Damp-proofing in Johannesburg
A damp patch on a wall is a symptom, and it has several possible causes: rising damp from the ground, water getting in from outside, a roof or gutter leak, or plain condensation. They need different trades, so the cause comes first.
Four kinds of damp, and why they are not the same
Rising damp comes up from the ground through a wall that has no working damp-proof course, or whose course has failed. It usually shows as a band of damp along the bottom of a wall, with a tide mark and often a powdery white salt deposit. External water is different: it gets in through a cracked render, a failed seal around a window, a leaking gutter or water that collects against the wall, and it usually appears after rain.
A roof or gutter leak can look like a wall problem from inside, because water travels. Condensation is the fourth kind: warm, moist air in a room meeting a cold wall, common in bathrooms and kitchens and in bedrooms where there is no ventilation. Each of those has a different fix, and a damp-proofing treatment applied to a condensation problem will not work.
Finding the cause before treating it
The first step is to rule out the cheap causes. Water against the outside of a wall, a leaking gutter, a broken downpipe or a roof leak above the damp patch should all be checked and fixed before anyone proposes a rising-damp treatment. A contractor who diagnoses rising damp without checking those is guessing.
Telling the causes apart is mostly about pattern and timing. Rising damp is persistent and worst at the lowest part of the wall. Water coming in from outside tracks a crack, a window or a gutter and follows the rain. Condensation appears in cold weather and in certain rooms, and it often comes with mould on the surface. A damp-proofing contractor deals with the first and can advise on the rest.
What a damp-proofing treatment involves
Where rising damp is confirmed, the usual remedy is a remedial damp-proof course: a barrier introduced into the base of the wall, most often by injecting a chemical damp-proof course through a series of holes drilled along the wall, or by a physical method in some walls. The wall is then re-plastered above the barrier with a salt-resistant render, because the old plaster holds salts that would otherwise keep drawing moisture.
The work has limits. It deals with rising damp; it does not stop water coming in from a leaking roof, a gutter or a cracked render, and it does not fix condensation. Older Johannesburg houses, many of them built in the middle of the last century, are the ones most likely to have a failed or missing course, but the diagnosis still has to be done house by house.
Keeping damp out afterwards
Once the treatment is done, the outside of the house matters. Making sure the ground outside is below the damp-proof level, keeping the gutters and downpipes clear, and sealing cracked render and window frames all stop water getting back in. So does ventilating the rooms where condensation forms, and heating them rather than closing them up.
Damp-proofing is priced by the length of wall treated and the access to it, which is often the biggest variable inside a house. A clear external wall is straightforward. Walls behind fitted cupboards, along a kitchen, or in a room that has to be kept usable add to the work. Ask the contractor what the price includes: the injection, the re-plastering, the making good, and the removal of waste.
What moves the quote
We do not publish prices. The contractor quotes you directly once they understand the job. These are the factors that usually make the difference:
- The length of wall that has to be treated.
- Whether the cause is confirmed rising damp, or water coming in from outside.
- The access to the wall, inside a house that is in use.
- The re-plastering and making good after the barrier is introduced.
- Whether more than one wall or room is affected.
- Whether condensation or ventilation also needs to be dealt with.
Our guide to what moves a waterproofing quote in Johannesburg explains how to compare quotes fairly.
Frequently asked questions
How do I know if it is rising damp or a leak?
Rising damp is persistent and worst low down, with a tide mark. A leak tracks rain and follows a crack, a window or a gutter. A contractor will check the outside of the wall and the roof above before deciding.
Can rising damp be cured permanently?
A correctly installed remedial damp-proof course deals with the rising damp in the wall, but the result also depends on keeping water out from outside. No one can promise a dry wall regardless of how the outside is maintained.
Is damp bad for my health?
Damp and mould can affect indoor air quality and are a known trigger for some respiratory problems. If you have damp in a bedroom or a living area, it is worth dealing with. This is general information, not medical advice.
Does damp-proofing work on a solid wall?
Older solid walls can be treated, but they need a diagnosis first and sometimes a different approach to a cavity wall. The contractor will explain what your wall needs after seeing it.
Who does damp-proofing in my suburb?
Send your suburb and where you are seeing the damp. We pass the enquiry to an independent contractor who covers your area and diagnoses the cause before treating it.
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