That puddle on your windowsill every morning is your home telling you that warm, moist air has nowhere to escape and is hitting the coldest surfaces repeatedly. Left untreated, condensation becomes black mould, damaged plaster and timber problems that cost thousands to fix.
“The fundamental issue is that modern homes are sealed tight,” says George Edwards, MD, Timberwise, drawing on recent projects his team have worked on in London flats, Sheffield homes, and Bristol apartments. “We have double glazing, draught-proofing, insulation – all excellent for heat retention. But we have forgotten to account for the moisture that cooking, washing, showers and simply breathing produces every single day.
Without controlled ventilation, that moisture condenses on cold glass and walls. A consistent condensation issue can result in mould growth which can be detrimental to the occupants health.
Here George shares his top tips to stop condensation before it becomes serious.
1. Your extractor fan is the first line of defence
“In almost every kitchen and bathroom we inspect, there is an extractor fan that barely runs. In a London flat I surveyed recently, the kitchen hit 79 per cent humidity. That is because the extractor fan was inadequate and was being used intermittently, moisture was pooling.
“If you are cooking, turn on the extractor from the start and leave it running for 20 minutes after you finish. After a shower, let the extractor run on for 30 minutes. Most people open a window for five minutes and think that is enough. It is not, especially in winter when you do not want to lose heat.”
2. Check every vent and air brick is actually open
“I often find trickle vents painted shut, clogged with dust or permanently blocked. I find air bricks buried behind flower beds and decking. In a Sheffield semi, the lack of air bricks meant the sub-floor void beneath the floorboards could not regulate properly. Combined with a blocked drainage gulley, moisture was backing up against the walls lowering the temperature of the structure and condensation was forming on every cold surface.”
“These vents are meant to allow constant, gentle air movement that stops moisture building up in still pockets. Walk around your home. Make sure every single vent is visible and clear on both the inside and outside. It takes five minutes. In many homes I visit, it solves half the problem immediately. You cannot have effective ventilation if the vents themselves are blocked or non-existent.”
3. Stop indoor habits that aid moisture trapping
“I recently surveyed a property where the wardrobe sat directly against the external wall and the occupants were drying and washing indoors daily. That created a cold, stagnant pocket where moisture settled and mould thrived. Black spot mould grew inside the wardrobe and around wall vents because the air could not move.”
“Pull furniture slightly away from outside walls. Leave wardrobe doors ajar now and then so air can flow through. Dry clothes outside or in a room with an extractor fan running.”
4. Keep consistent, modest heat rather than cold spots
“Homes where the living room is warm but bedrooms are deliberately kept cool see the worst condensation. Cold rooms with poor air movement are where wet windows and mould appear. You do not need to heat everywhere to 22 degrees. Keep a steady background temperature throughout the winter months.”
5. Repair defects that make surfaces colder and wetter
“In a London flat, we found slipped roof tiles, defective mortar in the chimney stack, render bridging the DPC and high ground levels. In another Sheffield semi, a blocked drainage gulley was causing water to splash back onto the brickwork. Cracked render on the front elevation. Together, these problems introduce moisture into the walls whilst ventilation defects trap it inside.”
“Check your roof, gutters, external walls and window frames regularly. If water is getting in through the building fabric on top of everyday moisture, you are fighting on two fronts.”
6. Call a surveyor when habits and ventilation are not enough
“If black mould is appearing on your plaster walls rather than just window frames, or if condensation continues despite better ventilation, then there is an imbalance between your heating, ventilation and extraction- or external defects that are contributing the internal problem, no amount of opening windows is going to fix the issue.
“A proper assessment of the problem and the root causes should be undertaken by an expert in this field.”
