Foam for door core

[Steve Juhasz]

I am going to be building a carriage door style garage door, each of the two slabs 58" wide x 78" high x 2" thick. Basic design is 2 stiles, three rails. Between the upper two rails (about 12") is glass. Between the bottom two rails is a large raised panel. The raised panel is what I would like to do with a foam core, as it will be nearly 42" x 42" and since the door will be made of Cumaru (a denser than water exotic wood often sold as "brazilian teak") it would be too heavy and wasteful to be solid wood.

Question is this: what foam product have you used instead of a normal hardwood stave core which could be about 1.5" thick and take 1/4" veneers of cumaru glued to it to make the raised panel. Also, what glue adheres both to this oily wood and the foam in the long term?

[Mel Fulks]

About five years ago I made up some small samples using polyurethane glue on pine faces over the plastic foam sheet insulation commonly available in 4x8 sheets at big box stores. Did it mainly to demonstrate that cores don't have to be rigid. Have not actually made a door like that ,but have used mdf core.

[Steve Juhasz]

I too have used MDF before, but would never dare to do so on an exterior door. Even the humidity (100%) for months on end around here would sog that up and warp it. It will have to be foam, like in the polyurethane foam they spray into fire doors but i need to find a rigid product that is not sprayed.

[Mel Fulks]

I used EXTERA (spelling?) exterior grade. It's good. I think the foam I mentioned would work but if I do one I will use 1/4 inch thick ,finished,faces just to offset the soft core. Would be strong and not dent like the popular metal doors and insulated ,too.

[Bill ThompsonNM]

Look at the Owens Corning foam website. "Pink core" is the type they use for composite garage doors. They have glue recommendations also

[Kevin Jenness]

We have used Dow Styrofoam (the blue and pink board available at building suppliers) for insulating door panels, but it is not calibrated for thickness and is a mess to dimension in the wide belt sander. For sandwich panels like Extira over foam that need to be a consistent thickness we have used foamboard used in the boatbuilding industry like Divynicell or Klegecell, but they are considerably more expensive. Typically they are laid up with epoxy resin. Epoxy will bond well to oily woods if first wiped down with acetone.
I would be leery of laminating a 1/4" thickness of solid wood to a rigid substrate as checking may ensue. We usually use a thinner (1/8" max.) veneer on such panels. A 42" wide solid panel laminated to a stable substrate will exert considerable stress on the glue bond and may delaminate. It's possible the foam will be forgiving enough to move with the wood, but it's iffy. I would suggest a sample panel be laid up and subjected to several moisture cycles before proceeding.For your application you might be better served by making loose solid wood raised panels not bonded to a foam insulation layer.

[peter gagliardi]

Build the door with the foam free floating between your wood skins unless you like to do on site repair work! IMHO you should NEVER fix a breathing ,moving item such as wood to a relatively inert and unmoving item such as foam. I have made dozens if not hundreds of insulated doors with wood facings on panels, no one has called yet!
Peter

[Peter Quinn]

What Peter G said.....don't glue wood to foam. Maybe silicone or elastometric adhesive caulking, the wood has to move. And Cumaru is going to move. Stable is not its middle name. Have you worked with this before for exterior? We use full KD material, acclimate it well, it still goes wild when it gets wet. They sell it for decking now, but they are selling lots of things for decking these days. We have had issues with decks twisting in the breeze, pulling up fasteners, not well behaved. I took some drops and made a light post for my house, its all QS material, beautiful stuff, but it too moves a bit. In my case the movement is not relevant, but on a door it may be a problem. Just saying proceed at your own risk. And may sure the hinges and framing are up to the challenge of swinging a door that heavy.


As an alternative, here's a product I'm considering for my own carriage house doors....when I get there....I built a quick and dirty pair to fill the opening during construction, plan to build a proper set in the next few years. I found these foam filled torsion panels that can be skinned, you could easily make a solid looking door, much less weight than even a stave core. Unless Genghis Kahn arrives at your house, the solid or stave core that large is pretty heavy for not much reason. Anyway, check these out, food for thought.


http://singcore.com

http://singcore.com/education/carriage-doors

[Mel Fulks]

The foam panels are interesting but from what I just read about cumaru ,panels that big are probably not a good idea.

[Peter Quinn]

The foam panels are interesting but from what I just read about cumaru, panels that big are probably not a good idea.

The OP use the phrase " 1/4" veneers"....uh...at that thickness, its not veneer anymore, is it?, and all those good aspects for which we rely on veneer are now gone. A single 42" solid wood panel strikes me as a poor idea in any event, I'd consider breaking that up into smaller pieces with center stiles, or actually using veneer, laying it up on plywood, or getting it laid up, and letting it float.