Fire Blocking

So summer is gone and so is most of the busy yard work and weekend activities that somehow absorbed all free time available. The basement is getting some renewed priority in life, and I'm making good progress again.

I passed rough-in inspection with no problems back in September. A framing inspection wasn't required because of the scope of the job. The electrical inspector only had one comment about considering fire-blocking the airgaps between the stud walls and the ceiling space. He noted that this is required for new contruction, but that it was up to me whether I wanted to do it or not here. It seemed like a good suggestion, so I did it.

There are two instances to resolve with fireblocking. The first is that the stud walls are offset from the foundation wall. As a result, there is a continuous air-gap behind the wall. In the event of a fire, the fire can travel continuously around the room with no inhibitors. To stop this, it is recommended to block in behind a stud every 10 feet. The second issue is at the top of the stud wall, where again, there is a air gap. Here, there is an uninhibited path for fire to run up into the joist space and travel from there. The solution here is that you fill this space to eliminate the gap.

Picture on the left shows the airpath for the 2nd issue, and the picture on the right shows the fire blocking element in place (purple).

A quick online search revealed several approved methods for accomplishing this. Rock wool was the most popular for hard to fill spaces that didn't have a lot of flat surfaces. It's basically fireproof insulation that you can jam just about anywhere. The two other methods were to install fire-resistant drywall and/or use fire-resistant expanding foam.

I chose a combination of the latter two because I had simple, straight sections to fill.

I found this great stuff fireblock expanding foam at home depot. It was just under $10 a can.

In this picture, you can see the expanding foam along the top and behind one of the vertical studs.

Here, you can see the fire-resistant drywall installed between the stud spaces. I then used the foam to fill the gap behind the studs, and around any wire-drops.

The vertical gap was too big for the foam in all but two locations. So I just used the drywall.