Is rising damp a myth?

The myth argument, put at its strongest

The case is most associated with Jeff Howell — a bricklayer, lecturer and long-running newspaper columnist — who argued in The Rising Damp Myth (2008) that rising damp in buildings essentially does not exist. His central experiment is easy to picture and easy to repeat: build a brick pillar, stand it in a tray of water, and watch the water fail to climb. He argued that the pore spaces in bricks and blocks are too coarse for meaningful capillary action, contrasting them with the very fine vessels in a tree, and that cement-based and most lime-based mortars will not pass water at all. He reported managing to produce rising dampness only once, using a mortar so weak it would never be used in real construction.

That is the laboratory half. The commercial half is the one that did the real damage to this industry's credibility, and it is worth stating accurately rather than as a slogan. The complaint is not that a damp specialist will look at your wall for nothing — plenty of trades look for nothing and quote for nothing, and there is no scandal in it. It is that in too many of those visits nothing is actually diagnosed: a meter is waved at a skirting, a number is announced, a price follows, and nobody accounts for where the water is coming from. A verdict is not a diagnosis. The reasoning is the diagnosis.

The position gained genuine traction in Britain, and a former RICS chief has been quoted supporting the framing. It deserves to be answered on the evidence rather than waved away, so that is what the rest of this page does — starting with the parts where the critics are simply correct.

Five things the sceptics are right about

What follows concedes considerably more than anyone connected to this trade is supposed to concede. Each of these is either published, documented in a government technical guide, or a straightforward consequence of how the instruments work.

• The label goes on before the alternatives come off. Condensation, a bridged damp course, a leaking shower and a blocked downpipe all present as a damp band at the bottom of a wall. What separates them is reasoning about the building — levels, falls, discharge points, the shape of the stain — and that reasoning is frequently skipped.
• The instrument critique is correct on the physics, not merely on the ethics. A two-pin meter measures electrical conductivity between two pins. Soluble salts are electrolytes. A dry, salty wall reads higher than a wet, clean one, and the meter cannot separate them. That makes it one input alongside drainage and ground levels, not the case on its own.
• The lookalikes are at least as common as the real thing, and several are far cheaper to fix. Condensation, a bridged damp course, ground built up over the damp course, a blocked gutter or downpipe, a concealed plumbing leak, failed shower waterproofing and lateral damp from higher ground together account for a very large share of what gets presented as rising damp. Archicentre Australia's own technical sheet puts about 70% of mould problems down to condensation and about 30% to rising damp, and the three of them separate on sight.
• The treatment is frequently sold to people who did not need it — and where it does appear to have worked, the replastering that came with it may be doing whatever good is being observed, rather than the chemistry.
• Injection is routinely sold without any of the drainage and ground-level work that would have solved the problem for a fraction of the price. The Australian heritage guide sets out an explicit order of operations, puts damp-course insertion at step six of seven, and the industry sells step six to people who needed step two.

The instrument everyone argues about

Almost every damp inspection in Australia involves a two-pin electrical resistance moisture meter at some point. It passes a small current between two pins and reports the conductivity between them. It is calibrated for timber, where the relationship between moisture content and conductivity is well characterised. Masonry is not timber, and masonry carrying a century of accumulated salt is not remotely close. That does not make the instrument worthless. It makes it an instrument with a known bias, which is a different thing, and it is used the way a mechanic uses a torch: to find where to look.

The bias runs one way, which is worth knowing. Soluble salts are electrolytes. A wall that is bone dry but salt-loaded conducts as well as, or better than, a wall that is genuinely wet and clean, and the meter has no way to report which one it is looking at. The Australian heritage guide records that it is common on salty walls to get readings above 100% moisture content — a figure that leaves no room in the sample for the masonry itself. Foil-backed plasterboard, buried cables, pipes, nails, conductive paints and carbon in some finishes all produce the same false highs.

