How to Deal With Condensation Damp
Banish damp walls, mouldy patches and steamy windows with our expert guide
We spoke to three experts about how to spot condensation damp in your property, what causes it and how to treat it.
Professional advice from: Cat Hoad of Absolute Project Management; Lior Brosh of Brosh Architects, who specialises in period properties; John Klee, heating content specialist at BestHeating
It’s the most common type of damp in UK homes. It tends to get worse in winter, and is often found in period properties, especially ones that aren’t well insulated or ventilated.
“Condensation is created when warm, humid air meets a colder surface, such as a wall or window,” Lior Brosh says. “As the temperature drops, this creates water droplets on the surface.”
This makes condensation damp different, for example, from rising damp, “which comes from an external source, such as ground water, damaged drains, or roof or window leaks,” he says.
You don’t need to panic every time a window is a bit wet, steamed up or chilly – some condensation is normal in most houses, Cat Hoad explains. But you do need to keep an eye out. “It becomes problematic if the water that condenses isn’t removed,” she says, “either by running off to a suitable drain, say, or by evaporation – naturally or via an extractor fan.”
Humidity in our houses is created through normal, everyday activities, such as breathing or boiling a kettle. “Other activities that create moisture in the air include cooking, showering, exercising and drying clothes on radiators,” Lior says.
However, certain things will make matters worse. “If your house isn’t ventilated properly and humidity or moisture is trapped inside the house for a long period of time without airflow, it can create the perfect environment for condensation damp,” he explains.
Cat says it’s common to see condensation damp in unventilated bathrooms or kitchens. “For example, if you’ve had a shower in a small bathroom with no extractor fan, and your door and windows are closed, the steam from the shower will condense into water on any cold surface, such as a window pane or uninsulated external wall,” she says. “If this water doesn’t have the chance to pour away or evaporate quickly, it will sit on the surface.”
Take a good look at your walls, windows and ceilings. “Condensation damp is usually identifiable as soft-edged patches of black mould, or water trickling down surfaces such as windows,” John Klee says. “Wallpaper and paint may start to peel and unpleasant odours infiltrate your space.”
Wooden areas can also rot. Lior advises you look out for damage to windows, skirting boards and floors.
Check for water obviously sitting on walls, as well as dripping from ceilings, Cat adds. “You might see rotting wood and fabric, such as curtains. Often, black mildew forms in corners where damp air has accumulated, or on shower curtains.
“In extreme cases, you see actual fungus,” she says. “I lived in a student flat that had mushrooms growing round the bath! And there’s usually a musty smell.”
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“Condensation damp occurs most often in older, poorly insulated period houses that don’t have adequate, or any, ventilation,” Cat says.
“Unlike modern homes that are required to follow the latest Building Regulations, guidelines and inspections, period homes are more likely to have single rather than double glazing,” Lior says. “So there’s a minimal barrier between the cold air on the outside and warm internal air. Their walls are normally solid brick, rather than cavity or insulated, which prevent internal cold surfaces.”
However, that’s not to say you can totally relax if your house is modern. “Condensation can happen anywhere there’s a build-up of water vapour and a cold surface,” Cat says. “A typical example would be a bathroom in a home with an external uninsulated wall that doesn’t have an efficient extractor fan. Often these rooms have a spinning fan set into a window, which is better than nothing, but not very efficient – and they tend to be draughty, so people wedge them shut.
“Another example where condensation can occur is in a cupboard containing a washing machine or tumble dryer, unless ventilated or used with the doors open – which they often aren’t, as the machines are noisy,” she adds.
While condensation damp can be easy to fix, it can cause untold damage if left unchecked.
“In more severe instances, where condensation damp has built up over plenty of time, permanent damage can be caused to essential building materials, such as timber and plaster, which could result in the plummeting of a property’s value,” John warns.
“Over time, condensation will cause windows to rot; this takes a few months to take hold,” Cat says. “Plaster and brick surfaces can start to bubble, deform and crumble. Unsealed plaster would be affected in a few weeks, painted plaster would show evidence after a few months and brickwork after perhaps a year.”
“It can even damage your furniture,” Lior adds, “since, in many cases, pieces such as sofas can be touching a damp wall.”
But as well as your property, damp can affect your health. “It encourages the growth of dust mites, and might trigger the development of allergies and breathing problems, such as asthma,” Lior says.
If you have damp issues, the experts recommend contacting a professional. “A lot of specialists carry out damp surveys for free to assess how big the problem is and probable costs to resolve the issue,” Lior says.
However, there are plenty of steps you can take immediately to reduce condensation.
“Make sure your house is ventilated and there’s decent air flow, especially during warm weather, when you can keep windows open during the day,” Lior says.
“Close kitchen and bathroom doors when cooking and bathing, so moisture won’t travel around the house. And make sure your furniture isn’t touching a wall,” he continues.
Avoid using your clothes airer in the house as much as you can, too. “Where possible, dry your clothes outside your home,” he says.
“Wipe down your windows and windowsills on a daily basis,” John adds.
When it comes to bigger measures, John advises you ensure your home is fitted with double-glazed windows. “While this might be expensive, in the long-run it will protect the fabric of your home,” he says. Decent thermal insulation is advisable, too, if possible.
A good electric ventilator fan in kitchens and bathrooms is absolutely crucial for fighting condensation. “These move damp air out of your room to be replaced by dry air,” Cat says.
The good news is they aren’t a big investment. “Smaller models can be sourced for upwards of £30, though larger, more powerful designs cost more,” John says.
“People sometimes don’t like extractor fans, as they’re often noisy and can be set on a timer to stay on for several minutes after the room is used, which can be annoying in the middle of the night,” Cat says. “However, you can get extremely quiet models and adjust the timer so the fan only runs for a short period.
“Humidistat fans also work well,” she continues. “They have sensors, so the fan operates when a certain level of humidity is reached. Look out also for extractors fitted with heat exchangers – these will ‘capture’ some of the heat from the air you’re extracting and use it to warm the air coming into the room, reducing heat loss and energy costs.”
Another option to consider, John suggests, is one or several air dehumidifiers or similar devices. “These can go a long way towards tackling condensation damp,” he says.
Yes. Condensation damp is common, but it’s important to address it. “It can be difficult to know what to do about damp, so people are often tempted to just ignore the problem,” Cat says.
“However, persistent condensation can cause damage to the components of your room and, perhaps more importantly on a day-to-day basis, will make rooms smell horrible and unwelcoming,” she says.
“Be methodical about the approach you choose and keep an eye on time of year,” she advises. “Condensation will be less of a problem in warmer, dryer weather, more so if it’s very cold and damp, especially for long periods.”
The good news? “Luckily, condensation is usually easy to treat by enabling good ventilation,” Cat says.
Coming soon: How to Deal With Penetrating Damp.
Have you had condensation damp, and how did you solve your issue? Share your experiences in the Comments.