On the common wood moisture equivalent (%WME) scale, a damp meter reading below about 17 is dry, 17 to 20 is borderline (worth monitoring), and above 20 is wet and needs action. Timber becomes prone to decay above roughly 19 to 20%. Wall and floor readings work differently and are a guide, not an exact percentage. Always calibrate to the material and your meter's manual.
A damp meter gives you a number, but the number only helps if you know which band it falls into. This page is built around a straightforward reference chart: the dry, at-risk and wet ranges for timber and for masonry, what each band actually indicates, and the point at which a reading stops being "a bit of damp" and starts looking like a hidden leak. For the wider picture on what readings mean and what counts as normal, see our pillar guide to moisture meter readings explained. This article focuses on the chart itself.
On this page
First, which scale is your meter using?
Before you read a single band off a chart, check what your meter is actually measuring, because two meters can show very different numbers on the same wall and both be right.
- %MC (moisture content): the true percentage of water by weight. Only reliable on timber, where the meter is calibrated to wood.
- %WME (wood moisture equivalent): what most pin-type meters show on non-wood materials. It tells you the moisture level a piece of wood would reach if it sat in the same conditions as the material you're testing. According to Protimeter, a leading meter maker, this is the scale most surveyors work to.
- Relative / search-mode scale: a non-invasive reading (no pins) on an arbitrary scale, used to scan walls and floors quickly. It shows comparative wetness, not a real percentage.
The charts below use the %WME pin scale for the dry/at-risk/wet bands, then explain how wall and floor readings differ. The bands are a widely used industry guide. Your specific meter's manual is the final word.
Damp meter readings chart: timber (%WME)
For timber, the meter reads close to true moisture content, so these bands are the most dependable. The dry / borderline / wet split below follows the green, amber and red zone system manufacturers build into their meters, with the numeric breakpoints commonly cited across surveying and meter-maker guidance.
| Reading (%WME) | Band | What it indicates |
|---|---|---|
| Below 17 | Dry / safe (green) | Air-dry, stable timber. Settled interior joinery and structural wood usually sits here. No action needed. |
| 17 to 20 | Borderline / at risk (amber) | Higher than you'd want indoors. Worth re-checking and monitoring. Could be a damp environment, drying-out, or the early edge of a problem. |
| Above 20 | Wet / action (red) | Too wet. Timber becomes prone to mould and decay; investigate the moisture source rather than just treating the symptom. |
Two reputable reference points back this up. The published moisture meter reading chart from iDry Columbus puts structural timber below 17 WME as dry, 17 to 20 as at risk, and above 20 as wet, and notes that wood-decay fungi become active around 20% MC. Separately, Wagner Meters gives 6 to 8% as a normal settled range for interior wood (up to around 10% in coastal, humid areas) and flags anything above 19% as susceptible to mould and decay. So while the headline safe number is around 17 WME, a well-settled piece of interior timber often reads lower still.
Damp meter readings chart: walls & masonry
This is where charts get misread most often. A pin meter on plaster or brick does not give you a true moisture percentage. It gives a wood-equivalent value, and dissolved salts in masonry can push that figure up even when the wall isn't especially wet. That's why surveyors usually start with a non-invasive search-mode scan, then confirm with a more reliable method.
As a relative guide, the non-invasive search scale on a typical professional meter (such as the Protimeter SurveyMaster, on its 0 to 999 relative scale) is commonly described in three zones:
| Search-mode reading (relative) | Band | What it suggests |
|---|---|---|
| Roughly 60 to 169 | Dry (green) | No significant elevated moisture detected behind the surface. |
| Roughly 170 to 199 | At risk (amber) | Elevated moisture. Investigate further and compare against a known-dry area. |
| Roughly 200 and above | Wet (red) | Clearly elevated. Find the source: leak, rising/penetrating damp or condensation. |
Concrete and screed floors
Solid floors hold construction moisture for months and can also hide leaks beneath the slab, so they get their own benchmark. Meter maker Tramex treats roughly 3 to 6% moisture content as the window where concrete is generally considered "dry enough", depending on the ambient conditions and the meter used, with around 4 to 4.5% being a common "dry" mark on clean concrete in normal conditions.
