The inspection — what it looks at, and what it can prove

Who is advising you, and what do they sell?

The Australian heritage guide Salt attack and rising damp — published jointly by the Heritage Council of NSW, Heritage Victoria, the South Australian Department for Environment and Heritage and Adelaide City Council — puts it plainly in its list of things to do: get independent advice, so there is no pressure to use a particular product or system. That is worth taking seriously. A contractor with exactly one product in the van has an obvious reason to keep finding the problem that product solves.

Surveying practice in the United Kingdom requires that conflict to be declared where a surveyor's recommendations may include sales. Australian damp contractors do not generally declare it anywhere on their websites. It is worth asking who is advising, and what they sell, before the reading starts.

What keeps a site visit honest is the size of the box it can sell out of. A licensed waterproofer do two things. Everything else that causes damp — drainage, landscaping, plumbing, subfloor ventilation, wet-area waterproofing, render and desalination — is somebody else's trade and somebody else's invoice, and a diagnosis that lands there earns them nothing. The findings are yours either way, and you can walk them down the road to whoever you like.

The test of any inspection, paid or not, is whether it shows its working: what was ruled out, on what evidence, and what would change the answer. A diagnosis that names only the thing being sold has not been shown its working. Ask for the reasoning before you ask for the price.

What an experienced eye reads on the wall

Rising damp has a shape. Moisture is highest at the base of the wall and falls away as you go up, because the wall is behaving as a slow pump and the top of the wetted zone is simply where inflow and evaporation balance. That shape — where the damp stops, whether the line is roughly level, whether it follows the mortar courses, whether inside and outside agree — carries more information than any single number taken at skirting height.

In Australia the external limit of genuine rising damp usually sits between 1.0 and 1.5 metres, with the most active evaporation zone between about 0.5 and 1.2 metres and little evaporation below 0.3 metres. Damp that stops in a level line at 900 mm, runs the length of a wall and dries out above it is behaving like groundwater. Damp that is highest at 1.8 metres, or worst around one window, or confined to a single square metre of a long wall, is not — and is telling you the water is arriving from somewhere other than the ground.

1. Levels firstWhere the ground, the paving, the patio and the garden beds sit relative to the damp-proof course, and whether a damp course can be found at all. On a Gold Coast brick house this is regularly the most productive ten minutes of the visit.
2. The height and the line of the dampRead inside and out at the same points. A wall wet from the ground, a wall wet from a leak on the other side and a wall wet from condensation do not produce the same picture on both faces, and comparing the two faces is free.
3. Where the salt is sittingA band of bloom at the top of the damp is a classic evaporation-front signature. Salt scattered around a downpipe, under a window or across one patch of wall is not. Fretting bricks and powdery mortar say how long it has been running.
4. Where the water goes when it rainsGutters, downpipes, rainwater heads and their discharge points, surface fall away from the building, air-conditioner condensate lines, irrigation, and the water meter watched for movement with everything inside turned off.
5. The meter, used as a mapOn one wall, with one instrument, in one session, it shows relative variation faster than anything else on site and points at the parts worth arguing about. It measures conductivity rather than water, so it narrows the search rather than settling it. The next section is why.
6. Where the answer is genuinely contestedWhere competent people disagree about a wall, or the finding has to satisfy an insurer, a tribunal or a buyer walking away from a contract, drilled samples and laboratory analysis are the escalation. That is a separate paid investigation, and it is set out below.

Total moisture, and the part of it that is only salt

This section is reference rather than a description of the site visit. It is what a full laboratory investigation involves, so that you can recognise one when it is offered to you, and judge when it is worth paying for.

In a laboratory investigation each drilled sample is weighed, oven-dried to constant mass and weighed again. The mass lost is water, and expressed against the dry weight it gives true moisture content. That figure is better evidence than any surface instrument produces, and on its own it still cannot tell you whether you have rising damp.

