Condensation in a garden room: causes and fixes

Why it happens

Air holds more moisture when it's warm. When it touches something cold, it cools and drops that moisture as water. In a garden room, the coldest surfaces are usually the windows, the door, the corners and an uninsulated floor.

Ireland's mild, damp climate adds to it: the outside air is often already humid, and a room left unheated between uses gets cold enough for condensation to form whenever it's warmed up again.

How to fix it

• Ventilate. Trickle vents in the windows, a window on latch, or a small extractor fan.
• Keep a little heat on through the coldest months, so the surfaces never get cold enough to collect water.
• Avoid adding moisture. Don't dry clothes inside, and don't use a portable gas heater.
• Use a dehumidifier in winter if the room is used heavily, such as a gym.
• Wipe windows in the morning so water doesn't soak into frames and sills.

Getting the build right

Most serious damp problems start with the build. Before you buy, check:

• The floor, walls and roof are all insulated, not just the walls.
• There's a vapour control layer on the warm side of the insulation.
• The glazing is double or triple, with sealed frames.
• There's ventilation under the floor if the room sits on screws or pads.

See insulated garden rooms for what each layer does.

When it's a bigger problem