What rising damp treatment actually costs in Australia

The per-linear-metre rate, and what it does and does not buy

A chemical damp-proof course is priced by the linear metre of wall treated. The published Australian band is $120 to $400 per linear metre, commonly $180 to $300. That band is wide because the work behind it genuinely varies, not because the trade is being coy.

What the rate covers is the injection itself: drilling holes of 10 to 15 mm diameter at roughly 120 mm centres — about eight holes per linear metre — to within about 30 mm of the far face of the wall, and introducing a silane or siloxane cream or fluid so that a continuous water-repellent zone forms through the full thickness of the masonry. On a 230 mm one-brick wall the header course is drilled by preference; where a stretcher course is drilled instead, the stretchers on the other side of the wall have to be treated too, either from the far face or by re-drilling through the same holes in a second phase. That single detail can double the hole count and the product volume on the same run of wall.

What the rate does not cover, unless a quote says in writing that it does: excavation or paving removal to reach the correct set-out height, render cut back where it is bridging the course, grouting of voids in thick or rubble walls before injection, desalination, removal of salt-contaminated render or plaster, replastering, redecoration, skirting replacement, and any internal work, which requires plaster to come off and go back.

A whole-house injection component commonly lands between $3,500 and $15,000 before any replastering. An 18 metre terrace perimeter commonly runs $4,000 to $8,000 for the injection alone. On most properly sequenced jobs the injection is not the largest number on the page.

Published rates, item by item

The table below is the whole job, not just our part of it. Items marked as ours are the two things S&S Remedial performs: a chemical damp-proof course injected into the mortar bed of external brickwork, and a Hydropoxy epoxy moisture barrier applied to the top of an internal concrete slab before new flooring. Everything else belongs to another trade, and the figure is here so you know roughly what you are looking at before you ring them.

What moves a job inside those ranges

Nine variables account for most of the spread. If a quote sits at an unexpected point in the band, one of these usually explains it, and a contractor should be able to say which.

• Wall thickness, and whether one face or both need treating. A 230 mm one-brick wall drilled on the stretcher course needs the far-side stretchers treated as well, which changes hole count, product volume and labour on the same run of wall.
• Hole count at correct spacing. Roughly 120 mm centres means about eight holes per linear metre. Wider spacing is cheaper to deliver and produces incomplete coverage.
• Material. Regular brickwork with continuous mortar joints is the straightforward case. Rubble stone can need enveloping patterns of holes above, below and beside each unit, and voids in thick or rubble walls swallow product and must be grouted before injection.
• Product. Active silane or siloxane content varies from roughly 15 per cent to roughly 80 per cent between certified products. The certificate for the specific product matters more than the word on the tin.
• Access. Internal work means plaster removal and reinstatement. Two-storey work means scaffold. Both are cost step-changes rather than increments.
• Wall condition. Very wet masonry limits diffusion, and crumbling mortar will not hold the treatment and needs repointing first — which then has to be allowed to cure, because extensive repointing can bridge the treated course and force re-treatment.
• Set-out height. The course must sit 150 to 250 mm above finished ground, with 200 mm the recommended target, and below all floor timbers. Where the ground or paving sits above that, the level work comes first and concrete cutting and disposal is the main cost step-change in it.
• Salt loading. Above about 0.5 per cent salt by weight, desalination enters the scope, and on a heavily loaded wall it can exceed the cost of the damp course.
• Location and occupancy. Regional and remote work carries a substantial premium, and an occupied house costs more to work in than an empty one.

Four things that turn a cheap quote into an expensive job

These are the four items most often absent from a low quote and most often present on the final invoice. None of them is a surprise to the trade. All of them are foreseeable at the point of diagnosis, which is exactly why the diagnosis should come before the price.

