Material "swelling"

TL;DR: It ain’t a thing.

My weather station needs replacing, and the new outdoor sensor has a different design and won’t fit in the shield I had made, so I took it down and had an idea.

It was constructed from draftboard, untreated. It’s been hanging under the soffit outside my kitchen since I made it in early 2018, so over two years. I live in Atlanta, and it’s known to get quite humid here. I also have the GoGMs and snap-and-store boxes which I cut from the same sheets provided in the original materials pack.

All parts from that those sheets measure 0.128-0.1285". I have about a dozen unused sheets of draftboard, about 10 from the same “batch” last time I ordered. They measure (with masking peeled back) between 0.128-0.1315". All have been in the same stack for about a year.

I had noted thicker sheets from that order a while back, because I had issues with getting parts to fit into slots that had previously worked, and I had to adjust the slot size slightly.

On a related side-note, I had issues cutting a part from that thick sheet some time in the fall last year, and at first thought it was the change in thickness, but it turns out it was only in the lower right corner of the bed, and reverted to normal operation (working perfectly with PG settings) after I cleaned the optics, probably only for the 3rd time in 2 years.

I’ve been working with wood for over 25 years, I’m well aware of moisture content causing mechanical issues. I have a surface moisture meter which I have used to pick thru lumber for certain projects when warping would be an issue. Every piece of draftboard and PG ply reads 0 or 1% - compared to the hardwoods which have reading 4-7%. My ice mallet (maple I think) is 4%, and the cedar I cooked some salmon on last week (then washed) is 6%. I didn’t want to prod my furniture. :smile:

Oh - the draftboard that’s lived outside for two years? Same 0-1% (depending on where and how hard I poke it) as the parts that have lived indoors all this time as well.

So, as I was saying, it ain’t a thing.


I’m guessing the moisture probe is basically a resistance meter? If so I wonder if the glues in the draft board would or could cause a false low reading? Not saying I think they are false just curious.

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I do think the adhesives are playing a role in resisting moisture, as ply (of all brands) reads substantially lower than hardwoods. That includes a couple of different sources of BB, and cheap underlayment. All virtually 0.

I’ve never had reason to doubt the readings, and this meter gets high marks for accuracy.

In any case, there is no measurable change in dimension, which was the point I was trying to make.


cool beans was just curious, never held a moisture meter and was wondering if something like that might effect the readings. Point was received about the dimension change or lack there of, my mind just goes off in different directions than most people hehe.


I just checked outdoors - my ~5yr decking (bare but treated pine) and fence (untreated cedar, same age) also read 0-2%. The bark of the tree closest to my deck reads 40%…

But this has nothing to do with swelling. Look what you made me do! :laughing:


I had actually Googled this awhile back out of curiousity since it kept coming up. :slight_smile: It might help to clarify in your TL;DR that the material you’re talking about is MDF, not wood.


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