Moisture Meter: Pin vs Pinless and How to Read It

Quick answer

A moisture meter is a handheld instrument that estimates how much water is in a solid building material, such as wood or drywall, by sending a small electrical signal into it and reading how the material responds.

Pin meters push two probes into the surface and measure resistance. Pinless meters rest a flat sensor on the surface and read through it with a radio-frequency field. Both give an estimate, not a lab measurement, and the number only means something when it is compared with a dry reference.

Quick facts

The key facts about Moisture Meter, with sources:

What it measures: An electrical property of the material that changes with water content, shown as a number ¹³
Two main designs: Pin (resistance) and pinless (radio-frequency scanning); many meters do both ²³
Wood reading: Percent moisture content, which is water mass divided by oven-dry wood mass ¹
Drywall and other non-wood: A relative reference scale on reference-scale meters, not a percentage of water ³
Not the same as: A hygrometer, which reads humidity in the air, not water inside a material ⁷
Known false signals: Metal behind the surface, such as studs or conduit, can raise a reading ⁵
Best use: Comparing a wet area with a known dry area of the same material ³⁵

Key takeaways

A moisture meter reads an electrical response and turns it into a number. It does not count water directly ¹.
On wood, the number is percent moisture content. On drywall and many other materials, it is a relative scale that is not a percentage ³.
Pin meters read the small space between the pins. Pinless meters average over a wider patch under a flat sensor ³.
A single reading proves little. Compare the wet area with a dry area of the same material, as NIH’s guide does ⁵.
Metal under the surface, treated wood and temperature can all shift a reading, so the number is a clue, not a verdict ⁵¹.

What a moisture meter is and what it reads

After a leak, the hard question is not “is it wet?” but “is it dry yet?” Wet drywall can look normal. A wall can feel dry at the surface and hold water inside. A moisture meter helps answer that question without cutting the wall open.

The idea rests on how water changes electricity. Wood is a poor conductor when dry and a far better one when wet.

The USDA Forest Products Laboratory’s Wood Handbook says the conductivity of wood is a strong function of moisture content, and that as wood goes from near zero moisture to fiber saturation, conductivity can rise by a factor of more than 10 billion ¹.

A meter uses that effect. It sends a small signal in, measures the response and converts it into a displayed value.

The EPA lists moisture meters among the tools that measure moisture in building materials after water damage and can help monitor the drying process.

Its guide says they can be used on materials such as carpet, wallboard, wood, brick and concrete ⁶.

The EPA’s separate mention of a “moisture or humidity meter” in its brief mold guide refers to measuring relative humidity in the air, which is a different job.

This page covers the material meter. The air-side tool is covered under hygrometer.

Restorers use the meter at three points in a job. They use it early to find how far the water went, during the job to see whether materials are drying, and at the end to show that wet areas now match dry ones.

The readings then go into the daily record that backs up the drying work, which you can see described in the structural drying guide.

How a moisture meter works, step by step

Pin and pinless meters get to a number by different paths. This is the plain-language version of what the manufacturer and Forest Service documents describe.

Signal goes in. A pin meter sends a small current between two probes pushed into the material. A pinless meter sends a radio-frequency field out of a flat sensor pressed against the surface ³².
The material responds. Water changes how easily the material carries current and how it stores electrical charge. The Wood Handbook describes both effects, resistance and dielectric behavior, as strongly tied to moisture content ¹.
The meter converts the response. For wood, the meter applies a table that turns the response into percent moisture content. Some meters add corrections for wood species and temperature ³.
A scale is chosen. The user picks a wood setting or a reference setting. Delmhorst describes its reference scale as “a non-specific scale that provides a qualitative assessment of moisture content rather than a quantitative one” ⁴.
The reading is compared. The user takes the same reading on a material known to be dry. NIH’s guide says to compare drywall in the affected area with an unaffected area, and that readings should be the same ⁵.

