Wood Drying Question

[Yonak Hawkins]

When stacking green wood, such that warm air is directed (but not blown) to rise up through the stack, and then dry wood stacked on top, is it best to continue stickering the dry wood so the air has a place to rise once it reaches the dry section or is it ok to dead stack the dry wood figuring the air will go out the sides uninhibited ? ..Or does it even matter ?

[peter gagliardi]

Sticker it all. Then you don't have boards that get aired on one side, and nothing on the other creating cupping and stress.

[Jim Andrew]

Dry wood does not need to be stickered.

[Yonak Hawkins]

Thank you for your replies.

[Jim Matthews]

This requires clarification - are you storing this outdoors, in a shed, or in a basement?

The amount of condensation in a basement can lead to mold, and mildew.
Dry wood is like a sponge, it absorbs humidity with the seasons.

More humid spaces require airflow management.

[Yonak Hawkins]

This requires clarification - are you storing this outdoors, in a shed, or in a basement?

The amount of condensation in a basement can lead to mold, and mildew.
Dry wood is like a sponge, it absorbs humidity with the seasons.

More humid spaces require airflow management.

This wood is in a separate, enclosed building which is 16' X 24' X 12' high, mostly above ground but built on a slab and is mostly filled with dry wood except for the 500 bf of fresh-cut ash. I have not yet stacked the dry wood on top. I was wanting to get some advice before I finished the job which I will do Monday morning.

Right now I have a dehumidifier in the building and a fan blowing the air generally around but not directly on the green wood. When the stacking is finished I will have a system directing sun-warmed air to the bottom of the stack. I will also continue with the dehumidifier. Unless I hear different advice before tomorrow morning I will sticker a few levels of dry wood above the green to leave some space for circulating air above the green stack and then dead stack the rest. I would be very interested in getting other opinions before I continue stacking. Thanks.

[Bradley Gray]

If I was drying wood this way I would use some thinned white glue (or a commercial product) to seal the end grain on the green wood. A proper dehumidification kiln is a closed air system - the air stays in and a hose removes water so the moisture in the air and the wood decline at the same time. Drying just the air may cause stress and or checking ends.

[Yonak Hawkins]

Thanks for the advice, Bradley. Could you expand on the concept of a closed-air system causing the wood and the air to dry at the same rate ? Does a closed-air system reduce moisture at a slower or more consistent rate somehow ? I mean, I could modify the ambient moisture content by changing the settings on the dehumidifier or the solar assist. Thanks for the help.

[Jim Andrew]

You need to go to forestryforum.com, and check out the threads regarding solar kilns. The wood doctor is on the site, along with some old timers who have lots of experience with drying wood.

[Bradley Gray]

Lowering the whole system's moisture content is exactly what you want. The kiln system I use is built around an Ebac dehumidifier/heater unit. The kiln is basically an insulated box with a plenum built along the back of the box. I cover the stack with plastic to force the air returning from the dehumidifier between the stickers, out the front of the stack and back to the humidifier. I have added a couple electric baseboard heaters to speed start-up. There is an external control box that controls the temp. as well as the % of time the dehumidifier runs. Below 30 C the humidifier should not run more than 80% of the time as the coil can ice up. Thicker stock needs slower drying to avoid checking.
Another thing to keep in mind: A dehumidifier designed to dry wood has stainless steel coils while a household unit is aluminum and won't last long if you dry acidic woods like oak.

more info: http://www.ebacusa.com

[Scott T Smith]

Hi Yonak, like Bradley I am also a kiln operator.

Wood dries based upon several factors. Species, thickness, initial moisture content, temperature, airflow and relative humidity. Drying too quickly - or too slowly can damage your lumber. Additionally, rewetting boards that are already dry can also damage them.

In my Nyle DH kiln, a typical hardwood schedule will dry 4/4 green hardwoods at 80% RH for a couple of weeks, then drop to 60% RH for a couple of weeks, and then down to 40% RH. Sometimes the final RH% is lowered below 40% in order to wick the moisture from the center of the boards, and then the RH% is increased at the end of the cycle in order to condition the boards.

Most lumber is stacked flat, horizontally with air flowing through the stacks on a horizontal plane. Lumber dries best from the face of the boards as opposed to the edges or ends.

If your lumber is stacked flat, you might want to reconfigure your airflow so that it enters the stacks from one side and flows through them. If your lumber is standing on edge, then your bottom up airflow should work fine.

[peter gagliardi]

In reply to Jim Andrew above, dry wood DOES need to be stickered off the top of the pile of wet wood it is on. And should be in between as well, or you will reintroduce stresses in the dried wood as the exposed faces are free to take on and give off moisture, while the hidden face can't. I also operate a Nyle dehumidification kiln in my shop, so I am not coming at this "green" so to speak.
In short, ANY wood that is in the kiln that is of value needs the same attention.

[Yonak Hawkins]

Thank you all for your responses and your valuable information.

I had already gone ahead and did what you suggested, peter, because I already had the stickers out and it was just as easy to put them between the boards as to gather them up and put them away. I figured it couldn't hurt and could only help .. I just didn't know why and your messge told me why. Thanks.

Jim, thank you for the suggestion of the forestryforum.com message board. That will be a valuable resource for the future.

[Danny Hamsley]

I also operate a Nyle Dehumidification kiln. If you sticker the dry lumber over the wet lumber, your dry lumber will pick up moisture from the evaporation of the water in the wet lumber. You need to get rid of the water vapor. A dehumidification kiln condenses the water and the water moves outside the kiln via a hose.