Managing a property - information for landlords

Damp and mould

Most homes will be affected by damp at some point. Damp can be caused in different ways and if you can work out the cause of the damp, this will help you to treat the problem in the right way.

Penetrating dampness

Penetrating dampness is where any external source of water (predominantly rainwater) can enter your home through gaps in the walls (missing mortar or cracked render) or roof (missing tiles or flashings), from around poorly fitting doors and windows, or from blocked gutters.

Signs of penetrating dampness are damp patches on walls or ceilings that get worse after rain and feels damp to the touch. Black mould is not usually seen on areas of penetrating dampness because the affected area is usually too wet.

Rising damp

Rising damp is caused by water rising from the ground into the home, either by way of a defective damp proof course, if there’s no damp proof course present or if the outside ground level resting against the house wall is higher than the damp course. Rising damp affects ground floor walls and basements and will not usually rise more than 1 meter above the ground level. It will typically leave a ‘tide mark’ at its highest point on the wall and you might notice white salts on the affected wall. If left untreated, plaster can become saturated and crumbly and can lead to dry or wet rot to timber and masonry.

Black mould is rarely seen on areas of rising damp because the dampness contains salts picked up when passing through the wall which stops its growth. The ground level immediately adjacent to the external wall of your home should ideally be at least 150mm lower than the damp proof course or internal floor levels.

Defective plumbing

Defects in rainwater gutters and downpipes, leaking water supply pipes, damaged waste water drainage pipework, water storage tanks or overflow pipes. Leaks are typically noticeable in kitchens and bathrooms, or in rooms adjacent to or below these rooms. Damp patches will remain damp to the touch, whatever the weather is like outside. This issue will require further investigation and should be remedied as soon as possible.

Black mould is rarely seen on this type of dampness because the area is too wet and the chemicals in the water will prevent mould growth.

Condensation

Condensation is the most common cause for dampness. Moisture is always present in the air, even if you can’t see it.

Condensation is mostly a problem in cold weather and is the most likely cause of black mould in your home. When warm air cools, the moisture in the air turns into droplets of water which appears on cold surfaces and in places where there is little air movement – in corners, on or around windows, in or behind wardrobes and cupboards, and this is made worse by inadequate ventilation, insulation and heating.

We create condensation in our everyday activities – cooking, bathing, washing up, drying clothes and even by breathing. Typically, most condensation is created in kitchens and bathrooms, so if you can ventilate these rooms well and keep the doors to these rooms closed, moister laden air will be prevented from travelling elsewhere around your home. If you have an extractor fan in your bathroom and/or kitchen, make sure it works and is used when cooking or bathing.

Preventing condensation

Make sure your loft is insulated to the correct height.
Draught-proof windows and external doors.
Consider cavity wall insulation and secondary glazing.
Make sure your property is watertight and free from leaks.
Make sure your windows can open and any extractor fans work for ventilation.
Make sure your heating system heats your whole property.

Removing mould

Carefully remove excess mould with a damp cloth, then throw it away. Do not brush mould as it releases spores into the air.
Wipe affected areas with a proprietary fungicidal wash (mould and mildew cleaner) or diluted bleach. Follow the manufacturers instructions carefully. These are available at most supermarkets and DIY shops. Wear rubber gloves and goggles.
After treatment, redecorate using a good quality fungicidal paint or fungicidal wallpaper paste. Don’t paint over with ordinary paints or wallpapers. If necessary, dry clean mildewed clothes and shampoo carpets.