A door doesn’t sound like a significant project, until there are other details added like annual outdoor temperature fluctuation of 150° F, 90-100° F temp difference between in/outdoors, and a sporadic humidity level.
Approved SketchUp Design
One day I received a phone call from a lady who wanted an arched, solid wood door for her daughter’s upcoming new construction this May. Not one to turn down a challenge, I agreed and began a ton of research. Building a stylish, 36″ x 80″ door isn’t a problem. Preventing said door from exploding and/or tearing itself apart in Interior Alaska conditions is quite a problem.
Resawing Hi-Grade D-Fir
I initially tried to obtain a sheet of material specifically engineered for this purpose; a laminate core, dead-flat @ 1 3/8″ thick made just for exterior door construction, but it proved out of reach for all of my local suppliers (I even gave them the number to the corporate HQ).
Creating the half-lap joints
So on to plan “B”, which was to make a plan “B” if needed. After considering a few options, I went with a marine-grade approach. The idea was to make the inner core frame from Douglas Fir and sheath it in marine-grade 1/4″ plywood. The D-Fir we got was incredibly gorgeous. I was picking through a standing stack of 16′ long 2×4 boards instinctively looking for the best boards, but that was unnecessary. At 16 feet long, every board was dead flat. I’ve never seen anything like it. Across each face (the radial grain) ran 20-30 parallel, tight grain lines the entire length of the board. What could possibly be considered more stable than this?
We got the boards back and prepared them for the frame. In order to create a door at normal 1 3/4″ thickness within the clients requirements, the inner frame had to be 1/2″ thick, with 1/4″ sheathing on both sides and 3/8″ hardwoods on each face. We re-sawed the D-Fir to a little over 1/2″ and ran them through the planer and sander. The results we exceptional.
The next step was to identify, mark and cut out the lap joints that would interconnect all parts for the frame. Before glue-up, we tuned up each joint using a classic, and most effective process. My Lie-Neilsen rabbet block plane is my favorite tool to perfect joints like this. Prior to adding the plywood, we had to cut out the window hole for a 10″ x 12″ dual pane, gas-sealed (argon), inch-thick assembly, safety glass window.
Sheathing glue up
We left the plywood proud along each edge which allowed us to center the window hole and trim each edge of the plywood to the frame after glue up (again with the favored block plane).
1/2” insulation, decreases weight also
Before the second sheet of plywood was added, we took a little time to add R-Max insulation between frame parts.
Now that the frame was assembled, secured and dead-square it was time to prepare the hardwood face panels. The choice material was Red Oak which has favorable low characteristics concerning movement (contraction and expansion).
Laminating upper and lower panels
Regardless, this type of construction requires allowance for any and all movement, so the door face panels were prepared with 1/4″ tongue and groove with 1/8″ spacing between all boards. In order to create the arch, we figured out the radius in accordance with the designs and made a compass to scribe the upper and lower arcs.
The arc for the bottom of the top face panel was completed using the band saw and oscillating spindle sander. The door arch will be cut later. Once all T&G and arch cuts were done, we sealed the back of the boards with three coats of a catalyzed vinyl sealant using our HVLP system, in under one hour.
The next challenge was securing the panels to the core frame. Flexibility remained key so silicone and nails became choice which worked out very well. Hardboard strips made for excellent 1/8″ spacers.
After several dry-fits, we got the clamps out and lined up everything. Happy with the overall fit, we turned over all the boards and spread the silicone carefully away from all edges (this is not the time for squeeze out). I wasn’t sure what to expect, but the boards sat nice and flat on the frame while the silicone provided just the right amount of adhesion and movement. A generous number of nails finished the job and locked everything in as well as I could expect.
This ends Parts I of the door construction. Hopefully it’s done in a few days cause despite what you may think, there is still very much to do.
Thanks for reading!
Your Arctic Woodworking Friend,
-- Troy Bouffard || Master Sergeant, US Army (Retired) || http://www.birchhillwoodcrafts.com