The guide's caution box states the limit without hedging: moisture meters should never be used as the sole basis for diagnosing a damp problem, and never used on their own to prove that a wall is unacceptably damp. That is not a blogger's opinion. It is Salt attack and rising damp, written by David Young OAM and published jointly by the Heritage Council of NSW, Heritage Victoria, the South Australian Department for Environment and Heritage and Adelaide City Council, at Section 11.2. It is a free download, and Australian damp contractors' websites almost never cite it.

So what carries the weight? The building does. The height of the damp and whether its top edge runs level. Where the salt band stops. The soil, turf and paving levels against the wall, and where the damp course sits relative to all three. Which way the ground falls, where the downpipes discharge, whether that garden bed is watered every evening. An experienced inspector reads those together, the way a doctor reads a patient rather than a thermometer, with the meter as one input among them. That is a real diagnosis, and it is what a licensed waterproofer do on the site visit.

What capillary rise is, and how well it is actually quantified

Rising damp is groundwater drawn upward through the connected pore network of brick, stone, mortar or render by capillary suction. It is the same effect that pulls a spill up a paper towel: the finer the pore, the stronger the pull. It needs three things at once — liquid water in contact with the base of the wall, a continuous capillary path upward, and evaporation from the wall face. Break any one of the three and it stops. That is the whole mechanism.

In 2007 Hall and Hoff published a sharp-front model of it in Proceedings of the Royal Society A, deriving the steady height of rise from properties you can measure in a laboratory: the sorptivity of the material, the thickness of the wall, the evaporation rate from its face and the water content of the wetted region. Three consequences fall straight out. Height rises in direct proportion to how absorbent the material is. It rises with the square root of wall thickness, not with thickness itself. And it rises inversely with the square root of the evaporation rate — reduce evaporation and the damp climbs.

Note what is absent from that list. The depth or pressure of groundwater below the wall barely matters. Neither, to any real degree, does gravity: the same authors computed cases with no-gravity steady heights of 500 mm and 1000 mm and found that including gravitational drainage reduced them to about 488 mm and 951 mm. That is a 2–5% correction. The common objection that water cannot climb that far against gravity has been calculated, and the answer is that gravity was never the limiting factor. Evaporation is.

The worked example in the paper is a 150 mm limestone wall with a sorptivity of 1.0 mm/min^0.5 and an evaporation rate of 0.001 mm/min. It predicts a steady height of 0.61 m — squarely inside the range surveyors have been observing on real buildings for decades. Double the wall to 300 mm and the height only moves to 0.87 m, because of the square-root scaling. Quarter the evaporation rate and it doubles to 1.2 m. The Australian heritage guide gives the normal exterior limit here as 1.0–1.5 m above ground, with the active evaporative zone typically 0.5–1.2 m and very little evaporation below 0.3 m. At the extreme, Massari and Massari recorded 5.3 m of rise in the Church of San Bernardo in Rome — because that wall is 4 m thick, which is exactly what the model says should happen.

One more figure is worth carrying around, because it explains the damage rather than the wetness. At steady state the wall is not a static wet object; it is a slow pump. The 150 mm example moves roughly 0.88 litres per day per metre of wall length — about 320 litres per year per metre. A 10 m run of affected wall is therefore transporting on the order of 3,000 litres a year, and every litre leaves its dissolved salt behind. On a coastline where the shallow groundwater is brackish and the air delivers chloride to the brickwork, that is a great deal of salt. That flux, not the dampness, is what destroys masonry.

Why the brick pillar in the tray of water does not climb

The pillar experiment is real, repeatable and genuinely awkward for the damp-proofing industry, which is presumably why that industry has never answered it in public. It has an answer, and it is in the same Royal Society paper, in a section written specifically to address it.

It is difficult to replicate rising damp in the laboratory, principally because it is difficult to produce a mortar sufficiently sorptive. Fresh mortars, and cement-containing mortars in particular, act as a barrier to rising damp rather than a conduit for it. Mamillan and Bouineau's limestone test walls make the point neatly: rise halted at the first mortar joint even though the properties of the stone itself predicted far greater height.

