Moisture Meters in Pest Control: Finding Termite Risk Before the Damage Shows

Building InspectionToby Bredhauer
Moisture Meters in Pest Control: Finding Termite Risk Before the Damage Shows

Termites don't announce themselves. By the time a skirting board sounds hollow or a door frame gives under a screwdriver, the colony has usually been feeding for months. What they do leave behind, almost always, is moisture — and moisture is something you can measure long before you can see damage.

That is why a moisture meter sits alongside the sounding tool, torch and probe in every competent timber pest inspector's kit. The national competency unit for timber pest inspection (CPPUPM3008 Inspect for and report on timber pests) lists it as standard equipment, and an inspection carried out to AS 4349.3 is expected to identify and report conditions conducive to timber pest attack — of which moisture is the big one.

This article covers how moisture meters fit into pest work in Australia, what the readings mean, and which type of meter suits which job.

Why moisture matters to timber pests

The three timber pests that inspectors report on — subterranean termites, wood borers and fungal decay — all need moisture to get established.

  • Subterranean termites must keep their workings humid to survive. They carry moisture up from the soil, build mud-packed leads, and preferentially attack timber that is already damp. A persistently wet subfloor, a leaking shower or a garden bed built against a weep hole is an open invitation.
  • Fungal decay (rot) needs timber above roughly 20% moisture content to take hold, and it accelerates as timber approaches fibre saturation (around 28–30%). Dry timber simply doesn't rot.
  • Wood borers such as the Anobium (furniture) beetle prefer damp, poorly ventilated timber — the classic case being old pine flooring over a wet subfloor.

Decayed timber is also softer and more attractive to termites, so moisture, rot and termite attack tend to arrive together. Find the moisture and you have found where to look hardest.

Four ways pest technicians use a moisture meter

1. Identifying conducive conditions

AS 4349.3 inspections have to report conditions that make a property more susceptible to timber pest attack. Elevated moisture readings in subfloor bearers and joists, wall framing behind wet areas, or timber in contact with slab edges are exactly the evidence you need to back a "conducive conditions" finding — with a number, not just an opinion. A reading of 25% in a bearer under the bathroom carries far more weight in a report than "appeared damp".

2. Locating concealed termite activity

Termites keep their galleries moist, so active workings behind plaster or inside a door jamb will usually read wetter than the surrounding timber or wall. Scanning a wall with a pinless meter and watching for a localised rise is one of the fastest ways to narrow down where to open up or where to point a thermal camera. It won't tell you what is causing the moisture — that's your job — but it tells you where.

3. Verifying moisture after a leak or treatment

Once a leak has been fixed or a subfloor ventilation problem addressed, a follow-up reading proves the timber has dried back below the risk threshold. The same applies after treating fungal decay: if the timber is still reading 22%, the problem is not solved. Recording the before-and-after figures gives you a documented result on the file.

4. Tracking subfloor humidity over time

Subfloor moisture is often a ventilation problem rather than a leak. A thermo-hygrometer reading of relative humidity and dew point in the subfloor space, taken on each visit, shows whether the conditions that attracted termites in the first place are still present. For managed-property or annual-inspection clients this is a straightforward way to demonstrate value on every return visit.

Pin or pinless?

Both have a place in pest work, and most technicians end up carrying one of each. (For a deeper comparison, see The Best Times to Use Pin or Pinless Moisture Meters.)

Pin meters (resistance meters) push two steel pins into the timber and read the electrical resistance between them. They give a true percentage moisture content for the species being tested and tell you how deep the moisture goes when used with a hammer probe or insulated pins. Use a pin meter when you need a defensible number for a report, when checking bearers, joists, stumps and framing in the subfloor, and when confirming whether decay-affected timber has dried.

Pinless meters (capacitance or electromagnetic meters) read through the surface without marking it, typically to 20–25 mm depth. They are ideal for scanning large areas quickly — a whole wall, a run of skirting, a floor — and for finished surfaces in occupied homes where leaving pin holes is not acceptable. Use a pinless meter to find the wet spot, then a pin meter to quantify it.

Combination meters such as the Protimeter SurveyMaster, Tramex ME5 or Delmhorst TechCheck Plus do both in one body. For a technician who moves between subfloor and living areas on every job, a combination meter is usually the most practical single purchase.

What readings should concern you?

Meter readings are a guide, not a verdict, but these are the working rules of thumb in Australian conditions:

  • Below 15% MC in timber: normal for internal framing and flooring in most of Australia. No action on moisture grounds.
  • 15–20%: elevated. Worth noting and worth finding the cause, particularly in subfloors and around wet areas.
  • Above 20%: the timber is at risk of fungal decay and is attractive to termites. Report it as a conducive condition and investigate the source.
  • A localised reading well above its surroundings: treat as a lead until proven otherwise, regardless of the absolute number.

Always take a reference reading on timber you know to be dry in the same building. The comparison is often more informative than the raw figure, and it corrects for species and temperature differences.

Two cautions. First, pin meters are calibrated for timber; readings on plaster, masonry or concrete are relative scale readings and should be reported as such. Second, foil-backed insulation, metal flashings and pipes will all give a false high on a pinless meter — if a wall reads wet from top to bottom in a perfectly straight band, you have probably found a stud with a cable on it, not a termite lead.

Choosing a meter for pest work

For the subfloor and framing — pin meters. The Delmhorst J-Lite is a straightforward, robust LED pin meter at an entry price point. The Delmhorst BDX-20 and BDX-30 step up to a digital readout and species corrections, and the BDX-20 Behind-the-Wall package includes a 21-E extended electrode for reaching into wall cavities and under floors. The Protimeter Digital Mini is a compact alternative with a plug-in probe.

For scanning walls and floors — pinless meters. The Protimeter Aquant is the standard non-invasive survey meter. The Wagner Orion 910 and Orion 930 are pinless meters designed for timber, with the 930 offering dual-depth scanning.

For doing both — combination meters. The Protimeter SurveyMaster 2, Tramex ME5 and Delmhorst TechCheck Plus each combine pin and pinless modes, and the SurveyMaster adds a hygrometer input for RH readings.

For subfloor humidity — thermo-hygrometers. The Protimeter Hygromaster L and Delmhorst HT-4000 read temperature, RH and dew point. For unattended monitoring between visits, the Tramex Feedback dataloggers and the Protimeter BLE Bluetooth logger record conditions continuously.

Everything above is in our Building & Pest Inspection range at The Moisture Meter Company and ships Australia-wide. If you are not sure which meter suits your work, call us — we have been supplying inspectors and pest technicians for years and can usually narrow it down in a couple of minutes.

References and further reading

Tags: Building inspection, Delmhorst, Pest control, Protimeter, Termites, Tramex