A chemical damp course is a barrier injected into the mortar line. It is the right fix when there is no working damp course — and the wrong one when the problem is a buried one.
Talk it throughRising Damp Perth arranges damp assessments across Perth metropolitan area.
A silicone or silane cream is injected into holes drilled along a mortar course. It spreads through the pores and cures into a water-repellent band the moisture cannot cross. The wall above it then dries downward over months.
Perth's limestone is more porous and less uniform than fired brick, so achieving a continuous barrier generally takes more material and more care with hole spacing. That is why limestone sits at the upper end of the per-metre range rather than a quote being padded.
If paving or a garden bed has buried the existing damp course, the water is going over the top of it. Injecting a second course below the bridge changes nothing. The levels get corrected first, and sometimes that is the entire job.
Years of evaporation leave salt in the plaster. Salt draws moisture from the air on its own, so a wall with a perfect new damp course and its original contaminated render will still look damp. Replastering with a salt-retarding system is not an upsell; it is the half of the job that makes the other half hold.
What follows is indicative. Every one of these is a range because the wall decides, not the website.
| Work | Indicative range | What it covers |
|---|---|---|
| Assessment and moisture survey | $250 - $450 | Moisture readings across the affected walls, a look at ground levels and drainage, and a written finding on which of the four common causes you actually have. |
| Chemical damp-proof course, per metre | $180 - $340 | Injected into the mortar course. Limestone generally sits at the upper end because it takes more material to achieve a continuous barrier. |
| Salt-retarding replaster, per square metre | $120 - $260 | Old contaminated render off, breathable system on. Frequently the larger part of the job. |
| Drainage and ground-level correction | $900 - $6,000 | Lowering paving, cutting back garden beds, adding a drain. Where the cause is bridging rather than a failed damp course, this is the fix. |
| Subfloor ventilation improvement | $1,200 - $4,500 | Less common in Perth than Brisbane because fewer homes have a ventilated subfloor, but it applies to the older timber-floored stock. |
Prices are indicative ranges only. Limestone, double brick and rendered walls each cost differently to treat, and every fixed price follows an on-site assessment.
We arrange assessments across the Perth metropolitan area, including:
Rising Damp Perth