Process From a signal to a decision

Signal inPins or a flat RF sensor send energy into the material
Material respondsWater changes conductivity and dielectric behavior
Meter convertsWood %MC or a relative reference number
CompareWet area against a known dry area of the same material
DecideKeep drying, look deeper, or record the area as dry

The last two steps are done by a person. The meter supplies only the number. Source: [3] [5] [1]

Types of moisture meters: pin, pinless and combination

Descriptions follow manufacturer and Forest Service documents. Individual models differ, so the manual for the meter in use controls.
Type	How it reads	Strength	Watch for
Pin (resistance)	Two probes pressed into the material; measures electrical resistance	Wood readings in percent moisture content; reads the small space between the pins ³⁴	Leaves small holes; reads only that spot ⁴
Pinless (radio-frequency)	Flat sensor held on the surface; RF scanning detects moisture without damaging the surface	Fast scanning of large areas to find problem spots ³	Averages over a wider patch; needs a large, flat surface for the sensor plate ⁴
Combination (dual mode)	One body with a pin mode and a pinless mode	Scan first, then confirm at a spot ³	The user must pick the right mode and scale for each material
Humidity or thermo-hygrometer	Reads air temperature and relative humidity, not material moisture	Tracks room conditions during drying ⁶⁴	Not a substitute for a material reading ⁷

Example: reading a wall against a dry reference

The reading numbers in this example are invented for illustration. They are not a standard and not typical values. They show the method NIH describes: compare the affected area with an unaffected area of the same material ⁵. The readings are on a relative reference scale, so they are plain numbers and not percentages.

Spot on the wall	Illustrative reading	What the comparison suggests	Sensible next step
Dry reference wall in another room, same drywall	14	This is the baseline for this meter, this material and this day	Record it with the date and the meter mode
Wall above the leak, day one	71	Far above the baseline, so the material is holding water	Mark the area and take readings at set points
Same spot, two days later	38	Dropping but still above the baseline	Keep drying; do not close the wall
Same spot, later still	15	Close to the baseline	Check nearby spots and the cavity before recording it as dry
Stud line beside the spot	52	Could be wet wood, or could be metal behind the board	Check the material type; confirm with another method ⁵

Decision guide What to do with a reading

If Reading matches the dry reference of the same material: Then Likely dry at that spot; check the spots around it
If Reading is higher than the dry reference: Then Treat the area as wet; keep drying and keep recording
If One spot is high next to metal framing or conduit: Then Possible false signal; confirm another way ⁵
If Readings drop, then rise again: Then A hidden source may remain; ask the restorer to look for it

Source: [5]

Two ideas matter here. The reference reading came from the same material, which keeps the comparison fair. And a number near the baseline is one piece of evidence.

The restorer still checks the cavity, the framing and the surrounding areas before calling a wall dry. The drying time tool explains why drying ends on readings and not on a day count.

Where moisture readings show up on your job

In the moisture log. A written drying job records readings by location and date, so anyone can see whether a wall is trending toward the dry reference. Ask to see the log. The how restoration works guide shows where those records sit in the project.

On the estimate or scope. A line that keeps a wall in place or takes it out should rest on readings, not on a guess. If a scope removes drywall that read near the dry reference, ask why. The estimate review tool helps frame that question.

In the insurance file. Dated readings and photos help show the extent of the water and the progress of drying. Policy wording varies, and the insurance claims guide explains how documentation fits a claim.

At the end of the job. A closing reading on each wet area, set against the dry reference, is the evidence that drying is complete. A job that ends with no readings has no evidence to show.

What a moisture meter does well

A moisture meter finds water you cannot see. Wet material behind paint, flooring or a baseboard can look normal, and a meter can flag it without opening the wall ⁶.
It makes drying measurable. Readings taken over several visits show whether materials are moving toward the dry reference.
It is non-destructive in pinless mode. Delmhorst describes pinless scanning as detecting moisture “without damaging the surface” ³.
It is quick for screening. A pinless meter can sweep a large area to find the spots that need a closer look ³.
It gives both sides a shared number. A reading with a date and a location is easier to discuss with a restorer or adjuster than a verbal “it feels dry.”

