Q : My brick house appears to have rising damp. The most affected area is the wall outside. A concrete path about one meter wide runs the entire length of the house – could the path be contributing to the damp problems?
A : Damp houses can be unhealthy and costly to remedy – knowing more about the issue can reduce the worry and expense. Most dampness problems can be cured or minimised by simple remedial work but a few will need substantial outlays, so it’s important to know what you’re dealing with.
Rising damp occurs at the bases of walls. Water accumulating there can “wick up” through bricks, blocks or stones and through the mortar in which they are laid. Damp-proof courses (DPC) are there to block this upward movement of moisture but they can sometimes be ineffective
The most common sign that we see of rising damp is a lifted surface finish. As a wall with rising damp dries, moisture will be drawn to the surface and find itself trapped beneath the wall lining and coating, resulting in staining, blistering of the wall coating and eventually crumbling of the wall lining. Another common indicator is efflorescence – salt crystalline formations on an external wall surface.
The causes of rising damp are various, but the problem is usually caused by a damp-proof course being disrupted, breached and failing.
The minor movements of all structures sometimes cause brittle DPC’s to crack thereby creating a path of wicking moisture. The slate and mortar DPC’s in older brick homes are most likely to suffer, but tar and sand DPC’s can also become brittle enough to crack.
A change to the conditions at the base of the wall is the most common reason for a building to develop a dampness problem. Raised garden beds or paving are a common cause of a DPC breach, particularly if the new surface level is above the line of the DPC. The best DPC in the world won’t work underground! Dampness caused by poorly-laid paths can be cured by rebuilding the path below the DPC and by sloping it away from the house or installing drainage grilles in the path nearest the wall and connecting to stormwater.
Blocked sub-floor vents are another common cause, preventing natural evaporation beneath a building – removing the obstruction will frequently fix the problem. Increasing the number of vents will further improve air circulation and assist the evaporation of wicking moisture.
Repair of leaking water pipes or drains will eliminate them as a cause of the problem, but remedying the damage will often require additional effort.
Where these remedies are ineffective or impossible it may be necessary to embark on a process or replacing the damp-proof course. There are variety of ways of doing this, with the most common being the insertion of a new membrane or the creation of a chemical damp-proof course.
In either case, expertise is everything. Contact us to know more.