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My wood shop is outdoors since I don't have a garage in my current house that I'm renting. As such, everything stays outside for the most part (except small power tools).

I've been buying construction grade lumber from HD for making all sorts of things whether it's wood shop upgrades or furniture. I can't seem to justify buying the 'select' grade stuff so I usually just buy stuff like white-wood stud, etc. but from my reading, construction grade lumber is usually wetter than ideal. I was wondering if I could store the lumber outdoors so that it could dry to 8-10%? I live in a somewhat humid area so I'm unsure how well this would work (East TN near Knoxville).

Since outdoors would be ideal, I'd do anything reasonable if outdoors is feasible. I do my woodworking on a deck so I could maybe even store the lumber below the deck and cover the spot with a tarp so it is covered from the rain. I'm not looking to build any permanent fixtures here that would be hard to move once I buy a house. At the moment, it just sits below the overhanging roof which gets like 4-6 hours of sunlight on a clear day and shields it mostly from the rain.

Also since it is close to winter, the temps will be lower but usually no less than 25-30F on the coldest days. Would it dry out at all in those temps?

If necessary, I can convert this small storage room inside my house into a wood drying area but it would be cramped and I'd probably have a fan circulating air 24/7 and maybe even a space heater so I'm sure it'd add onto my electricity bill. However, if drying outside would take a long time, I may just prefer to dry it inside.

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  • 'Wetter than ideal' can be an understatement! I watched a video a couple of weeks ago and someone was power-driving a threaded rod into the bottom of one of the legs and towards the end water bubbled out of the hole O_O It's not always that bad, but yeah, the MC is way way higher than you want for furniture work.
    – Graphus
    Oct 26, 2020 at 9:40
  • "I was wondering if I could store the lumber outdoors so that it could dry to 8-10%?" Nope, not unless you live in a particularly dry climate. This is the lowww end of air-dry MC, and is only achievable if the humidity is particularly low (like single digits). It also requires the wood to be properly stickered, and takes time (more than you have). Briefly the rule of thumb is this: if you want the wood for interior use, acclimate it to your interior. Unless you build a wood-drying kiln of course. Expect this to take bare minimum 2-3 weeks, but ideally a month or longer.
    – Graphus
    Oct 26, 2020 at 9:45
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    IOW, buy the lumber for this project then store it inside for about a month, then build the project. Take the wood outside to work it, but bring it back inside for overnight storage. As soon as it's back outside, it will start absorbing moisture, but, if you're working for 6 hours, it won't absorb nearly as much as it lost over the last 6 weeks of inside storage.
    – FreeMan
    Oct 26, 2020 at 10:29
  • Thanks for the information everyone. Everything I've read so far is pretty general information and just gives generic advice like "leave it in a well ventilated place" and "7-10% is ideal for furniture". So I'm trying to fill in the missing details. I might even do some testing and report results in a blog post or something. Humidity here can be bad so I'll be converting my storage room into a wood drying room (luckily this room is attached to my back deck so it's not terrible access) and monitoring it with a moisture meter.
    – cchoe1
    Oct 26, 2020 at 13:58
  • If you're building furniture in Eastern Tennessee, from wood you purchased in Eastern Tennessee, and will keep the completed furniture in Eastern Tennessee, you might not have a huge problem with relative humidity, etc....like you might if you sent the furniture to Arizona when it's done. OTOH, I've purchased wood from HD/Lowe's, etc. that literally dripped when worked....
    – gnicko
    Oct 26, 2020 at 23:00

1 Answer 1

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I did some more research and thought I'd share some of my findings.

One thing is that relative humidity and moisture content both use percentages but they are describing the idea of "water saturation" in a much different way. It seems obvious but having humidity of 80% would not mean your wood would try to reach 80% moisture. Equilibrium would be achieved much much lower. There is actually some charts that show what kind of equilibrium moisture content would be at for a given RH.

https://www.woodworkerssource.com/wood-moisture-content.html

So looking at the chart above, we can see what kind of equilibrium moisture content we will achieve given a constant temperature and relative humidity. In my specific area, we've been seeing temps at this time of year (mid autumn) around 70F. Today, we had a RH of 80%. If left alone in this exact condition for a long period of time, EMC would reach around 16%. In other words, it would not be possible to achieve my goal of 6-8% moisture (amended after further research, not 8-10% as I initially thought).

I've created a drying room today that I just checked on and has a RH of 45% in there. Not bad but it's still getting started since I just added the dehumidifier into the room and those boards I'm sure are still releasing moisture, as I have about 150-200 board feet of wood in perhaps a 588 ft^3 space--quite a small space (12L x 7W x 7H). In a real world scenario, I am expecting the maximum RH in this space to drop as the moisture within the wood also drops, as my dehumidifier is constantly condensing water in the air and eventually, there will simply be less water to pull out. In other words, very wet wood will release a lot of moisture quickly, dry wood will release a little moisture slowly. This effect is why furniture might take months or years after being put into a real home before it warps. So ideally, I think this room can achieve 30% RH (I suppose this will be a good test of the insulation in that room, since outdoor RH is usually 50-90% here). With those numbers, I can achieve EMC of about 6%.

One thing to note is that cold air does not hold as much moisture as warm air. So at colder temperatures, EMC is reached at a much higher moisture content than warmer temperatures, given a constant RH. So attempting to dry wood in the winter outdoors would be even more difficult than in the summer time, on average.

Another thing to note is that RH is much more of a factor in a lower EMC than temperature. If you can adequately control RH to about 30%, then your lumber should adequately dry for furniture anywhere from 30F to 130F. A bonus would be controlling temperature as well but you should be careful with increasing temperature if you do not control RH. While higher temperatures means lower EMC, if you do not control RH, then you have a chance for fungal growth, which can happen anywhere after 50% RH.

So to summarize, your best bet is to control humidity in some fashion. If you can reach 30% humidity or lower, you should be able to adequately reach a moisture content adequate for furniture. To help speed things up, increasing temperature also helps but you should not try to dry wood by only controlling temperature, unless using high heat like in the case of kiln-drying.

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  • 2
    Excellent self-Answer, +2 if I could.
    – Graphus
    Oct 27, 2020 at 9:01
  • I'd give you the check mark if I could, but only you can do that.
    – FreeMan
    Oct 27, 2020 at 10:45
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    Thanks! I still have a few hours before I can accept my own answer so I'll probably wait to see if anyone else has any further information to add and select from that point. Thanks for the tips, it helped to guide my research more. At first I was obsessed with trying to make outside work but after some rearranging, the storage room worked out quite well, although it is a bit cramped.
    – cchoe1
    Oct 27, 2020 at 11:46
  • When all you have is a hammer, everything looks like a nail. Sometimes a little rubber ducking is all you need to realize that there's a forest beyond all the trees.
    – FreeMan
    Oct 28, 2020 at 12:20

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