Where a moisture meter falls short

Metal can mislead it. NIH notes that a meter responds to the electrical properties of water, so metal such as studs and conduit under the surface may register and give a false positive ⁵.
Wood is not all alike. The Wood Handbook says wood conductivity depends on temperature, grain direction and water-soluble salts, and that preservative or fire-retardant treatment can substantially raise conductivity ¹. Treated lumber can read high without being wet.
A pinless reading is an average. It averages over a wider area, and a pin reading covers only the space between the pins ⁴. Neither one maps the whole wall.
Relative numbers are not percentages. A drywall reading of 40 on a reference scale is not 40 percent water. Delmhorst says the reference scale is qualitative, not quantitative ⁴.
It reads the material, not the cause. A meter cannot say where the water came from or whether it is still arriving. It also cannot say whether mold is present.

What drives the cost of owning or paying for meter work

Moisture meter work has no price on this page. A meter is a tool a restoration company brings, so the cost shows up inside a line on the estimate for monitoring or drying visits. What changes that line is the number of visits, the size of the affected area and how many materials need tracking.

If you are buying a meter yourself, the main cost drivers are the design (pin only, pinless only or both), which material scales it includes, whether it adds species and temperature corrections, and its build quality. Manufacturer manuals state each model’s ranges and corrections. Check the manual rather than a retail listing.

Meters do not last forever. Probes wear and electronics drift. The manual for the model sets the care and check procedure. Ask the maker how to verify a given model.

To see how monitoring fits into a whole job, read the cost guide and try the cost estimator. Neither one reduces a meter reading to a dollar figure.

How a careful reading session goes

A restoration technician runs the meter in a drying job, but the steps are simple enough to follow when you watch. No permit applies to taking readings. The steps below follow the logic in the NIH and manufacturer documents, not a standard text.

Choose the right scale. Wood uses a percent moisture content scale. Drywall, plaster and other non-wood materials use a reference scale ³.
Find a dry reference. Pick the same material, in an unaffected area, and take a baseline reading ⁵.
Scan first, then confirm. Use a pinless sweep to find high spots, then check a spot with the pins if the meter does both ³.
Hold the sensor flat. A pinless sensor plate needs a large, flat surface to make contact ⁴.
Mark and log each spot. Write the location, the date, the scale and the reading, so the next visit repeats the same spots.
Check around the edges. Move outward until readings match the baseline, which shows where the wet area ends.

Photograph the display

Take a photo of the meter showing the reading beside the material, with the date visible. A photo with the scale setting shown is much more useful later than a number alone.

Keeping readings trustworthy

A meter is only as good as the way it is used. Keep the sensor plate or pins clean and undamaged, because dirt, corrosion or bent pins change the signal. Store the meter as the manual says, and replace the battery before a job, since a weak battery can cause odd readings.

Note the conditions each time. Temperature changes the electrical behavior of wood. The Wood Handbook says conductivity of wood increases with temperature ¹, and some meters compensate for it ³.

A reading in a cold crawl space and one in a warm living room are not directly comparable unless the meter corrects for it.

Take the dry reference again on each visit. A baseline taken on day one may drift as the building’s air conditions change. A fresh baseline keeps the comparison fair.

Ask how a meter was checked. If a company relies on readings to decide what comes out, a reasonable question is how the meter is verified. The hiring guide lists other questions worth asking.

Warning signs a reading may be wrong or incomplete

The same wall is called dry by one visit and wet by another, with no change in conditions. One possible cause is that the scale or mode changed, not the wall.
A report lists numbers with no scale, no dry reference and no dates. A number alone cannot be checked.
Readings were taken only on the surface after a leak behind a finish. Water can sit in the cavity or the subfloor while the surface reads low.
A high reading sits right on a stud line, pipe or conduit run. That pattern can be metal, not water ⁵.
The job stopped when the surface felt dry, with no closing readings. A damp cavity can then feed mold. The EPA notes that if wet materials are dried within 24 to 48 hours, mold will not grow in most cases ⁷.

Safety and risk

Do not push meter pins into a wall near outlets, wiring or pipes, and do not use a meter on a wet floor near live electrical equipment.

Wet areas near power can be dangerous. Turn the power off at the panel only if it is safe to reach the panel, and leave electrical work to a licensed electrician.

Standards, laws and where the rules come from

No federal law sets a required reading. The EPA’s guidance tells users to dry wet materials quickly, and names moisture meters among the tools that help monitor drying ⁶⁷. It sets no number that every wall must reach.