The reason is that not all of the water in a salty wall came up from the ground. Hygroscopic salts pull water vapour straight out of the air. Sodium chloride dissolves into liquid at about 75% relative humidity. Sodium nitrate goes wet in the low-to-mid 70s. Calcium nitrate goes at roughly 47 to 55%, magnesium chloride at around 33%, calcium chloride at 29 to 32%. Mixtures go wet earlier than either salt alone. In humid subtropical south-east Queensland, a chloride-loaded wall spends much of the year above its critical humidity with no liquid water source anywhere near it.

So the oven-dried samples are equilibrated in a controlled 75% relative humidity atmosphere and reweighed. The mass they take back on is the hygroscopic moisture content: the water the salt in that sample will hold out of the air by itself. Subtract it from total moisture content and what remains is free capillary water — the water that is genuinely rising.

This comparison is what BRE Digest 245 is built on, and it is the only method that cleanly separates moisture due to rising damp from moisture held by hygroscopic salt. It is also several days of laboratory work, and most damp jobs are settled long before anyone needs it. An inspector looking at a garden bed sitting 200 mm over the damp course, with a downpipe discharging into it, does not need an oven to tell you what to fix first. Where the laboratory earns its money is the contested case: a building dispute, an insurance claim, expert evidence, or a purchase you are about to walk away from. That is investigation work rather than remedial work, and it is what a forensic consultancy such as an investigation-only consultancy exists to do — they investigate and carry out no rectification at all, which is precisely the point of commissioning them. Such consultancies set their own fees, and no number for that work is published here.

Which salts, and how much of them

Salts are not interchangeable. The species points at the source, and the quantity decides whether anything needs to be done about them at all. On site, the position and pattern of the bloom is the first clue. Species is a laboratory answer, and worth buying when the source is disputed rather than obvious.

• On this coast chloride is the default assumption rather than a surprise — sea spray and saline groundwater load masonry with it without any help from a leak
• More than about 0.5% salt by weight is cause for concern and reason to consider desalination — that threshold is a laboratory figure, not something a meter can give you
• Below that, with free water accounted for, the honest recommendation is often to leave the wall alone and watch it through a wet season
• Where full ion chromatography is not warranted, total dissolved solids by conductivity on a crushed, weighed sample plus sulfate and nitrate test strips gives enough to manage the work
• Salts are distributed unevenly, so a single sample can mislead — any result you are shown should state the height and depth it came from, and which method produced it

Why the meter reads high on a wall that is bone dry

A two-pin electrical resistance meter measures the conductivity between its pins. It does not measure water. It is calibrated for timber, where the relationship between conductivity and moisture content is well characterised, and it is still read against that timber scale when it is pressed into a brick wall.

Soluble salts are electrolytes. A dry, salt-loaded wall conducts as well as or better than a wet, salt-free one, and the instrument cannot separate them. This is not a contested position. The Australian heritage guide carries a formal caution that moisture meters should never be used as the sole basis for diagnosing a damp problem, and never on their own to prove that a wall is unacceptably damp.

The clearest tell is the number itself. On salty walls it is common to record readings above 100% moisture content. Moisture content is expressed against the dry weight of the material, so a reading above 100% describes a wall holding more water than masonry — a figure that leaves no room for the bricks. It is an artefact of conductivity, and it is not something to build a scope of works on.

Foil-backed plasterboard, buried cables, water pipes, nails, wall ties, conductive paints and carbon black in some finishes all produce the same false highs.

None of which makes the meter a toy, and it is why one still comes along. On one wall, with one instrument, in one session, it maps relative variation quickly and shows the inspection where to concentrate. That is a real job and it does it well. It is simply one input alongside ground levels, drainage and the shape of the damp — which is exactly what the heritage guide says it should be.

The half of the inspection that happens outside

The most common cause of genuine rising damp in Australian houses is not a failed damp course. It is a damp course that has been buried. Soil creeps up as mulch is added, a path is poured over the old one, a patio is laid at door height, and the barrier ends up below ground where it can do nothing at all. This is why the tape measure comes out before the meter does.