Old walls behave differently, and the difference is time. Mortars become more sorptive over decades of continuous water passage through them. Gummerson's work showed that steady capillary flow through a single clay brick led to complete saturation only after about two years, as trapped air slowly diffused out — which means short laboratory tests systematically underestimate both sorptivity and long-term water content in real walls.

So a test pillar built with new mortar failing to wick is not a disproof of rising damp. It is precisely what the theory predicts. It tells you nothing about a 120-year-old lime-mortared wall whose joints have been transmitting water for a century.

And it cuts both ways at least as often, which is the part nobody in this trade volunteers. A 2005 brick-veneer house, built on fresh cement mortar over an intact 0.5 mm polyethylene damp-proof course, is very close to being that pillar in the tray. On a twenty-year-old house with damp at the base of a wall, rising damp starts a long way down the list — with one large local exception, which is that the ground may not be where the builder left it. Turf, pavers, a new driveway and a raised garden bed have buried a great many perfectly good damp courses on this coast, and once the damp course is under the dirt the age of the house stops protecting it.

In 2022 the damp industry's own trade body signed the critique

In September 2022 the Royal Institution of Chartered Surveyors, Historic England and the Property Care Association jointly published a position statement titled Investigation of moisture and its effects on traditional buildings: Principles and competencies. It was supported by Cadw, Historic Environment Scotland, the SPAB and the IHBC. That is a surveying body, a heritage regulator and the damp-proofing industry's own trade association, signing the same document.

Its two central principles are the ones that matter to a homeowner. Traditional solid-walled buildings do not perform like modern ones and should not be expected to. And the observation of moisture in an old building should not automatically be treated as a problem requiring a fix.

Its limits are worth being straight about. It is a British document about British buildings. It has no standing in Queensland, it is not an Australian Standard, and it does not tell you anything about your wall. What makes it worth citing is who put their name to it. When the trade association for damp proofing co-signs a statement saying moisture in an old building is not automatically a defect, the diagnostic critique has stopped being a fringe complaint.

The half of the argument that does not survive the flight from Britain

The myth argument is a British argument grown in a British climate, and the climate is doing more work in it than anyone admits. The building tradition here is British; the weather is not. Hotter, drier conditions drive far higher evaporation, and higher evaporation means far higher moisture throughput through the same wall — more litres a year, more salt delivered, faster decay. Combine that with genuinely saline Australian soils and younger Australian buildings can be in worse condition than far older northern European ones. The national heritage guide's phrasing is that the result is much higher rates of decay in this country than in the UK.

Adelaide is the national worst case: hot drying summers, very salty soils, and a housing stock of solid stone and brick much of which never had a damp course. It has been serious enough for long enough that the South Australian government established a Salt Damp Research Committee, which ran from 1974 to 1982, after the volume of complaints to consumer affairs about failed damp treatments. That committee is evidence for both sides of this argument at once. The problem was real enough to need one. The treatments were bad enough to need one too.

South East Queensland is not Adelaide, and for a while that looked like a reason to be sceptical about local rising damp. It was the wrong conclusion. The Gold Coast and the coastal strip either side of it are close to purpose-built for capillary rise, and the reasons are mechanical rather than rhetorical. Much of the residential stock sits on low-lying canal and reclaimed land where the water table is shallow enough to be an ordinary fact of gardening. That groundwater is brackish, and the air off the sea deposits chloride into masonry whether or not anything is rising. Subtropical rainfall keeps the first metre of soil around a footing saturated for days at a stretch. And on top of all of it sits a large stock of older brickwork where the ground has been raised since the day it was built — turf, pavers, a shed slab, a driveway, a garden bed against the sunny wall — until the damp course is level with the dirt or under it. Rising damp here is common, not exotic, and there is no honest way to keep implying otherwise.

