A stitch in time saves nine and to monitor the health of your wooden structures, be introduced to the Wood Moisture Meter.
This unsexy instrument is used on a daily basis by lumber merchants, construction foremen, finish carpenters, etc., and each has their own reasons. One reason is that different kinds of lumber have different optimal moisture content. Too low, and the wood will split or get chipped grain while being worked. If the moisture content is too high, then warping and opened joints will occur sooner or later.
Another reason is that when gluing up a panel, if adjacent planks that are otherwise identical have moisture content varying by three percent or more, they will shrink differently and they will appear to be of slightly different thicknesses (which they will have become).
Parquet and flooring contractors have to watch out for crowning and cupping. Although professionals use precision moisture meters that retail for a few hundred quid, the inexpensive ones reviewed here are perfectly suitable for handymen and amateurs who want approximate readings.
Moisture-related problems such as those described above are forestalled if moisture content is kept within narrow bounds, depending on the type of wood and the nature of its use. In order to do this, a wood moisture meter is necessary to be able to measure the moisture content in the first place.
Factors and Variables
Moisture content is not the sole discriminator as to the health and fate of your wooden structures; that is determined by a function of the wood’s moisture content, the relative humidity of the surrounding air, and the temperature.
Normal moisture content of structural wood ranges from 8 percent to 25 percent by weight depending on the relative humidity of the surrounding air. It is normal for the relative humidity to be higher than wooden structures’ moisture content and, depending on the relative values, a relative humidity percentage that is greater than the wooden structure’s moisture content may well cause the wooden structure to get dryer and shrink as it reaches its equilibrium moisture content.
The ‘tipping point’ for relative humidity is 70 percent; anything over this level will almost surely raise wood’s moisture content and cause it to become mouldy, the first step towards decay. Finally, assuming the presence of these two factors, if the ambient air temperature is above freezing, mould and decay can develop on wood, and the higher the temperature, the faster the rate of mould and decay.
Finally, one last variable: the cut of the wood. Different styles of cut for the same type of wood behave differently with respect to relative humidity and moisture content. Vertical-grain wood also called quarter-sawn wood is less susceptible to relative humidity-induced moisture-content contraction and expansion than flat-grain or flat-sawn, also called plain-sawn, wood.
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Accuracy, robustness, reliability and smart design are the calling cards of Brennenstuhl’s ergonomic instrument – making it the best-selling moisture meter.
Brennenstuhl’s moisture meter is by design a double-duty product that measures moisture content in wood from 5 to 50 percent, and also in building substrates such as concrete, drywall, sheetrock, plasterboard, etc. from 1.5 to 33 percent. It has a button to toggle between two measuring modes, one for wood and the other for building substrates.
The percentage resolution is in increments of 0.1 percent and precision is rated at ±3 percent.
The LCD numerals are large but the LCD itself is dull and at certain angles reading the numbers is difficult. An icon indicating the moisture range by way of displaying one, two, or three drops is a nice touch.
Brennenstuhl’s meter includes an acoustic cue; it beeps to signal moisture and the greater the moisture content, the more rapid the beeping in three steps. Though it can be turned off this acoustic notification turns out to be an unexpectedly helpful design. If you are testing a surface area of some material, say, sheetrock, to try to locate a moisture trouble spot, then you would keep taking readings at different points while simply paying attention to the rate and pitch at which the meter beeps at each point.
This meter gives readings that are quite accurate and are also consistent. The ergonomic grip is very comfortable.
This instrument has a low-battery indicator on the LCD.
This meter feels sturdy in the hand; it has unusually good build quality and machining which probably contribute to its popularity and sales.
A heads-up: the sticker on the LCD panel is a little too realistic so do not be deceived by it and peel it off! A 9-volt battery is not included so be sure to buy one.
It is on the costly side but then, you pay a premium price for a premium product; indeed, this Brennenstuhl meter is the best-seller in its class.
- One of the most reliable and also sturdy meters with unusually good build quality in its class.
- Possibly the most accurate and consistent moisture readings of all amateur moisture meters.
- The three-step beeping sound to indicate moisture range is unexpectedly useful design.
- Quite costly compared to similar meters.
- A battery is not included even though the meter is so costly for its class.
- Although you can toggle between wood and masonry, there is only a setting for all woods; there is no separate setting for even hardwoods and softwoods.
Measuring mode settable for four classes of woods, excellent LCD, and useful features set apart Proster’s device; this is a lot of meter for little moolah.
Proster’s inexpensive meter is devised to measure moisture content in a wide range of woods from trees of about 50 kinds grouped into four classes, selectable by a button that cycles through ‘Modes’ A through D to select the class of the wood being tested. The flip side is that you have to know what type of wood you are examining so that you can set the mode correctly.
Proster publicise their meter as suitable for detecting the moisture content of building materials and substrates but the instructions neglect even to mention this and the sticker on the meter provides no clues. As it happens, moisture content of building materials and substrates can be checked with the meter set to Mode D.
