There are three reasons why a property may be exhibiting signs of dampness to walls or floors:
- Rising damp
- Penetrating damp
In some cases a combination of factors could at the root of the problem.
A property may have been built without a Damp Proof Course (DPC) or the DPC may have broken down over time. It is also possible to ‘bridge’ a DPC, for example an external structure, such as steps or a flower bed, which joins the wall above the DPC allowing moisture access.
Rising damp soaks up from the ground through the porous building materials and makes its way through the pores of the material. The height the moisture travels will depend on the structure of the building materials, products with lots of fine pores will allow greater progression up the wall.
Generally rising damp would be noticed as tide marks, salts (often at the top of the tide mark known as a ‘salt belt’) lifting and damage to wall coverings and painted finishes. It is not usual for these signs to be noted above 1.2 metres.
Signs may also be visible in a solid concrete floor, where the floor covering has spoiled, wet rot to the skirting boards or gripper rods or in extreme cases water pooling on the surface.
The causes of penetrating damp vary from high external ground level and uncapped chimneys to cracked external render, poorly sealed windows, faulty rainwater goods and roofing. Also common is water tracking thorough points where external structures join the property, such as stone garden boundary walls.
Signs can be similar to rising damp, however they can occur at any height or location.
Commonly condensation is misdiagnosed as damp. Condensation is water vapour in the air, which is attracted to cold surfaces (usually external walls and windows) where it condenses to water.
The most obvious sign of condensation is Black Mould Growth. The black mould associated with condensation NEVER grows on areas with rising or penetrating damp, as it requires pure water. Water which has entered a building through the ground or walls contains hydroscopic salts or material from the building itself, which inhibits the black mould growth.
Furniture, clothes and soft furnishings will be constantly wet, black mould will develop and have a strong musty odour. If left untreated the building can be permanently damaged, with wet rot decay to timber and plasterwork will become perished, both will require replacement.
Many of the causes of condensation are lifestyle related. Drying washing indoors (especially on radiators) not opening windows frequently, using heating in hot blasts rather than consistently warm and the lack of suitable extractor fans in bathrooms and kitchens.
Remedially the installation of sub-floor vents, suitably powerful extractor fans which are humidistat controlled will help considerably.