Adelaide bluestone, sandstone and early brick
Adelaide calls it salt damp, and it is the same mechanism as rising damp with a harsher ending. Groundwater climbs the base of a wall, the summer dries it out, and the salt it was carrying stays behind in the stone. We arrange an on-site assessment that tells you which of several problems you actually have, in writing, before anyone quotes a repair.
Six things Adelaide owners describe when they ring. Any one of them is worth metering; two together usually settle it.
Efflorescence. The salt the water carried up and left behind when it evaporated. Brushing it away treats the symptom and nothing else — it returns because the water still does.
On bluestone this is usually the first real sign. The salt crystallises inside the joint and pushes the lime mortar apart from within until it has no strength left.
Sandstone fretting. The face of the stone spalls away while the joints stand proud. It is slow, expensive and cannot be reversed, so it tells you the problem has been running for years.
Paint or plaster failing along a horizontal line, usually under a metre. Level is the giveaway — water from a leak runs down and makes a patch, not a straight edge.
Timber in contact with a wet wall. By the time a skirting is spongy the wall behind it has been wet for a long time.
Particularly a south-facing room in winter. Damp masonry smells before it looks like anything, and people usually notice it after being away for a week.
It is not that Adelaide is wet. The city records about 540.6mm of rain a year across 82.0 days — less than Hobart gets. What Adelaide has is the cycle: a wet, cool winter followed by a hot dry summer that pulls the moisture straight back out of the stone.
Each time that happens the water evaporates from the face of the wall and the salt it was carrying stays behind inside the masonry. Do that for a hundred summers and the crystals accumulate. Salt crystallising inside a joint or a pore exerts real pressure, and that pressure is what turns lime mortar to sand and takes the face off sandstone. The damage is done by the drying, not the wetting, which is why the same wall fails faster here than it would in a wetter, milder city.
| Month | Rainfall | 9am humidity | 3pm humidity | Mean max |
|---|---|---|---|---|
| January | 20.1 mm | 53% | 36% | 29.6 °C |
| February | 16.1 mm | 54% | 36% | 29.5 °C |
| March | 25.9 mm | 58% | 41% | 26.5 °C |
| April | 39.5 mm | 61% | 47% | 22.8 °C |
| May | 61.4 mm | 71% | 55% | 19.0 °C |
| June | 78.1 mm | 79% | 61% | 16.1 °C |
| July | 75.3 mm | 78% | 60% | 15.4 °C |
| August | 67.7 mm | 70% | 55% | 16.6 °C |
| September | 58.5 mm | 62% | 51% | 19.1 °C |
| October | 40.9 mm | 55% | 45% | 22.2 °C |
| November | 29.6 mm | 54% | 40% | 25.3 °C |
| December | 28.4 mm | 52% | 39% | 27.4 °C |
Source: Bureau of Meteorology, Adelaide (Kent Town), station 023090. Annual rainfall 540.6mm across 82.0 days of rain of 1mm or more.
Look at the February and June rows together. Rain falls almost entirely between May and September, then the 3pm humidity drops to 36 per cent with a mean maximum of 29.5 °C. That is the engine.
Every figure in that table is the Bureau of Meteorology thirty-year average for station 023090, not our estimate.
The material decides where the water travels, and therefore what the repair actually is. Adelaide has four broad groups.
The Adelaide signature. Bluestone is dense basalt and does not absorb much itself — the water travels up the wide, soft lime mortar joints between the stones. That is why a bluestone wall can look sound while the mortar between the courses has gone to sand, and why repointing it in hard cement makes the problem worse rather than better.
Often with red brick quoins at the corners and around openings. Sandstone is porous, so unlike bluestone it takes the water into the stone itself and fails at the face — the surface dishes, flakes and drops away while the mortar joints stand proud.
These generally do have a damp course, slate or bituminous felt. So the question here is not whether one exists but whether it has cracked, been bridged by a later path or garden bed, or been rendered over. Different question, different repair, usually cheaper.
A damp course exists and is rarely the fault. Damp at the base of one of these is almost always a bridged course, a failed shower or a leaking service — worth ruling out before anyone talks about injecting anything.
Rising damp, a bridged damp course, lateral damp off a slope, a plumbing leak and plain condensation all produce a wet wall, and in Adelaide reactive clay adds a sixth possibility — a damp course that was sound when it was laid and has since cracked as the ground moved beneath it. Those six have different repairs and wildly different prices.
An assessment that meters the wall at several heights, checks the ground levels against the internal floor and rules out plumbing costs you nothing here and produces a written answer. That document is what lets you judge a quote rather than trust one. It is also what stops you paying for a damp course when the actual problem is a garden bed.
