How to prevent and manage condensation damp

How to prevent and manage condensation mould

Black mould is the bane of many households, especially at this time of year. In this article I’ll be discussing what causes this type of mould and the best methods for dealing with it.

Firstly its good to understand the different types of household damp

Rising Damp

You’ll notice a damp, musty smell and there will be damp on the lower parts of the ground floor walls, rising up to about a meter.  You may also see tide marks on the wall, wallpaper pealing off and mould lower down near ground level. The wall will feel damp to the touch.

Penetrating Damp

Similar to rising damp, the wall will often feel damp to the touch.  However, in this instance, the damp spot is often in an isolated place. You can see an example of this here on a fireplace wall.

Rising and penetrating damp – what to do?

If you suspect your property is suffering from one of these types of damp problems, then its best to speak with a specialist. If you’re in a rental property, give your landlord or agent a call.  Its important to quickly establish the cause, so that remedial action can be taken.

Condensation damp

This is the most common household mould.  Its identified as a black, sooty mould growth and can appear in a matter of days, given the right conditions.

Whist it looks unsightly, its the one type of mould that you’ll be able to manage yourself in the majority of cases and if dealt with quickly.

The first and most obvious location where this sort of mould occurs is around windows (especially in bathrooms and kitchens).

Why does condensation damp occur?

Condensation damp needs need warm, humid air, Lack of ventilation and/or poor air circulation. The warm moist air will then find cool/cold spots in the house where it condenses back to water droplets as it cools.

The most common places to find condensation in a house is on windows. However, if the warm air, or condensed water droplets are left and not given an escape route or removed, it will settle in other places in the house too.  This is often the coldest room of the house, normally on external walls, wooden doors and furniture, or anywhere that has poor air circulation or ventilation, such as behind wardrobes and beds.

If left, the damp patches will start to grow mould spores.  Given more time these will develop into colonies.  These very quickly spread into unsightly black patches, which will release more spores that can affect the health of people in your home.

What are the main causes of condensation damp in a homes?

For condensation damp to occur, you first need condensation.  This is an excess of moisture rich air that condenses into water droplets on cold surfaces.  This type of air can be caused by many factors but most commonly:

  • Washing being dried indoors  
  • Cooking
  • People breathing
  • Showering and bathing

None of the above would be a problem in isolation (especially breathing!!) but if you then add the following factors, you’ll have a far higher chance of black mould forming:

Lack of ventilation.  This means there’s nowhere for the warm moist air to go, so it condenses in the room, rather than being extracted to outside. 

Lack of insulation.  If a property is poorly insulated this will mean interior walls (often north facing walls) may be colder.  This provides a perfect environment for moisture to gather.

Areas of poor air circulation.  Warm moist air seeks out cold spots to condense, but it also relies on poor air circulation.  If air circulates in a room, the condensed air does not have anywhere to gather. So its favourite hiding spots are behind (and even in wardrobes).  In these areas it can settle down, undisturbed and start multiplying.

Cold weather.  Most houses will have areas where surface mould forms during the winter.  This is because it’s a time of year when a few of the above factors tend to come together at the same time.  We keep windows closed, cook more and dry clothes more often indoors.  Winter is also a time (pre and post Covid) where we congregate with friends and family indoors. This means that there’s often, larger number of people in households, breathing out warm air in small, often unventilated, spaces.

Its also a bit of a myth that its only old properties this affects.  Mould specialists regularly get called out to modern, well insulated properties.  All houses have cold spots and areas where air can’t circulate so well.  Therefore, if the occupiers don’t regularly ventilate that room or area, black mould will occur.

Tips for reducing the chances of condensation mould forming in your home

The standard advice for homes is to keep all rooms warm and well ventilated.  However, in these days of ever rising fuel costs, this isn’t always going to be possible or affordable.  Therefore, I’ve listed below, some simple, cost-effective tips: 

  1. If you discover a small area of mould (for example around a window), the simplest option is to wash it down with warm soapy water (or spray with a 50/50 mix of white wine vinegar and water) then dry off as best you can and well vent the area until dry.
  2. Avoid bleach and cheap mould cleaning sprays.  The reason is that they all contain salts, which encourages the mould to return, so it will be false economy in the long term. However, if you have a large mould area that’s been around for a while then this might be a quick and cheap solution. In this instance, once you’ve sprayed and left the bleach or specialist cleaner to do its job, make sure you also wash the area with warm soapy water to remove the salts afterwards. Remembering to wear a mask when dealing with the mould and then heat and vent the area until dry.
  3. Regularly check behind furniture.  Wipe down to ensure dust and damp spots are kept clean and dry.  Where possible, try to make sure cupboards, bed headboards have space behind them for air to circulate. 
  4. Open windows as often as you can.  This helps any warm moist air to escape and kill mould off.  Its also heathy to have fresh air circulation in your home.  Even if you just open your bathroom window after a shower for 5 minutes, this will help the damp air to escape.  Remember to close the door, to avoid the damp air escaping to other parts of the house.
  5. Keep wardrobes as uncluttered as possible.  Also if possible, especially during the winter months, leave the wardrobe doors open.  This allows air to get inside and stop mould growing on clothes, shoes and boxes.
  6. Wipe down walls and windows that become wet from condensation.  You should dry them down as soon as you see condensation. If the moisture is dried up, the mould spores cannot grow.
  7. When cooking and showering. Keep the door to that room closed and open a window to help the damp air to escape. 
  8. Dry clothes outside.  If this isn’t possible, allocate a small room, open the window and close the door.  Or if funds will allow, consider investing in a dehumidifier (see below).

