Why does damp occur in buildings and how can it be prevented and treated? Phil Llewellyn, chairman of the Damp-proofing and Waterproofing Association of Southern Africa, gives advice.

Damp in buildings is not only unsightly, but it threatens the structural integrity of the building as well as the health and wellbeing of occupants.

According to Phil Llewellyn, chairman of the Damp-proofing and Waterproofing Association of Southern Africa (DWASA), damp problems typically occur when building specifications aren’t properly adhered to.

“In my experience, modern builders add to the problems of damp in new buildings by failing to adhere to proper building practices, which require a V-joint to be cut in the plaster at the height of the damp-proof course,” he states.

This results in moisture rising above the height of the damp-proof course, bypassing it and then not only causing severe damage to the plaster on the exterior surface, but transferring moisture to the inner surface of the wall and causing damp there. “That is 90% of all rising damp problems in South Africa today,” he says.

“Most buildings these days are fitted with damp-proof course plastic sheeting beneath the floor slab and in the brickwork of the walls. Damp-proof course sheeting in the brickwork is specified to exit the brickwork a minimum of two brick courses above the finished ground level.

“But if plaster is applied onto the brickwork at 25mm thick, all the way down to the ground level, it creates a channel for moisture to rise in the plaster through capillary action. If there is no V-joint cut into the plaster, the moisture bypasses the damp-proof course and affects the areas above and laterally,” he explains.

Stick to the specification
According to Llewellyn, this might be due to people either being unaware of building standards or just blatantly ignoring them. “Architects are very good at drawing up specifications in accordance with national building regulations, but it is the transference of that specification, knowledge and skill at the contractor level that I think is the biggest problem,” he adds.

“If the architects, developers and contractors build to specification, there should not be an issue. It is only when the specifications are not properly adhered to that you get problems.”

Full thanks and acknowledgement are given to DWASA for the information given to write this article.

Dealing with damp DWASA1

Caption (Main Image at top):
The absence of a damp proof course in in the brickwork of walls can lead to severe damage.
Courtesy of DWASA