Can Large Solid-Wood Panels be Stable?
A high-end customer asks for enormous solid wood glued-up panels. But is there any practical way to avoid major warping? November 28, 2011
Question
I need to make about 40 panels 4 feet wide by 8 to 9 feet high in solid wood 1 inch thick. What would be the best way to do that without having the panels warp? Woods I need for these panels are maple, oak, cherry, walnut, hickory, and mahogany.
Forum Responses
(Adhesive Forum)
From contributor J:
If at all possible, figure out a way to do it with veneer. Panels that large are going to warp, shuck and jive no matter what you do. What's the application? Maybe we can figure out another way to skin this cat.
From the original questioner:
The application is for a custom millwork application by an interesting designer. He only wants solid because "it works with the essence of his design." Most of the panels will be for wall height wainscoting. Some will be put behind a glass on both sides and put in as a display piece. It’s good money and now I just need to be able to do it without it warping. Is there a special glue I should use? All my lumber is at 7-9 % MC.
From contributor J:
I know it's not the direction you want to go, but I'm thinking you might want to educate your designer on the limitations of solid wood as the chosen material here, and like most things in life, it's not what you say but how you say it. Emphasize that veneer is indeed solid wood, that because of sequence matching it allows a consistency unattainable with solid wood, and that veneer over a substrate is going to be much more dimensionally stable.
That said, in order to make these panels you'll need access to a really huge jointer and planer, and a widebelt big enough to sand them relatively flat. The glue you use isn't going to have much of an effect on warpage - it's all a property of the wood. You can mitigate moisture transfer by sealing the wood with epoxy, but it won't be a bulletproof solution. There are a hundred clarifying questions, but just because you can do something doesn't mean you should.
From contributor O:
Can you go to two inch? You might find a bit more stability up there. I agree with Contributor J - the glue makes no difference, the bugger is in the wood. Full quarter sawn, big logs and featureless wood would produce the most stable wood (wood cut from big logs, but not wide planks), also check species as they behave differently. The wood also needs to be mounted if possible so that both sides see the same moisture, and the panels must be installed at the same humidity they will live in. If you restrain the edges and the humidity drops the panels will crack. Does the installation allow for the seasonal (humidity) changes that will see a four foot panel change width by as much as a half inch? Sounds like fun as long as you have it in writing that the designer and not you are responsible for warp.
From contributor O:
You might suggest to the designer that his ability to make a "wood statement" would be vastly improved if he had any idea how wood behaves as a substance. Sugar coat that any way you want to and slip it in - he needs to go to school on wood.
From contributor B:
If the designer is still adamant about solid wood then you might want to run some cost numbers for him - veneer vs. solid. I'm thinking of bd/ft quantity and considering the sizes - quartersawn , yikes! Plus, as others have said there’s no warranty for warp or cracks.
From the original questioner:
The price of this project, well let’s just say it was an offer I couldn't have refused. The warranty issue has also been clarified to him. I've been thinking of making 20 panels and then putting them on top of one another and putting more weight on the top one to keep them straight so I could cut them down the road. I'm still worried about warpage.
From contributor H:
I have run into this before. I had a guy that wanted African walnut floor to ceiling about 15' in a cement wall. We used stainless steel button pins in the back every 12" and hung the panels on stainless steel studs with key holes cut at a slight taper to snug the panel, then hung each panel. The engineer did a great job on the design. We did it three years ago and there haven’t been any problems. I’ve been back to do other jobs and it looks good. What part of the country are you in?
From contributor K:
Each of the posters has made a valid point. If the final decision is to be solid wood, then the nitty-gritty is:
1. Be aware that the wood will expand and contract across the grain by a substantial amount at 4' or 8' widths (in an un-conditioned shop, an 18" - wide piece oak can move 3/8" to 1/2" across the grain over the course of a year.
2. Use wood that has as much straight grain as possible.
2A. Use quarter-sawn wood.
3. Don't use any case-hardened wood.
4. Rip the boards into narrower slats
5. Alternate the growth-ring orientation of the boards (as warpage takes place, you tend to get "wavy" instead of "u-shaped").
6. Use splines to help glue the boards together.
7. Do everything else right
From contributor P:
Is there room behind the panels to include a structure to keep the boards flat? I'm thinking of the same way you would do an apron for a solid tabletop. Of course you'd have to provide a fastening mechanism, like slotted screw holes that will allow the panel to expand and contract without splitting.
From contributor M:
If the "designer" just has to have this poor design, have him "design" its construction and be responsible for the outcome.
From contributor C:
Like everyone else I would not go down the solid route. Maybe you should look at veneer, but instead of using book match from any supplier get some mismatch specially made. This will give the appearance of solid wood as each leaf would be different and because it is laid out by hand you can control what leaves are used. I use this method a lot. It looks as good as solid but is nice and stable.
