I previously posted a question here about drying lumber indoors, and am currently attempting to do so in a heated room with a dehumidifier running. I purchased a $50 moisture meter which seems to give consistent and reliable results that make sense. The MC of recently milled boards goes down steadily to below the 8% limit of the meter when measured from the face or edge of the board with the pins pushed in with moderate pressure. However, if a fresh cut is made, the MC is considerably higher. Is it standard practice to make a fresh cut every time you want to check the MC? I haven't seen much discussion of this issue in my reading so far.
(Sawing and Drying Forum)
From contributor L:
Sounds like you are checking the MC in the wood's end grain? Trying checking at least 2' from the board end/any knots. If you are checking 1" lumber push pins in 1/2".
As I 'pre-plane' my surface-dry boards down to 7/8 or so, the meter will then register anywhere from 10 to 20 %, depending on how long the original log has been milled. I then re-stack them in my moisture controlled room. We plan to start woodwork in a couple of weeks.
So, is it safe to say if the core MC of my boards is not eight or less, I will kick myself when my trim joints open up in a few months? I can mask some of the potential shrinkage, for example by notching my header casings into the side casings. The face trim around doors will be tougher and more visible. I am planning on using a lot of this lumber for flooring, which as I understand it shrinks and swells quite a bit with the seasons anyway. Any suggestions for better dealing with this would of course be appreciated.
The in-use MC this time of year is often 6.0% MC (30% RH) in homes and offices. As a general rule, wood shrinks 1% in width and thickness for each 4% MC loss. So, you can see why with 10% to 20% MC in the core, you will get substantial drying and shrinkage. You mention that you have a moisture controlled room. If you are trying to dry lumber for interior use, it should be at about 20-25% RH in order to achieve the required low MC’s. Note that wood products in use generally range from 6 to 8% MC. That includes flooring.