Strap-Clamping Stacked Lumber for Air-Drying

A discussion of a proposal to keep stacked sycamore strapped tight with loading straps during air-drying. June 28, 2006

I have about 400 bf of persimmon that I am going to have sawed soon (along with 350 bf of black walnut). I know that persimmon is a bugger for twisting and warping so I plan to slab it up thick to around 1 1/2" and finish milling it after it air dries a couple years.

I am considering using 3,000 lb capacity ratchet straps to clamp my lumber stack. I will use 16 straps for the 16' lumber stack that I have (placed around the stack at each sticker) and I plan to cut 2x4's slightly wider than my stack for where the strap fits over the bundle so I don't squeeze the lumber together.

Since this is a unique lumber I am stacking it right beside my home driveway so it's easy for me to check the tension in the straps often. Other than future failure to the ratchets due to the stack being covered but still outside for maybe 2 years, do you see any downside to what I plan to do?

I am not really talking about it being practical since I have yet to find a buyer or particular project for this lumber and I am more wandering if it will work or not? 3K lb load capacity for the straps seems adequate if I can actually get that much tension in the ratcheting of them. Sorry if I was long winded but I have dried other species of wood just none that are reportedly so temperamental.

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
By the end of June, the 4/4 through 6/4 wood will be as dry as it is going to get (within a few percent MC). Dry wood that then gets rain blowing on it and sun will then warp and lose quality. So, you need to get this wood into a sheltered area in about June to get the best quality. Incidentally, make sure you use a nice size roof to keep rain of the lumber while drying. Good air flow will also help minimize warp.

From contributor W:
So you're saying that it'll only take about 3 months to get this mostly dry?

From contributor J:
Sounds like a good idea, but I would get the larger straps 20,000 load capacity, like at the truck stops. I would also cover the top pieces and weight them down with sandbags or cement. Remember that the webbing of those straps will mold where they are touching the wood, so move them periodically. I would build a frame and then use weight and a pipe clamp or so to compress and hold the sides together. Keep the sunlight off and ensure that plenty of air flow is available. Make sure to seal the ends also.

From Gene Wengert, forum technical advisor:
You can check the MC yourself, but you will find that after about 60 days of warm weather, the wood will be roughly as dry as it is going to get. Further air drying results in little moisture loss, but a high risk of stain, mold, checks and warp (and maybe insect infestation as well).

From the original questioner:
I have air dried 4/4 + 5/4 oak and poplar before and it's been my experience that after 6 months or so it will be down below 20% mc and air drying here in southern KY. I have had little or no success drying it below 15%. I did stack some 4/4 poplar and left it uncovered within the canopy of the forest last summer and it was by far the driest stack of lumber I got last year. I didn't test it, but I am sure it was below 15% mc.

The 5/4 and 4/4 oak I try to air dry for 2 summers and have had good results with very little degrade, but this year I will test the mc in some of my stacks this fall to see what they are after 1 summer. I am sure Dr. Wengert is right that it will be acceptable mc by the end of 1 summer (seems like red oak dries faster than white oak).

Contributor J - I plan to keep the straps out of contact with all the drying lumber and I will cover the stack in metal and wax the ends of every board. You mentioned that you would compress the sides with pipe clamps. I have never done this before as normally the weight on top is sufficient to keep the boards from bowing. In fact I was under the impression it's not good to tightly stack your lumber side by side instead placing them so they are barely touching or not quite touching at all.

Do you think compressing this lumber in all directions is a good idea? If I don't get any poor feedback on the technique I will have this stack of lumber tightly bundled up all the way around. The stack will be sitting in a wind tunnel here so I don't think air flow will be a problem (wind that blows from the north, west and south funnels up between the buildings and privacy fence here). One thing I am not looking forward to is the final milling of this stuff. It seems denser that hedge apple wood.

From Gene Wengert, forum technical advisor:
If it is dry at the end of June, the quality will drop if you wait until the end of August. Do not over air dry.

From contributor F:
Gene, can you elaborate on not over drying it? As long as you keep the weather and sun off of it, how can you over dry it? Also, I have a large pin oak that I am going to saw up, and want some 8/4 and 16/4. I have read that you cannot air dry oak that thick and it is almost not economically feasible to kiln dry it. Is that correct?

From Gene Wengert, forum technical advisor:
"Over air-drying" is sort of a circular definition. If you air-dry too much, you will see an increase in defects and that means you over air-dried. Keep the sun and rain off the lumber and you cannot generally over air-dry. Open air-drying is not suggested for thick stock, it is better to use open sheds or partially open sheds.

From contributor F:
So if I keep the weather and sun off my 4" thick oak, it is feasible to "air" dry it without severe defects?

From Gene Wengert, forum technical advisor:
In general you cannot dry red oak over 12/4 and even 12/4 is very difficult with many defective pieces.

From contributor K:
To the original questioner: You had mentioned about stacking the lumber next to your driveway. Not a bad idea for reminding yourself, but it can be a bad idea if you have a dirt or gravel driveway. Many lumber yards take many precautions to keep dust to a minimum around lumber that is being air dried. Dust and dirt in a crack or check will not allow it to close later on as the lumber dries - just a thought.