A chemical course is a barrier injected into the mortar line. It is right when there is no working damp course, and wrong when there is one that has been buried.
Talk it throughRising Damp Newcastle arranges damp assessments across Newcastle and the Hunter.
A silicone or silane cream goes into holes drilled along a single mortar course near the base of the wall. It spreads through the pores and cures into a water-repellent band that capillary action cannot cross. Everything above it then dries downward, over months.
In a terrace the wall can usually only be drilled from one side. That means tighter hole spacing, more care about reaching the full thickness, and longer on site — which is why the per-metre range on our cost page runs higher than it would for a detached house. It is also why the neighbour needs to know before work starts rather than after.
If a path, a lane resurfacing or a garden bed has lifted the ground above the existing course, water is travelling over the top of a barrier that still works. A second course below the bridge changes nothing at all. Correcting the levels is the fix, and sometimes it is the whole job.
And if the wall is cracked in a stepped pattern through the joints, the question is not damp at all — see mine subsidence or damp.
Years of evaporation leave salt in the plaster, and salt draws moisture from the air by itself. A wall with a perfect new course and its original contaminated render will still read damp. Replastering is not an upsell — it is the half of the job that makes the other half hold.
These are the ranges we see quoted around Newcastle. They are wide on purpose. A single-skin cottage wall in Lambton and a double-brick party wall in Cooks Hill are the same line on this table and nowhere near the same job.
| Work | Indicative range | What it covers |
|---|---|---|
| Assessment and moisture survey | $250 - $450 | Readings taken at intervals up each affected wall, an external check of levels, lanes and downpipes, and a written finding. Where there is cracking it also says whether you should be calling Subsidence Advisory NSW instead. |
| Chemical damp-proof course, per metre | $170 - $330 | Injected into the mortar course. A shared terrace wall sits at the upper end because of access and because it can only be worked from one side. |
| Salt-retarding replaster, per square metre | $120 - $260 | Contaminated render off, breathable system on. Near the water this is rarely optional — the southerly loads the wall with salt from outside while the damp loads it from within. |
| Drainage and ground-level correction | $900 - $6,000 | Dropping a path, cutting a bed back, taking a downpipe away from the wall. On the terraces this often means the rear lane, where decades of resurfacing have raised the ground against the back wall. |
| Subfloor ventilation improvement | $1,200 - $4,500 | For the timber-floored cottages, where a closed subfloor holds moisture under the house. |
Prices are indicative ranges only. A terrace with a shared wall, a heritage-listed facade and an ordinary inter-war cottage all cost differently to treat, and every fixed price follows an on-site assessment.
We arrange assessments across Newcastle and the lower Hunter, including:
Rising Damp Newcastle