How long for rain soaked lumber to dry?

[Jim Massey]

I was forced to store a bunk of 4/4 rough alder outside over the winter. I got it out yesterday, and the top half was soaked. It seems the tarp had a hole. It also had sporadic mold on it. I've stickered (3/4" stickers) the lot in the heated garage, but I'm concerned about the dry time. I live at 9400 feet, and inside RH is ~15%. I hope to use the alder for trim in about 6 weeks.

Will rain soaked wood dry at the same rate as green wood? It is going to take 6 months to get to equilibrium? With the mold, I guess I'll see when I plane the wood, but any indication if its any good still?

[Mark Bolton]

Faster.. It's just surface water.. If it was kd the cells should be collapsed and uptake is minimal.

[Jim Massey]

Faster.. It's just surface water.. If it was kd the cells should be collapsed and uptake is minimal.

Yes, it was KD.

Even if it was soaked for ~6 months? Not sure how long the tarp leaked.

[Mel Fulks]

I agree with Mark. KD is considered a permanent change. It takes prolonged thorough soakings to reverse. I experimented with some pieces only 3 or 4 inches long and it took a couple of under water soakings to reverse effects of
KD. You will probably remove all the soaked wood in surfacing.

[bill tindall]

1. It doesn't need to be "furniture grade dry" for trim. If it gets down in the range of 12% or less it will be ok to use for trim , providing you are not using wide (say 8" pieces for trim.


2.If mold is growing on it it likely had water in contact with the lumber. The mold will enhance the ability of water to soak these areas. Where there isn't advanced mold attack the moisture content may have gotten up in the range of 25%. It is hard to get lumber above this level after thorough drying, KD or otherwise.

3. How quick you can get the lumber from where it is at , say 25% MC, to usable depends on relative humidity, air circulation through the pile and temperature. This time could range from a week to infinite. The drying rate will be the same as "green lumber" except you will be starting at around 25% MC where water sat on the wood, not 100% MC.

4. Mold penetrates lumber rapidly. Mold can shoot through 4/4 lumber in 2 days under good mold growing conditions(hot summer and green lumber).

For the bystanders......NEVER dead pack lumber outdoors where rain or snow can contact it. If you must, and with a garage it is unclear why one must ( the car will not be affected by rain) put the lumber on sticks even if it is KD and, cover the top of the pile to prevent water trickling through it.

[bill tindall]

I don't agree. Where water contacted the wood for even days the moisture content in these areas will be in the neighborhood of 25% throughout the lumber thickness. I would call that reversing the KD process. Where there is significant mold attack the moisture content will be substantially greater. Surface planing will not uncover 8% MC lumber within. This pile will have a MC that depends on the relative humidity inside the tarp. If that value is 100%, which it will be if there is liquid water in there, I will leave it to you to look up the MC of the lumber in a table of RH vs MC for lumber.

[Curt Harms]

Would it be worthwhile to buy a moisture meter then sell it if you have no further use for it?

[Bradley Gray]

A box fan or two blowing through the pile parallel to the stickers would speed the drying. Adding some weight on top would be good too.

[Mark Bolton]

I don't agree. Where water contacted the wood for even days the moisture content in these areas will be in the neighborhood of 25% throughout the lumber thickness. I would call that reversing the KD process. Where there is significant mold attack the moisture content will be substantially greater. Surface planing will not uncover 8% MC lumber within. This pile will have a MC that depends on the relative humidity inside the tarp. If that value is 100%, which it will be if there is liquid water in there, I will leave it to you to look up the MC of the lumber in a table of RH vs MC for lumber.

There is no need to get into a debate here. While I know its just conversation, there is no "reversing the KD process". Kiln drying affects a permanent change in the cell structure of the wood. So it simply can not be reversed but of course its a technicality. The material stored outside, even if its in a dry shed or building is going to increase in moisture content regardless until it reaches the ambient just like it does in the wholesalers warehouse or covered storage sheds before it reaches your retailer and then your shop. Its increasing in moisture content the instant the latch is released on the kiln door.

