The fixed-fee diagnosis — and what's actually in it

Why this inspection isn't free

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 not an aside. Most damp contractors offer exactly one treatment method, and in this market the diagnosis almost always arrives from the party selling it.

Surveying practice in the United Kingdom requires that conflict to be declared where a surveyor's recommendations may include sales. We cannot find an Australian damp contractor who declares it anywhere on their website. So here is ours, at the top of the page rather than the bottom.

A paid report also buys something a free one structurally cannot: the ability to write the words no treatment required without losing money. That sentence appears in these reports regularly. It cannot appear often in a free one, because a business giving away its time has to convert to survive.

What we drill, where, and why

Rising damp has a shape. Moisture content is highest at the base of the wall and falls 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. It is the shape of that vertical profile, not any single number at skirting height, that is the actual evidence. A profile that does not decrease with height is telling you the water is arriving from somewhere other than the ground.

1. Sample linesA line runs up the wall from below the visible mark to past the last sign of damp — typically six to eight heights. 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, so sampling deliberately continues above that band.
2. Three depths at each heightSamples are taken at 0-10, 10-20 and 20-40 mm into the wall. The surface is the least informative part of a wall. The gradient inwards is what separates a wall wet from the inside from a wall wet from the outside.
3. Mortar first, brick where it mattersSamples come from mortar joints in preference to face brick, because the holes are less disfiguring and easier to make good. Where the mortar is markedly less permeable than the bricks, salts concentrate in the bricks instead, and then the bricks are what gets sampled.
4. Slow drilling, immediate sealingDrilling is done at low speed so the bit does not drive moisture off as heat, and the dust is sealed into airtight containers on the spot and weighed. A sample left open on a warm day is not a sample.
5. Locations recordedEvery hole is photographed and dimensioned. That is what makes the report re-testable — anyone can drill alongside it in twelve months and establish whether the wall actually changed.

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

In the laboratory each 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 alone 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 then equilibrated in a controlled 75% relative humidity atmosphere and reweighed. The mass they take back on is the hygroscopic moisture content: the water that 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 will distinguish moisture due to rising damp from moisture due to hygroscopic salts. It is also, on the evidence of every competitor website we can find in this country, not performed here at all.

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.

• More than about 0.5% salt by weight is cause for concern and reason to consider desalination
• Below that, with free water accounted for, the honest recommendation is often to leave the wall alone and monitor it
• 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 — results are reported by height and by depth interval, and the report states which method produced them

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. Readings like that are converted into dollars somewhere in this country every week.

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

The meter is not useless. On one wall, with one instrument, over time, it maps relative variation quickly and tells us where to drill. That is the job it can do, and the report says that is the job it did.

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 cannot be seen, we excavate a small inspection pit and measure it.

• 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 recorded 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

Ten minutes with a borescope regularly converts a presumed rising damp case into a diagnosed bridged cavity. Mortar droppings sitting on wall ties, a cavity base full of the same, missing or torn cavity flashing, blocked weepholes, standing water in the cavity base. Damp from a bridged cavity is frequently higher than the damp course, which is the giveaway, and a chemical damp course does nothing whatsoever for it.

Under a suspended floor we record 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, and the report says which one your subfloor needs.

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 an underfloor inspection belongs in the diagnosis and again in the sign-off, not only at the start.

What is in the report, and what it will not say

What it will not do is equally fixed. It will not conclude rising damp because an instrument read high: where free water is negligible, the conclusion is not rising damp regardless of what any meter said. It will not diagnose from photographs, which narrow the list without closing it. It will not price work we do not perform — where the answer is drainage, plumbing, a licensed waterproofer or a plasterer, it names the trade and what to ask them for, and leaves the number to them.

It will not declare a wall cured because the month happened to be dry. A long dry spell produces much the same readings as a successful repair, which is why the monitoring plan carries dates rather than impressions. And it will not 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 extent of what we will say, and it is worth knowing that around 70% of mould problems trace to condensation rather than to rising damp.

