First time posing here. I am used to building historically appropriate rail and stile entry doors. That is my bread and butter... but more recently I have had inquiries on more modern designs, which more or less require vac-press lay ups on exterior grade sheet substrates. I am thinking either extira or marine grade fir with the edges and ends capped in hardwood before the lamination.
One that I am going to do involves a sort of "ship-lap" look to it on each face. I plan on laminating 3/8 thick hardwood (white oak) to each face with west system epoxy in my vac-press, widebelt sanding the face flat, then routing the 3/16 deep grooves into the face at the joints to create the ship-lap look. Has anyone had any experience on this type of door construction? Will there be problems with the boards splitting since it wont be allowed to float like it would in a rail and stile door?
It will essentially be like a piece of veneered plywood, but the veneers are 3/8 thick... instincts tell me that may be a problem. I know big-time door manufacturers do this with some of their engineered raised panels where the "cores" are 1/2" mdf with 3/8"+ solid wood material laminated on each face... open to tips and suggestions. Thanks!

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Me thinks your 3/8" skins will get some pushback.

Yup, not loving the 3/8" skins. Look for 1/16" veneer from certainlywood.com or other suppliers. The sequence match of the thinner veneer will be better, the quality of the wood tends to be superior with veneer and you won't have the stress issues.

You could have a chance if you use quarter sawn white oak, but it goes against a law of nature of gluing hardwood to mdf. I"m no fan of mdf anywhere in an exterior door. Get water in around the lockset, or the bottom of the door and you are in for a call back. What is your experience with exterior mdf usage? What is the success rate of those "big time" manufacturers? Just doing it doesn't count unless you know how long it lasts!

Tom,
Yes I agree with the 1/16" veneers. I resaw them myself for all of my stave core stiles for my rail and stile doors. The issue is that the design calls for grooves to be routed into the face of the door. I would route right through the veneers into the substrate... that wouldn't be a great look.

Rich
The specs call for flatsawn... as far as exterior mdf, it seems to hold up very well and obviously much more stable than solid wood or even plywood. I soaked a raw piece in a 5 gal bucket of water for 3 months and measured absolutely zero change in edge thickness, i.e. zero swelling due to moisture... It definitely has applications where I wouldnt use it, like in cases were screw retention is needed. But it seems to be a great product.

Anyone on here that has real world experience building these particular styles of doors that can weigh in? Any advice would be much appreciated.

You could prepare your core with routed grooves filled with solid oak. Veneer then rout through into the oak filled grooves.

You may consider inletting small strips of oak into the substrate so you can route "through" the face veneer essentially breaking them up from pushing on the next piece, yes it's a pain. Even at that I wouldn't exceed 1/8" in thickness for the faces.

Another work around is instead of a v-groove a narrow 1/8" square groove that is straight into the substrate but looks more like a shadow line and would be impossible to see what the core is. Key once again it is breaking up that solid wood from pushing on the next piece.

You would have to do something similar for veneer I'm guessing.

Hi Jack,
We have build doors like this by routing and inserting solid strips into the core first. We then glued boards to the surface. It is essential to give booth sides of the door the same treatment. Obviously narrower board and vertical grain material are a better choice. Often we add the final vertical edge banding after the horizontals are installed mostly do to weather stripping needs. We have also build doors with added boards on the exterior only. In that case we use T & G or ship lap products ( often matching the siding)and there is no glue or grooving of the core. A lot of it really depends on the location and protection that's provided. We refuse to build doors like this for the wrong location.
Personal I prefer veneer especially if wider boards are requested.

What is your approach to weather sealing the horizontal gaps in the door face in the exterior?

Hi Mark,
It depend on type of gap we have need. We do prefer to prefinished the inset if we can. That way if we have a bit of movement with the seasons it does not show. Sometimes we have metal insets in the core. Attached is a picture of a door I was worried about wide 3/8 thick boards boards are overlapping the inserts. The boards are way wider than we are comfortable with and flat sawn material as well. This door was build 9 years ago and we had on problems with it.

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If V grooves are allowed I usually use solid wood for this type door with the cladding over a ladder frame. The walnut door is 5/8” T&G over a ladder frame both sides. Cladding is glued to the frame but they are not glued to each other so each board can move. Most of our doors are euro rebated so no issue with air leaking through the v grooves. For a conventional door I would make a small rebate around the door edges to allow the gaskets to sit to a flush surface.
The fir door in the picture is a outhouse door I built for my son’s yurt. It is one side clad over a ladder frame. No worries about air leaks on that one. It has held up well for 3 years at 11,000 feet.

I would never use MDF for a door core. I would like to try Tricoa for a moder door core but difficult to source here,

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About 15 years ago I was hired to build a pair of french slab exterior doors. The builder liked to think he "knew" what he was doing. They speced a ladder frame with pink foam. 3/8" quatersawn white oak "veneer". Stained jet black on the exterior, clear on the interior. Contemporary house with (2) big 7' tall black slab doors. Not my house...

I told them that I wasn't excited about the 3/8" thickness, they thought the thicker the better. We had done 1/4" then run the doors thru the wide belt in the past. The doors were built to finish at 2 1/4" thick. Several days after layup with epoxy, the boards started to cup. There was no debonding, but you could feel the boards. We ended up grinding the doors down 1/8" per side. They ended up as 2" thick door slabs. The final thickness didn't matter as far as hinges. They were speced to have some weird ugly super expensive pivot hinges top & bot and a matching handle.

Thick "veneer" can be vary sketchy. Personally I think 3/16" is about right. Cut them 1/4" glue up your door then grind it down.
I believe the t&g doors appear fine because each board is separated. If you put a straight edge on it there will be discrepancies between each board.

We first build an egg crate core, then skin it both sides with 1/4" exterior rated MDF or ply. We add blocking for latches, and edge band the vertical sides.

The cedar face parts were all shiplapped, and laid with a strong 1/32" gap between pcs. The were not nailed, but glued in place. Identical on both sided. These doors were about 10' tall, and 3" thick. Hung on Tectus hinges for the bit of adjustment they provide. We aded two lines of bulb type weather strip to the vertical sides and top, with bronze interlock at the sill.

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