It is also why this site is regional rather than national. Along the Gold Coast and the coastal strip either side of it, the ground conditions do half the work: shallow water tables through the low-lying canal and reclaimed estates, saline groundwater and marine aerosol loading masonry with chloride, subtropical rainfall that arrives in quantity, and a large stock of mid-century brickwork that has since acquired a concrete path, a raised garden and thirty years of mulch. Put those together and rising damp here is an ordinary finding rather than an exotic one. What varies from house to house is which of them is driving your wall, and that is the thing worth establishing before anyone quotes.

Where the damp course cannot be found at all, that is a finding in itself. On much older or heavily altered brickwork there may never have been one, or the render may have been carried straight down over it and across the gap it was meant to keep open.

• For a remedial damp course the heritage guide recommends 150 to 250 mm above finished ground, with 200 mm as the ideal, because the clearance has to survive future gardening
• Ground should fall roughly 50 mm over the first metre away from the building, with the low point 1.5 to 2.0 metres out
• Any sterile zone against the wall should be at least 300 mm wide, preferably more than 500 mm, surfaced in coarse gravel so rain does not splash up and soil moisture can still evaporate away
• Sprinklers replaced with drippers kept at least 500 mm off the wall, and garden beds noted where they are delivering nitrate straight into the masonry
• Gutters, downpipes, rainwater heads, flashings and their discharge points, plus the water meter isolated and watched for movement, and air-conditioner condensate lines traced

Under the floor and inside the cavity

A bridged cavity is regularly mistaken for rising damp, and the two are not treated the same way at all. Mortar droppings sitting on wall ties, a cavity base full of the same, missing or torn cavity flashing, weepholes blocked or rendered over, standing water at the cavity base. The giveaway is usually height and pattern: damp from a bridged cavity is frequently higher than the damp course and often patchy rather than continuous, and a chemical damp course does nothing whatsoever for it. Weepholes get looked at first, because they are the one part of a cavity visible from the garden.

Under a suspended floor the inspection takes in ground clearance, debris, grading and the state of the vents. The Housing Provisions set minimum aggregate subfloor ventilation openings by climate zone — of the order of 2,000, 4,000 and 6,000 square millimetres per metre of wall for zones A, B and C without a ground membrane, roughly halved where an impervious ground membrane is installed — with openings evenly spaced, within about 600 mm of corners, and no dead air pockets. Ground clearance is commonly 150 mm, or 400 mm where termite inspection access is required.

There is a genuine tension here that gets glossed over in sales copy. More ventilation lowers the height of rise, because it raises evaporation from the wall face. It also increases the rate at which salt crystallises inside the masonry, which is what actually breaks bricks and mortar down. The target is adequate ventilation, not maximum ventilation.

The subfloor is also where a treatment can do harm. Work at the base of a wall sits directly alongside bearers, joists and floor timbers, so what is happening under the floor belongs in the diagnosis rather than being discovered halfway through the job.

What you should be told — and what to ask for

Whether the diagnosis arrives as a written report or as a conversation on the day with photographs behind it, the content is the part that matters. This is the checklist to hold it against, and the list of things to ask for if they are not offered.

• Where the ground, paving and garden bed levels sit relative to the damp-proof course, in millimetres rather than adjectives
• Where the damp course is, what type it is, what condition it is in, and whether it is intact and merely bridged
• What was found on drainage, stormwater and plumbing — including which exclusion checks were not possible on the day
• What the cavity and the subfloor look like, or an honest statement that neither could be accessed
• The height and extent of the damp, inside and out, with the instrument named wherever a reading is quoted
• Which lookalike causes were considered and ruled out: condensation, a failed shower on the other side of the wall, a downpipe, a bridged cavity, salt left behind by a problem already solved
• A clear separation between what is proven and what is inferred
• The order of works, with the prerequisites first, and which trade does each part
• Photographs of what is being described, taken close enough that somebody else can find the same spot
• What would change the conclusion — because a diagnosis that nothing could disprove is not a diagnosis

What happens after the visit

No inspection can honestly conclude rising damp because an instrument read high. A high reading on salt-loaded masonry is what the instrument does; it is a reason to keep looking, not a conclusion. Nor can anyone diagnose from photographs emailed in — photographs narrow the list, they do not close it. And nobody should price work they do not perform: where the answer is drainage, plumbing, a licensed waterproofer or a plasterer, the useful output is the trade to call and what to ask them for, with the number left to them.

