Damp can be caused by a number of issues and they are not necessarily difficult to deal with. But damp can cause mould on walls and furnishings and increases in dust mites, which can lead to respiratory problems.

What causes damp?

The 3 main causes are:

• Rising damp

• Penetrating damp

• Condensation

Rising dampis water from the ground entering the structure of the house by capillary action; only rising damp can be cured by the installation of a chemical damp proof course. It is important that the problem is diagnosed and treated by a suitably qualified person.

 Signs of rising damp

• Decayed skirting boards.

• Crumbling or salt stained plaster, discoloration and staining.

• Decayed timber floors.

• Peeling paint and wallpaper

 Penetrating damp occurs as a result of problems with the fabric of the building that can allow water to leak into the walls or floors. It can move about within a building horizontally or from a higher to a lower level. Typical defects leading to penetrating damp are defective guttering or down pipes, faulty flashings, poor pointing, cracked rendering and built up external ground levels.

Penetrating damp is most common in older homes that have solid walls. A new build property with cavity walls offers more protection against driven rain. Penetrating damp can be tricky to
pin-point, and may often require expert help.

 Signs of penetrating damp

• The first sign of damp penetration is often the appearance of damp patches on walls, ceilings or floors. These tend to grow or darken after periods of heavy or prolonged rain.

• The long term effects of water penetration can include damage to decoration and plaster, decay in exposed timber, and mould growth.

Rising damp and penetrating damp occur as a result of issues with the property and are the responsibility of the landlord to rectify. It is advisable to use a suitably qualified person to secure a permanent solution. Tenants should be encouraged to report signs of damp before the damage becomes too extensive, and it is advisable to check for such issues during the regular inspections of the property.

 Condensation

The air in buildings can have a high level of relative humidity due to human activity (cooking, drying clothes, breathing and so on). When this water laden air comes into contact with cold surfaces such as windows and cold walls it can condense, causing water to be deposited. The point at which the water held in the air changes from vapour to liquid is known as the 'dew point'.

Condensation is often associated with poor heating and ventilation in buildings, but that is not the whole story. Condensation is chiefly a winter problem, the external air temperature is low and external walls and windows are cold.

 Signs of condensation

• Running water on windows and walls is perhaps the most immediate indication of a condensation problem. If ignored this can lead to a deterioration in the decorative condition of the property, stained curtains and decay in window frames.

• The appearance of moulds on the surface of wallpapers and paints in poorly ventilated areas, such as behind bedroom furniture,

• Condensation can occur under suspended floors greatly increasing the chances of a fungal decay in floor timbers.

Landlords should ensure that their properties have adequate heating, insulation and means of ventilation to help prevent condensation.  If condensation occurs, it is important to establish what is causing it and then to advise the tenants of ways to prevent it reoccurring – for more information on how to deal with it, see the DASH leaflet - Condensation.

http://www.dashservices.org.uk/Media/Default/Docs/landlord%20library/Condensation.pdf

First published: December 2012

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