Guide to Damp and Mould in your home

Black Mould growth and condensation in your home are the visible signs that the air in your home is too wet.

Air always contains a certain amount of water vapour and this varies with air temperature. The warmer air is the more water vapour it can hold. The cooler air is the less it can hold.
Condensation occurs when water vapour in the air inside the house condenses on a cold surface. It can occur at any time of the year and is seen as misting or water droplets on windows, walls, tiled areas, concrete floors and toilet cisterns. Condensation can even occur inside tightly packed clothes in the wardrobe and chests of drawers!

Mould Growth. Mould spores are always in the air and growth occurs when mould spores germinate on contact with surfaces that are damp through condensation or rain water penetration. The mould takes the appearance of small black (most common), grey or green spots on the wall or other surfaces. Mould is most commonly seen around window reveals, on external walls and at high level in extremal corners. If you have black mould growth at low level, it is not likely to be rising damp, but due to moisture in your home fuelling mould growth.

Water Vapour is created by normal, everyday living in your house such as breathing, perspiration, washing, cooking, bathing, drying clothes, and burning fuel, such as gas or paraffin.
This information is provided for you to use in controlling your condensation and mould growth problem. The mould won’t go away by itself. Tenants as much as landlords have to take the steps needed to prevent or control it.

Please read carefully.

Damp and Mould Growth

Associated with increased prevalence of house dust mites, mould and fungal growth, associated mental health and social well-being issues, cardiovascular and respiratory illness.

The average household will produce 112 pints of moisture per week through cooking, bathing and breathing. The moisture is increased when clothing is dried in the home.

Why does it matter if there’s condensation or mould growth in the home?
Mould spores are the “seeds” of mould growth and are released in to the atmosphere when mould grows. The spores are microscopic, easily breathed in and are potent allergens too. They are always in the air and just require a source of moisture (condensation) and food (dust) to start growing.
House dust mites live in your carpets, mattresses, pillows and soft furnishings. They are invisible to the naked eye. The mites themselves are not the problem – they won’t cause you any direct harm. The problem is their droppings. They are so small that they are easily breathed in and are allergy causing agents (allergens). Lots of warm moisture encourages them to breed — rapidly!


Exposure to either or both allergens at high concentrations over a long period can cause increased sensitivity to them. Once a person is sensitised, relatively low concentrations of these allergens can trigger allergic reactions such as sneezing, runny nose, eye infections, irritation, eczema, coughs and wheezing.
For some sensitised people, long term exposure can lead to asthma.
Around 1,500 people die from asthma every year. Research has shown that the severity of asthma increases with increasing levels of humidity, house dust mite and mould levels.
Whilst mould and dust mites are the most important parts of the problem, there are other things you need to know about high humidity levels.
• “Wet” air is a very efficient conductor of heat. You will use more energy keeping yourself and your house warm if the relative humidity in your home is too high and your clothes and your walls are damp as a result.
• Elderly people, young children and the chronically ill have difficulty in regulating their body temperature. It is particularly important that these groups live in homes that are warm and dry.
• High humidity and condensation present threats to the physical fabric of your home, it can cause wallpaper and paint to peel, timbers to rot, floorboards and other timbers to warp and swell, and metal components to corrode. There is also a danger of electric shock if switches are used whilst they are wet from condensation.
• If you are a tenant, you may face losing part or all of your deposit to pay for the damage caused.
The appearance of condensation and mould growth is a sign that the building or room in question is not being adequately heated and ventilated.
The average family produces 20 pints (5 gallons or approximately 12L) of moisture every day. Think of it as two and a half builders buckets full of water and you will see the scale of the problem that the house has to cope with.

You can reduce moisture in your home by:

Drying clothes outside or piping the tumble dryer’s moist exhaust air to the outside.

Leave the bathroom door closed whilst the bath is filling to reduce the spread of steam. When you have finished, open the window wide for an hour or so, or until the last beads of moisture have disappeared from the windows and walls. If there is an extract fan in this room, leave the window closed and leave the fan running for an hour or so. If you have a heater in the bathroom, turn it on at least one hour before you go in to the bathroom. If you have central heating, make sure that the air temperature in this room is not less than 21C. This is particularly important for people under 5 and over 60, or who have a long-standing illness.

Not drying your clothes indoors on airers or over radiators.
Not using liquid paraffin or bottled gas room heaters. These produce 8 pints (5L) of water vapour for every gallon of fuel burned. The water will end up condensing on your walls and windows.
Keeping lids on pans when cooking, keeping the kitchen door closed and leaving the window open/extract fan on.

In 99.99% of cases, the cure for condensation and mould growth is heating and ventilating a property. This is why tenants must take responsibility for the way they live in their home.