For trim I would have zero issue with moving the pack inside, opening it up, stickering it in the shop for a short period, and moving on. For furniture or cabinetry I would give it a bit more time.

6 weeks would be fine by me for either though I'd really hate to tie up the shop space.

[Prashun Patel]

Coincidentally, I am facing the same issue with green wood that I've had 'drying' outside for about 1.5 years. I bought a pinned moisture meter - a cheap one (like $25) and I gotta say it's the best purchase I made this year. I bought it with the idea that I don't need it to be super precise and I don't need it to last for 100 years. I've tested it on a mess of green wood turning blanks of scattered ages in the basement. It is surprisingly accurate and consistent (at least, it's more accurate than my guessing and hoping.) To test below the surface, you just drill two pilot holes almost as deep as the pins into an inconspicuous part of the wood and insert the pins.

[Mel Fulks]

I have a couple of old posts on this subject. I compared movement of a kiln dried piece with an air dried,that was
formerly ADJASCENT in THE SAME PIECE of wood. At first the kiln dried piece moved less than air dried after soaking for
days . On third test cycle they moved the same amount in all conditions. I still have them. The pieces were short to allow
HOT water to soak all the way through. For the op's purpose ,yes the moisture content has been raised but KD will allow
some types of projects to be made after brief drying time as wood movement might be insignificant while drying more.

[Mark Bolton]

I have a couple of old posts on this subject. I compared movement of a kiln dried piece with an air dried,that was
formerly ADJASCENT in THE SAME PIECE of wood. At first the kiln dried piece moved less than air dried after soaking for
days . On third test cycle they moved the same amount in all conditions. I still have them. The pieces were short to allow
HOT water to soak all the way through. For the op's purpose ,yes the moisture content has been raised but KD will allow
some types of projects to be made after brief drying time as wood movement might be insignificant while drying more.

I remember these posts Mel and found them very informative especially given the extremes of your test (complete soaking, multiple cycles, and hot water). While its always best to be cautious and gauge whats best for the type of work being done, I highly doubt many people with some KD material that got rained on or dampened are anywhere near having a pack of lumber completely submerged in hot water repeatedly. :) Your test gives me a sense of calm.

There was a local lumberyard near here that had a huge full millwork shop as well. They were at one time the premier supplier for high end wood products in the area. Many distributors would complain endlessly about them that when the tractor trailer that had come half way across the country arrived in the yard with their load of lumber, before the tarp even came off the receivers were out there with moisture meters checking the material and would on occasion refuse a load. Needless to say they are out of business and towards the end were in short supply and I can only imagine due to a lack of wholesale vendors who would deal with them or could satisfy them.

Its great to be cautious but the worlds gotta keep turning..

[Mel Fulks]

Complete agreement. I've never seen any bad lumber come in from our best suppliers even if meter readings seemed high. "Good deal" lumber is usually a bad deal.

[Jim Massey]

Sounds like I need a moisture meter. I turned the heat up to 78 in the shop. I'll see about getting a couple box fans.

[Scott T Smith]

Hi Jim, lots of good advise on this thread. Here are some thoughts from a kiln operator.

Yes - buy a moisture meter and get a couple of box fans on the stickered stack. I personally think that you will be fine in 3 - 4 weeks. You can fell which boards have a higher MC% because they will be much heavier per bd. ft than the drier boards. You may want to separate the boards based upon weight and get your fans on the wettest ones.

Wood cells contain both bound and free water. Free water comes out easy, bound water less so. Bound water is contained within the walls of the cell, versus free water that is stored in the middle of the cell. When previously kiln dried wood is rewetted, usually (but not always) the new moisture is stored in the center of the cell; ie free water. In extreme instances, it can be reabsorbed within the cell wall also but most likely you will be ok.

One thing to expect is more surface checking on the boards that were wet after they have dried out. This is due to the fact that the wood cells expanded when they were rewetted and when they dry/shrink surface checks will open up.

Your three factors that affect drying are temp, RH% and air flow. You should be able to air dry just fine in the 60 - 70 degree range. Don't overdue the heat or airflow through the stack, or you risk damaging the lumber.