A floor reading that stays above that window, particularly damp that seems to be rising up through the slab rather than drying out, can mean trapped build moisture or water tracking from below. We cover that specific symptom in our guide to moisture coming up through a concrete floor, which walks through the usual causes and when to suspect a leak under the slab.
When a reading points to a leak (not condensation)
A high number confirms moisture is present, but it does not tell you where the water came from. Condensation, rising damp, penetrating damp from outside and a plumbing or heating leak can all light up the red band. The pattern is what separates them:
- Condensation tends to be widespread and surface-level, worse on cold walls, in corners, behind furniture, and in winter or in steamy rooms. Readings are often only mildly elevated and improve with ventilation.
- Rising or penetrating damp usually follows a clear geography, such as a tide-mark low on a wall, or a patch tied to an outside defect, and is fairly stable over time.
- A leak is more likely when the damp is localised, getting worse, warm to the touch (heating leaks), or sits near pipework, a bathroom above, or a kitchen run, especially if it appears alongside an unexplained jump in your water bill.
If a reading is climbing, concentrated, and you can't tie it to obvious condensation, that's the point to rule out a hidden pipe. Non-invasive professional water leak detection uses thermal imaging, acoustic sensors and tracer gas to pinpoint the source before anything is opened up, so you're not chasing a number around the house with a handheld meter.
Reading damp in Cornwall & Devon homes
The South West's mild, wet, coastal climate means higher background humidity than much of the UK, so it's normal for timber and walls here to read a touch higher than inland averages, without that automatically meaning a leak. The skill is telling ordinary seasonal damp apart from a genuine water escape. Across Cornwall and Devon we do exactly that every week: we confirm whether an elevated reading is condensation, structural damp or a hidden leak, and where it's a leak, we find it with minimal disruption and document it for your insurer. For the full background on interpreting readings, our guide to what moisture meter readings mean is the companion to this chart.
Frequently asked questions
What is a normal damp meter reading?
On the wood moisture equivalent (%WME) scale used by most pin meters, a reading below about 17 is in the dry, safe band. Interior timber typically sits around 6 to 11% moisture content when settled. Always read your own meter's manual, as scales differ between models.
What damp meter reading is too high?
On the %WME scale, readings above 20 are generally treated as wet and a cause for action, because timber becomes prone to decay and mould above roughly 19 to 20%. Between 17 and 20 is a borderline band worth monitoring. The exact figures vary by meter and material.
Do damp meters read walls and timber the same way?
Not exactly. Pin meters give a true %WME on timber but only an equivalent value on plaster or masonry, where salts can skew the result. Many surveyors first scan walls with a non-invasive search mode on a relative scale, then confirm with a calibrated method, so a wall figure is a guide rather than an exact percentage.
Does a high damp meter reading mean I have a leak?
Not on its own. A high reading confirms moisture is present but not where it came from. Condensation, rising or penetrating damp and a plumbing leak can all read high. A leak is more likely when the damp is localised, worsening, or sits near pipework, which is when professional leak detection helps.
What moisture reading is acceptable for concrete or a screed floor?
Manufacturers such as Tramex treat roughly 3 to 6% moisture content as the window where concrete is usually considered dry enough, depending on conditions and the meter. Persistent readings above that, especially rising up through a floor, can point to trapped construction moisture or a hidden leak below the slab.
Are damp meter charts the same for every meter?
No. The dry, at-risk and wet bands described here follow the widely used %WME pin scale, but different makes and search-mode scales use different numbers. Treat any chart as a general guide, calibrate to the material, and check the manufacturer's instructions for your specific meter.
High reading you can't explain? Let's find out if it's a leak
If a damp meter keeps reading wet and you can't pin it on condensation, we'll trace the source across Cornwall & Devon with non-invasive equipment, and document it for your insurer if it's a leak. Fast response, minimal damage.
Call Dickie on 07822 025 911 No Find, No Fee on residential leak detection (subject to terms)