Green Wood on top of Drywall - Potential Problems

gman997 · April 25, 2020, 09:44:17 PM

Hi everyone,

New to the forum and as an aspiring DIY'er I may be coming up with ideas that will cause me grief in the long run.

I'm looking to update a room in my house and put up cedar planks on top of the drywall. I plan to put an oil based stain on one side of the cedar.

Now, the cedar I procured was not kiln dried and still is green. I purchased an inexpensive probe based moisture gauge and I'm getting readings of 12 to 18% across some random samples.

I'm expecting some shrinkage so I plan to dado cut the wood, stain, and overlap the planks so that the drywall will not be exposed once the wood shrinks. Outside of that are there other problems I could potentially run into - mold issues with the drywall, stain getting damaged or other things?

Thanks!!!

Southside · April 25, 2020, 09:59:31 PM

Welcome to the Forum. What type of cedar? Depending on the accuracy of your meter you may or may not be some what OK, or in for a real mess. ERC will develop a white, crystal looking mold on it, if it's too wet and does not have enough air flow. If you really are at 12% then you should be fine, if you are really at 25% or more then, results will be largely impacted by ambient moisture of the area, overlap, etc.

Additional info can only help.

Don P · April 25, 2020, 11:02:32 PM

All the cedars dry pretty easily and quickly. Sticker it in the warmest place you've got, put some fans on it and get it dry first.

Ianab · April 25, 2020, 11:43:10 PM

If the 12-18% reading is correct then you wont need to worry about mould, below ~20% it's not an issue (this is why construction lumber is dried to ~19%) Test some random dry wood with your meter, if it's under 10% in your house, and 10-15% outside, then the meter is reading what you should expect, even if it's not super accurate. +/- A few % wont matter in this application.

Cedar shrinks less than most woods, so a shiplap profile should take care of any movement.

ideally stickering it and getting it down to under 10% would be great, and should only take a few weeks. But if the moisture readings are close to correct you should get away with putting it up now.

low_48 · April 26, 2020, 11:38:23 PM

I wouldn't be so sure you won't get some mold on the drywall paper. Depends of course how accurate your inexpensive moisture meter is. You should probably edit your title, 12-18% moisture level is far from green lumber.

kantuckid · April 27, 2020, 06:33:48 PM

FWIW, my moisture meter is a gunpowder scale and a microwave oven. Weigh a sacrificial piece of wood (I do a small piece say 1 x1 or slightly larger), microwave it until bone dry then reweigh it. If you passed grade school math your home free with a spot on moisture content. :D
I agree, cedar is the easiest of all woods I've dried.

Bruno of NH · April 27, 2020, 06:38:22 PM

Put up 15lb roofing felt over the drywall.
That way the drywall face paper won't be in contact with the wood.
Don't use poly sheeting

Southside · April 27, 2020, 09:27:24 PM

Wouldn't that be kinda stinky there Bruno? Maybe rosin paper instead?

gman997 · May 12, 2020, 11:52:17 AM

Hi everyone,

Thank you all for the great advice!

So I ended up not using the cedar, which I'm not sure on the type, I know it's not red for certain though. I used Ianab's advice and tested some other random samples of wood that was dry which did register about 4 to 6 % lower, so I think it's off as once I pulled out and got out the router the wood was clearly moist, very moist. So all I can think of is my moisture meter is not that effective given the prongs only go in so far.

I ended up going a different direction with my project and used kiln dried pine that was already tongue and grooved. I used Tung oil for the finish and I love the look. This is for a walk-in closet that will be used as pseudo mudroom for the kids and misses to put away and organize all their stuff. I still have some trimming to finish up and complete the bench; but, it's come along.

I also love the idea of using a barrier like felt or rosin paper, would have not thought of that. I'll file that idea away for the future!

Thanks everyone!