Real ranges, published. Most trades will not put a number on a page, which is precisely why this one is here.
| Work | Indicative range | What it covers |
|---|---|---|
| On-site assessment and written diagnosis | Free | Arranged through us. You get the cause in writing before anyone quotes a repair. |
| Independent damp report for a purchase or dispute | $400 – $700 | A standalone technical report. Worth it inside a cooling-off period or where two parties disagree. |
| Correcting ground and paving levels | $900 – $3,500 | Cutting back paths, garden beds and paving that bridge the damp course. Frequently the whole fix, and always the first thing to check. |
| Chemical damp course injection | $180 – $260 per metre | Installing a new damp course into a wall that never had one, or replacing one that has failed. Bluestone costs more per metre than brick because the joints are wider. |
| Repointing in lime mortar | $120 – $220 per square metre | Raking out failed joints and repointing in a lime mix that lets the wall breathe. Cement pointing on old stone traps water and accelerates the damage. |
| Salt-retardant render and internal replaster | $90 – $180 per square metre | Removing salt-contaminated plaster and replacing it. Done too early it simply fails again, so it belongs at the end of the job, not the start. |
| Full treatment, typical bluestone cottage frontage | $6,000 – $18,000 | Injection, drainage and levels, repointing and replaster together. The range is wide because access and the amount of stone repair vary enormously. |
Prices are indicative ranges only. A fixed quote follows an on-site assessment.
Step 1
A short description and a photo or two of the worst wall. Most of the time that is enough for us to say whether an assessment is worth your time.
Step 2
About an hour. Moisture readings taken through the wall at several heights, inside and out, plus the ground levels, the drainage and any plumbing that runs nearby.
Step 3
Which mechanism is at work, how far it extends, and what is causing it. This is the document worth having — it is what lets you judge a quote instead of trusting one.
Step 4
Itemised, so you can see what is drainage, what is damp course, what is stone repair and what is finishing. You are free to take it elsewhere.
Step 5
Levels and drainage first, then the damp course, then stone and mortar, and plaster last. Out of order the finish fails and gets blamed on the treatment.
Step 6
Masonry takes months to give up its moisture, and salt keeps coming to the surface while it does. Replastering too early is the most common way a good repair looks bad.
The questions people ask before they spend anything.
The Adelaide word for it, what makes it different from plain rising damp, and why this city gets the worst of it.
Salt dampWhy the joints fail before the stone does, and why repointing in cement makes it worse.
Bluestone repointingWhen the face of the stone starts dishing and powdering away. The expensive failure.
Sandstone frettingInstalling a damp course into a wall that never had one, and what it costs in stone versus brick.
DPC injectionPaths and garden beds that bridge the damp course. Often the whole fix, and the cheapest one.
Damp proofingAdelaide soils move more than most, and that movement cracks damp courses that were perfectly good.
Clay and movementSemaphore, Glenelg and the Port, where the groundwater carries salt of its own.
Coastal stockThey look similar on a wall and the fixes have nothing in common.
Telling them apartWhat to check before you commit, and what a building report will and will not tell you.
Pre-purchase checksWhy black mould here is usually condensation rather than salt damp, and what to try before paying anyone.
Damp and mouldIt is the same mechanism with a local name and a nastier ending. Groundwater rises through the base of a wall by capillary action. What makes Adelaide different is what happens next: the summer drives the water back out of the stone and the dissolved salt stays behind. Over enough cycles the crystals do the damage, not the water.
Because we get the wet winter and the hard dry summer, and it is the cycling between them that concentrates the salt. Adelaide records about 540.6mm of rain a year across 82.0 days, with a 3pm humidity of 36 per cent in February. That is less rain than Hobart gets, and the damage here is worse. Wetter is not the same as damper.
Yes, and that is the usual pattern. Bluestone is dense and takes up very little water itself, so the moisture and the salt travel in the lime mortar joints instead. Check the joints, not the faces — if you can rake mortar out with a key, that is your answer.
No, and this is the single most expensive mistake made on Adelaide stone. Hard cement pointing does not stop the water; it stops the wall breathing, so the moisture leaves through the stone instead and takes the face of the stone with it. Lime mortar is softer than the stone on purpose — it is meant to be the part that fails.
Often not. If a path, a garden bed or later paving sits above the internal floor level, it bridges any damp course you install, and the new one fails the same way the old one did. Levels and drainage come first. Sometimes they are the whole job.
It does, and it is a genuine local factor. Adelaide soils shrink and swell more than most, and that movement cracks walls and breaks slate or bituminous damp courses that were perfectly good when they went in. On a 1920s brick bungalow a cracked damp course is a far more likely explanation than no damp course at all.
The treatment is quick; the drying is not. A solid masonry wall gives up moisture over months, and salt keeps migrating to the surface the whole time. Anyone offering to treat and replaster in the same week is setting the finish up to fail.
Rising Damp Adelaide is a lead referral service. We arrange assessments with independent, appropriately licensed damp specialists working across Adelaide. We do not carry out the work ourselves. Any specialist we refer you to holds the licences the work requires in South Australia.
The oldest stone stock sits in the inner ring and along the coast, and that is where most of the calls come from.
Tell us what the wall is doing. We will arrange someone to meter it and put the cause in writing.