I am making a standard size slab style door from VG Douglas Fir. It will be hung in a trimless aluminum frame and will incorporate a rabbet detail on sides and top, final thickness will be 2". Located in San Fransisco, it faces north, and is recessed in an alcove.

Having read many of the door posts on this forum, I've settled on the following approach: Ladder frame with 5" stiles and 5 or so rails joined with stub tenons + xl dominoes (could do full M+T if need be. would rather not). Voids filled with rigid insulation, skinned with 1/8" marine ply. 1" rail applied on both long sides, lipping planed flush. 3/32" shop sawn veneer (or 1/16" from certainlywood) applied over that. Marine ply and veneer to be glued using west systems epoxy in a veneer press. Would rather not use resorcinol but could be swayed to a pre catalyzed urea resin glue or polyurethane glue.

Finish has not been decided, though I am leaning toward spraying something like GF Exterior 450.
As has been my experience in the past, client does not love the appearance of freshly milled fir, and is looking for a more amber tone. One thought I had was to leave unfinished door in the sun for an hour or two, another though was to let the sun do its work over time. I will also be supplying a small run of T&G siding to match door for the alcove, ideally sprayed with same finish.

Have made exterior doors, but never a veneered one. Have done plenty veneer work, but not exterior. Does this approach seem sound? If there are any other finishes you can recommend, or any other pointers or admonitions, much appreciated.

-Revel

Your approach to building the slab-style door with VG Douglas Fir is solid: using a ladder frame with 5" stiles and rails joined with stub tenons or Dominoes, filling voids with rigid insulation, and skimming with 1/8" marine ply is a robust choice. Applying a 1" rail and lipping for a clean finish is smart, and using 3/32" or 1/16" veneer with West Systems epoxy will ensure durability. For an amber tone, exposing the unfinished door to sunlight can help, but a controlled stain might offer more consistent results. GF Exterior 450 is a good finish choice for durability, and spraying the matching T&G siding with the same finish will ensure uniformity. Test the finish on scrap wood first, and make sure all edges are sealed well to prevent moisture issues.

thank you 'fir' your response, and the finishing advise is much appreciated.... only thing I'm worried about is the strength of those voids. once that foam is skinned (rigid pink XPS 1.5") it will effectively be a torsion box, but it would seem you could still kick / punch a hole through if so inclined. SO I'm wondering if a true torsion box would ameliorate this potential issue ala the way David Sochar and others have illustrated; egg crate construction with voids filled with foam. the marine ply is hydrotek, and closer to 3/16"... I would use a thicker skin, but was constrained by the foam thickness (either 1" or 1.5") and the overall door finish thickness (2"). Don't want to over think this door, but don't want to deliver a flimsy product. I suppose I could vac bag a prototype panel. Another little wrench in the gears is that now the client does not want a typical aka functional threshold, but rather wants no threshold. Told them how this was silly and we had a chat about water etc, and now we are looking into drop down door bottoms from pemko... but that won't solve the water shedding issue. Going to work on this a bit more