How to fireblock framing - Page 8 - DIY Chatroom

Maintenance 6 · 05-12-2009, 09:27 AM

The blue can does not have a UL rating. If the building inspector is telling you to use a product without a proper rating or UL listing in place of one that does, then he is setting himself up for a great deal of liability, regardless of what your torch test shows. Unscientific tailgate product tests performed by amatuer fire protection specialists don't hold up in court. Insurance companies love those. They can weasel out of a claim easier when a homeowner uses an untested, unrated product in place of the proper one. On the other hand, if you had a problem. you might be able to sue the inspector for having told you to use the wrong product.

Clutchcargo · 05-12-2009, 09:40 AM

That's a good point about the UL listing. The next time I see the inspector, I'm going to ask him about that.

**thekctermite** · 05-12-2009, 10:22 AM

Maintenance 6 is 100% right, your inspector is wrong in giving the option he's giving. Listings, my friend. Listings.

tjeieio · 06-04-2009, 03:37 PM

Okay - I have read this entire thread and have learned a great deal. Thanks for posting the excellent photos. One thing I have not fully understood is how to install the vertical @ 10' blocking. I have a 1" gap between my concrete basement wall and the 2x4 framing. If I stuff fiberglass insulation or rock wool behind one of the studs, how is that supposed to stay there? On the other hand, if I use P/T lumber or green sheetrock, how does this create a tight fit? Thanks in advance.

**thekctermite** · 06-05-2009, 10:44 AM

Quote:

Originally Posted by tjeieio

Okay - I have read this entire thread and have learned a great deal. Thanks for posting the excellent photos. One thing I have not fully understood is how to install the vertical @ 10' blocking. I have a 1" gap between my concrete basement wall and the 2x4 framing. If I stuff fiberglass insulation or rock wool behind one of the studs, how is that supposed to stay there? On the other hand, if I use P/T lumber or green sheetrock, how does this create a tight fit? Thanks in advance.

You've got a couple options when doing this.

The first is to use unfaced fiberglass insulation. Roll it up and pack it in very tight. When packed in it definitely won't go anywhere. Rock wool is pretty tough to pack in comparatively, unless you use something to retain it. In my experience most jurisdictions will allow fiberglass, since the code allows it in other fireblocking applications.

As you mentioned the other option is to use another piece of wood. Personally I wouldn't necessarily use treated material. Regular untreated 2x dimension lumber is fine, assuming it doesn't physically make contact with the concrete. Either wood you choose, there will be a bit of a gap...Perhaps less than 1/8". Such gaps MUST be sealed tight with orange fireblocking foam, which does a good job of bridging the gap.

tjeieio · 06-05-2009, 12:09 PM

Thanks for the quick reply. It makes some sense now. Hopefully our building dept will okay the fiberglass use. Waiting for my plan review.

avshockey · 07-19-2009, 11:25 PM

I wish I would have stumbled upon this before I started to frame my basement. I have some questions on the best way to fireblock my basement. I had blanket insulation on my foundation walls. When I framed my perimeter walls, I failed to get the wall as tight as I would have liked to the blanket insulation. The result is anywhere from a .25 to 2 inch gap behind my studs and a gap behind the top plate. What would be the easiest method to fireblock this dead space? I was thinking of just buying thicker bat fiberglass insulation for between the studs to take up that extra space. Does that count for fireblock to stop fire from going vertical or horizontal? Or do I still need wood or insulation wedged in behind the top plate and behind a stud every 10' horizontally?
I also have a soffit and reading this thread I will need to 2X block between the studs to keep a fire from rolling from vertical to horizontal in the soffit. However, do I have to block the joist spaces where my soffit
meets the ceiling (where the red X's are)?

tjeieio · 07-20-2009, 02:07 AM

Turns out the city is requiring R-21 insulation in my perimeter walls, plus waterproofing. As such, the 1 inch gap will be filled tightly with the fiberglass batts (3 1/2" studs plus 1 inch = 4 1/2") since the batts are 5 1/2" thick. Telephone conversations suggest this will suffice for horizontal blocking. Vertical blocking will still require the insulation to be installed between floor joists and above the top plate.

**thekctermite** · 07-20-2009, 10:20 AM

Avshockey-

The joists above your soffit do not require fireblocking. You can insulate them if you wish though. Blocking the stud spaces from opening up into the soffit is required, as stated.

The gap between the foundation wall and the framed wall at the top plate is a judgement call. I would require that you pack the gap at the plateline with fiberglass. Simply using thicker batts fills the gap at the stud spaces but not behind the studs themselves. I'd suggest packing it with fiberglass just to be safe.