Fire blocking at top of walls

[75gmck25]

I insulated my basement's concrete walls with 1" XPS foam and then framed a 2x4 wall in front of the foam. However, the concrete slopes back some at the top, so at the top I have at least 1" of space between the 2x4 top plate and the XPS foam (which is right against the sill plate).

I know I need fire blocking to close off the space between the top of the wall and the sill plate and I'm looking at alternatives. Some folks use OSB, while others use drywall. However both of those are relatively hard to nail or screw in place because I have only about 10" clearance between the sill plate and the floor above. Its also a lot of cutting and filling to put a filler piece between every floor joist, and I will have to work them around the gas line and plumbing lines that go down into the new framed wall.

I've also read that it is acceptable to close the space at the top off with spray foam, but I don't know if I need any particular type of foam (e.g. fire retardant).

Any recommendations on fire blocking methods for the top of the wall?

Thanks,

Bruce

 

[mooseracing]

I've also read that it is acceptable to close the space at the top off with spray foam, but I don't know if I need any particular type of foam (e.g. fire retardant).

Great Stuff sells a fire blocking foam. It is with there regular foam products at HD or Lowes type store.

 

[NUTTSGT]

Bruce, I think I understand where you're talking about but a picture would help. If we're on the same page, what about adding some blocking (same size as the floor joists) then screwing drywall to the face of the blocking. Any small gaps could be filled with a fire barrier caulk and larger gaps with the Great Stuff fireblock foam.


http://www.homedepot.com/p/3M-10-1-fl-oz-Fire-Barrier-Sealant-Caulk-CP-25WB/100166701

http://www.homedepot.com/p/GREAT-STUFF-Fireblock-Insulating-Foam-Sealant-16-oz-345372/202023037

 

[75gmck25]

NUTTSGT - This site has some pictures of what I am talking about. They seem to favor a combination of drywall and foam, but I've also seen recommendations for OSB. In my case the gap is small enough in some areas that I might be able to fill it with just foam. http://www.ifinishedmybasement.com/framing-basement/fire-block/
They also nail the drywall blocking on from inside the stud bay, which might be easier than putting it on top between the joists.

Bruce

 

[NUTTSGT]

Now I see what you are talking about, I think that would work.

 

[boobag]

code allows the use of stone wool (or called rock wool insulation). it is used all the time in new construction for draft stopping.
the insulation is made from stone and doesnt burn. just cut it into pieces and stuff in the gaps. you can also use it to fill gaps around pipes and wire openings. and in your exterior wall, i'd stuff it between the xps and vertical wall stud every 10 to 20 feet or so, to prevent fire from traveling horizontaly behind the wall.

here is an example home depot sells.
http://www.homedepot.com/b/Building-Materials-Insulation-Rock-Wool/N-5yc1vZboco