1. The wall needs both faces treated, not oneOn a 230 mm one-brick wall, the header course is drilled by preference. Where a stretcher course is drilled instead, the stretchers on the other side must also be treated — from the far face, or by re-drilling through the same holes in a second phase. A quote priced for one face on a wall that needs two is not cheaper; it is a different, smaller job that will not form a continuous barrier. If the second face is internal, plaster removal and reinstatement comes with it at $40 to $120 per m² to remove and $80 to $180 per m² to replaster.
2. The course has to be set out at the correct height, and getting there is excavationA remedial damp course belongs 150 to 250 mm above finished ground, 200 mm being the recommended target, and the NCC requires a damp course not less than 150 mm above adjacent ground level. Where soil, mulch, paving or a path sits above that line, the levels are corrected first: $500 to $6,000, with concrete cutting and disposal the main step-change inside that range. Render that is bridging the course has to be cut back and a clean drip formed. Neither of those is included in a per-linear-metre injection rate.
3. Salt above about 0.5 per cent by weight means desalinationA chemical damp course stops water rising past it and does nothing whatever about salt already in the wall above it. Those salts keep dissolving in humid weather and re-crystallising in dry weather, and each cycle breaks the masonry down further. Desalination runs $80 to $250 per m², often $2,000 to $10,000 per job, it is iterative — you re-sample and re-treat until salt drops below target — and it should begin before or alongside injection, because injecting a wall can displace saline moisture upward into masonry that was previously undamaged. It is the single line item most often missing from a cheap quote.
4. Making good usually costs more than the injection didRender removal at $40 to $120 per m², replastering at $80 to $180 per m² in a standard system or $200 to $400 per m² in heritage lime, redecoration at $40 to $90 per m², and skirting replacement at $40 to $90 per linear metre. On a wall stripped to 1.25 metres over a long perimeter, those four lines together routinely exceed the injection. And if the render or paint is pre-1990, asbestos and lead obligations apply before anything is disturbed, which changes the cost category rather than the cost.

Why a rate below the band is a warning, not a bargain

This is the part of the page that costs us money to publish, so it is worth being precise about the mechanism rather than gesturing at it.

Damp-coursing fluid and cream are expensive materials. That creates direct cost pressure on a contractor bidding low, and the Australian heritage guide names the two responses in print: diluting the fluid with extra solvent, or spacing the drill holes wider than recommended. Both produce incomplete coverage. A third mechanism is treating a wall from one side when it needs both. Good operators do the opposite — they deliberately over-apply to be certain of penetration, and that costs more per metre, not less.

What makes this different from ordinary corner-cutting is that the failure is invisible and delayed. The evidence is sealed inside a wall. Change in masonry is slow in both directions: in the standard worked example it takes about 31 days to reach 95 per cent of the steady height of rise, and that figure runs inversely with evaporation rate, so behind a coating or in a poorly ventilated space it can be years. A wall rendered to 1.25 metres takes roughly 425 days for the damp front to re-emerge above the render. A treatment that still looks fine at three months has proved nothing at all, and by the time an under-dosed course announces itself, two or three years of trading has happened.

So the useful response to a low number is not relief and it is not suspicion. It is six written questions, and any competent contractor can answer all of them in a paragraph.

The published Australian figures disagree by a factor of seven

Ranges published in Australia for the same chemical damp-proof course include $55 to $160, $70 to $350, $150 to $350 and $200 to $400 per linear metre. Two operators publish no rate at all and instead undertake to beat any written quote, which is price competition without price disclosure — and downward price pressure on this particular trade is the exact condition the heritage guide identifies as producing dilution and widened drill spacing.

A five-fold or seven-fold internal spread is not pricing transparency either. A range that wide, published without the scope beside it, tells a homeowner nothing they can act on.

The band we quote against is $120 to $400 per linear metre, commonly $180 to $300, and every figure on this page is scoped so it can be checked.

The cost of the things that are not a damp course

Most of what is presented as rising damp in South East Queensland is something else, and most of those something-elses are cheaper. This is the part of the market nobody quotes, because there is no product attached to it.

The comparison worth making is not between two damp course quotes. It is between the cheapest correct answer and the most expensive incorrect one.

Drying time is a cost, and it appears on nobody's quote

Cutting the source does not dry the wall. It stops the wall being resupplied. Everything already in the masonry then leaves by evaporation on the wall's schedule.

The working rule of thumb, from BRE Digest 163, is roughly one month of drying per 25 mm of wall thickness, which puts a 230 mm solid or double-brick wall at around nine months. The Australian heritage guide arrives at the same broad answer from a different direction: 3 to 6 months after replastering, or up to 12 months for wet thick walls. Treat the 25 mm rule as an order-of-magnitude expectation rather than a specification — it was framed around drying construction moisture, not a salt-loaded wall recovering from decades of rising damp.