The industry standard is voluntary. The IICRC’s ANSI/IICRC S500 water damage standard is where the idea of a dry standard for drying comes from. It is a purchased document, and this page does not reproduce it. NIH’s guide points readers to the S500 standard for the fuller equipment list ⁵.

Manufacturers set the meter’s rules. Scale ranges, corrections and accuracy come from the maker’s manual for each model. Delmhorst, for one, states a wood scale from 5 to 30 percent and a 0 to 100 reference scale for non-wood materials on its combination meter ³. Other makers and models differ.

Your contract and policy set the rest. What must be measured, recorded and shown at the end of the job is a matter for the written scope of work and your insurer, and both vary.

Moisture meter vs related tools

Each tool answers a different question. Used together they give a fuller picture than any one alone.
Tool	What it tells you	What it does not tell you	Where to read more
Moisture meter (this page)	How wet a solid material is at the point read ⁶	Where the water came from; mold presence	This page
Thermal camera	Surface temperature patterns that can point to wet areas ⁵	Moisture itself; a meter must confirm it ⁵	Thermal imaging
Hygrometer	Relative humidity of the air ⁷	How wet the materials are	Air humidity readers
Mold test	What a sample contains, in some cases ⁸	Whether a material is dry	Mold inspection vs testing

Side by side Pin and pinless side by side

Pin meter

Resistance between two probes ³
Reads the small space between the pins ⁴
Wood scale in percent moisture content ³

Pinless meter

Radio-frequency scanning from a flat sensor ³
Averages over a wider area ⁴
Needs a large, flat surface ⁴

Source: [3] [4]

Common myths about moisture meters

Myth A reading of 60 on drywall means 60 percent water.: Reality On a reference-scale meter, non-wood materials read on a relative scale. Delmhorst calls its reference scale qualitative, not quantitative ⁴.
Myth A moisture meter can tell you if there is mold.: Reality It measures moisture in a material. Finding mold is a separate question, and the EPA says that in most cases sampling is unnecessary when mold is visible ⁷⁸.
Myth A pinless meter reads deep inside a wall.: Reality A pinless meter reads a limited depth under its flat sensor and averages over that patch ⁴. Cavities and subfloors may need other checks.
Myth Any high reading means wet.: Reality Metal behind the surface can register as a false positive ⁵, and treated wood can read high ¹.
Myth A dry surface reading means the job is done.: Reality Dry is shown by readings that match a dry reference across the area, not by touch.

How climate changes the readings you should expect

No state sets a legal moisture reading for a home, so there is no verified state rule to cite here. What does vary by region is the dry reference itself.

Wood and other hygroscopic materials settle at a moisture level that depends on the humidity and temperature of the surrounding air, as the Wood Handbook explains ¹.

A home in a humid coastal climate will have a different normal for wood than a home in a dry inland climate.

That is why a dry reference taken from the same building matters more than a number from a chart.

When this matters to you, and what to do next

A moisture meter matters whenever someone says a wall, floor or ceiling is dry or wet and you need to know how they know. If you are in the first day or two after a leak, follow the safe steps in the first 24 hours guide, then ask for readings with a dry reference.

If a company proposes tearing out material, ask to see the readings behind that choice. If it proposes leaving material in place, ask for the closing readings. The water damage restoration page shows where measurement fits in the work, and the FAQ covers common follow-up questions.

If you are checking a small leak yourself and want a meter, buy one that matches your material, read the manual, and take a reference reading first. When readings stay high or the source is unclear, call a professional. A meter helps you decide; it does not replace a trained look at the cause.

One question that helps

Ask: “What is the dry reference for this material, and what is today’s reading next to it?” A restorer who works from readings can answer that in a sentence.

Questions about Moisture Meter

What does a moisture meter measure?

A moisture meter measures an electrical response in a material, which changes with the amount of water in it, and shows it as a number.

On wood the number is percent moisture content. On drywall and many other materials it is a relative reference scale ¹³. It estimates; it does not count water directly.

What is the difference between a pin and a pinless moisture meter?

