A guide for surveyors and damp inspectors

Moisture meter readings: how to record them.

Which meter, which scale, the exact place, a dry comparison and the conditions on the day. Why there is no universal readings chart, why a photo is not a reading, and a recording sheet for the visit.

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For buildings in the UK. Written 12 October 2026. Next review by 12 April 2027.

Why the details matter

A number on its own says very little.

A reading is only useful if someone else can understand it later, or you can on the next visit. The number alone cannot do that: different meters, modes and scales give different numbers on the same wall.

Meter makers are careful about what a reading means. Protimeter's manual puts it plainly:

"Readings from moisture meters are not definitive but are used to help a professional make informed judgment to the material's moisture condition."Protimeter Surveymaster instruction manual, INS5375 Rev. A, June 2023

So the reading needs its context written down with it:

  • The meter: make, model, and whether it was used with pins or pinless.
  • The scale or mode it was set to, written as the meter shows it.
  • The exact place: room, wall, height and distance from a fixed point.
  • The surface: what material, and what finish.
  • A comparison reading from a dry area of the same material nearby.
  • The date and the conditions on the day.
  • A photo of the spot, as supporting evidence.

Pin and pinless meters

Know what your meter actually measures.

Damp meters generally work in one of two ways, and some do both. Record which one you used for each reading, in the maker's own words.

Pin meters

Two pins are pressed into or onto the material. Protimeter says its Surveymaster, in this mode, "uses electrical conductance principles to measure the moisture level of the material between two electrodes". The reading is for that point only: its manual says these readings are "precise and specific to the area of contact between the electrode tips". Deep wall probes can take readings further into a wall.

Pinless meters

A flat sensor is pressed against the surface and reads the material beneath it without making holes. Tramex describes its Moisture Encounter 5 like this:

"The instrument operates on the principle that the electrical impedance of a material varies in proportion to its moisture content."Tramex Moisture Encounter 5 user guide

The Tramex guide gives the reading depth as about 30 mm, or 10 mm in its shallow mode. Protimeter's pinless Search mode reads "in relative terms" up to 19 mm below the surface. Both makers advise placing the meter, taking the reading and lifting it, rather than sliding it across the surface.

So a pin reading and a pinless reading at the same spot are not the same measurement. Note which is which.

Scales and what they show

A wood scale on a brick wall is not a moisture content.

On timber, a meter set to its wood scale can give a moisture content. On plaster, brick or block, the figure means something different, and the makers say so.

Wood moisture equivalent

Protimeter's pin readings on anything other than wood are wood moisture equivalent (WME) values:

"Measurements taken in wood are actual % moisture content values, whereas readings taken in material other than wood are % Wood Moisture Equivalent (%WME) values"Protimeter Surveymaster instruction manual, INS5375 Rev. A, June 2023

The manual explains WME as the moisture content a piece of wood would reach if it were in balance with the material at that point. It is a useful indicator, read on the meter's own scale. It is not the moisture content of the plaster or brick itself, so write the unit as the meter shows it: "%WME", not "%".

Comparative scales

Tramex uses a comparative 0 to 100 scale for plaster, masonry, drywall, tile and roofing. For plaster, its guide says:

"As calibration is not practical on this type of construction, readings should be taken from the comparative bottom line of the meter dial (0-100)."Tramex Moisture Encounter 5 user guide, Scale 4: Plaster

Protimeter's pinless Search mode is also relative, shown as REL on the meter. Write down the scale and mode for every reading, for example "Scale 5, masonry, comparative" or "Search mode, REL".

Is there a readings chart?

No universal chart. Keep your own instead.

There is no single chart that turns a reading into a verdict for every meter and material. The useful chart is the one you fill in on site.

On its comparative scale, Tramex says results "do not necessarily indicate low, medium or high levels of moisture but indicate the area of the 0-100 comparative scale where the readings lie". It adds that plaster and brick take up moisture from the air, so their readings "are affected by ambient humidity and thus can vary according to the climate conditions".

Its advice is to compare: "It is best practice to find a known acceptably dry area to compare to." Protimeter's Surveymaster has a Reference mode for the same purpose, which its manual describes as useful "when establishing a dry standard in the building and comparing other readings against this dry standard".

Some meters show coloured bands for their own scale. Those bands belong to that meter and mode. Note what the meter showed, but treat it as part of the reading, not as a finding about the wall.

A readings chart worth keeping: one row for each reading

  1. a
    Reading numberSo photos and notes can point to it.
  2. b
    PlaceRoom, wall, height above the floor, distance from a corner or opening.
  3. c
    SurfaceThe material and its finish.
  4. d
    Meter, mode and scaleAs the meter shows them.
  5. e
    ReadingThe figure, with its unit or scale.
  6. f
    Dry referenceThe comparison reading, and where it was taken.
  7. g
    PhotoThe photo number for this spot.
  8. h
    NoteWhat you saw: staining, salts, mould, a leak, ventilation.

Where, when and compared with what

So the next person can find the same spot.

The exact place

"Bedroom, damp" cannot be checked again. "Rear bedroom, north wall, 300 mm above the floor, 500 mm from the left corner, painted plaster" can. Measure from something that will still be there next time: the floor, a corner, a window reveal or a door frame.

