Emily Hartley
Why Older Properties Trap So Much Moisture
If you live in a Victorian terrace, a stone cottage or a pre-war semi, you are probably fighting a battle your neighbours in a new-build simply do not face. Older homes were built to be draughty. Open fireplaces, sash windows, air bricks and unplastered loft spaces all allowed air to move freely through the building. When we sealed those gaps to keep the heat in, we also trapped the moisture we create every day.
A typical household produces ten litres or more of water vapour daily, just from breathing, cooking, showering and drying clothes. In a well-ventilated house that moisture finds its way out. In a sealed older house it lands on the coldest surfaces it can find, which in a period property usually means single-glazed windows, external wall corners and the patch of wall behind a wardrobe. That is condensation, and left unchecked it becomes black mould and that familiar musty smell.
Ventilation Is the Cheapest Fix You Have
Before spending money on remedies, make sure the ventilation your home was designed with is still working. Many older properties have had their air bricks blocked up, their chimneys capped without a vent and their sash windows painted shut. Restoring a little airflow costs very little and solves a surprising number of damp complaints.
- Check the air bricks along the outside walls. If they have been covered to stop a draught, fit a ventilated cover with a baffle instead of blocking them completely.
- If a chimney is no longer used, have a ventilated cap or an air vent fitted so the flue can breathe.
- Open windows wide for five to ten minutes, two or three times a day, rather than leaving a small gap all day in cold weather. A short purge changes the air without cooling the walls.
- Where possible, open windows on opposite sides of the house to create a cross-flow.
- Keep the trickle vents on modern replacement windows open, even in winter. That is what they are for.
Extraction: Cooking and Bathing
Kitchens and bathrooms are where most of your moisture is generated, and both should have extraction that actually works. A recirculating cooker hood simply filters grease and pushes the steam back into the room, so if yours is not ducted to the outside, open a window while you cook.
- Run the extractor fan during cooking and for at least ten to fifteen minutes afterwards.
- In the bathroom, keep the fan running through your shower or bath and for fifteen minutes after you finish.
- Hold a piece of tissue against the bathroom fan grille. If it will not stay put, the fan is not extracting properly and may need cleaning or replacing.
- Keep the bathroom door closed while the fan or window is doing its work, so moisture does not drift into colder bedrooms and hallways.
- Wipe down shower screens and tiles after use, and keep the shower door or curtain spread out to dry.
Stop Water Getting In From Outside
Condensation is only half the story. Penetrating damp from a leaking gutter or cracked render can look very similar but needs a different response, and it will never improve on its own. Once a week, ideally during or just after heavy rain, walk around your property with a torch.
- Clear leaves from gutters and hopper heads. Overflowing water running down a wall soaks into brickwork and appears indoors weeks later.
- Check downpipes for cracks and joints that have pulled apart, and make sure they discharge into a drain rather than onto the ground.
- Look for slipped slates, damaged flashing around chimneys and cracks in external render.
- Check that outside ground levels sit at least two courses below the damp-proof course. Raised patios and flower beds are a common culprit.
- Indoors, fix dripping taps, leaking radiator valves and slow leaks under sinks and washing machines straight away. A drip behind a kitchen unit can quietly rot a floor for months.
Warmth, Cold Spots and Drying Laundry
Condensation forms on cold surfaces, so keeping the fabric of the building gently warm matters as much as ventilation. Background heating on a low, steady setting suits older properties far better than short bursts of intense heat, which warm the air but leave the walls cold.
Drying laundry indoors is the single biggest contributor to mould problems in many homes. If you cannot dry outside, use a heated airer in one room with the door shut, the window open or an extractor running, or use a dehumidifier alongside it. A desiccant dehumidifier works better in cold rooms; a refrigerant model suits warmer spaces. If you own a hygrometer, aim for relative humidity of roughly 50 to 60 per cent.
Pull furniture a few inches away from external walls, leave wardrobe doors ajar and avoid stacking items against cold corners. Never use a paraffin or bottled gas heater indoors, as they release large amounts of water vapour.
Keeping Mould From Coming Back
If mould has already appeared, clean it off with a proprietary mould remover or a diluted bleach solution, working in a ventilated room and wearing gloves. Anti-mould paint can help on a stubborn wall, but it is a dressing rather than a cure, and the mould will return if the underlying moisture is still there.
Longer term, think about insulation and draught-proofing. Secondary glazing on sash windows, solid wall insulation and a properly insulated loft all raise surface temperatures and make condensation far less likely. Remember that older buildings need to breathe, so use breathable paints and lime-based mortars where appropriate. If damp persists despite your best efforts, or you see a tide mark rising up a ground-floor wall, ask a qualified surveyor to take a look, as genuine rising damp is less common than people assume and often turns out to be a leak or a bridged damp course. With a few consistent habits, most older homes can be kept dry, warm and free of that telltale black speckling.
