Basement – How to frame around an egress window

Jay's plan to use beam pockets in the front wall will work fine. Dbl. top plates with no additional structure supporting a roof over a SIX foot span (as per Tester101's first suggestion) is entirely inadequate. Whether a 2x beam on edge is adequate, and how deep it is, depends on what the roof snowload is, if any.

There are also hardware beam hangers available that support the end of the beam and are nailed or bolted to the supporting studs in the front wall, eliminating the need to frame pockets. Tester101's second suggestion to use a ledger to support the beam end is a viable idea, but the connection of the ledger under the beam, into the studs needs to be carefully detailed.

A metal plate tying the two walls together is an important detail. Alternately, extend the dbl. top plates over the beam, lowering the beam 3" so the plates can still lap in a conventional manner. If you go with a hardware hanger or a ledger, the beam should be strapped to the sidewall top plate to hold it to the main structure in a wind storm or possibly an earthquake.

Along wind storm lines, be sure the beam is well connected to the outer post, and the post tied into the foundation, as there can be significant uplift forces on an open porch roof.

2X12 is great, 3/4" plywood would be easier to handle and to drill through when you need to. Chalk your plate line where the wall will go on the room side, rip your plywood to go to the basement wall and 1/4" shy of the chalk line. That way when you set your upper plate you can still see the line to accurately set your wall. To answer your question, using nails will work, it is only fireblocking, you only really need enough to keep it up, since it is not structural, but do it anyway. Screws would work better, especially if it needs to be adjusted after it is up in place, and you see it needs to move a bit, it does happen. Shear or expansion should not be a concern. material usually shrinks once installed.