Why We Take Datum Points

Different materials have different “normal” readings
Concrete, block, timber, and plasterboard each respond differently to the meter’s signal. For example, a dry concrete wall may naturally read higher than a dry plasterboard wall, so relying on the raw number alone can be misleading.

Environmental factors change results
Temperature, humidity, and material density all affect readings. A dry concrete wall in winter may show a different value than the same wall in summer.

Datum points make results meaningful
By taking a reading from a known dry area on the same material in the same building, we establish a baseline. Every other reading is compared to that baseline, so we can accurately identify areas that are damp or saturated.

Aries Builders Best Practice for Moisture Testing

• Always take a datum point for every type of material being tested on a job.
• If testing multiple materials in the same room (e.g., concrete and plasterboard), take a separate dry reference reading for each.
• Compare all results against the correct baseline — never against a generic “one size fits all” number.

By following this method, our moisture testing is precise, consistent, and trusted across the building industry. It’s one of the reasons insurance companies, property managers, and homeowners choose Aries Builders for accurate building moisture inspections.

Why We Choose a Non-Destructive Meter (Like the Trotec T660)

When testing within finished homes—where surfaces are painted, wallpapered, or otherwise protected—we rely on the Trotec T660 non-destructive moisture meter. This type of pinless meter uses electromagnetic waves to scan surfaces up to ~40 mm deep, delivering quick readings without damaging finishes. It’s especially effective for sweeping across walls, floors, and ceilings without leaving any trace.

The Role of Pin-Type (Two-Prong) Meters

Pin-type moisture meters, which measure electrical resistance by inserting probes into the material, are more precise for raw materials—especially unprotected timber. They excel at pinpointing moisture content at specific depths.

However, they leave small marks, making them less suitable for finished or delicate surfaces. Plus, their readings are strictly localized, whereas non‑destructive meters offer faster scans across larger areas.

Why Both Tools Matter—But We Lean on Pinless for Homes

• Non-destructive meters like the T660 allow us to scan wide surfaces quickly, without disturbing interior finishes. That efficiency and care are central to our approach in residential settings.
• Pin-type meters remain useful when we’re working with exposed or raw materials and need exact moisture levels.
• By combining both tools, we ensure maximum accuracy while preserving our clients’ home interiors.

The Meter We Use — and the One We're Waiting For

  The model our team runs is the Trotec T660 — and along with its predecessor the T650, it became one of the most widely used non-destructive moisture meters in New Zealand over the past couple of decades, trusted by building inspectors, insurance assessors, real estate agents and homeowners alike. It's a proven, reliable tool, and it's the one we rely on every day.

The T660 was discontinued some years ago, and ever since, the whole industry has been waiting for its successor — us included. And it's been a genuinely long wait. The T670 has been "coming soon" for a few years now. More recently the images and spec sheets have started appearing on supplier websites, which is encouraging — but as far as we can tell, no one actually has stock to sell yet. It's close, but it's not here.

As of July 2026, we still can't get a T670 anywhere in New Zealand. If anyone is able to get hold of one for our team to try, we'd be genuinely excited to put it through its paces — so please do get in touch.

From what the specs promise, there's plenty to look forward to. The T670 keeps the same capacitive, non-destructive measuring method and 40mm scanning depth as our T660, so the performance we trust should carry straight over. The feature we're most interested in is grid measurement — the T670 is said to map moisture across a surface as a grid of up to 2,000 measurement points. For us, that would be a real step up: a systematic, thorough version of the moisture-mapping we already do by hand, producing exactly the kind of clear, defensible record that insurance assessors and property managers rely on. On top of that it's set to add Bluetooth connectivity, long-term data logging through Trotec's MultiMeasure mobile app, a photo-capture feature, a colour display, and a settable alarm that flags when a reading crosses your limit.

For now, though, we're doing what we've always done: getting the very best out of the meters we have, which we remain absolutely delighted with. The moment we can get a T670 in our hands, we'll put it to work and update this page with how it performs in the real world.

Frequently Asked Questions

What is a good moisture meter reading?
It depends on the material and the meter, which is why we don't rely on a single "magic number." We start by taking a dry reference reading — a datum point — from a known dry area of the same material in the same building. On our Trotec T660, readings in the 0–40 range (close to that baseline) indicate dry. Around 40 above the baseline suggests damp worth investigating, and 80 or more above baseline points to wet, likely saturated material. The key is always comparing against the correct baseline, not a one-size-fits-all figure.

Is the Trotec T660 still available?
No — the T660 was discontinued some years ago, and the industry has been waiting a long time for its replacement. It and the earlier T650 were two of the most widely used non-destructive moisture meters in New Zealand for the better part of two decades. Its successor, the T670, has been "coming soon" for a few years; specs and images have recently appeared on supplier sites, but as of July 2026 it still isn't actually available to buy in New Zealand. In the meantime our team keeps using our T660 meters, which remain accurate and reliable, and we're keen to try the T670 the moment we can get one.

What moisture meter reading means a wall is wet?
On our meters, a reading around 80 or more above the dry baseline indicates the material is wet and likely saturated — a serious risk to the bonding of plasterboard or man-made timber products. But context matters: a raw number on its own can mislead, because different materials read differently. That's why we always compare to a dry reference reading taken on the same material.

Is the Trotec T660 (and T670) accurate?
In our experience, yes — it's why we use it on every job. It's a German-made, industry-standard meter trusted by building surveyors and restoration specialists. Just as importantly, we get our meters calibrated so that every member of our team gets the same reading from the same spot — consistency we haven't always had with other brands. The new T670 is set to carry on the same capacitive measuring method with added features like data logging and grid mapping.

What's the difference between a pinless and a pin-type moisture meter?
A pinless (non-destructive) meter like the T660 uses electromagnetic waves to scan up to around 40mm below the surface without marking it — ideal for finished homes with painted or wallpapered walls. A pin-type meter inserts small probes to measure resistance, which is more precise for raw materials like unprotected timber, but it leaves small marks and only reads a single localised spot. We use both, and lean on the pinless meter inside finished homes to protect the interior.

Can you check for damp without damaging the wall?
Yes — that's exactly what a non-destructive meter is for. The Trotec T660 scans through the surface without drilling or cutting, so we can sweep across walls, floors and ceilings and build up a moisture map without leaving a mark. It's how we investigate damp in a finished home before deciding whether anything needs to be opened up.



What is a datum point in moisture testing?
A datum point is a dry reference reading. Before we assess any damp, we take a reading from a known dry area of the same material — for example an internal wall with no plumbing or exterior exposure. Every other reading is then compared to that baseline, so we can tell genuine damp apart from a material's normal "dry" value. We take a separate datum point for each type of material on a job, because concrete, timber and plasterboard all read differently.