[Marty S.]

We're doing a room by room remodel at home(built in 55) including upgrading insulation and new drywall. The exterior sheathing is a fiber like material,heard it called blackjack and sound board. Between the 16" on center studs there's 3- 2x4's spaced and toe nailed as backers for the blackjack which really limits insulation,has 1 1/2" rockwool batts now. If I remove those backers to have the whole 3 1/2" stud space for insulation will it compromise the structure? The house has brick on the bottom 3' and siding above that so replacing the blackjack with osb and house wrap like I want isn't really an option for the whole wall. Willing to do the area above the brick if it will help but not sure if it's worth the trouble since we're talking a lot of work to eliminate 7" of compressed insulation.
Suggestions or advice?

 

[jklingel]

I don't think those "fire stops" do stink for structural integrity. What is preventing the wall from racking now? That blackjack? Is the blackjack as tough as plywood? If not, I'd remove it, remove the fire stops, and plywood it. OSB is not good if it ever gets wet. I guess that would mean tearing off the siding, too, but then you'd have a nice wall. Do it in small sections, of course.

 

[Gary in WA]

Similar to this structural insulating board? http://www.inspectapedia.com/structure/Fiberboard_Sheathing.htm

Leave the blocking if at the brick/siding elevation...... I'd add foamboard at the blocking line only, other in the rest.

Gary

 

[Marty S.]

Thanks guys. That's the stuff GBR. All the older houses in this neighborhood were built for officer quarters when there was an air base in town. Guessing the fiberboard was used to cut back on sound. Looks like the cross bracing stays for now. I'll get rid of it next year when we work on the exterior of the house and use plywood instead.

 

[Gary in WA]

I agree with Jk, OSB-no, plywood-yes. On bracing: http://bct.eco.umass.edu/index.php/publications/by-title/insulating-on-the-outside/

Gary