The findings are yours. Take them to any contractor you like — nothing about the diagnosis depends on who does the work, and pricing it around is a reasonable thing to do.

If the answer is a chemical damp-proof course injected into the mortar bed of external brickwork, that is one of the two things a licensed waterproofer do, and it is quoted after the diagnosis rather than written on the same page as it. If the answer is an internal concrete slab that needs a moisture barrier before new flooring goes down, that is the other: ground back, prepared, epoxy barrier applied, then your floor.

If the answer is something else, you get told that instead, along with who to call. Lowering ground levels and pulling a garden bed back. Site drainage. A plumber for a leaking waste line. A licensed waterproofer for a failed shower under AS 3740. A plasterer for salt-loaded render removal and a breathable replacement. Subfloor ventilation. None of that is the waterproofer's work and none of it earns them anything, which is why the honest scope is usually longer than the quote.

One caution on timing. A wall inspected at the end of a long dry spell reads much like a wall that has been successfully repaired, so a house that has just been through a wet season tells you considerably more than one looked at in September. And nobody here will make claims about your health: persistently damp surfaces support mould growth, and the accepted control threshold is keeping surface relative humidity below about 80% over month-long periods. That is the whole of what can responsibly be said about it.

What this costs

The diagnosis costs nothing. There is no inspection fee and no report fee, so there is nothing to credit against anything and nothing to lose if the answer is that your wall is fine. A waterproofer makes their money performing those two treatments, on the jobs where one of them turns out to be the answer.

What costs money is the work, and the figure depends entirely on what the wall turns out to need. Chemical damp-course injection to external brickwork commonly lands at $180 to $300 per linear metre; internal slab treatment is priced by the square metre; and the items that most often dominate a total — excavation and level correction, drainage, render removal, desalination and replastering — belong to other trades and are quoted by them. The treatment cost page sets out the full sequence and where the money actually goes.

The one thing that does carry a fee is evidence-grade investigation: drilled samples, gravimetric and hygroscopic moisture testing, salt speciation, and a report written to be read by somebody who intends to disagree with it. That is a separate commission from a forensic consultancy such as an investigation-only consultancy, who set and quote their own fees. It is worth it when there is a dispute, an insurer, an expert-evidence requirement or a purchase riding on the answer. For an ordinary wet wall on an ordinary Gold Coast brick house, it is not where you start.

What it costs

Questions that actually get asked

My building and pest report said elevated moisture readings, further investigation recommended. What does that actually mean?

It means the inspector did their job and stopped at the edge of it. A pre-purchase inspection under AS 4349.1 is a broad visual assessment of a whole building; it is not a damp investigation, and no part of it involves testing salt. The reading tells you that something at the base of that wall conducted electricity. It does not tell you whether that was water or salt, or where the water came from if it was water. The next step for most buyers is a damp inspection, which normally carries no charge: someone who does this all day looks at ground levels, drainage and the pattern of the damp and tells you which it is. If the purchase is contested — the vendor disputes it, you are negotiating a reduction, or you may need to justify walking away — that is one of the cases where a paid forensic investigation, commissioned under AS 4349.0 as an inspection of particular technical aspects, is worth the money. Say which situation you are in when you book, because the site visit can happen quickly and laboratory work cannot be rushed.

Does anybody drill my wall?

