29/09/2026
【Building Knowledge|What Does the Number on a Moisture Meter Mean?】
A common question during a building inspection is:
“Does 50 or 80 on the moisture meter mean there is 50% or 80% moisture in the wall?”
Usually, no.
Many non-invasive moisture meters do not show actual moisture content percentage. Their main purpose is to compare one area with another and identify unusual patterns.
For example:
If most of a wall gives similar readings, but the area below a window suddenly shows a much higher result, the important question is not just “What is the number?”
The real question is:
Why is this area different from the surrounding wall?
A professional inspector will then consider:
• Visible staining or paint damage
• Sealant condition
• Window and cladding junctions
• Reading patterns
• Nearby control areas
• Recent weather conditions
• Whether further investigation is needed
It is also important to understand that metal, different materials, coatings, density changes, contaminants, and temperature can all influence readings.
So:
High reading ≠ confirmed leak
Low reading ≠ guaranteed dry
A moisture meter provides evidence. It does not provide the full diagnosis on its own.
The real value is knowing how to interpret the readings together with the building details and other inspection evidence.
Cozy Building Compliance Ltd
Pre-purchase Building Inspections | Pre-sale Inspections
LBP Builder | BOINZ Accredited Building Surveyor
Auckland-wide
022 193 5800
www.cozybuildingcompliance.co.nz