The financial consequence is that making good is deferred, not cancelled. Replastering, repainting and skirting replacement — the $40 to $120, $80 to $180, $40 to $90 per square metre and $40 to $90 per linear metre lines — get spent months after the injection, sometimes in a different financial year, and they get spent twice if they are spent early. Repainting a wall that has not dried produces blistering that is close to guaranteed. Wallpaper should not go on for at least 12 months, longer on thick walls.

There are two further costs that never appear on a quotation. A room may be out of use, or half-finished, for the better part of a year. And a salt-contaminated wall may never read dry on a meter at all, because hygroscopic salts hold atmospheric moisture indefinitely — which is why acceptance has to be judged on gravimetric free-water content from drilled samples, and why that final round of testing belongs in the budget rather than in an argument.

A worked sum at the cheap end

The two sums that follow are arithmetic, not case studies. They are not jobs we have done and no property, owner or outcome is being described. Every unit rate is taken from the published bands in the table above, so the sums can be checked line by line.

The first is the common case: a 1970s brick veneer house, damp along one external wall to about 400 mm, a garden bed built up against that wall over the years, and a downpipe discharging beside it. Eleven metres of affected wall.

A worked sum at the expensive end

The second is the case the whole industry advertises and rarely sequences properly: a pre-1900 solid brick house with no damp course, 34 linear metres of affected external wall, salt analysis returning above the 0.5 per cent by weight threshold, and render drummy to about 1.25 metres internally — roughly 42 square metres of wall face to strip and reinstate.

Note the proportion. The chemical damp course, which is the only line on this list that is our work, is $8,160 of $41,340. That is just under a fifth of the job. A quote that consists only of that line, at a rate below the band, is not a cheaper version of this sum. It is a fifth of it.

What an independent inspection costs, and what it can save

An independent damp investigation with a written report runs $600 to $2,000, with laboratory analysis adding $400 to $1,500, typically $60 to $200 per sample set. A report at the bottom of that band, anywhere in this market, is usually a visual and meter survey with no drilled samples at all. Ask what testing the number buys before comparing it to anything.

What you are paying for is a specific comparison. Drilled samples are oven-dried to give total moisture content by dry weight, then re-equilibrated in a controlled 75 per cent relative humidity atmosphere to give hygroscopic moisture content — the water the salt in that sample will hold from the air alone. Total moisture minus hygroscopic moisture is free capillary water, and it is the shape of that profile, decreasing with height, that is the actual evidence for rising damp.

That subtraction is the whole economic argument for paying for the test. A wall with high hygroscopic moisture content and negligible free water is salt-contaminated with no live source. There is nothing rising. That wall needs desalination and replastering, and a damp course installed on it would be money spent on the wrong problem entirely. It is the difference between a $2,000 job and a $25,000 one, and no instrument held against the surface can tell you which of the two you are standing in front of.

One further condition, and it is the one that does the work: commission the assessment from someone who will not be performing the remedial treatment. The Australian heritage guide recommends independent advice explicitly, to avoid bias toward a particular commercial treatment. We sell chemical damp-proof courses. Read anything we conclude about your wall with that in mind, and check it against the citations.

The option with no invoice attached to it

There is a course of action that costs nothing in masonry work, and it is the one nobody quotes because there is nothing in it for the contractor.

Correct the prerequisites first — ground levels, garden beds, paving, falls, drainage, gutters, downpipes, flashings, plumbing leaks, condensate lines, wet-area membranes and subfloor ventilation. Those cost money to other trades, between $400 and $12,000 a line depending on which of them apply. Then monitor for at least twelve months before any damp course is considered.

Twelve months is the review stage built into the Australian heritage guide's own sequence, and it is there to absorb storms, floods, drought and seasonal humidity. A long dry spell looks exactly like a successful treatment. So does a wet season looking like a failed one. Twelve months of dated readings from recorded sample locations is the only thing that separates the two.