The meter is rated to measure moisture ranging from zero to 99.9 percent with accuracy within ±0.5 percent.
The LCD numerals are large and the LCD readout is especially bright and contrasty. The meter has a data hold button to retain the reading. The LCD includes a battery icon which comes on when the battery’s power becomes low.
The meter automatically turns off after about 15 minutes. Although the meter is sturdy enough the build quality and materials are nothing to shout about but that is to be expected in so inexpensive an item.
Features like auto-off and low-power icon in so low-priced a meter are worth taking special notice of.
Proster’s meter sells at about half the price of our Best Pick. Amazingly for a rock-bottom-priced unit, a 9-volt battery is included.
This meter and the GOCHANGE meter reviewed underneath are direct competitors.
A great value-for-money device for the DIYer on a budget.
- Remarkably low, low price.
- A few helpful and useful features are especially notable in such a rock-bottom-priced meter.
- Measures moisture content of not only woods but also of masonry and building substrates.
- The build quality and finishing are below par.
- Instructions and ‘cheat sheet’ on the meter itself do not inform which mode to use for masonry and building materials.
- In order to obtain the most accurate reading by selecting the correct class of wood, you need to know the type of wood you are measuring.
Stanley, the UK’s 170-year-old trusted brand of tools, produces a reliable and rugged meter with a ‘pro-style’ readout but with a couple of peculiar quirks.
Stanley’s meter indicates moisture by displaying a bar graph gauge that rises and falls against percentage markings and calibrations.
It is rated to measure moisture in wood from 6 to 44 percent, and in mortar, concrete, and plaster from 0.2 to 2.0 percent.
Stanley’s meter is not as straightforward as it looks. It has no button or switches to select the material that is being tested for moisture. You simply press the pins into the structure or material to be measured for moisture and read the values on the left scale of the bar graph if it is any type of wood, and to the right if it is masonry. The value that is indicated by the bar graph may or may not be the final word, however.
If you are measuring the moisture content of beech or any of three other woods, you have to use a conversion table in the booklet to convert the percentage reading to the actual percentage for that particular wood. Similarly, a conversion chart is provided for four types of masonry but that is even harder to interpret because the scale going from 0.2 to 2.0 percent on the meter is not reproduced in the table for tallying purposes.
The meter includes a digital readout of ambient temperature.
The LCD is backlit by LEDs.
The lack of a button to hold or retain the reading is an unfortunate omission because the reading is displayed for only about five seconds after you remove the meter from the object whose moisture content is being measured. When measuring the moisture content of building materials in hard-to-access nooks and crannies or high overhead is being measured, a ‘Hold’ button is very useful.
The package includes a zippered pouch. Meter testing sockets are built into the cap.
This is a rugged and especially well-finished meter with four AAA batteries included.
For a DIY meter such as the ones being reviewed here, this Stanley is on the costly side. This unit is probably made for the handyman who wants a robust meter and a design mimicking pro instruments.
- One of the most rugged, durable, and well-finished meters of its class.
- A fresh, graphical design to indicate moisture content by way of bar graphs against a percentage scale.
- Useful test sockets and temperature measurement are unique pluses for meters in its class.
- The reading is displayed for only about five seconds after pins are removed from material or structure and the meter lacks a data hold function
- For several woods and most masonry, you must remember to convert the percentage reading of the meter to the actual percentage by consulting a table.
- Somewhat costly among meters in its class.
Another device with mode settable for four classes of woods, excellent LCD, and useful features; a value-for-money GOCHANGE meter is available for small change.
GOCHANGE’s moisture meter is rated to measure moisture from zero to 99.9 percent in increments of 0.1 percent, and its accuracy is rated within ±0.5 percent.
This inexpensive meter can measure moisture content in a wide range of woods from trees of about many different kinds grouped into four classes; the class of wood is selectable by a button that cycles through ‘Modes’ A through D. We suspect that Mode D can be used to measure the moisture content of masonry materials.
The flip side of this customisation is that you have to know the type of wood whose moisture content you are measuring so that you can set the mode correctly.
The LCD is large and bright and the numerals are easy-to-read and contrasty. The backlight button enhances readability in low light conditions. All-in-all the readout is truly excellent.
The meter has a helpful data hold button to retain the reading.
The LCD includes a battery icon which comes on when the battery’s power becomes low. To conserve battery power the meter automatically turns off after about 15 minutes.
The protective cover is very tight and hard to remove – unless you know the trick! Simply squeeze it before trying to remove it.
For 4 AAA batteries to be included with such a rock-bottom-priced meter is amazing.
This meter and the Proster meter reviewed above are direct competitors. The bargain-basement price at which this moisture meter retails meant that it was a toss-up whether this one or the Proster would be our Value Pick.
Another great value-for-money meter for the DIYer on a budget.
- Remarkably low, low price.
