It's an old adage, but the key to a good property is a watertight roof and secure foundations. And the reason is simple because dampness is at the heart of all building materials' decay.
Masonry staining and plant growth indicate serious damp problems
Dampness in buildings falls into three categories. Firstly, and most importantly, rain penetration which results most commonly from roofing failures (such as broken tiles or slates), defective flashings (around chimney stacks for instance), leaking rainwater disposal systems and defects in masonry such as bad pointing. The older the property, of course, the greater is the likelihood of building materials beginning to fail as they reach the end of their natural life.
Roofing and guttering are in general terms the major weak points and failures here are the most damaging as they allow water to spread over large areas before being discovered. Quite apart from the problems of direct water penetration, the resulting dampness will lead eventually to timber decay as this, combined with lack of ventilation, provides the ideal conditions for wet rot, and more seriously dry rot, to flourish. Decay will occur in roofing timbers particularly wall plates and beam ends embedded in masonry walls.
The second cause, rising damp is more of an issue with pre-war property and can arise for various reasons - the failure of an existing dpc (damp proof course), bridging due to the raising of external ground level (e.g. by a path or patio) or, rarely these days, the complete absence of a dpc.
Most bricks, building stone and mortar are porous, allowing damp from the ground to rise by capillary action. This carries with it ground salts including hygroscopic chlorides and nitrates which absorb moisture from the atmosphere and can lead to plasterwork damage and ruin of decorations.
Where necessary remedial damp proof courses can be installed, generally using a silicone based formulation into the masonry to form a water resistant barrier. However, this must be accompanied by the repair of all the other defects giving rise to dampness.
Thirdly, condensation is probably the most common form of dampness although it is frequently not immediately visible. It's a modern issue, however, and largely the consequence of today's improved standards of insulation and draught proofing, particularly where older properties have been upgraded. Lack of adequate ventilation allied to modern occupancy lifestyles - cooking, washing and bathing - can lead to excessive humidity and moisture. This leads to condensation forming on cooler surfaces which can result in peeling decorations, unhealthy living conditions and unsightly mould growth. |
