Where/How to put in sheetrock backing?

I dont know how to put in sheet-rock backing when my floor joists are 2 ft from the outside framed wall, but the outside wall has 2 2x4's on top of one another with a black tar inbetween the 2x4's and spray foam all over them.
Ideas on what I can do in this situation?
I have a lot of outside walls to put backing on and unknown how to do this.

Dig out all that spray foam? Or take off top 12 inch peice of sheetrock like in the picture and lay celine rock on top of the edge and have it floating? (seems like a not good idea). Clips? Need help please!

 

In the picture we are looking at a truss system.

Are you asking about a nailer to fasten the ceiling sheetrock ?

 

The blocking should have been installed before the wall was spray foamed. Yes, you would want to dig out a little spray foam and lay a 2x4 flat on top of the top plate, perpendicular to the wall, then toenail it to the bottom chord of the floor joist. Do this every 24" on center so that your ceiling seams will break on solid backing.

Drywall should always be hung on the ceiling first, then the walls second. For 9' walls, you want to use 54" wide drywall, hung horizontally.

 

It's best to use full sheets of drywall when you can. As long as there isn't more than 2' between the lumber a piece of drywall is attached to it usually doesn't need extra lumber to nail to. I'd only remove the spray foam as a last resort! If the spray foam is built up on the 2xs or otherwise goes past them - that excess needs to be removed.

 

Ill have to see where the bottom of the floor truss I believe lays even with the top plate of the double 2x4 on the outside wall.
Also, if its level across would it be ok to do what you say and toenail a 2x4 inbetween on BOTH sides 1 side level with the floor truss and the other beside the top of the 2x4? Seems like that would not be very secure method, although would save me from digging out all that insulation that is already there...
The wall are 8 ft 8in so its kind of a odd size either way you look at it
(also the builder put the sheetrock on the outside walls before i moved in)

 

The 2x4 will lay on TOP of the top plate and butt up against the side of the bottom chord of the floor joist.... where you will toenail it.

Normally a 2x4 would have been nailed across the length of the top plate so that it protrudes about 1 1/2, giving you continuous backing along the wall. I doubt you want to dig out that much foam on the ENTIRE wall.

 

Let me measure but I'm almost sure that if the 2x4 laid over the TOP plate it would be on TOP of the floor truss. Let me get back to you all!!!
Thanks for the quick reply's this fourm is awesome!



Looks like I can put it on top of the double 2x4 on the outside and then toe nail it into the floor trusses?

 

What is the end of that floor truss setting on? The top plate.

 

Thats exactly what I said.