In a meaningful share of cases that stage removes the need for a five-figure treatment entirely, and the masonry line on the invoice stays at zero. Where it does not, you arrive at the damp course conversation with the prerequisites already corrected — which is the only condition under which a chemical damp course is a good buy at any price per metre.

What it costs

Questions we actually get asked

Why won't you give me a per-metre price over the phone?

Because the per-metre rate is the smallest decision on the job and the least useful thing to settle first. Before a rate means anything, four things have to be known: whether it is rising damp at all, which is settled by drilled samples rather than by description; whether one face or both faces of the wall need treating, which changes hole count and product volume; whether the ground levels allow the course to be set out 150 to 250 mm above finished ground or whether excavation comes first; and whether salt exceeds about 0.5 per cent by weight, which brings desalination at $80 to $250 per square metre into scope. A number quoted before those are known is a number that will change, and the direction it changes in is not usually downward.

Another contractor has quoted half your rate. What should I ask them?

Six things, in writing: hole diameter in millimetres, hole spacing centre to centre, drilled depth relative to the wall thickness, the product name with its active silane or siloxane content and certificate, the volume of product per linear metre against the manufacturer's stated rate, and which faces of the wall are being treated. A low rate is legitimate if it reflects a genuinely smaller scope — a thin single-skin wall, external face only, no excavation, no make-good — and that should be stated on the quote rather than discovered later. The three mechanisms that produce an artificially low rate are diluting the fluid with extra solvent, spacing the holes wider than about 120 mm, and treating one side of a wall that needs both. All three are invisible from outside the wall, which is why the questions have to be asked before the work rather than after it.

Should this be priced per square metre instead?

Not the damp course. A chemical damp-proof course is a single horizontal band of treatment through the wall, so it is correctly priced by the linear metre of wall, at $120 to $400 with about eight holes in each of those metres. Several other line items genuinely are area-based and should be quoted that way: desalination at $80 to $250 per square metre, render removal at $40 to $120, replastering at $80 to $180 or $200 to $400 for heritage lime, redecoration at $40 to $90, and a Hydropoxy barrier to an internal slab at $60 to $140 per square metre. If a quote prices the injection by the square metre, ask what area is being multiplied and by what, because the answer determines the total.

Can the work be staged so we spread the cost?

Yes, and on a correctly sequenced job it is staged anyway. The prerequisites come first — levels, drainage, gutters, plumbing, subfloor ventilation — at $400 to $12,000 a line depending on which apply, and those are the highest-return dollars on the whole job. Then twelve months of monitoring, which costs nothing in masonry work. Then, if drilled samples still show free water rising, the injection at $120 to $400 per linear metre. Then desalination and drying. Then making good, which cannot happen until the wall has dried — roughly nine months on a 230 mm wall — so it is deferred whether you want it staged or not. What cannot sensibly be staged is the diagnosis. Splitting that produces a scope built on partial evidence, and the cost of getting the scope wrong is larger than the cost of the testing.

Will insurance or a warranty cover any of this?

Rising damp is generally excluded from home insurance as gradual deterioration rather than a sudden event, and the answer for your policy is in its product disclosure statement rather than in anything we can tell you. Where a concealed plumbing leak turns out to be the actual cause, the leak and its damage may be treated differently to gradual damp, which is one more reason the diagnosis is worth doing properly before a claim is framed. Separately, building work in Queensland above a threshold commonly stated as $3,300 including materials and GST requires a licensed contractor and triggers the QBCC Home Warranty Scheme — confirm the current figure with the QBCC. A guarantee offered by a contractor is a contractual promise from that contractor, so read what voids it: blocked gutters and a garden bed rebuilt over the treated course are the two standard exclusions in this trade, and both are things that happen quietly over a few years.

How much of a typical total is actually your work?

On the expensive worked sum on this page, $8,160 of $41,340 — just under a fifth. On the cheap one, none of it. That proportion is the honest shape of this trade and it is why the diagnosis has to be independent of the treatment. We perform two things: a chemical damp-proof course injected into external brickwork, and a Hydropoxy epoxy moisture barrier applied to an internal slab before new flooring at $60 to $140 per square metre. The drainage, the ground levels, the gutters, the plumbing, the subfloor vents, the desalination, the render and the paint are other trades, and we will name who does what rather than mark it up.