Mould in the bedroom: the overnight moisture problem

A bedroom is one of the places most likely to get mould, because it's where the most moisture is made in a home. People breathe out water all night, the door is usually shut, and the windows are often closed. If the room is cold, that moisture condenses on the coldest walls and furniture, and mould settles in. The fix is mostly about letting the air move and keeping the walls warm enough.

Why bedrooms get it

A person gives off a surprising amount of moisture in their sleep. Two people in a closed room for eight hours put a lot of water into the air, and it has to go somewhere. In a room with a shut door, a closed window and no extractor fan, it settles on the coldest surface it can find.

Furniture makes it worse. A bed, a wardrobe or a chest of drawers pushed against an outside wall stops air moving behind it, and the wall stays cold. Corners behind furniture, and the wall at the head of the bed, are common places to find mould in a bedroom. In older Scottish homes, cold solid walls and draughty windows can keep those surfaces colder still.

What you can do this week

Small habits make a difference, and most of them cost nothing.

• Leave the bedroom door open a crack overnight, so the moist air can move into the rest of the home.
• When you get up, open the window for a few minutes and pull the bedding back to let it air.
• Move the bed and other furniture a few centimetres off outside walls, so air can circulate behind them.
• Dry wet clothes, towels and sports kit outside, or in another room with a window open, rather than in the bedroom.
• Keep the room at a steady warmth. Cold rooms are where condensation forms first.
• If there is an extractor fan in the room or the bathroom next to it, run it when you're getting up and when you're drying washing.

When the room is dry, clean any mould off the walls and furniture with a mould-killing spray and a damp cloth. Wear gloves and let the area dry fully. Wash bedding and any soft furnishings that have been affected. Don't paint over the mould until the wall is dry and the room has a steady airflow.

When it's more than condensation

Condensation mould in a bedroom usually shows up on the outside walls, in corners and behind furniture, and it comes back each winter. Other causes look different:

• A tide mark or crumbling plaster low down on the wall can point to rising damp.
• A stain that grows after heavy rain, or sits below a gutter or a crack in the render, suggests water getting in from outside.
• A patch near a ceiling, a pipe or a window that doesn't follow the weather may be a leak.

If the mould keeps returning after you've improved the airflow and moved the furniture, get the wall checked.

Your health

The NHS says mould can trigger asthma in people who are allergic to it. If you, or anyone who sleeps in the room, has asthma or a mould allergy, keep an eye on night-time coughing or wheezing and speak to your GP if it gets worse. The NHS asthma causes page lists mould among the common triggers. Government guidance for rented homes in England, Damp and mould: understanding and addressing the health risks for rented housing providers (MHCLG, DHSC and UKHSA), lists children, older people, pregnant women and people with conditions such as asthma among those at greater risk.

When to get a specialist

Get a damp specialist to look if the mould covers a large area of the bedroom, keeps returning after the airflow has been improved, or you suspect damp coming through the wall. Tell us what's happening and we'll pass it to one independent local specialist to visit and quote. It's free to ask.

Last checked 26 October 2026. This is general guidance, not legal or building advice.