There are four main types of dampness that could affect your home. It is important to understand the difference between them so that you can effectively understand the
This is caused by water rising from the ground into the home. The water gets through or round a broken damp proof course (DPC) or passes through the natural brickwork if the property was built without a DPC. A DPC is a horizontal layer of waterproof material put in the walls of a building just above ground level. It stops moisture rising through the walls by capillary action.
Rising damp will only affect basements and ground floor rooms. It will normally rise no more than 12 to 24 inches above ground level internally (300 to 600mm) and usually leaves a ‘tidemark’ low down
on the wall. Rising damp can travel around 1000mm from the source of the moisture which is usually well above ground level.
You may notice white salts on the affected areas. These are building salts that are present in many building materials such as sand, cement, bricks,
plaster and so on. Rising damp will be present all year round but is more noticeable in winter. If left untreated it may cause wall plaster to crumble and paper to lift in the affected area.
Black mould will rarely be seen where there is rising damp (and then only in the early stages). This is because rising damp carries with it ground salts which prevent the growth of black mould.
This type of dampness will usually be found on external walls or in the case of roof leaks, on ceilings below. It only appears because of a defect outside the
home, such as missing pointing to the brickwork, cracked rendering or missing roof tiles, flowerbeds bridging the DPC course, etc. These defects then allow
water to pass from the outside to the inner surfaces through debris usually found in the cavity.
Penetrating dampness is far more noticeable following a period of rainfall and will normally appear as a well defined damp patch which looks and feels damp to the touch
Black mould is rarely seen on areas of penetrating dampness. This is because the affected area is usually too wet and the dampness contains salts picked up when passing through the wall, which can prevent the growth of black mould.
Leaks from water and waste pipes, especially in bathrooms and kitchens ,are relatively common. Check around your appliance connections and wastepipes. Leaks can affect both external and internal walls and ceilings. The affected area looks and feels damp to the touch and remains damp whatever the weather conditions outside. A quick examination of the water and waste pipes serving the kitchen and bathroom, and the seals around the bath, shower
and sinks; plus the external pipework, such as guttering will usually find the source of the problem.
It is uncommon for mould to be seen on this type of dampness because the area is usually too wet and the detergent in a waste water leak will usually prevent mould growth.
This is by far the most common cause of dampness experienced by tenants, resulting in a large number
of enquiries or complaints received by RBH. Condensation is caused by water vapour or moisture from inside the dwelling coming into contact with
a colder surface, such as a window or wall. The resultant water drops (condensation) appear on colder
surfaces such as walls, windows, ceilings or mirrors.
Black mould is frequently seen on this type of dampness. The cold surface and lack of ventilation
allows mould to happily colonise these areas.