Skip to content
AkerminMeasure. Monitor. Improve. Compare Products
Guide

How to Use a Moisture Meter on Drywall

Drywall gives a relative reading, not a true percentage, so the method is comparison: a known-dry spot, then the suspect area, then a map. This guide gives the procedure for pinless and pin meters, the readings that matter, and the false positives that catch people out.

By the Akermin Editorial Team · 3 min read

As an Amazon Associate, Akermin earns from qualifying purchases. Product links on this page are affiliate links.

Set the meter to its drywall or reference scale. Find a known-dry area of the same wall type and take a baseline reading. Scan the suspect area with a pinless meter in a grid of about 150 mm, holding the pad flat, and note readings that exceed the baseline by a clear margin (commonly 20 or more points on a relative scale, or above about 1 percent on a drywall percentage scale). Mark the wet edge. Confirm the wettest spot with a pin meter if marks are acceptable. Ignore regular spikes at stud spacing and near known wiring or pipes, and trace the wet area toward its highest readings to find the source.

Why drywall is a relative measurement

Gypsum board has no single moisture-to-resistance curve, so meters show a relative scale or an approximate drywall percentage rather than a true content. The number only means something against a dry baseline of the same material in the same building. See why moisture meter readings vary by material.

Procedure with a pinless meter

  1. Select the drywall scale or the reference mode.
  2. Choose a dry reference on the same wall, away from bathrooms, windows and the suspect area, at the same height. Read it; in reference mode, zero here.
  3. Hold the pad flat against the surface with light, consistent pressure; keep your fingers off the sensing area.
  4. Scan in a grid, 100 to 150 mm apart, across and beyond the suspect area.
  5. Note readings and mark the boundary where they drop back to baseline with masking tape or pencil.
  6. Identify the highest reading; that is usually closest to the source.

Procedure with a pin meter

  1. Select the drywall or non-wood scale.
  2. Push both pins fully into the board at the reference spot; read.
  3. Repeat at the wettest pinless location and at a few points across the wet area.
  4. For depth information, use insulated pins or read at the base of the pins versus surface.

Interpreting

Reading Meaning
At or near baseline Dry at the meter’s depth
Slightly above baseline, consistent over a large area Possibly a different board or paint; compare with another dry wall
Clearly above baseline in a defined patch Moisture; map and trace
Saturated or maximum Wet board; likely needs replacement if sustained
Regular spikes at 400 to 600 mm Studs; ignore
Spike along a horizontal or vertical line Wiring, pipe or metal; confirm before assuming water

False positives

  • Metal: studs, corner beads, screws, foil-backed board and pipes push pinless readings high. Move 50 mm and re-read.
  • Wiring: cables behind the board register on pinless meters.
  • Dense finishes: tile, thick plaster skims and some paints shift the baseline; take the reference on the same finish.
  • Condensation on the surface: wipe and wait, then re-read.
  • Salts in old plaster affect pin readings.

Tracing the source

Water travels down and along. The highest readings are usually nearest the entry: below a window, under a bathroom, at a pipe run, at the base of the wall for rising damp. A thermal camera speeds the search over large areas; see using thermal imaging to look for moisture. Confirm what is inside with a borescope where needed. Record readings with locations and the scale used, and re-check after repairs to confirm drying. Meter selection is covered in how to choose a moisture meter.

Klein Tools ET140 Pinless Moisture Meter, Detects up to 3/4-Inch Deep

Klein Tools ET140 Pinless Moisture Meter, Detects up to 3/4-Inch

View on Amazon
Extech MO265 Combination Pin and Pinless Moisture Meter with RJ45

Extech MO265 Combination Pin and Pinless Moisture Meter with RJ45

View on Amazon
Extech MO257 Pinless Moisture Meter, Depth 0.78 to 1.6 in

Extech MO257 Pinless Moisture Meter, Depth 0.78 to 1.6 in

View on Amazon

Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.

Frequently Asked Questions

What is a normal moisture reading for drywall?

On a drywall percentage scale, under about 1 percent is dry and over 1 percent indicates moisture. On relative scales, the dry baseline in the same room is the reference; readings 20 or more points above it are wet.

Why does the meter spike on a vertical line every 400 mm?

Studs. Pinless meters respond to the denser stud behind the board, and metal studs give a strong false high. Read between studs, or note the pattern and ignore it.

Can I use a pin meter on painted drywall?

Yes; the pins pierce paint. They leave two small holes and paint can slightly insulate the tips, so push them fully in.

Affiliate disclosure: Akermin earns a commission from qualifying Amazon purchases made through links on this page. Our editorial picks are based on documented specifications and owner feedback, not commissions.