Rising damp is groundwater climbing a wall. Everything else — the salt, the lifting paint, the smell — follows from that one fact.
Talk it throughRising Damp Perth assesses and treats damp across the Perth metropolitan area.
Perth's older suburbs are largely built from what was quarried out of the ground beneath them. Limestone cut from local quarries went into Fremantle, Cottesloe and Claremont; double brick took over from about the 1900s. Both are porous, both sit on sand, and an older wall may have been laid with no damp-proof course.
What has changed most recently is not the ground — it is what has been built on it. Across the older suburbs, back gardens have been subdivided, second dwellings put up behind existing homes, and driveways run down the side of houses that never had one. Each of those can raise or re-level the ground against a wall, and paving laid above the old damp course bridges it completely. So when damp appears on a wall that coped for decades, the first question is what has been built against it.
Sand drains beautifully until it does not. In a Perth winter the ground under the lower river and coastal streets can stay wet for months, and a wall standing in damp sand behaves like a wick. How close the water table sits under one address is a question for the WA Government's Perth Groundwater Map, not for a suburb name. The moisture climbs until the rate it evaporates from the wall face matches the rate it arrives, which is what sets the height of the tide-mark.
Salt is the second half of it. Groundwater carries dissolved salts up into the wall and leaves them behind when the water evaporates. On the coast, more salt arrives on the wind. Those crystals expand as they form, and that is what blows render off limestone and crumbles the face of a brick — the water moves it, but the salt does the damage.
Perth gets about 727mm of rain a year on about 78 days of 1mm or more, and three quarters of it falls between May and September. That concentration is the whole problem. A wall spends the wet months taking up groundwater faster than it can release it, then the rest of the year drying out — so the damage builds every winter and appears to heal every summer. Where an affected wall has been painted over, the paint can look blistered or bubbled rather than stained, because the moisture pushes the new coat back off.
An even horizontal line, roughly 600mm to 1.2m above the floor, on a ground-floor wall. It marks where the water stops climbing and starts evaporating. Condensation does not produce a level line like this.
Salts left behind as the water evaporates. On limestone it often looks like a fine bloom; on brick it can be gritty. Brushing it off works until the next winter.
Usually a sign of a non-breathable coating applied over a wall that needs to dry outward. The coating is not failing — it is doing its job and trapping the moisture behind it.
Salt crystallisation forcing the surface apart. It is usually well advanced before anyone calls it damp.
Bore water. Perth's reticulation draws iron-rich groundwater, and where it hits a wall the iron stains it. It is not rising damp, it is cosmetic, and it is worth knowing before you pay to treat the wrong thing.
A smell that comes back each winter points to a seasonal source, such as ground water or condensation, rather than a leak that runs all year.
The order matters. Injecting a damp course into a wall whose real problem is a paved garden bed is money spent on the wrong thing, which is why the assessment comes first and the quote comes after.
Moisture meter readings at height intervals up the wall, an external check of ground levels, paving and reticulation, and a look at what coatings are already on the wall.
Rising damp, lateral damp through a retaining or buried wall, a plumbing or reticulation leak, condensation, or bore-water staining. They look alike and cost very differently.
If paving has buried the damp course or a garden bed sits against the wall, that is corrected before any chemical course is considered. Injecting around a bridge does nothing.
A chemical course injected into the mortar line, sized to the wall material.
Contaminated render removed and replaced with a salt-retarding, breathable system. Skipping this is why treated walls come back.
A treated wall dries over months, not days. Anyone promising a finished wall in a fortnight is telling you what you want to hear.
We carry out assessments across the Perth metropolitan area, including:
Rising Damp Perth