Sheet goods for Exterior Door

[Jim Becker]

John, I could send you a small sample of the Extiera if you cover the postage for a small flat rate box. I have some scraps left over from the architectural stuff. Message me if you want to do that.

[Mel Fulks]

I like MDO but in most respects it's no better than standard fir plywood covered with painted canvas. The cloth is actually
thicker than the treated paper on MDO. MDO is many times the cost, but I would only buy 'good two sides' . I've used
the one good side stuff a couple of times and it came in non flat and stayed that way until fasteners put it down.

[Edward Dyas]

I'm going to build an exterior house door that will be a flat slab door veneered on both sides. What type of sheet good would be suitable for the core of the door? Seems like I've heard of an exterior rated particle board or MDF type product but the name escapes me. Anyone have some insight on appropriate materials for this? Thanks.

John

The "exterior" sheet good would just need to be plywood rated for exterior use, meaning it was laminated with veneers with a water resistant adhesive. If you cut apart an exterior slab door you will find out the core is particle board with a little strip of solid wood around the parameter. Actually in recent years I haven't been able to find one of these doors that was the least bit water resistant. Even with a good coat of paint the first time it's rained on the doors start swelling up. Particle board is actually a good product for this if it were made water resistant. A large slab door warps very easily and particle board is very stable. If you made the door out of 3/4" plywood with just 1/4" strips of wood between it would probably warp so bad you would have to replace it within a year. You could also make the door hollow. You could make like a torsion box and cover it on both sides with 1/4" plywood. It would also be a lot lighter in weight.

[Mel Fulks]

Edward, you have been more lucky than I have with "exterior " plywood. I see it used and painted,too. But mainly on
dog houses and tool sheds. And it can last a long time in those uses, but I've never seen it look any where close to the
quality of
MDO, or exterior plywood covered with painted canvas.

[Jim Becker]

John, in retrospect, I think doing the insulated core with something like MDO skins is the way to go for weight and energy efficiency.

[Mark Bolton]

I like MDO but in most respects it's no better than standard fir plywood covered with painted canvas.

I may be dealing with a different MDO than you because the material Ive gotten consistently has no connection to even the best grades of exterior ply Ive ever had access to. Like I say, Im talking scraps completely un-treated, left outside, under roof overhangs, submerged in water, small scraps left to sit in 5 gallon buckets full of water for months and months. I actually have an old MDO saw top I made years ago leaning against a trailer that has been outside untreated for years (like 8-10) and while its a little ragged it is still sound.

No idea whats different about the core but Ive long abandoned any exterior ply for much of anything as it delaminates when a bead of sweat drops off your brow and lands on the sheet.

[Mel Fulks]

Mark , I agree MDO is a great product, but I've done tests,too. If the edges are not at least painted well the wood plys
split . That is not an improvement over delamination. A little Titebond 2 and a strip of canvas greatly improves it. Just as
that makes the standard ply faces as good as MDO.

[John TenEyck]

John, in retrospect, I think doing the insulated core with something like MDO skins is the way to go for weight and energy efficiency.

That's the way I'm leaning if I build a new door. Sometime last night it occurred to me that I might be able to reskin the existing door. It's a slab door and still dead flat after something like 60 years. I could rip off the edges and replace them with solid Sapele, then rout off the existing veneer skins with a router sled or take it to someone with a CNC. Seems pretty straight forward. I'd still build a new Sapele frame and moldings and install modern weather seals and threshold.

John

[Mark Bolton]

That's the way I'm leaning if I build a new door. Sometime last night it occurred to me that I might be able to reskin the existing door. It's a slab door and still dead flat after something like 60 years. I could rip off the edges and replace them with solid Sapele, then rout off the existing veneer skins with a router sled or take it to someone with a CNC. Seems pretty straight forward. I'd still build a new Sapele frame and moldings and install modern weather seals and threshold.

John

That sounds like a major winner. You'd have a core that has obviously proven itself and done all the misbehaving its ever going to.

[lowell holmes]

We have Sapele floors in our house. We had to replace the wood floors in our house after Hurricane Harvey flood. We bought it at Lowes.
I have a spare box in case I need it.

Also, I made an exterior door for my back door. I glued 1 1/4 strips for a core and glued 1/4" exterior plywood to both sides of the core.
The door is painted, has a safety glass window in it. It is a heavy strong door and has survived Hurricane Harvey.

I also made a front door with leaded glass panes that rotted and I made a new solid core door for it with raised panels in it.

Use your imagination, doors are fun projects. Solid core doors are stable and if needed repairable.

[Kevin Jenness]

Reusing the existing core sounds like a good choice.

That said,Extira, MDO and marine plywood are all good substrates for exterior doors. 1/4" is thick enough when well glued to a foam core combined with a substantial perimeter frame and blocking for hardware. A ladder core really is not necessary.

The largest doors I have made are a pair sized 4 1/2"x48"x90" for a walk-out basement. The cores are extruded polystyrene (Dupont blueboard) sanded to consistent thickness wrapped with a 1 1/2" pine edge frame, skinned with 6mm ocoume marine ply, edgebanded with 1/4" red cedar and faced with 1/16" red cedar veneer, all bonded with epoxy.Miles' cellar doors 1000px.JPG

[John TenEyck]

Thanks very much Kevin. What epoxy are you using to glue the plywood to the foam core? Did you put it in a vacuum bag or just put some weight on it?

John

[Kevin Jenness]

I used this "basic no blush marine epoxy" https://www.epoxyproducts.com/marine_epoxy_resin.html. It seems to perform as well as WEST System at a lower cost. I did use a vacuum press. The shop I was working at has a 5'x10' frame press which is a great deal easier than a bag for big pieces like these doors.

[Edward Dyas]

Edward, you have been more lucky than I have with "exterior " plywood. I see it used and painted,too. But mainly on
dog houses and tool sheds. And it can last a long time in those uses, but I've never seen it look any where close to the
quality of
MDO, or exterior plywood covered with painted canvas.

Sometimes it just takes a lot of elbow grease. I sometimes use pressure treated plywood which is usually rough as H. I use a lot of spackle and sand it and the paint ends up looking as smooth as if you painted masonite.

[John TenEyck]

Thanks for the added information, Kevin. Very much appreciated. I have a shop built 4 x 8 frame press which works well for large bonding jobs like this.

John