source.Isolate the appliance, close the stopcock, or if it is rainwater, put a container under it and deal with the roof or gutter as soon as it is safe. Everything else waits for this.
- Isolate the lighting circuit for that room.At the consumer unit. Water runs along cables and collects in ceiling roses and downlight housings. Do not operate the light switch.
- Clear the room and protect the floor.Furniture out, sheets and towels down, buckets positioned. Assume more water is coming than you can see.
- Drain a bulge deliberately.A bulge is a pocket of water sitting on the paint film. Stand to one side, not underneath, and pierce it at its lowest point with a screwdriver into a bucket. A controlled 6mm hole is a repair; a burst bulge is a ceiling on the floor.
- Make several small holes rather than one large one.Water spreads across the ceiling and pools in more than one place. Work from the lowest point outwards until the flow stops.
- Dry the space above as well as below.Lift a floorboard or access the loft if you safely can, and get air moving both sides. Insulation that has been soaked holds water against the ceiling for weeks and must be removed and replaced — wet mineral wool does not dry in place and does not insulate.
- Ventilate and dehumidify, and be patient.Weeks rather than days for a thoroughly wet ceiling, and longer if it is closed on both sides. Heating the room hard without ventilation just moves the water elsewhere in the house.
- Once dry, test the board properly.Press it firmly across the affected area. Sound board is hard and unyielding. Board that gives, feels spongy, or lets a fingernail in has lost its core strength and will not recover.
- Check the fixings and the joints.Screw heads that have pulled through, joints that have opened, tape that has lifted, and paper that has bubbled away from the core are all signs the board is finished.
- Check for sagging with a straightedge.Wet plasterboard sags between joists and does not come back. Any visible dip means replacement of at least those boards.
- Deal with the staining even if the board is sound.Water stains bleed through emulsion indefinitely. A stain-blocking primer is the only thing that stops them, and it needs to go on before any topcoat.
- Consider what got wet that you cannot see.Insulation, timber, electrical fittings and any board on the other side of a wall. Trapped moisture in a closed ceiling void is where mould starts.
Tips
- Photograph everything before you touch it, including the source, the ceiling, the room and any damaged possessions. Insurers ask, and escape of water is one of the most common household claims.
- Ring your insurer early. Many policies cover the damage but not the failed part that caused it, and most want to be told before remedial work starts.
- Do not put new board or new decoration onto anything that is still damp. Moisture meters are more useful on timber than on plaster, but a cold, dark patch that has not changed in a fortnight is not dry.
If it doesn't work
Stain only, board firm and flat once dry
Cause: Brief wetting — Fix: Stain-block primer and redecorate. No replacement needed.
Board soft or spongy when pressed
Cause: Core has been saturated and lost strength — Fix: Cut out to the centres of the joists either side and replace the affected boards.
Visible sag between the joists
Cause: Board has deformed while wet and set that way — Fix: Replace. Sagged board does not recover, and a sagging ceiling gets worse.
Paper face bubbled or peeling
Cause: Delamination — the paper is the tension face of the board — Fix: Replace that section. The board has lost most of its strength.
Musty smell weeks later, or dark speckling
Cause: Trapped moisture in the void, insulation still wet, mould growing — Fix: Open it up, remove wet insulation, dry properly, treat and re-board.
Lath and plaster ceiling soaked
Cause: Water softens the plaster and rusts the lath nails, and the keys fail — Fix: Assess very carefully once dry. Wet lath and plaster commonly loses its keys over a much wider area than the wet patch.
Questions people ask
How long does a soaked ceiling take to dry?
Anything from a fortnight to a couple of months, depending on how much water, whether insulation above is holding it, ventilation and season. There is no shortcut and decorating early wastes the decoration.
Can I dry it with a heat gun or a fan heater?
No. Heat without ventilation raises the humidity in the room and moves the water into other surfaces. A dehumidifier with the doors closed, or good cross-ventilation, is the right approach.
Is it always the whole ceiling?
No. Plasterboard is replaced in board-sized units, cut back to the centre of a joist, so a localised soaking usually means one or two boards. It becomes a whole-ceiling job when the damage crosses most of the room or the ceiling is lath and plaster.