Home / Seasonal / Autumn condensation help
Condensation and mould as the weather turns
Every autumn our phones follow the same pattern. The windows close, the heating goes on, the washing dries indoors, and within a few weeks the first black spots appear behind wardrobes and in the corners of bedrooms. Most of it is condensation rather than damp coming in from outside, and most of it can be controlled. The trick is being sure that is what it is.
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Signs to look for
- Streaming windows first thing in the morning
- Black mould in the corners of outside walls, behind furniture and on sealant
- A musty smell in wardrobes and on clothes
- Peeling paint or wallpaper in the bathroom and kitchen
- Mould worse in the coldest rooms, often a north facing bedroom
What causes it
Warm air holds more moisture than cold air. Cooking, washing, drying clothes and simply breathing put litres of water into the air of a home every day, and when that air reaches a cold surface, a window, an outside wall, a corner behind a wardrobe, it condenses. Mould follows within days.
Autumn is when the balance tips: the house is shut up, the outside walls are cold, and the habits of summer, open windows and washing on the line, stop. Homes with blocked or missing extract fans, sealed up chimneys or new windows without trickle vents are hit hardest.
Not every patch of mould is condensation. A leaking gutter, bridged cavity or failed render puts water into a wall from outside, and treating that as condensation never works.
What we do
If the pattern fits condensation, the first steps cost little: extract fans on and working in the kitchen and bathroom, trickle vents open, lids on pans, washing dried outside or in a vented room, furniture a few centimetres off outside walls, and the heating kept low and steady rather than off and on.
If it persists, or appears where condensation would not explain it, we survey with meters, a thermal camera and a hygrometer, find the cause in writing, and specify the works that would fix it, from ventilation upgrades to the defect letting water in. We sell none of it, so the advice is the cheapest that will work.
What it usually costs
Our survey fees are published on our prices page. We do not carry out works, so you know what the problem is before anybody asks you to pay to fix it.
Questions
Is black mould dangerous?
It can affect people with asthma, allergies and weakened immune systems, and children and older people are most at risk. It is worth dealing with rather than repainting over.
Will a dehumidifier fix it?
It helps a lot in a home with a moisture problem, and is often part of the answer. It will not fix water coming in from outside.
Should I bleach the mould?
A mould wash made for the job is better than bleach, which can leave the roots behind. Cleaning treats the symptom; the cause still needs dealing with.