- The excellent LCD readout is one of the very best.
- Low-battery icon, backlight button, hold button, and batteries are unexpected and welcome bonuses in a bargain-basement priced meter.
- Although the meter has four selectable modes, no mention is made whether or not materials other than wood can be measured for moisture content.
- In order to obtain the most accurate reading by selecting the correct class of wood, you need to know the type of wood you are measuring.
- The protective cap is so tight and hard to remove that if you don’t know the trick, you get a minor workout taking it off!
Dr. Meter makes an easy-to-use ‘plug-and-play’ meter that is as thoughtfully accessorised as it is thoughtfully designed.
Dr. Meter’s simple moisture meter is rated to measure moisture content in a range of 5 to 40 percent in increments of 1 percent with accuracy within ±1 percent.
This meter is advertised as capable of measuring the moisture content of – besides wood – sheetrock, plaster, carpet, and sub-flooring but it has no setting for these types of materials and there is no reference table against which to convert the raw percentage.
The LCD has ultra-large, easy-to-read numerals. While the useful ‘Hold’ button only needs to be pressed for the data to be retained, and an ‘H’ icon appears on the LCD.
Unlike most meters, Dr. Meter’s product does not turn itself off automatically after a period of inactivity. The light-touch power button is easy to turn on unintentionally with the slightest pressure, including when the meter is being carried in its pouch! Compounding the flaw is the lack of an auto-off feature.
The meter has a low-battery indicator icon (an offsetting feature in view of the above flaws!)
The exceptionally pointed pins/probes make for easy piercing without much pressure but are also a hazard.
In look-and-feel, it is lightweight and not particularly robust but it is a well-machined and well-finished instrument.
A set of two spare pins/probes are included, as is a carry pouch, and a 9-volt battery. As a result of such liberality, this meter is the only one in our review to score an accessories hat-trick: spare probes, carry pouch, and batteries!
For the novice who wants the simplest and easiest-to-use meter.
- In terms of usability, Dr. Meter’s no-frills instrument is the most simple and straightforward meter.
- Although it may not feel robust, it is well-machined and well-finished.
- Scores a hat-trick: the only meter in this review to come with a spare set of probes, a carry pouch, and batteries.
- The light-touch power button is easily turned on unintentionally.
- The meter lacks an auto power-off feature.
- Although the meter is advertised as capable of measuring the moisture content of building materials other than wood, there is no explanation of how it does this or how the user may do so.
How To Calculate The Moisture Content Of Wood
In general, the moisture content of wood is the ratio of the mass of water contained within the wood and the mass of only the wood itself. Thus, if a block of lumber having a mass of 90 kilogrammes is comprised of 30 kilogrammes of water, then the moisture content is 50 percent.
We arrive at this percentage by first subtracting the 30 kilos of water from the 90 kilo mass of the wood, with the difference of 60 kilos being the mass of only the wood itself. Next, we divide the mass of water, 30 kilos, by the mass of the wood, 60 kilos, obtaining 0.5, and multiply by 100 to arrive at the percentage, 50. This simple computation holds good for all kinds of wood.
Although 50 percent is on the low side for a freshly-cut tree’s moisture content, for finished woods this level of moisture content is exceedingly high and puts the wood or structure at risk of mould or decay.
How Wood Moisture Meters Work
Wood Moisture Meters are of two types, pin (invasive) and pinless (non-invasive). (The present review covers pin meters.) Many pin meters or probe meters can be used, albeit not always precisely, to measure the moisture content of materials other than wood, such as bricks, concrete, ground, carpeting, leather, and so forth.
The pins (or probes) of a pin meter are actually electrodes. They pierce the wood and detect electrical resistance, using which values the meter derives moisture content. On the other hand a pinless meter emits HF electromagnetic waves directly to detect moisture content at a depth of two centimetres from the surface of the wood.
Many moisture meters are pre-calibrated with characteristic moisture-content curves for various kinds of woods; therefore, prior to measurement the appropriate class of woods has to be selected on such a meter.
How To Use A Wood Moisture Meter
Using a wood moisture meter is a straightforward exercise.
Remove the protective cap and turn on the meter. Then, regardless of which type of meter you are using, if the meter has settings for different woods or materials, the all-important first step is to ‘tell’ the meter what type of wood group or class you are measuring. This function is typically labelled ‘Mode’.
If the meter has pins, place it so that the pins or probes are parallel to the grain on the surface of the wood, i.e. so that the two pins are aligned or follow one another along the grain rather than spanning the grain, and press it gently and firmly so that the pins pierce the wood to 3 to 5 millimetres. If the meter is pinless, simply place it on the surface of the wood. Then take your reading. To retain the reading, press the ‘Hold’ button, if the meter has one.
If the wood being measured for moisture content has more than one plane surface exposed, take a reading on another plane surface. If you are checking a panel or structure for dampness, take multiple readings over the (same) plane surface.