• The brief, the weather and site conditions on the day, and the limits of what could be accessed
• External ground, paving and garden bed levels measured relative to the damp-proof course
• The location, type and condition of any existing damp course, including whether it is intact and simply bridged
• A drainage, stormwater and plumbing review, naming the exclusion tests that were and were not performed
• Cavity and subfloor inspection findings
• Moisture mapping, with the instrument named and its limitations stated on the same page as its readings
• The vertical gravimetric moisture profile, sample by sample, with hygroscopic moisture content alongside it and free water calculated
• Salt species and percentage by weight where salt attack is suspected
• Every lookalike cause considered and explicitly ruled in or out
• A clear separation of what is proven from what is inferred
• A staged sequence of works with the prerequisites first, and a monitoring plan with dates
• Photographs, with every sample location recorded so the wall can be re-tested later

What you do with it afterwards

The report is yours. Take it to any contractor you like — it is written to be read by someone who is not us, and the sample locations are recorded precisely so that a third party can check the work.

If the answer is a chemical damp-proof course injected into the mortar bed of external brickwork, that is one of the two things we do, and it is quoted as a separate document with hole diameter, spacing, depth and fluid volume per linear metre stated on the page. 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 anything else — and it very often is — the report names the trade. 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 our work, and none of it earns us anything.

Fee, turnaround and the credit

The fee is fixed and quoted before we attend, based on the size of the building, the number of walls in question and the number of sample lines required. As a market reference, an independent specialist damp investigation with a written report runs roughly $600 to $2,000 in Australia, and laboratory work — gravimetric and hygroscopic moisture profiling plus salt analysis — typically adds $400 to $1,500 depending on how many sample sets are sent. Australian laboratory pricing for building-materials salt analysis is not consistently published, so treat those figures as indicative; the actual laboratory quotation is attached to yours.

Site work is normally a single visit. Laboratory results take several days, and the report follows the results rather than preceding them. Nobody issues a conclusion on the day.

If you engage us for treatment, the report fee is credited in full against the cost of that work.

If the report concludes that no treatment is required, nothing further is owed and there is nothing to decline. That outcome is not a failed sale. It is the product.

What it costs

Questions we 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 drilling the wall or testing salt. The reading tells you something conducted electricity at the base of that wall. It does not tell you whether that was water or salt, or where the water came from if it was water. A damp investigation can be commissioned separately as an inspection of particular technical aspects under AS 4349.0, which is what this report is. If you are mid-purchase and working to a deadline, say so when you book — the site work is one visit, but the laboratory results are the part that cannot be rushed.

How much of my wall gets drilled, and what does it look like afterwards?

Six to eight small holes per vertical sample line, plus a few at depth intervals, taken from mortar joints wherever the mortar is representative. Mortar is chosen partly because it usually gives the truer reading and partly because it is far easier to make good than a face brick. The holes are filled and colour-matched, and their positions are photographed and dimensioned in the report. That record is the point: it means somebody can drill alongside them in twelve months and establish whether the wall has genuinely changed, rather than arguing about it.

Can you test a rendered or painted wall?

Yes. The samples come from behind the coating, which is where the information is. Two things do change. First, a coating conceals the pattern, so the visual half of the inspection is worth less and the drilled half is worth more. Second, the coating itself becomes part of the diagnosis — 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 the report to have something to say about it.

Will the report tell me what the repair will cost?

It gives you a staged sequence of works with a defined scope for each stage, which is the thing you need in order to get comparable prices. It does not put a number against work performed by other trades — a plumber, a licensed waterproofer, an excavator or a plasterer quotes their own work, and a number invented by us would only mislead you when you go to market. For the two treatments we do perform, we quote separately, after the report, as its own document.

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 correct method 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 test is the normative one referenced by AS 1884:2021 for assessing a slab before moisture-sensitive floor coverings go down. 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 we perform.

Is the report suitable for a heritage-listed or character-overlay property?

Yes, and the sampling method is chosen with that in mind — mortar joints in preference to face brick or stone, minimum hole count consistent with a defensible profile, and every location recorded. One thing to plan for: on a listed property or one in a character overlay, works including render removal, repointing and even changes to external ground levels may require approval before they start. The report identifies where that is likely so you are not discovering it after you have booked a contractor.

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

Yes, and we would rather you did. It is written to be read by someone who is not us, the standards behind each conclusion are cited, and the sample locations are recorded so any competent party can verify or challenge the findings. If the quotes you get back diverge wildly from each other or from the report's scope, that is worth a conversation — reviewing somebody else's damp quote against the evidence behind it is a separate service we offer, and it does not require you to have bought this report first.