As the air in your house circulates, it draws moist air to the outside through open windows, doors, trickle vents, extractor fans, airbricks and chimneys and is replaced by fresh air- Outside air is always drier than the air inside your house. If this exchange of air is poor or prevented, the air in the house becomes saturated and water vapour will condense on the nearest surface at or below dew point temperature. To allow fresh air to circulate you should consider some of these:
Fit extractor fans to shower rooms, bathrooms and kitchens. Bathrooms require an extract rate of not less than 15 litres per second. The kitchen extractor to ventilate at 30 litres per second (if adjacent to cooker hood), or 60 litres per second if situated elsewhere, on intermittent operation. A cooker hood is not an extractor fan unless you know it extracts to outside. There are extract fan systems available that can remove most of the heat from the extracted air and blow it back into the room (Mechanical Ventilation with Heat Recovery). Tenants will need to ask landlords to provide extractor fans if felt

Ensure that trickle vents are open in double glazed windows (image below).
Avoid still air pockets – areas between furniture and external walls and behind heavy curtains will encourage condensation to form, because there is no circulation of warm air to warm the wall and furniture. If it is not possible to put the furniture against an inside wall, leave a gap of at least 3″ to 4″ (75mm to 100mm). Do not over fill wardrobes, cupboards and chests of drawers.
If you have a hot water storage tank in a cupboard with a feed and expansion tank above it, make sure the feed and expansion tank has a tight fitting (but not air tight) lid.
If you have nowhere to dry your clothes, take them to the launderette and dry them there. Failing this put them in the bathroom, turn on the heating, open the window or turn on the extract fan and close the door.
Open all windows wide until the condensation disappears and then close them, leaving a 1/4inch (5mm) gap between the sash and the frame in each room (image below).
Keep bathroom and kitchen doors shut to help prevent moist air circulating to the rest of the home.
Do not put your mattress directly on the floor.
Open windows when ironing.

Warm air can hold more moisture than cold air so if your house is heated adequately you are less likely to suffer from condensation.
Warm air cooling in the night will still result in condensation, especially on or around windows during cold weather. Most of this will evaporate as heating is turned on again in the morning and windows are opened.
Your walls store heat. The amount of heat stored will depend upon how heavy the materials are, their insulation standards and the period for which it has been heated.
Condensation cools walls even more, resulting in even more condensation occurring. This will continue happening until you do something about it.
A wall may be cold and attract condensation for several reason:

A leak from a gutter or pipe may make part of a wall colder. Locate the leak and get it repaired.
It may only be a 4 inch thick brick wall, especially where an old external toilet or coal house has been incorporated into the main house
If the house is too cold you will notice that:
Your house, clothing and bedding will feel cold and damp. There will be a musty, damp smell. You may see mould growth on furniture, external walls, in cupboards, drawers, on or around windows and on your clothing or bedding.
Wallpaper may peel off around windows or other adequately heated or not heated at all,
If the house is new, it may still be drying out.
Trees, shrubs, alleyways or an adjacent building may shade the room or walls, preventing the sun from heating it up.
It takes a long time before your heating begins to take effect, your walls stay cold to the touch and you will not feel properly warm as a result.
Your fuel bills will increase substantially.

You will find it more difficult to keep yourself warm, especially if you are elderly, ill, or spend a great part of your day in the house
Provide heating in the affected rooms. In damp affected cupboards, an electric green house heater can provide sufficient warmth to prevent or reduce mould growth. Similarly, if there is a light fitting within the cupboard, leaving the light on can do the same. (Make sure that there is a large gap between the bulb and any flammables).
The cure to this problem is to put more heat in the property until the wall is warmed to a temperature above dew point (but don’t forget ventilation as well as this is very important too.) Yes, it will cost more initially to get the walls warmed up, but when they are properly dry your heating bills will reduce.
Removing Mould Growth
If you do have mould growth you should remove it as soon as it can be seen
The steps to take are:
1. Wash the affected area thoroughly% Use non-ammonia soap or detergent, or a commercial cleaner, in hot water, and scrub the entire area affected by the mould. Use a stiff brush or cleaning pad on cement-block walls or other uneven surfaces. Wet the surface first with detergent solution before scrubbing.
2. Rinse and Dry. Use a damp cloth to rinse any residual detergent off the treated surface. A wet/dry vacuum cleaner can be helpful for removing water and cleaning items.
REMEMBER All this information and more is available at:
3. Disinfection. Disinfectants are intended to be applied to thoroughly cleaned materials and are used to ensure that most micro-organisms have been killed. Therefore, do not use disinfectants instead of, or before, cleaning materials with soap or detergent. After thoroughly cleaning and rinsing contaminated materials, a solution of 10% household bleach (1 1/2 cup household bleach per gallon of water) should be used as a disinfectant. Using bleach straight from the bottle is less effective than diluted bleach. Keep the disinfectant on the treated material for the prescribed time before rinsing or drying; typically 10 minutes is recommended for a bleach solution. When disinfecting a large structure, make sure that the entire surface is wetted (e.g, the floors, joists and posts). Properly collect and dispose of extra disinfectant and runoff.
WARNING: Bleach and disinfectant should be handled with caution. Bleach should never be added to ammonia or other chemicals; toxic gas will be produced. Wear gloves, mask and eye protection when using disinfectants. Bleach fumes can irritate the eyes, nose, and throat, and damage clothing and shoes. Make sure working areas are well ventilated.
4. Clean Up. Discard any loose porous materials where mould growth cannot be removed or has become ingrained into the material (e.g, ceiling tiles, plasterboard, carpeting, and wood products). Bag and discard mouldy items; if properly wrapped, items can be disposed with household rubbish. Ensure humidity levels are kept down and place a fan heater near the affected area to dry out the treated materials. Dry the affected areas for 2 or 3 days. Then follow the instructions at the beginning of this leaflet to prevent it happening again.

