Installing interior basement door for walkout bulkhead

[Marc]

I'm looking into putting an interior door leading to our walkout
bulkhead in our basement. The rough opening is 41X83 with the top third wood
and the lower two thirds being the concrete foundation. I plan to put a
36x80 door in that space but am unsure of how to build in the opening to
accommodate a 36X80. Is it just a matter of attaching some 2x6 pieces to the
opening until I get the 36X80 opening? If so, what's the best way to secure
the 2x6 to the concrete foundation. First time doing this some I'm looking
for some assistance. Thanks...Marc

[Eunoia Eigensinn]

To answer your question as asked, you'd pre-fabricate the frame out of your
2x6s, stick it in the opening and use shim blocks at the points of attachment
to get it plumb and square take up the ~1 inch gap then fill the balance of
the gap with canned foam insulation.

If the opening is already reasonbly plumb and square you could rip strips of
1" stryofoam to take up the ~1" gaps.

Tapcon screws or lag bolts with expansion shields can be used to attach the
frame to the concrete. The holes for the lag bolts should be counterbored to
accommodate the heads of the bolts + washers.

That being said, rather than use a stock 36" door, I'd look at making a door
to fit, using 1/4" plywood skins glued onto a picture frame of 2x3 lumber,
filling the void with sheets of 1" +1.5" stryofoam, laminating the whole
schmozzle together to make a stressed-skin panel.

As a refinement, galvalume sheet could be applied to the exterior face if 48"
wide flat stock is available in your area (36" is more typical), with the
edges of the steel sheet bent with a lip to fit into saw kerfs milled into the
edges of the 2x3s.

In addition to providing a moisture-proff cladding for the plywood, it would
enable you to use magnetic weatherstripping to provide a good seal.

Any exposed foam around the door frame should be sprayed with a dilute
solution of boric acid to serve as a deterrent to ants before covering.

[x]

>
> Any exposed foam around the door frame should be sprayed with a dilute
> solution of boric acid to serve as a deterrent to ants before covering.
>

Really? Do they start nesting in the foam or something?

[John Smith]

They could. While the foam in indigestible, it does provide an easy medim
which to bore into and is warm(er) in the winter.