Not on the site visit. That is a visual and site-conditions inspection — levels, drainage, the height and shape of the damp, salt, and a meter where it helps — and it leaves your brickwork exactly as it found it. Drilling belongs to a laboratory investigation, which is a separate paid commission and one most jobs never need. If you do commission one, this is what it looks like: six to eight small holes up a vertical line from below the visible mark to past the last sign of damp, sampled at 0-10, 10-20 and 20-40 mm into the wall, taken from mortar joints in preference to face brick because they are easier to make good and usually more representative. The heights matter because a profile that falls with height behaves like rising damp and one that does not is telling you the water arrived some other way. The depths matter because the surface of a wall is the least informative part of it. Holes are filled and colour-matched afterwards.

Can anything be worked out on a rendered or painted wall?

Yes, though the weighting shifts. A coating conceals the pattern, so the outside half of the inspection carries more of the load — levels, drainage, where the water goes in a downpour, where the render stops. The coating also becomes part of the diagnosis in its own right. Render carried down over a damp course is one of the most common ways an intact barrier gets bridged, and a hard cement render or a water-repellent coating reduces evaporation from the wall face, which pushes the damp front higher rather than stopping it. If there is render below the damp course line, expect it to come up in conversation. Where a coating makes a wall genuinely unreadable and a great deal rides on the answer, that is one of the cases where drilled samples earn their keep.

Will I be told what the repair will cost?

For the two treatments a licensed waterproofer performs, yes — they quote their own work, after the diagnosis, as its own document. For everything else, no, and you should be suspicious of anyone who does. A plumber, a licensed waterproofer, an excavator or a plasterer quotes their own trade, and a number invented on their behalf would only mislead you when you go to market. What you should get is a defined scope for each stage in the right order, which is the thing you need to obtain comparable prices. Price the prerequisites first: they routinely change the scope of everything that follows them.

Do you inspect concrete slabs, and is it the same testing?

No, and this matters because slabs get sold masonry treatments they cannot use. A slab is a single monolithic element sitting on the ground: there is no mortar course to sample and nothing to inject. The test that governs before moisture-sensitive floor coverings go down is in-situ relative humidity probe testing to ASTM F2170, with sleeved holes drilled to about 40% of slab depth for a slab drying from one side, sealed and left to equilibrate. That is the normative reference in AS 1884:2021 for assessing a slab before flooring. It tells you the slab is wet; it does not tell you why, so slab age, membrane evidence and repeat testing come into it. An under-slab membrane cannot be retrofitted after the house is built, whatever anyone tells you. What can be done is drainage, levels, slab-edge detailing, and a surface epoxy moisture barrier before new flooring — which is the second of the two treatments a licensed waterproofer performs.

If the inspection is free, what is the catch?

The catch, such as it is, is the obvious one: a contractor hopes the answer is one of the things they do. What stops that being a problem is how narrow those two things are. A chemical damp course to external brickwork and an epoxy barrier to an internal slab is the entire menu, so drainage, landscaping, plumbing, subfloor ventilation, wet-area waterproofing, render and desalination are all outcomes that earn them nothing and get handed to somebody else. You keep the findings and you are free to price the work anywhere. What you should still do is ask what was ruled out and on what evidence — that question costs nothing and is the fastest way to tell a diagnosis from a sales call. And be ready for the answer to be rising damp: on this coast it very often genuinely is, which is a fact about the water table rather than a sales line.

Is any of this suitable for a heritage-listed or character-overlay property?

Yes, and the constraints are worth raising early. Where sampling is warranted at all, mortar joints are preferred to face brick or stone, the hole count is the minimum consistent with a defensible profile, and locations are recorded. The bigger issue on a listed property or one in a character overlay is approvals: works including render removal, repointing and even changes to external ground levels may require consent before they start. Better to find that out during the inspection than after you have booked a contractor and taken delivery of a skip.

Can I take the findings to other contractors and get competing quotes?

Yes, and it is the right instinct. Nothing about a competent diagnosis should lock anyone in — the standards behind each conclusion are cited on this site, and any competent party can verify or challenge what you are told. If the quotes you get back diverge wildly from each other, or from the scope you were given, that is worth a conversation before you sign anything. Reading somebody else's damp quote against the evidence behind it is covered separately on this site, and it does not require having used any particular contractor first.