The humidity changes its character rather than its frequency. High ambient humidity suppresses evaporation from the wall face, and because the steady height of rise goes as one over the square root of the evaporation rate, that lowers the rate of decay — which is good — while raising the height the damp reaches. So the local picture is this: rising damp is common, it can sit higher on the wall than the textbook figure suggests, and it shares the ground floor with condensation, bridged damp courses and stormwater faults that look identical from the sofa. Which of them you have is the whole job.

Which is also why importing "it's all condensation" wholesale into an Australian context is its own diagnostic error, with its own victims. Treating the myth as settled means somebody with a genuine, progressive, structurally significant salt-damp problem gets told to open a window and comes back in ten years with 50 mm of mortar loss across five courses.

What a licensed waterproofer does, and what they will tell you for nothing

Here is the trade's actual scope, so everything above can be weighed against it. Where it turns out to be rising damp, the work belongs to a licensed waterproofer, and it is exactly two things. They inject a chemical damp-proof course into the mortar bed of external brickwork. And they grind back internal concrete slabs, prepare the surface and apply a Hydropoxy epoxy moisture barrier to the top of the slab before new flooring goes down. They are waterproofing and concrete repair specialists, not builders. They do not do landscaping, drainage, plumbing, subfloor ventilation, wet-area waterproofing, physical or saw-cut damp courses, undercutting, or render replacement.

The visit that works out which problem you have costs nothing, and it is worth stating what it consists of, so anyone can be held to the same standard. A competent contractor diagnoses by deep visual inspection of the wall and everything around it, an analysis of the drainage and ground conditions — falls, levels, paving and soil heights, where the stormwater actually discharges — and identification of the factors genuinely causing the damp, with a moisture meter used where it helps rather than as the verdict. That is the method, and it is the same reading of a building that produced correct diagnoses for decades before anybody owned a meter.

So where the honest answer is that a garden bed sits 200 mm above the damp course, there is nothing in it for anyone to sell. That is not altruism and it is not worth dressing up as any. It is that a job which was never going to work ends with an installer's name on a wall that is still wet, and the jobs that work are the ones that get talked about.

Even where it genuinely is rising damp, injection is not the whole scope, and the industry's silence on this point is the single most predictable cause of unhappy customers. A correctly installed chemical damp-proof course forms a continuous water-repellent zone that capillary moisture cannot climb past. It does nothing at all about salt already in the wall above it. Sodium chloride goes wet at around 75% relative humidity, which is an ordinary humid day on the Gold Coast. Calcium nitrate goes wet at roughly 47–55%. Magnesium chloride at about 33%, which is drier than an occupied Australian house realistically gets. Above about 0.5% salt by weight, desalination and replastering in lime is required as well — and that is masonry restoration work a licensed waterproofer does not carry out. They say so before the quote, not after it.

