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Community and Q&A

Long-Probed Wood Moisture Meter

KevinKeegan | Posted in GBA Pro Help on

Hello Pro’s,
I am following up on a previous question concerning a potential moisture problem in a sill beam and it was recommended that I use a wood moisture meter with a long probe to check to see if there is a to high moisture level in the sill beam. I have not had any experience with moisture meters and I would like to know how I should go about testing the sill beam. I ordered a moisture meter on Amazon. It is a GM620 Digital adjustable detector moisture detector for wood, building materials, firewood, paper and flooring. It also shows a set of long probes. I can reach the sill beam along its entire length and I guess what I’m trying to understand is what do I need the long probes for? is that just a question of being able to make contact with the beam?  The thickness of the beam is most likely 6″ to 8″ in width and 10″ to 12″ in height. I assume I do not want to drill into the beam.
Thank you, Kevin

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  1. Doug McEvers | | #1

    Delmhorst makes a moisture tester with a long probe for testing hay. I believe the range is 8% to 25%, I use one to test the drying of native grass seed. They may offer other moisture testing equipment specific to construction, they make a quality instrument.

    1. KevinKeegan | | #4

      Hi Doug,
      Do you know if a Delmhorst long probe moisture meter can be rented? I called Delmhorst and the price to purchase is steep, and I don't know if I will be using it enough to validate the purchase. Even a used one with probes will run about $400. I purchased a GM620 moisture meter with long probes and I have no way of knowing how accurate it is, but I am wondering what your thoughts are base on what i have used it for? Which is to check the moisture level in a heavy timber sill beam.

      1. Doug McEvers | | #5


        Explain a bit more about the beam in question. Why do you think it may be in a moist environment? My guess is that mold remediation companies use moisture probes all the time to check for high moisture in hidden places. The Delmhorst I have has about a 12" probe. The probe is meant to be inserted into the material to be tested and the probe is about 5/16" wide with a metal point. The metal point I believe is what sends the moisture reading to the receiver so contact with the beam in question may provide some information. Would be better to drill a small hole in the beam. The range for that model tester is I think, 8% to 25%. That may not give you a reading of value. What is the normal moisture content of wood?

  2. GBA Editor
    Kiley Jacques | | #2

    Hi Kevin,

    This article and its recommended links should answer your question: Extending the Reach of a Moisture Meter.

    1. KevinKeegan | | #3

      Hi Kiley,
      Do you know if a quality long probe moisture meter can be rented? I talked to Delmhorst and the cost is steep for a new unit, close to $400, and a used one is close to $300 and the probes are another $140. They were very nice though.
      Thanks, Kevin

  3. Tyler Keniston | | #6

    >"I guess what I’m trying to understand is what do I need the long probes for?"

    Kevin, if you can reach the sill beam without long probes, it sounds like you don't need them.
    I can not comment on the original intent of the comment someone made elsewhere, but the long probes are typically just to extend your reach, not to get deeper into wood. Though they certainly COULD be used that way if you drilled holes.

    That said, many probes do come with 2 sets of pins of different lengths, one being longer to penetrate deeper into the wood. I would use the longer set in that case. But those are different than truly 'long probes' like the ones shown In Peter Yost's article.

    It is true that wood moisture content (MC) could be different deep inside the beam vs nearer the surface, but a surface measurement will still give you some sense of what is going on.

    The relevance of the surface measurement will depend on what time of year the wetting is occurring (compared to when you are taking the measurement) and from which direction the wetting is occurring (compared to which side you are taking the measurement).

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