Energy Efficient,
Warm & Healthy Homes
If you are a landlord – Energy Efficient, Warm & Health Homes can give tips on how to improve the thermal effectiveness, ventilation & heating in your rented properties as well as tax incentives & advice on doing so.
Remember: If the tenant has done all they can to prevent & control condensation but there is still a problem, the Council could require landlords to do additional works.

What more can i do?

DO not wait until it starts to turn cold before putting your heating system on. Leaving the heating off until the weather turns cold will result in the walls losing all their stored heat. It will then take a lot longer (and more money) for the heating system to warm them up sufficiently for you to feel comfortable.

DO turn heating on at the end of September (or earlier if the weather cools), and set the main thermostat to a temperature of not less than 21 C. If you have thermostatic radiator valves in your rooms adjust these to achieve a temperature of not less than 18C (aim for 21-22C in living rooms). The heating system will then automatically provide enough heat to maintain the structure above dew-point.
Economy 7 or Night Storage Heaters, it is important to listen to the weather forecast and adjust the input control to take account of the temperatures for the next day.

On most E7 or Night Storage Heaters there will be 2 knobs. Generally, the right hand one will control the heat input and the left hand one will control the heat output. The left hand knob (the output control) controls a flap within the heater. To keep the room at a reasonable temperature you will need to adjust it to allow heat to escape gradually through out the day. The control knobs are often marked with the numbers 1 to 10 around the outside. As a rough guide in mild weather, (outside air temperatures between 10 to 17 Celsius), the input control should be somewhere between 4 and 8. In cold weather (10 Celsius and below), turn it to 8 or above.

These types of heaters will provide a minimum temperature of 18 Celsius, but however, this is not a comfortable temperature and you will find that it will probably be necessary to supplement the heating with a convector heater during periods of very cold weather.
DO not over-ventilate by leaving your windows wide open all day in cold weather — your walls will lose all of the heat stored in them.

DO open the windows wide for a short period of time in the morning say 30-60 minutes and then close them up, leaving a small gap between the sash and the frame of % of an inch (5mm), or at any time that you see condensation forming on the glass. (But do think about the security of any windows left open when no – one is home)

DO mop up any water that accumulates on the window glass or window sills. Wring the cloth out in the toilet or washbasin, don’t leave it wet on the sills. This will provide a moisture reservoir for future condensation.

DO not put your heating on for short periods of time (one hour or less) — this will actually ensure that the problem becomes worse. The air absorbs water vapour more quickly than the walls can warm up. When the heating is turned off, the air cools very quickly and condensation rapidly occurs, cooling the walls further.

DO put the heating on for at least 3 hours at a time. Set your timer to come on at 4 or 5 a.m (when the air is coldest) and to go off an hour after you leave for work. During the day, set it to come on at least an hour before you come home from work and to go off at least an hour after you go to bed.
If you are at home all day, put the heating on for not less than 3 hours at a time or leave the heating on full time, but at a lower temperature.
In extremely cold weather, it is a good idea to leave your heating on at a low level whether at home or not.

Washing, Cooking & Drying Clothes
Create moisture in your home – this needs to be removed by you„..
Open windows for Use extractor fans in Keep home
Open Trickle Vents short periods—kitchens, bathrooms keep consistent In Windows
Dry clothes inside without having a window open
Vent a Tumble Dryer inside your home: always outside

Important inform your Agent or Landlord immediately if you notice any mould or damp appearing…
You have a legal obligation to inform your Agent and Landlord as soon as you notice any issues or you could be in breach of your Tenancy.