Mould in the attic or roof space: causes and risks
What causes mould in a roof space
Mould in an attic or roof space almost always comes from one of two things: warm, damp air leaking up from the rooms below and condensing on the cold underside of the roof, or water getting in from outside through a leak. Poor airflow in the roof space lets either problem linger, because nothing carries the moisture away. Which one you have decides the fix, so look before you clean.
Not every Cyprus home has a roof space. Many have flat concrete roofs, with the top-floor ceiling sitting directly under the slab. Pitched, tiled roofs are common on villas, newer houses and village homes, though, and the gap between the ceiling and the tiles is where this kind of mould grows.
How warm air from the house ends up in the attic
Every home produces moisture from cooking, showers, breathing and drying clothes. Some of that air works its way upward through the loft hatch, gaps around ceiling lights, pipe holes and the edges of the ceiling boards. In winter the tiles and timbers are cold, so the moisture turns to water on the underside of the roof and on the rafters, the way a cold glass mists up. A bathroom or kitchen extractor that vents into the roof space rather than outside adds a great deal more.
Blocked eaves or a ridge with no vents make things worse, because the air that should dry the space sits still.
Condensation or a leak?
- Condensation tends to be widespread: dark speckling across many rafters, often worst on the north-facing slope, damp on the underside of the roof, and water drops on nail heads on cold mornings.
- A leak tends to be local: one stained area, tide-marks on a single timber, a wet patch of insulation, often below a cracked tile, a valley, a chimney or the fixings of a solar water heater.
- Both can happen at once, especially in an older roof after a wet winter.
Looking after heavy rain, and again on a cold dry morning, often tells the two apart. A roof leak has to be repaired before anything else will hold.
Looking safely
Take a good torch and a mask, and wear gloves if you will touch insulation. Step only on the joists or on boarded areas, because the ceiling between them won't take your weight. Look, take photos and leave it: brushing or pulling at mouldy timber or insulation throws spores into the air, and some of that air drifts back down through the hatch. A musty smell in the top-floor rooms with no mould in sight can be the first sign of trouble overhead, much like mould hidden inside a wall.
Why it is worth dealing with
Light speckling on dry timber is mostly cosmetic. Timber that stays wet season after season can weaken and start to rot, damp insulation stops insulating, and a roof space that grows mould will keep doing so for as long as the moisture keeps arriving. Spores and smell can also travel down into the bedrooms below. Growth stalls when the wood dries out, as explained in whether mould dies without moisture, but the stains and spores stay, and it starts again the next time the timber gets wet.
Stopping it coming back
Close the routes for warm air: fit a draught seal around the loft hatch, fill gaps around ceiling lights and pipes, and make sure every extractor fan is ducted to the outside, not into the roof. Keep eaves and ridge vents clear so air can move through. Insulation should stay dry and shouldn't be packed so tightly into the eaves that it blocks the airflow. Fix slipped tiles and failed flashings promptly, and check again after the first heavy rain of the season.
When to get help
If mould covers large areas of timber, the insulation is soaked, or you can't tell whether the moisture is coming from inside or outside, the cause needs finding first. We find the cause before we touch the mould, so the fix lasts. A check of the roof space and the rooms beneath it takes moisture readings in every affected room and ends with a room-by-room moisture map sent to your phone, plus a written report with the quote. Where timber and insulation are badly affected, remediation of the roof space covers containment, removal, repair and an anti-mould finish.
Mould in your roof space? book an inspection from €75 for an assessment, or call +357 99 759144.