Hello:

My 'not-so-super-insulated house', being constructed by my mutinous crew, now has all the rough framed, OSB sheathed, nine foot tall 2x6 walls in place.

My question is about whether I need to 'hit the studs' when applying the exterior 2" Roxul ComfortBoard IS and the 1x3 strapping, which will run vertically over the Roxul, so that the Canexel siding can be applied horizontally?

I was told that the OSB is strong enough to 'grab' the strapping nails - is that true? If so, do I need to use any special type of nail?

Thanks for any advice on this,

Rob.

FYI, the wall construction is, from the outside to inside: 7/16" Canexel siding, 1x3 strapping, Tyvec, 2" (R-8) Roxul ComfortBoard IS, 7/16" OSB, 2x6 studs with 5.5" (R-22) Roxul ComfortBatts, 6 mil Vapor barrier, 1x3 strapping & 1/2" drywall.

Consider taping all of the Tyvek and vapor barrier seams and staples if you haven't already done so.

Thanks jonr, I will definitely tape the Tyvec & VB joints.

I was thinking of 'taping' the OSB joints with the same rubber-ish membrane that is used around the window openings before applying the Roxul ComfortBoard IS - do you think that this be overkill?

My thinking is that doing this would greatly reduce air leakage.

Rob.

I would not want to rely on OSB to hold nails for the sheathing. We typically use screws in that application and screw thru into the studs.

Thanks Bob. :)

If you would not mind, I have another question...

Should my rubberized window flashing be applied to the OSB before installing the Roxul ComfortBoard IS? My actual windows have a flange that will be screwed to the 1x3 perimeter window strapping and that will be covered with a membrane as well.

Or, do I apply the Roxul & Tyvec and then the window flashing?

Thanks for any advice on this.

Rob.

we've been using 6" strips of Advantech (doesn't swell like regular OSB) all around the windows instead of strapping & flash to that. Better to fasten to & wide enough to accept window trim. We bring the building paper/drainage air barrier down to & over that. We use a thickness that matches the strapping.

My thinking is that doing this would greatly reduce air leakage.

I would think that once you have a well sealed air barrier on each side of the wall, there isn't much more to be gained. A blower test and perhaps smoke might be a better place to apply efforts.