Take readings in a pattern, not at random. Protimeter's MMS3 manual says "Far greater insight will be obtained from moisture readings taken in a methodical manner", and suggests moving up a wall "in regular steps of 4-6 in. (10-15 cm)".

A dry comparison

Take a reference reading on the same material, with the same meter and scale, in an area you believe is dry: for example the same wall higher up, or an internal wall in the same room. Record where you took it.

The date and the conditions

Note the date and time, the weather and any recent rain, and whether the heating was on. If you measure the room's humidity and temperature, record them too: Protimeter's MMS3 manual says these "should also be taken to assess the moisture condition of the room as a whole".

Salts, surface moisture and photos

When a reading can mislead.

Salts and other conductors

Pin meters work by electrical conductance, so anything else that conducts can raise the reading. Protimeter warns that "Conductive material such as salts, carbon and metal can give false positive readings." Its MMS3 manual goes further:

"Artificially high moisture meter readings may be obtained either in material that has been heavily contaminated by hygroscopic salts or in materials that are conductive by nature."Protimeter MMS3 instruction manual, INS9800 Rev B, September 2024

The manual explains that salts build up where rising dampness or wicking has occurred, and with a little moisture form a highly conductive solution. Note any salt bloom, foil or metal nearby, and say the reading may be affected.

Surface moisture

Moisture can sit on the surface of an otherwise dry wall, for example from condensation. Protimeter says this has little effect on its pinless Search mode, and recommends using pin and pinless readings together "to distinguish between surface and sub-surface moisture". Condensation itself is judged differently: the MMS3 manual says the surface temperature must be compared with the dew point, and that "many condensation situations are transient".

Why a photo is not a reading

Take two photos for each reading: a wide one showing where the spot is in the room, and a close one of the meter on the surface with its display readable. The photo supports the reading; it cannot replace it. A stain can stay after a wall has dried, and moisture below the surface may not show at all. A picture of a damp patch shows where to look, not how much moisture is there.

Finding the cause

A reading shows where moisture may be. It does not, on its own, show why. Protimeter's MMS3 manual describes "effective dampness diagnosis" as "a process that draws on the knowledge and expertise of the surveyor". Confirming the cause, whether a leak, condensation, penetrating or rising damp, may need further investigation by a qualified person. For social landlords, our Awaab's Law guide covers what to record when inspecting damp and mould.

The recording sheet

What to write down for every reading.

Use it on the visit, or as a check that your own damp form covers everything. Free to use and change.

The meter

  • Make and model
  • Pin or pinless, or which probe
  • Mode and scale, as the meter shows them
  • Its own check done, if it has one

The place

  • Room and wall, by direction or a fixed feature
  • Height above the floor
  • Distance from a corner, window or door
  • Surface material and finish

The reading

  • The figure, with its unit or scale
  • A numbered reading, linked to its photos
  • The dry reference reading, and where
  • A line of readings, not just one

Context

  • Date and time
  • Weather, and any recent rain
  • Heating, ventilation, room humidity if measured
  • Salts, staining, mould, metal or foil nearby

Before you leave

  • A wide photo and a close photo of each spot
  • The meter's display readable in the close photo
  • What you could not reach, and why
  • Anything that needs further investigation

Damp, mould and moisture · when you need it

The reading and the room. Together.

A launch workflow preview for Lite, there when a survey calls for it: record the affected element, add photographs and notes, and keep the meter reading with its location.

See it in the Lite mobile app Book a demo

This expanded workflow is being prepared for the mobile app release. Ask the team which controls are available in your build.

  1. 1

    Choose what you are inspecting

    Damp-proof course, rising damp, penetrating damp, condensation, mould growth, ventilation and extractor fans, or plumbing leaks.

  2. 2

    Add the evidence

    Record the condition, photograph the issue and note where it is. Add the meter make, model, scale and reading rather than inferring moisture from a photograph.

  3. 3

    Keep readings organised

    Review readings by element and across the survey. Correct an entry without losing its link to the place you inspected.

  4. 4

    Carry it into the report

    Bring findings, photographs and reading tables into the draft, then review the wording and recommendations.

SurveyNest records what your surveyor sees and measures. Reading the results and finding the cause of damp stay with your surveyor.

Questions

Moisture meter readings, answered.

What is a normal moisture meter reading for a wall?

There is no single figure. It depends on the meter, the mode and scale, the material and the conditions on the day. The makers advise comparing each reading with a reading from a known dry area of the same material.

Is there a moisture meter readings chart I can use?

Not one that works for every meter and material. Coloured bands on a meter belong to that meter and scale. The most useful chart is your own record of each reading, its place, its scale and its dry comparison.

What does %WME mean?

Wood moisture equivalent. Protimeter's pin readings on materials other than wood are WME values: the moisture content a piece of wood would reach in balance with the material at that point. It is not the moisture content of the plaster or brick itself.

Should I use pins or pinless?

Often both. Protimeter recommends using its pinless and pin modes in combination to map how far moisture reaches and to tell surface moisture from moisture deeper in the material. Record which one gave each reading.

Does a high reading low on a wall prove rising damp?

No. Protimeter warns that salts and other conductive materials can give artificially high readings. Note anything that may affect the reading, and confirm the cause with further investigation by a qualified person where needed.

Sources

Where these facts come from.

Every statement about how meters work comes from the makers' own manuals, read on 12 October 2026. The recording advice is our own good practice. Always follow the manual for your own meter.

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