What is WME (Wood Moisture Equivalent)?

WME is the standard unit for resistance-type moisture meters. The meter measures electrical resistance and displays a percentage calibrated against wood. For non-timber materials, conversion tables are needed because brick, plaster and concrete conduct differently. A reading of 17% WME on plaster does not mean 17% water content.

What moisture readings are acceptable?

Acceptable limits depend on material: Gypsum plaster should be below 5% WME, brickwork below 3% WME, timber below 20% WME (above 20% risks decay), concrete below 6% WME. Readings above these levels indicate excessive moisture that needs investigation and treatment.

How do I take accurate moisture readings?

Push the pins firmly into the material surface. Take readings at consistent heights — typically at 150mm intervals from floor level upward. Take multiple readings across the wall to identify patterns. Avoid readings near metal (radiator pipes, DPC trays) as they give false highs. Note the temperature and any salt contamination.

What affects moisture meter accuracy?

Salts from rising damp, de-icing or chimney deposits can give falsely high readings because salts increase conductivity. Temperature extremes also affect readings. Foil-backed plasterboard, metallic paint, carbonation in plaster and proximity to metal pipes all cause inaccurate readings.

When is a damp survey needed?

A damp survey is recommended when you see visible signs: staining, peeling wallpaper, white salt deposits (efflorescence), musty smell, condensation, or deteriorating plaster. A survey identifies the type of damp (rising, penetrating, condensation) and its cause, guiding the correct treatment.

TradeCalculator

Damp Survey Calculator — Interpret Moisture Meter Readings

Interpret moisture meter readings (WME%) against acceptable limits for plaster, brick, timber, concrete and stone materials.

Material Type

Acceptable: <5% WME

Measurement Height

Height from floor level

Reading 1

Reading 2

Reading 3

Reading 4 (optional)

Reading 5 (optional)

How We Calculate This

This calculator interprets moisture meter readings against accepted thresholds for different building materials.

Acceptable WME limits

Gypsum plaster: <5% WME
Brick: <3% WME
Timber: <20% WME (decay risk above 20%)
Concrete: <6% WME
Stone: <5% WME

Risk categories

Low risk: Below acceptable limit
Medium risk: Above limit, below high threshold
High risk: Significantly above limit — action needed

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.