My simple solution for removing small areas of condensation mould.

  1. Open a window before starting to clean any damp or areas where black mould is present.
  2. Also consider wearing a mask if you’re removing mould. Cleaning mould is the time spores become active.  Therefore, its best to wear a mask and keep infants or those with breathing problems out of the room whilst you’re cleaning.
  3. Spray the area with a 50/50 mix of white wine vinegar and water. Or if there’s bad staining, you can make it into a paste with bicarb of soda and leave it on for 30 minutes before wiping away.
  4. Repeat if very bad growth.
  5. Dry down with a clean dry cloth. 
  6. Keep the heating on, door closed and window open to help the area dry out further.


The phrase, ‘prevention is better than cure’ is definitely worth remembering.

Do not let black mould get out of control.  Follow the above tips and regularly check areas where there’s poor circulation and treat accordingly.

If however, you’re doing all of the above and still struggling to keep on top of the mould growth, then something else may be the cause.  This is when you should speak with a specialist, so they can investigate the cause and suggest solutions. 

If you’re a tenant then definitely flag the issue up to your landlord or agent at this point.  They may well be inundated with calls relating to mould issues at this time of year and in the main these will be caused by lifestyle, rather than the property.  Therefore, if you can explain what you’ve been doing to try to keep on top of the problem but that you’re still fighting a losing battle, then they should act.

Investments that will help reduce damp air in properties:

These won’t be for everyone but if your budget will stretch to one of the following, it will make your job of keeping condensation mould at bay much easier.  They are all cheaper to run than heating your home or certain rooms when you don’t need to.  Although please try to heat the house for at least a couple of hours a day in the colder months.  It will make all the difference to your home and most importantly, to your health.


These are particularly useful for drying your washing on days when doing so outside isn’t an option.  Due to their relatively low running costs, they’re fast becoming effective alternatives to tumble dryers.

How to dry clothes indoors using a dehumidifier

The best way to dry clothes using a dehumidifier is to allocate a small room (downstairs WC or small bedroom).  Hang the clothes on an airer that’s designed to let air circulate well between items (don’t overload it). A ceiling hanging type might be worth considering. Then turn on the dehumidifier (most modern ones have a dry clothing setting). Close the door and leave for 3-4 hours.  This might sound like a long time but this will still be far less cost than using a tumble dryer.   

The added bonus of a dehumidifier is that if you find a room that’s suffering with a damp problem that you need to tackle, you can use the dehumidifier to help dry the room out, which will reduce the chance of the problem quickly returning.

Extractor fans

Ideal for use in kitchens and bathrooms. They help to extract the warm air and often odours.  Make sure these come on every time you bathe, or cook and keep them on with the door closed for 10-30 minutes after you’ve finished.

PIV systems

Positive Input Ventilation (PIV’s),  sometimes referred to as positive pressure ventilation, is a whole house system.  Its purpose is to ventilate and create fresh and healthy household living environments by supplying filtered air into a property at a continuous rate.  

The idea is that air is drawn from outside, or from a roof space and pushed into a property.  This is then pushed throughout the house and out again through trickle vents, the opening and closing of doors etc.  The purpose of the system is to circulate air that will help combat condensation and mould build up, by pushing moist air out and replacing it with filtered fresh air. 

These are cheap to install and run.  You can get cold, or warm air systems. The warm air systems are slightly more expensive but reduce the ‘cold draught’ effect you can sometimes experience from the cold air versions.

In Summary

Please remember, that whilst condensation mould is not necessarily as bad for the fabric of the building as rising or penetrating damp and is often far easier to treat, it can spread rapidly if left untreated.  In severe cases it can also cause problems for those with breathing problems, or impaired immunity. If you ignore it, the issue will become a much bigger problem to resolve. Mould of all types loves being ignored!

This article has been written by Deborah from CAM Properties in Hayle. I’m not a damp or mould expert. So if you’re at all unsure about what’s causing the damp in your home then please speak with an expert.

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