Water Damage After a Leak: Drying Out Floors and Ceilings

First, is the leak really stopped?

There is no point drying a ceiling that is still being fed. Before you start, check the source is isolated or repaired, not just slowed. A pipe that has been clamped overnight, a shower tray with a failed seal that has only stopped because nobody has used the shower, or a heating pipe that is still under pressure will keep adding water.

If you do not know where it came from, our guide to hidden leak signs covers how to narrow it down, and the leak repairs visit finds and fixes the source before any drying starts. The pattern of damage is also a clue. A stain that grows only when a bath or shower is used points to a waste or seal. A patch that stays wet with nothing running points to a supply or heating pipe. A drip that only appears while the air conditioning is on is condensate the AC unit cannot get rid of.

Water that has come through a ceiling may have reached light fittings, cables and junction boxes. Do not switch on lights in the wet area. Turn off the lighting circuit at the consumer unit if you can reach it with dry hands and feet, and have an electrician check it before you use it again.

A sagging or bulging ceiling: what to do before it drops

A plasterboard ceiling holding water will bulge downwards like a bag. It can drop suddenly and bring a heavy load of water with it, so treat it as an emergency. Clear the room below, put down a bucket and dust sheets, and keep people out from underneath.

If the bulge is still filling, the standard move is to make a controlled hole at its lowest point with a screwdriver, standing to one side on a stable step, so the water drains into the bucket rather than breaking the board. Only do this with the lighting circuit off. A small hole is much cheaper to repair than a collapsed ceiling.

Older houses often have lath and plaster ceilings instead of plasterboard. These do not usually bag in the same way. Water soaks through and the plaster can lose its grip on the laths and fall in heavy pieces. If a lath and plaster ceiling is cracking, bowing or dropping flakes, keep the room empty and have it looked at. See ceiling water leak repair for what happens on the visit.

What can be saved and what usually has to go

How much can be dried depends on what the material is and what kind of water it met. Drying professionals classify water in three categories: clean water from a supply pipe or tank, grey water from a washing machine, dishwasher or bath waste, and black water from a toilet, soil stack or sewage. Clean-water damage dried quickly can often be saved. Grey water shortens the time you have. Anything soaked by black water that is soft or porous, such as carpet, underlay and plasterboard, is normally thrown away.

• Plasterboard: dries if it was only damp and has kept its shape. If it has sagged, crumbled or gone soft, it is cut out and replaced
• Carpet: can often be dried after a clean-water leak if lifted quickly. The underlay beneath is usually replaced because it holds water and smells
• Laminate and engineered boards: swell at the joints and rarely go back flat. Solid timber sometimes recovers if dried slowly
• Chipboard floor panels: common upstairs in newer homes. Once swollen they stay swollen and lose strength, so wet panels are replaced
• Suspended timber floors: the joists usually dry well if air can move through the void, so keep the air bricks in outside walls clear
• Solid concrete floors and screeds: hold water for a long time and dry slowly from the top down. Leave floor coverings off until they test dry

How to dry a room properly

Drying is about moving water out of the materials and into the air, then out of the air. That needs three things together: warmth, moving air and something to remove the moisture.

A dehumidifier does most of the work. Run it continuously with the door and windows closed, otherwise it spends its effort drying the outside air. Empty the tank or run the drain hose into a sink. Refrigerant dehumidifiers work best in a heated room; desiccant models keep working in cold spaces such as an unheated loft, garage or empty flat. Keep the heating at a normal comfortable level rather than turning it right up, because very fast drying can crack plaster and warp timber.

Fans help by moving air across wet surfaces. Point them at the wet wall or floor, not into the room. Lift the edge of carpet and prop it up so air reaches underneath, and take skirting boards off if water is trapped behind them. Open fitted cupboards and pull out kitchen plinths, because water collects under units and is easy to miss.

Expect it to take weeks rather than days for anything thicker than plasterboard. A solid wall or a screed floor that was soaked can take months. Mould can start to grow within 24 to 48 hours on damp organic materials, so get wet soft furnishings and cardboard out of the room first.

How to tell when it is really dry

Touch is not a reliable test. A surface can feel dry while the plaster or timber behind it is still wet. A pin-type moisture meter, the kind with two metal prongs, costs little from a DIY shop and gives a reading you can track day by day.

The useful comparison is with a dry area of the same material, not an absolute number, because meters read differently on plaster, masonry and timber. Take a reading on the same wall or floor in a room the leak did not reach, then check the wet area every day or two. When the readings match and stay level for several days, it is dry enough to repair. Write the readings down, with dates; an insurer or loss adjuster may ask for them.

Painting over a damp patch traps the moisture and the stain usually comes back. Once dry, seal water stains with a stain-blocking primer before the finishing coat.

Insurance, drying companies and who does what

Before you throw anything away, photograph the damage, the source of the leak and each damaged item. Keep samples of carpet and flooring if you can, as the insurer may want to see them. Most home policies treat this as escape of water; our guide to escape of water claims explains the process, and water damage insurance covers what is and is not usually included.

On a larger claim, the insurer often sends a specialist drying company that brings commercial dehumidifiers and air movers and records moisture readings until the property is signed off as dry. Repairs to ceilings, floors and decorating come after that sign-off. Ask the insurer before you start ripping out materials yourself, beyond what is needed to make safe.

The plumbing repair itself comes first. Our leak repair visit starts with the £60 call-out at any hour, and the repair price is agreed with you on site before any work starts. Keep the invoice, which usually names the cause of the leak and is often the first document an insurer asks for.