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Rules of Thumb for Max Exterior Door Veneer Thickness?5/26/15
I am working on the design for a rather unique and difficult entry door and was hoping for some advice....
The client has seen some of my work with maple and has decided he wants the door to be made out of big leaf maple burl, no matter what. To add to the fun, it will be a full or 3/4 lite door, without a latch rail. And last but certainly not least, the live edge of the burl will remain visible and form the inside border around the glass panel. Imagine all the rails and stiles being flat on their outside edges, and having the live edge, random, spiky burl-ness on the insides....
My plan for now is to essentially build the core of the door out of fir at 1 1/2" thick, full M&T construction, and skin it on either side with bookmatched slabs of the burl, each 3/8" thick.
On the exterior face I plan to leave the burl completely intact, while on the inside I will rip it so there is a seam down the middle and the inside live edge portion can be pinned down as a glass stop, and removed if necessary to replace the glass. (An alternative option I'm considering is to use laminated glass, that is basically permanently sandwiched in between the skins and is not removable to keep the burl intact on the inside. (This is far from the best choice, but it is desirable because if there is no seal to fail as in an IGU, and there is a low chance of breakage, then it simplifies the process a fair bit). To fill the space between the burl and the glass I will rout matching wood to match the live edge profile.
I want the burl veneer or skin to be as thick as I've suggested (3/8") both for its own stability, and for the effect it will give against the glass....the reveal will be over 1/2" depending on the thickness and placement of glass, and if it were very thin It wouldn't look nearly as attractive.
I intend to laminate these together with West System epoxy.
My main concerns are of course the stability of the door, and I'm wondering if the thickness of the maple would present a problem. Big leaf maple is not renowned for its stability, and one side will see the weather. Will 1 1/2" of good vg fir as a core be enough to resist warping with 3/8" of maple on both sides? Should I go with a thinner veneer? Anything else I'm missing here?
This has been covered before and commented on by the Wood Doctor. 3/8" isn't veneer and won't work like it. Check the archives.
Thanks Larry, I've searched the archives quite a bit before posting, as you surely know there is a lot of information out there, and it is difficult to find if you don't have the proper search terms....would you mind directing me towards the posts where Dr. Wengert chimed in? I've done various searches, for "skins" and "veneers", what would is the proper term to call a solid wood slab or board that is thicker than veneer and laminated to a solid core?
I know the design of this project goes against standard practices, but am trying to learn what the guidelines are, if any for this sort of thing.
I am a professional woodworker, but I do not specialize in making doors, so there is a lot to be learned on my end.
Isn't there going to be a water trap between the natural burl edge and the glass on the outside? No lock rail? Just a frame around the outside makes me even more nervous. Also I think all those butt joints on the thick veneer are all going to open during the first year. I just don't see this as a great design. Beautiful yes, practical and long living, don't think so.
As I understand it, the 3/8" faces are going onto long grain Fir cores, with (assumption) the grain of the face generally running the same direction as the cores, so this should (emphasis) act more like face laminations, and not cross grain or cross banded veneering. This is burl, so movement may not be as predictable, but I don't see a problem.
The wood to glass meeting should have a good quality sealant between the two on at least the exterior side, and would be good on the interior side also. I would minimize the 3/8" lapping onto the glass to 1" since it may want to curl one way or the other.
Make perfect mortise and tenon joints that are square and true, so the door dry fits absolutely co-planar. Start flat, stay flat.
I would mention that the customer's preferences have overidden your ability to warrant this product.
@Rich, i plan to bevel the live edge so it sheds the water away from the glass, and yes its a full light door, so no lock rail is possible. Full light doors are pretty common, and the goal here is to build the core in such a way that it is completely stable and strong, and the "veneer" on top is purely cosmetic, but will not cause the core to deform at all...
-David, you are correct, the grain of the VG fir core rails and stiles would have the obvious orientation, and the laminated burl slabs would also have the same direction....My hope is that the butt joints of the laminated burl pieces do not gap, but i realize it is a possibility with the different woods....
In general I agree with David's points (especially the warranty). In theory thick veneer aligned with and glued over a solid wood core should not generate a conflict aside from differing rates of movement between the two species. Burl complicates things as it's hard to establish grain direction in burls. There may be a potential for twisting in the composite with MC changes. I would expect some checking problems and gaps at butt joints, and I doubt that maple burl will hold up well to any real weather exposure. The thicker the core and thinner the veneer the better. Stave core or three board lamination would be worth considering over solid core. Be sure to have your customer accept responsibility for the implications of his chosen material.