Dampness in a House or Building.
Dampness In A House Or Building
During a Building Survey or a Home Buyers Report (HBR), the surveyor will use a damp meter in random locations within the walls of the property to check for any dampness.
The cause of any dampness is usually fairly obvious, although not always so, surveyors are trained to “follow the trail” so can usually provide a detailed report on the cause. On occasion, a surveyor requests a Damp Report, it is to confirm that the cause is rising damp, to determine the extent of the problem, and to get an estimate for remedying it.
There are three types of Damp, Rising Damp, Penetrating Damp, and Condensation. All of these occur because of different factors, are usually commonly found in different locations within the property and there are different remedies in their control and repair, should they have caused damage to the property.
Rising Damp
The most common type of dampness is rising damp. Moisture from the ground rises, by capillary action, up the walls. The moisture often carries salts which are deposited on the face of the wall when the moisture evaporates. Internal decorations are stained and damaged, plaster can lose its bond and become loose. Rising damp only extends up to approx 1 metre above ground level, the capillary forces cannot lift the moisture any higher. In most cases and properties from 1880 onwards, walls are protected against rising damp by a damp proof course (DPC) built into the wall usually 150mm from external ground level. Very old properties do not have damp proof courses, and some old properties may have damp proof courses which have become ineffective. Sometimes the outside ground levels are raised above the damp proof course, this is called ‘bridging’.
The solution to rising damp is usually to inject a chemical damp proof course, and to re-plaster the internal walls with a waterproof layer up to 1.2 metres high. This work usually comes with a 10, 20 or sometimes even 30-year guarantee by experienced contractors.
Ground floor slabs are equally likely to be affected by rising dampness. It is only modern properties that have proper damp-proof membranes beneath the floor slabs. Older properties often relied on tile finishes to control dampness. If there is a damp problem with a ground floor it is either controlled with an impermeable covering such as vinyl sheet flooring, or the slab must be replaced with a new one incorporating a damp proof membrane.
Penetrating Damp
Penetrating damp is caused by moisture that penetrates through the roof or walls due to a defect that has arisen due to the breakdown of elements in the building. Roof problems are usually evident. Damp penetrating through walls, which includes flashings at roof and chimney abutments, is usually quite evident, but it is usually very difficult to pinpoint and cure the precise cause of the problem and very often there is no quick or easy solution. Penetrating damp can sometimes be caused by gutter or roof problems which allow rainwater to spill onto and saturate areas of walls or ceilings. If external walls are rendered, hairline cracks may have occurred, rainwater penetrates the render and tracts into the building where it emerges as a damp patch on a wall or ceiling.
Condensation
Condensation is the third type of damp. This is usually caused by the lifestyle of the occupants, rather than a defect with the property. Lack of ventilation and a tendency to use radiators for drying clothes are common causes. Opening windows and management of the internal moisture levels must be assessed.
A typical Damp Report will identify those (readily accessible) areas where damp is present and will identify the cause, along with recommendations for any necessary repairs or remedial works.
