I have a new home with an unfinished basement. I decided to statr finishing
it this month. Currently there is insullation with a vapor barrier already on it.
I decided to just frame over it since it's perfectly fine insullation and I didn't want to deal with fiberglass all over me.

anyways, the question lies in fires blocking/stoping. Since I'm framing over the insullation there's about an 1.5 inch gap been the framed wall and concrete/insullation. Can I i just use a (cut to size) 3/4 board and nail that to the top of the framed wall to the concrete wall and considered that a viable fire stop?

How about just framing the wall right up to the wall thus crushing the insullation where the frammed wall meets the concrete wall? There still
will be a smaller gap so do I need to firestop that also?

Thanks in advance

 

There are a lot of code regulations about insulation and firestopping. If your community requires firestopping, as ours did, they will probably be very meticulous in checking that you did it and the insulation correctly.

Personally, depending on how the insulation is in there I would remove it and frame closer to the wall so that you don't lose all that space. A few inches may not sound like much, but it adds up. If you crush your insulation, you've ruined its R value. Your community may dictate exactly what R value you have to provide.

I would then frame normally and do the firestopping based on what the code in your area requires. Some communities allow plywood and some require 2x lumber. You really need to call your local inspector's office and find out what they require. When we had ours inspected, the inspector was impressed that we did it correctly. They said many homeowners fail it and have to be reinspected. It is a little tricky to get right.

In our area, we put plywood firestopping above the top plates running out to the sill plate over the concrete foundation. In areas such as above the electrical box, we used a special insulation that is made for this purpose. We bought it from a specialty shop as HD and Lowes did not carry it. For holes in the foundation and any small gaps in the wood firestopping they let us use a firestopping caulk that HD and Lowes carry. Again, the requirements in your area may be different. Soffits have to be firestopped so that the openings between them and the vertical cavities are closed.

After the walls are framed, firestopping complete, and electrical is done, your area might require a rough framing/electrical inspection. Then you would do the insulation and have it inspected, if required, before moving on to the drywall.

I know it sounds like a lot of work but that is generally how it is done. Good luck!

 

Thanks for your reply. I was debating whether to pull the insullatio off or not but it looks like I will have to. My code (Loundoun County, VA) does require firestopping and yes I can use either 2x4, plywood or sheet rock.
The only reason I decided to frame over the insullation was because the rough in for the show drain was laid off and if I frame it about 1.5 inches from the wall, the tub drain would fit very close to where it should be (59").
Now I will have to adjust the pipe or rip out the insullation and still frame it the same distance.

To clarify firestopping. It looks like you are putting a sheet over the top
of the header it touches the sill plate correct? So you would nail the plywood
to the header or the joist/blocking?. So I assume you would have to frame
3/4 less from the joist to acommodate the 3/4 plywood? The other way I can
think of is to cut the fame to the joist and cut small sections of ply wood that fits the gap from joist to joist tot he sill plate. Is that correct?

thanks,

 

First we fastened the base plates and marked out the stud positions. Before we did the top plate (header), we first put in any blocking and then nailed the firestopping plywood up onto the joists and blocking. The plywood extends from the sill to almost the front of where the top plate will be. We then nailed the top plate underneath the firestopping and toenailed the studs in between the base and top plates. Then you caulk any gaps that exist between the sill and the plywood with the firestopping caulk. The type of ceiling you are using will affect how careful you need to be with the plywood. Since we were using a dropped ceiling, we could make the firestopping larger than needed. If we had drywalled the ceiling, we would have to be sure it did not extend past the front of the wall.

Some people do the basement walls as one piece and then tilt them up. For our basement, it was easier to build in stick fashion as I described since you can't tilt up the wall and shim above the top plate. If you did that, you would defeat the firestopping. The Taunton Build Like a Pro basement book describes building a wall in stick fashion but does not address firestopping. I highly recommend this book.