How to settle it on your own wall, in order

1. Go outside in heavy rain and watchFree, and it resolves more cases than any instrument. Watch the gutters, the rainwater heads, the downpipes, where the stormwater actually discharges, and which way the driveway and paths fall. Falling damp is worst high on the wall, which is the giveaway, and salt appears where water evaporates rather than where it got in — so trace it back deliberately.
2. Find the damp course, with a shovel if you have toThe NCC's Housing Provisions set a damp-proof course not less than 150 mm above adjacent ground level, 75 mm above finished paving that slopes away, and 50 mm where protected by a carport or verandah. The heritage guidance recommends 150–250 mm for a remedial course, with 200 mm as the ideal. Dig a small inspection pit and measure. A buried damp course is the most common genuine finding in Australian houses, and it is a bridging problem rather than a failed-barrier problem — which matters, because the cure is a shovel and not a syringe.
3. Pull the garden bed back and fix the fallsLeave a sterile strip against the wall at least 300 mm wide, preferably more than 500 mm, surfaced in coarse gravel so rain cannot splash up and soil moisture can still evaporate to the sky. Move sprinklers to drippers kept at least 500 mm off the wall. Grade the first metre to fall about 25 mm away, with the low point 1.5–2.0 m out; AS 2870 and the NCC require a minimum fall of 50 mm over the first metre for slabs. On highly or extremely reactive clay sites, get engineering input before making large changes to soil moisture near footings.
4. Rule condensation in or out with a data loggerA moisture meter cannot see dew point, so this is the one question it genuinely cannot answer. Log internal air temperature and relative humidity along with wall surface temperature for at least a full week including cold nights. If the surface repeatedly falls below the room's dew point, you have condensation, and no damp course on earth will change it. A fortnight to a month is more realistic than a week, and genuinely seasonal behaviour can need a year.
5. Get someone who reads walls for a living to look at the whole pictureThis is where an amateur diagnosis stops being useful and a specialist's starts. A competent site visit covers a deep visual inspection, an analysis of the drainage and ground conditions, and identification of what is actually driving the damp, with a meter used where it helps. Bring what you found in the first four steps — the pit depth, the downpipe photographs, the logger data. It makes the visit shorter and the answer better. And if you have a stormwater problem rather than a masonry problem, that is the answer you will get.
6. Sample the wall when the answer has to satisfy someone who is not in the roomMost jobs never need this. Where it earns its cost is a building dispute, an insurance claim, an expert-evidence matter, a contested pre-purchase, or a wall where two competent people have looked and disagreed. The reference method is a vertical profile of six to eight drilled samples per line, taken past the last visible sign of damp, at known heights and known depths — commonly 0–10, 10–20 and 20–40 mm — sealed immediately, weighed, oven-dried and reweighed for total moisture, then re-equilibrated at 75% relative humidity for hygroscopic moisture content. BS 6576 and BRE Digest 245 set out that approach; the shape of the gradient, with free water decreasing as you go up, is the laboratory evidence. Add salt speciation where salt attack is suspected — more than about 0.5% by weight is cause for concern. That is forensic laboratory work rather than a trade inspection, and a separate profession: an investigation-only consultancy investigate and report and carry out no rectification at all, which is exactly what makes their findings useful to a third party.
7. Then give the housekeeping a full year before anyone injects anythingThe Australian guide is explicit: do not undertake insertion of any form of damp-proof course until all the basic housekeeping measures have been completed and their effectiveness assessed over a period of at least a year. There is a physical reason as well as a commercial one. The time to reach 95% of the steady height is about 31 days in the standard example but is inversely proportional to evaporation rate, so behind a coating or in a poorly ventilated space it can be years. A wall judged cured at three months has proved nothing whatsoever, in either direction.

What it costs

Questions that actually get asked

So is rising damp real, or not?

Real, quantified, and on this coastline common. Capillary rise through porous masonry is standard transport physics — sorptivity, unsaturated capillary flow, the Buckingham-Richards equation — and the sharp-front model published in Proceedings of the Royal Society A in 2007 predicts real-world heights from measurable material properties, matching British survey observations and Italian field data including a 4 m thick Roman church wall showing 5.3 m of rise. What is not defensible is the opposite extreme: treating every damp band at a skirting as rising damp without excluding condensation, a bridged damp course, a leak or a downpipe, all of which look the same from the doorway. In modern housing with an intact damp course and ground levels still where the builder left them it is uncommon. In pre-damp-course masonry, and in the very large number of houses where the damp course has since been buried or bridged, it is common — and on low-lying coastal ground over a shallow, brackish water table it is ordinary.

Does it cost anything to find out?

No. A licensed waterproofer attends, and the visit is a genuine diagnosis rather than a sales call: a deep visual inspection, an analysis of drainage and ground conditions, and identification of the factors actually causing the damp, with a moisture meter used where it helps. If the finding is a downpipe, a garden bed, a shower or condensation, that is what you will be told, and there is nothing in it for them. Paid forensic investigation exists as well, but it is for the contested cases described above — disputes, insurers, expert evidence — and it belongs to a different profession from the people who do the repair.

Does rising damp go away or dry out on its own?