A pin meter pushes two probes into the material and measures electrical resistance, so it reads the small space between the pins. A pinless meter uses radio-frequency scanning from a flat sensor, which does not damage the surface and averages over a wider patch ³⁴. Many meters offer both modes.

What is a normal moisture meter reading for drywall?

There is no single normal number. On a reference-scale meter, drywall reads on a relative scale that differs between meters, and Delmhorst calls that scale qualitative, not quantitative ⁴. The useful comparison is the wet area against a dry area of the same drywall, using the same meter and setting ⁵.

Can a moisture meter detect mold?

No. It reads moisture in a material, and mold is a different question. Moisture readings can show a place where mold could grow, but they cannot confirm it. The EPA says that in most cases sampling is unnecessary where mold is visible ⁸, and it says to fix the moisture problem ⁷.

Why does my moisture meter give a high reading on a dry wall?

Metal behind the surface, such as studs or conduit, can register as moisture and cause a false positive, according to NIH’s guide ⁵. Treated wood can also read high, since preservatives raise conductivity ¹. Check a dry area of the same material and confirm with another method.

Is a moisture meter the same as a hygrometer?

No. A moisture meter reads water inside a solid material. A hygrometer reads humidity in the air. The EPA says relative humidity can be measured with a moisture or humidity meter and advises keeping indoor humidity below 60 percent, ideally between 30 and 50 percent ⁷. They answer different questions.

How deep can a pinless moisture meter read?

It depends on the model. Delmhorst’s documents describe pinless scanning as reading through the surface without damage and averaging over a wider area, but the pages used for this entry did not state a depth ³⁴.

Check the manual for the meter in use, and do not assume it reads a full wall cavity.

Do moisture readings need to be recorded during drying?

Yes, in a well-run job. Dated readings by location show whether materials are moving toward a dry reference and give evidence at the end. No federal rule sets the numbers, and the EPA names moisture meters among tools that help monitor drying ⁶. Ask the restorer to share the log.

Can I use a moisture meter myself after a small leak?

You can, if you pick a meter that fits the material, read the manual and take a dry reference first. For small, clean-water leaks that is reasonable. If readings stay high, the source is unclear or the water was sewage or floodwater, call a professional rather than relying on your own readings.

Does a moisture reading tell me if I can file an insurance claim?

No. A reading shows how wet a material is, not whether your policy covers the cause. Coverage depends on your policy wording and the cause of the loss, which vary. Dated readings and photos can support a claim file, so keep them. The insurance claims guide explains how to read your policy.

Sources

USDA Forest Products Laboratory, Wood Handbook, Chapter 4: Moisture relations and physical properties of wood (Glass and Zelinka, 2021, FPL-GTR-282), retrieved October 14, 2026.
USDA Forest Products Laboratory, Electric Moisture Meters for Wood (James, FPL Research Note FPL-RN-08, 1963), retrieved October 14, 2026.
Delmhorst Instrument Co., Pin and Pinless Moisture Meters for the Construction and Building Industry, retrieved October 14, 2026.
Delmhorst Instrument Co., What Moisture Meter Should I Buy for Restoration Projects?, retrieved October 14, 2026.
National Institutes of Health, Moisture and Mold Remediation Standard Operating Procedures (2023), retrieved October 14, 2026.
U.S. EPA, Mold Remediation in Schools and Commercial Buildings Guide, Chapter 3, retrieved October 14, 2026.
U.S. EPA, A Brief Guide to Mold, Moisture and Your Home, retrieved October 14, 2026.
U.S. EPA, Is Sampling/Testing for Mold Necessary?, retrieved October 14, 2026.

Expert review

Written by the HyreRestore Research Desk. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.

How the numbers were checked: Meter design and scale statements were read from two Delmhorst documents, the USDA Forest Products Laboratory Wood Handbook chapter on wood-moisture electrical properties, and an FPL research note on meter types.

The false-positive and dry-reference guidance comes from NIH’s moisture and mold SOP, and EPA pages supplied the tool list and humidity guidance.

No dollar figures, drying times or required reading values are given, because the sources do not print universal ones. The reading example is labelled as invented. IICRC S500 is a paid standard and was not reviewed.

Suggest a correction. We fix errors and say what changed.