what is considered acceptable moisture in basement woodshop

40% seems kind of high to me. You should be able to install some form of vapor barrier, that with the dehumidifier should help reduce the humidity, you may also need to seal the floor with some form of moisture barrier as well. I hope this helps.

-- "At its best, life is completely unpredictable." - Christopher Walken

If you seal the walls that will help a lot, Even the floor should be sealed but you also need air circulation to prevent mold from forming. It should be less than half of what you are at now.

-- Sell it here> http://woodworkerslist.com

I just did a quick survey of various websites and think that 35% to 40% RH is good for outside temps above 20F. In winter with colder temps the humidity should go lower to prevent condensation on walls/windows depending on how well the house is insulated.

So I’d say you are in good shape. BTW – our house is 65% right this moment and it is very comfortable at a temp of 77F.

relative humidity

-- Joe

Paul,
40%! I wish.
I’m in eastern PA and my basement is an old stone foundation.
I installed a digital hygrometer in my basement shop a month ago and relative humitiy has consistantly been around 70% and the highest has been 81%. (I think it almost rained.)
I suggest you rough cut your lumber and then let it aclimate in your basement for 2 or 4 weeks before working it and it will be OK.
In the North East, where we are, we have wide swings of high humidity in the summer and very dry in the winter. You have to expect wood movement in any project unless the finished piece is in a climate controlled enviroment.
Dehumidifier eh?

-- HenryH - PA

It kind of depends on where you live and the relative conditions. Like Henry, I’m in the Northeast. 40% RH in the basement at this time of year is quite good. With my dehumidifiers running, I think mine is right around there (40%) right now. In the winter with forced-air heating running, I also try to keep the humidity at about that level in the basement. It usually gets a bit lower than that in the upper floors during the winter.

-- Mark, Webster New York, Visit my website at http://thecraftsmanspath.com

Does anybody have experience with a chemical DampRid? I see it at Home Depot, since I work there, and I would guess by the name that it gets rid of moisture.

I would consider 40% tolerable. Just don’t ship your products to Arizona. In you climate humidity must drop in the winter when everything is frozen??
DampRid looks fine for a closed or small RV (I use a similar product in my Camper) but I don’t think it will be much use in a basement. There are some pretty good moisture sealers for concrete walls you might try.

-- Les B, Oregon

I agree…40% sounds pretty good. I just went in and checked mine and its at 60%. Its a very warm day here today, 92 degrees and the humidity is quite high. My shop is a tuck under garage which is mostly underground so it usually stays pretty cool, but it does feel a bit warm in there. The shop temp shows 72.

-- Wayne - Plymouth MN

Hi Paul, northeast Pennsylvania here. Basement shop, with walls and wood floor at 40%. Run a dehumidifier just to make sure it doesn’t get to high. Have not had a problem with the wood stored in the shop or with rust on the equipment.

Henry H, where in the Northeast??

-- Guy Kroll

Just remember that high quality woodworking was done in pre-airconditioning times and still is in many places throughout the world. The RH is more for the human than for the wood, assuming like mentioned before that the wood has had time to reach equilibrium.

-- Joe

Hi Guy, and friends here at Lumberjocks,
I live in Bristol, Rhode Island. The RH seems to vary from 36 to 45 percent. I have a dehumidifier running, plus 2 fans in far corners of the shop 25’ x 40’.

-- Paul, Bristol,Rhode Island

Hi Paul, I’m close to you in Westport with a basement shop 30×60 with 10 foot tall ceiling and also all concrete. I keep 2 dehumidifiers going at all times. Your doing pretty good at 45 %. I’m at 50-55% these days and the basement temp is holding around 70 degrees. The temp in your basement will not move up and down with the outside temp but will stay about the same and take weeks to move up as the summer goes on. I did a lot of searching about this over the winter and this is what I found. Everything I read I had to read twice just to wrap my head around it. The relative humidity is just that “relative” to the air temperature. If you could seal the air in your basement (scientifically speaking) and warm it up the relative humidity would change even though no moisture could get in or out. Their is a rule of thumb as to air temp and humidity that of course I can’t remember but I do know that the humidity level I’m at is perfectly fine and so is yours. Their is a lot to read and formulas to drive you crazy but the bottom line is your fine and also think about were the project will end up I.E.> your home, customers home, by the water etc.

-- Mike, Westport MA.

Hi Mike,
First, thanks to all my friends here at LJ for their continuous help!
I’m considering building walls with vapor barriers, and doing something with the floor to keep the basement woodshop dry. Some years ago, I painted the floor with an epoxy, and it failed, leaving kind of a mess. What I’ll do with the floor will have to wait till the walls get done, that is if I ever do. I’ve got a loooong list of projects, and I want to make furniture, not walls.
I’ll keep you all posted as I progress.

-- Paul, Bristol,Rhode Island

I disagree with 40% if your doing woodworking I would think it needs to be closer to what your indoor RH is if you think about it when you buy lumber you look for 9% – 12% moisture content the reason you let it acclimate to your shop is to get it to adjust to Relative the humidity. What is the RH for the environment that the finish product will be kept 25% – 30%? so I would think that your goal would be no more then 30%. I guess its all relative and maybe moisture content has nothing to do with the RH this is mostly just an assumption on my part so please correct me if I am wrong.

-- Sell it here> http://woodworkerslist.com

The answer to all your questions about R.H. and moisture. Purplev posted a reference book in the forum that you posted this on today. Go to page 57.

-- Mike, Westport MA.

Probably the most important thing is how close is the workshop RH to the main level RH. Most of your projects will be going in your home right? Its the difference between these two areas that will give you problems. Two options, get a dehumidifier if it is too humid and/or maybe use a waterproofing coating like Drylok on the basement walls. I used the Drylok on the walls and an epoxy floor paint on the floor and that help a ton in the basement. Good luck.

-- Steven Naslund, Chicago IL