Foam board under bay window seat board
PatchogPhil
| Posted in Construction Techniques on
Finishing the interior of an Andersen bay window. The instructions say you can put “rigid foam insulation” on the inside, on the lower platform under the finish seat board. They show to put 2″ thick spacer boards around the perimeter of the lower platform and then cut the foam board to fit inside this perimeter.
Are the spacer boards really necessary? I know that foam board insulation is put under a slab for a building so I figure the FB can handle the weight of a seat board. Plus an occasional cat and some potted plants.
With this little weight, what kind of foam board would be OK? Best?
Walk Good.
Replies
Is this vertical in the "walls" of the bay or horinzontal under a window seat?
In an case foam is fairly strong, I think that even the light weight stuff has a compression stregth of 10 psi.
BUT, you knew there was a BUT, the load had to be distributed evenly. Since I am not sure where it is I am don't know how it is loaded. But if the load get consentrated then that area will compress.
Horizontal, under the seat board and the head board.
What I am getting at is does the foam have as much support on the bottom as force from the top. And whatever it contacs will not deflect.IE, a full sandwich and not point contacts where the foam hits it's the supports or a weak support that will bend and again concentrate the load to small areas.
Hello PatchogPhil,
I am currently installing my own Andersen bow window and have the same question you asked re: foam underlayment for seat board. I too am unsure that the suggested solid wood spacers/supports (presumably to carry any weight) are really necessary in combination with the foam. I would think that the foam should support the seat without the solid wood spacers added around the perimeter, but if the spacers are required to prevent sagging or foam breaking down over time, then one might as well make the entire underlayment solid wood. In my own case, my window is about 8’ W with a 10” projection, so after deducting 2” around the perimeter for the wood spacers/supports, I cannot see much benefit of such a small remaining area of 1.5 R-value foam.
Your post is from 2005. What is the construction of your head/seatboard? Mine is pine veneered MDF type material. I was disappointed it was not solid pine or at least veneered Ply.
I would appreciate learning what you decided and how it worked out for you so I might learn from your experience.
Regards,
Bryan
Bring Out Yer Dead!
Resurecting the dead posts!
Seat board is still doing fine, with no spacers. No apparent compression. Seat board came with the window, made of veneered real plywood. Not MDF.