What the percentage means (and why it is only a guide)
Pin meters measure how easily a small current passes between two pins and turn it into a percentage, usually on a scale set for a reference material such as timber. On plaster, render or concrete that number is not a true moisture content.
Pinless meters and masonry modes read the wall without pins and usually show a relative scale: a higher number means wetter than a lower number on the same material, nothing more.
So the bands on this page are indicative bands on a typical handheld meter scale. Readings differ between meters, materials and modes. The most useful number is the difference between your wall and a known dry wall of the same material.
Reading bands
| Reading | Band | What it usually means |
|---|---|---|
| 0–5 | Very low | Reads very dry. Fine to carry on if it stays that way. |
| 5–12 | Low | Normally fine for most finishing work, as long as readings are steady. |
| 12–17 | Moderate | Borderline. Find out why it is not lower and re-test before finishing. |
| 17–20 | High | Too damp to finish. Look for where the moisture is coming from. |
| 20+ | Very high | Active moisture is likely, such as a leak, rising damp or condensation. Stop and investigate. |
How to take readings
- 1Set a dry reference first: read a wall of the same material that you know is dry, ideally in the same room or elevation.
- 2Use the right meter mode for masonry or plaster, not the timber scale.
- 3Take a grid of readings about every 50 cm, including low down near the floor and around corners, windows and pipes.
- 4Re-test over several days, at a similar time of day, and write the numbers down.
Notes by material
Internal plaster
New plaster needs its drying time before painting, and the surface can read dry while deeper layers are still damp. Salts left by old damp can keep readings high after the wall has dried.
External render
Render takes up rain and dew, so test after a dry spell rather than the morning after rain. Near the coast, salts on the surface conduct well and can give false high readings.
Concrete and block
Dense and slow to dry, and a surface reading says little about moisture deeper down. Confirm with a calcium carbide or humidity probe test before sealing, tanking or laying floor coverings.
Common causes of high readings in North Cyprus homes
Roof or gutter leaks
Water running into the top of walls, often after the first heavy rain of autumn.
Blocked drains
Water pooling against walls and terraces when drains and grates are blocked.
Leaking pipes
Supply or waste pipes in or behind the wall, often showing as a patch that stays wet in dry weather.
Rising damp
Ground moisture drawn up the base of walls, with a tide mark low down.
Condensation
Warm, moist indoor air meeting cold walls in winter, often in corners and behind furniture.
Salts near the coast
Salt deposits on render that attract moisture and push meter readings up.
White salts and hair-like crystals
What it is
Efflorescence is soluble salts carried to the surface by water. As the water evaporates, the salts are left behind as white powder or fine, fibrous hair-like crystals.
Why it matters
It shows moisture is moving through the wall, even if the surface looks dry. Salts also hold moisture and can make a dry wall read high on a meter.
What to do
- 1Brush the salts off dry and bag them, so they do not go back into the wall.
- 2Do not wet-wash: water dissolves the salts and carries them back in.
- 3Fix the source, such as leaks, rising damp or blocked drains.
- 4Let the wall dry, then brush again. Repeat until no new salts appear.
Before finishing
Use breathable, salt-tolerant primers and paints as the manufacturer specifies. Sealing or painting over active salts usually fails.
Salty building sand or mixing water can add to the problem, and salts are common on walls near the coast.
When to confirm with a calcium carbide test or humidity probe
A handheld meter is a screening tool. Before work that traps moisture or costs a lot to redo, confirm with a calcium carbide test or a humidity probe, and follow the limit on the product data sheet:
- Sealing or waterproofing
- Tanking
- Floor coverings
- Premium paint systems
Frequently asked questions
Can I paint a wall that reads 15 on my meter?
That sits in the moderate band, which is borderline. Find out why it is not lower, compare it with a dry wall of the same material, and re-test on different days. Only paint once readings are low, steady and within the paint maker’s moisture limit.
Why does my pinless meter show a high number on a wall that feels dry?
Pinless and masonry modes usually show a relative scale, and dense materials, salts and metal in the wall can all push the number up. Take a reading on a known dry wall of the same material and compare the two.
How often should I re-test?
Re-test on several different days, at a similar time of day and in the same spots, ideally after a dry spell. You are looking for readings that stay steady and low, not one good number.
Does a low reading mean my damp problem is fixed?
Not on its own. It means the wall looks dry on this reading. If the source is still there, such as a gutter, pipe or rising damp, readings often climb again after rain or in winter. Track the readings and check the source.
Want someone to find the source?
365 Build & Design handle damp investigation, waterproofing, plastering and painting across Kyrenia and North Cyprus, with 40 years of UK experience and an English-speaking team.
WhatsApp usGuide only. This tool does not replace an on-site inspection or the manufacturer's instructions.