Solving Damp Problems
Damp. It's been the blight of many an old house, affecting not only its aesthetic appeal but also its structural integrity.

Tell-tale signs of dampness come in various forms. The most obvious is mould spots on walls and timber work. More advanced signs of dampness are blistered or stained paintwork and soft or crumbling plaster, brickwork or stone. Peeling wallpapers, rotting floorboards and visible salt deposits on wall surfaces are also indicators. There are four main types of damp.

Rising damp
Caused by ground moisture being absorbed into brick and masonry walls.

Horizontal penetrating damp
here rainwater seeps through defective brick walls or incomplete mortar joints.

Caused by inadequate ventilation or large variations between the internal and external temperature and humidity.

Falling damp
Resulting from defective roofing and plumbing equipment, such as leaking gutters, washings or pipes. Rising damp can be caused by a rise in the water table, the buildup of soil around external walls, a reduction in sub-floor ventilation or the coating of walls with a low permeability (for example, oil-based) paint. It is the most common type of damp and is also often the result of a defective or non-existent damp-proof course or bridging of the damp-proof course. The installation of a concrete slab in place of a timber floor can either cause or aggravate rising damp.

Introduced in the 1860's, damp-proof courses were originally formed by layers of slate in cement, or by layers of asphalt or bituminous felt. The usual location for them was a few inches (approximately 150mm) above ground level and below floor level. Today the most commonly used materials are bitumen-coated copper or aluminum, although heavy-duty polythene is sometimes used. Several solutions to treat rising damp are available but, first of all; don't assume that the problem is caused by a faulty damp-proof course.

  • Clear around and under the house. Remove any soil, rubbish or debris which impedes the flow of air or which bridges the damp-proof course, allowing moisture into upper walls. Cutting back or removing vegetation planted close to the walls will also allow damp to dry out.
  • Ensure that all water falls away from the walls and does not drain into the foundations. This may occur as a result of rainwater heads being too small or adjacent ground surfaces sloping towards the house walls. Installation of agricultural drainage lines, laid in gravel-filled trenches and connected to a suitable point of dispersion, may be a suitable remedy for this problem.
  • Check that the level of concrete paths directly against a wall is not above the level of the damp-proof course. If so, ground moisture may be penetrating through the concrete and back into the walls of the house.

For major cases of rising damp there are several effective treatments. However, appropriate conditions must be fully investigated before taking action.

For most effective solutions it is recommended that the problem is seen by a qualified personnel. A suitable solution should be recommended thereafter.

Refer to Ressichem Solution to Rising Dampness for further information.