Harm dried wood with dehumidifier

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Forum topic by Marcinchicago39 posted 10-06-2015 05:05 AM 1335 views 0 times favorited 8 replies Add to Favorites Watch
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10 posts in 992 days

10-06-2015 05:05 AM

Topic tags/keywords: dry dehumidifier damage wood

I have a question. I have some ash wood planks, which I chainsaw milled few months ago, I keep it in my basement where is not a lot of air movement, my wood dried to 13-15% and stopped. Two days ago I purchased used dehumidifier and few fans. I set up DH to work 14h a day and to 30% humidity what is maximum for this unit, btw is it OK to leave household DH working 24/7 without brake, if it isn’t commercial grade unit?
But, my main question is about other wood which I keep in same room, I have few nice pieces of purpleheart, walnut, zebra, cherry, maple, olive an red oak. This is kiln dry wood, which I bought at lumber yard, and today I start to worry that I can harm this dried lumber if I will keep it for longer time in same room where I’m drying other wood. Can someone tell me is it OK to keep my wood from woodstore there or it could be destroyed if it was already professionally dried in kiln. Problem is I have very limited space and moving all this wood will be a big headache for me, but I will do it if it could be destroyed if it will stay in room where DH is runnindg.
Help please! Thank you!

8 replies so far

View Tennessee's profile


2872 posts in 2509 days

#1 posted 10-06-2015 11:48 AM

The lumberyard where I buy a lot of my wood stores their kiln dried wood in a huge 1/2 acre covered shed, with doors at both ends open all day till they close. Basically ambient to whatever the local humidity is. They have no dehumidification in the building, or heat or air, for that matter. The wood stays just fine. They keep it all ricked and a lot of it is tight stacked in bundles to save space.

So, with that, what is the relative humidity of the room you store in with the dehumidifier off?
I find that air dried wood, if it goes down to 12-14%, that is about the best you can do when your relative humidity outside is in the 45-85% range. I have walnut stacked on my back covered outdoor area, and I just read it yesterday – 12-14%, according to my pin gauge. I’m about ready to plane one plank and see how it looks. We just went through over 8” of rain over four days here in SE Tennessee, and the wood is still 12-14%, but my ambient humidity was 100% for four days.

My main stash is kept in an unfinished basement room under my house. It includes both kiln dried and air dried, and none of it moves much, if at all over time. I think you might just want to turn off the dehumidifier and if there is ambient air moving through the room, go with that. Slow is better. Trying to buy 1-3% more might just cause some of the other wood to do things you might regret.

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

View WDHLT15's profile


1741 posts in 2470 days

#2 posted 10-06-2015 11:51 AM

When you dry wood in a basement, the evaporated water has to go some where. The bad thing is that it will go somewhere, like in your walls. A good dehumidifier is a must. In that environment with wet wood drying in a basement, your already dried wood will gain moisture and equalize with the environment. If your ash stopped drying at 13 – 15%, then you store bought wood will also equalize to this same moisture content, and your kiln dried wood will become “air” dried wood.

If you dry the wet wood somewhere else, and put a dehumidifier in the basement, you can store your dried wood there without any issues. Just don’t dry green wood in the same basement.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln.

View Fred Hargis's profile

Fred Hargis

4981 posts in 2487 days

#3 posted 10-06-2015 12:35 PM

In my experience (after going through 5 dehumdifiers) the home owner units have a finite, not real long, life. Even so, I’d keep the thing running to do the job. When it craps out replace it. Your other wood will be fine.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Marcinchicago39's profile


10 posts in 992 days

#4 posted 10-06-2015 01:18 PM

Thank you for your help.
Now I’m confused – WDHLT15 recommends not to keep green and kiln dried wood in the same room and Fred Hargis thinks my other wood should be fine. In this case I need more opinions of what other users think. Can I keep kiln dried ready to work hardwood in the same room where I recently milled ash wood? I bought my moisture meter at LeeValley, this is their cheapest model. When I check my fresh wood it shows 13-15% and my wood from store shows nothing. As far as I’m concerned, wood moisture level is lower than 8%.

View yvrdennis's profile


47 posts in 1071 days

#5 posted 10-06-2015 01:31 PM

Ideally you want to acclimatize your wood to the same humidity as the room where the finished furniture will be. In other words, the relative humidity in your wood storage room should be roughly the same as your living room.

If you don’t have good air circulation, the humidity will rise when you introduce a pile of green wood into the room. In that case you should use a dehumidifier, or circulate lots of outdoor air to keep the humidity at a “living room” level. But, if all of the wood in the room is already dry, then a dehumidifier is probably not necessary.

So, the short answer is, measure the relative humidity in the wood room and keep it at a reasonable level.

View Fred Hargis's profile

Fred Hargis

4981 posts in 2487 days

#6 posted 10-06-2015 02:08 PM

The reason I think your OK is the dehumidifier. Running it will keep the ambient air moisture controlled, all the time while the green wood is drying. You indicated your green wood is already down to 13-15%, so quite a bit of the water had already evaporated.

-- Our village hasn't lost it's idiot, he was elected to congress.

View Yonak's profile


986 posts in 1515 days

#7 posted 10-06-2015 04:12 PM

Marc, I’ve never gone wrong using Danny(WDHLT15)’s advice. The kiln dried wood is not the biggest problem with drying green wood in your basement. Without a good, reliable way of reducing the moisture from the air, the relative humidity in your shop would increase due to the high moisture content in the green wood and your tools would rust and mold would fester, not to mention the green wood would take longer to dry.

The best place to dry lumber would be a dedicated room equipped with a way to lower the humidity and expel the moisture (think some degree of kiln). When not available, I’ve dried lumber in my garage, leaving the doors and windows open and using fans to move the moisture from between the boards. This degree of air circulation would only be necessary in the first few weeks of drying green lumber and it sounds like your ash is past that point. Avoiding dead air between the boards and a way to move moist air out if the room periodically remains important until the wood is dry, however. You could also dry it outdoors, under a good, dry shelter, with open sides for good air flow, and up well off the ground so the green wood has a chance to dry most efficiently and without problems.

That said, to address your original question, even if kiln dried lumber increases in moisture content as it comes to equilibrium with the relative humidity in your area, it would not harm the kiln dried wood. It would just have to dry out again before you use it. It’s always a good idea, before starting a project, to take your lumber to an environment similar to where it will reside as a finished product and give it time to acclimate before cutting, anyway.

View pintodeluxe's profile


5654 posts in 2807 days

#8 posted 10-06-2015 04:58 PM

I think green vs air dried is the main deciding factor. I stack and sticker green lumber in an open air shed. This exposes it to wind, but not rain, to help air dry it. Once it is air dried to 15% moisture content, I take it in and dry it further. Once it is 15% or lower, you are okay to move it indoors as long as you run the dehumidifier, fans, and possibly heater. I have done this with no ill effects on cast iron tools etc.

As far as bringing green lumber indoors, I don’t do it. You might as well put a hot tub next to your cast iron tablesaw. Now that you are 15% or less, just keep it indoors with the drying equipment and you should be fine. Remember to take core moisture readings, not just surface readings.

If you take kiln dried lumber, and splash a bucket of water on it, the lumber will dry out again very quickly.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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