Crossbuck X Braces for a Door

Alternative methods for constructing a door with x-shaped cross braces. June 4, 2012

I'm building a walnut dutch door for a log cabin. The goal is a rustic look so it is a straight forward design, 1 3/4" stile and rails with 3/4" V-groove for the panels top and bottom. Over the V-groove inside the stiles and rails will be an X, like a traditional barn or plank door. It will be 1/2" thick so that it sits flush with the stiles and rails. I want to leave the panels free floating, but I don't know how I should fasten the X's. Glue and mechanical fastener's seem like they would restrict panel movement. Does anyone have any suggestions?

Forum Responses
(Architectural Woodworking Forum)
From contributor M:
Is this an exterior? I like mine true mullions as it is quite difficult to keep that exterior piece flat and attached exposed to any weather or climate change. It is of course a lot more work, but I have gone the way you're suggesting and it didn't work out well for me.

From contributor D:
We've done the crossmembers as true rails, with triangular panels floating, with mixed results. Some customers won't want to pay for all that, and the decorative surface applied crossbucks are then used. Always select the most perfectly vertical grained boards for this, glued only at the corners. We bed them in a few beads of flexible polyurethane caulk under the midsection, which allows the v-groove panel to move yet keep everything solid. To be honest, the failures were in the first, more labor intensive method. There's no place for water to escape when sheeting down the surface, and it collects in the trap where the V enters the groove in the rails. The easy method of surface applied crossbucks has worked better for us.

From contributor D:
I forgot to note that when bedding the crossbucks, apply the bedding compound to the panel, not the crossbuck, kept well away from the v-grooves. This assures the squeeze-out doesn't block the groove and trap water behind the crossbuck.

From the original questioner:
This is an exterior door, but it is under a large covered porch, so direct water contact isn't an issue. My biggest fear would be that it would warp and try to lift up in the middle or ends. I think the flexible adhesive route might be the way to go, but I don't have much experience with it. What brand would you recommend?

From contributor O:
Crossbuck doors utilized the 'x' - as you call it - for structural rigidity. They provide a diagonal, making a triangle, locking the frame as square. As such, they are not applied, but ploughed to receive the panels. Raised or flat panels are traditional, with v-joint avoided/redundant due to small size.

Larger barn type doors and thin passage rustic doors often have applied 'x' or 'z' boards for diagonal bracing, one side or rarely, two sides. Nailed members are the common method, with older examples using clinched nails.

From contributor S:
The door should be made of several boards milled with a tongue and groove, or ship lap profile. They should not be glued together to allow each board to expand and contract.

The "X" you describe holds the whole mess together, and keeps it from racking. Nail/screw each board close to the center. You could get away with a dab of glue or construction adhesive in the center as well. Writing this post from an 1840's house I am looking at an interior version of such a door right now.

From the original questioner:
At first I was opposed to using mechanical fasteners, for aesthetic reasons, but now Iím thinking wrought iron nails might compliment the look Iím going for. I know it was done with nails originally, but Iím still leery about it. That seems to go against everything I know about panel construction.

From contributor D:
Tremco U1600 is the caulk we use. Typically, we don't normally have a choice in construction methods like most of you guys do. We don't sell to homeowners, dealing exclusively with other millworks. Granted, most don't really care about the details as long as we use their profiles (stacked tooling they've paid for), but some are very particular, providing detailed prints. Applied crossbucks were first used by us with skepticism (anything drawn by an architect is) but they work. My personal feeling is you'll gain little structurally making them as rails for the slight weight of a dutch door. They would help on very large doors though. Warp issue is key for applied members, thus the reason I stressed vertical grain.