The water can stop arriving; the salt does not leave. If the source is removed — the ground lowered, the garden bed pulled back, the downpipe repaired — free capillary water in the wall will fall away over months. The Australian guide puts drying at 3–6 months after replastering, and up to 12 months for wet thick walls; the old BRE rule of thumb of roughly one month per 25 mm of thickness puts a 230 mm solid wall at around nine months. But the salt delivered over decades stays in the pores, and hygroscopic salts pull moisture straight back out of the air. That is why a wall with no live source at all can still read damp on a meter, and why the honest test of success is whether the damp band recedes and stays receded through a wet season, not whether a meter goes quiet.

Is rising damp a structural defect, or just cosmetic?

It can become structural, but slowly, and the timing is counter-intuitive. Salt-attack decay follows an accelerating curve rather than a straight line: salts accumulate for decades filling the pore space with almost no visible damage, and then deterioration speeds up sharply. The Australian guide's notional curve shows around 80 years of near-nothing followed by rapid acceleration, so a building that has looked much the same for a century may be twice as damaged after another ten years. Mortar loss of around 50 mm across five to ten courses puts you at risk of local collapse of the brickwork, and that is a now problem. What it is not, at any stage, is an emergency in the sense the advertising implies. This process is measured in decades.

Is rising damp common in Queensland houses?

On the Gold Coast and the coastal strip, yes — common rather than exotic, which is worth saying plainly rather than recycling a British generalisation. The drivers are local and checkable. Much of the canal and reclaimed stock sits over a shallow water table. That groundwater is brackish, and marine aerosol drives chloride into masonry regardless of what else is happening. Subtropical rainfall keeps the soil around footings saturated for days at a time. And a great deal of older brickwork has had its damp course buried under decades of turf, pavers, driveways and garden beds. Some of the housing stock genuinely does work against it — high-set timber on stumps has no continuous capillary path from ground to wall, and brick veneer and slab-on-ground from the 1960s onward generally has an intact polyethylene damp-proof course — which is why the answer is a diagnosis and not a postcode.

My building and pest report says "high moisture readings consistent with rising damp". Is that a diagnosis?

No, and a competent inspector would not claim it is. A pre-purchase inspection is carried out under AS 4349.1 and is not a damp investigation; it is a visual inspection with a hand-held meter, done to a tight time budget, and the phrase "consistent with" is doing a great deal of work. For a normal purchase, get a specialist to read the wall, the ground levels and the drainage before you accept anybody's treatment quote — that costs nothing and usually settles it. Where the sale is genuinely contested, and the finding is being argued about or used to move the price, that is one of the few situations where a paid forensic investigation earns its place, and it should come from a firm that investigates and does not rectify, such as an investigation-only consultancy. That kind of investigation can be commissioned as an inspection of particular technical aspects under AS 4349.0, which gives it a defined scope and reporting framework.

If it is common here, why do contractors keep telling people it is not rising damp?

Because common is not the same as automatic, and several of the alternatives are far cheaper. Plenty of damp problems are better solved by a plumber, a landscaper, a gutter contractor, a licensed waterproofer or a $40 spirit level, and it costs nothing to say so — none of those is a job a waterproofer does, so there is no version of that conversation where the trade loses work by being straight. The real cases tend to be walls where the ground levels have been corrected, the stormwater has been fixed, the salt is genuinely in the masonry and the damp is still there. That is the job a chemical damp-proof course is for. Doing the other ones badly is how this industry earned its reputation, and it is a reputation the whole trade has to live inside.

Can rising damp be fixed?

Where it is genuinely present, yes — with conditions worth being clear about. Removing the source comes first, and in a substantial proportion of Australian cases source control alone resolves it. Where a barrier is genuinely needed, a correctly installed chemical damp-proof course forms a continuous water-repellent zone that capillary moisture cannot climb past. But it does not remove salt already in the wall, it does not resist water under pressure, and it does not dry the wall for you. Where salt exceeds about 0.5% by weight, desalination and lime replastering has to happen too, or the masonry keeps decaying above a technically successful damp course — which is exactly the outcome documented in the Australian guide.