What are some of the wall bracing options if you want to use foam in leiu of typical OSB sheathing. Example:
(INSIDE) Drywall : 2×4 w/ FG : 1/2″ – 1″ Foam sheets : Vinyl siding (OUTSIDE)
I’m assuming I should use the OSB for the corners (4′), like the “Small House, Built Right” article in #172 shows. But is that sufficient for a typical (let’s say, 1432 SF, 1.5 story bungalow, not to be specific…) house? I’ve heard conflicting things about metal straps really helping. What side are they applied to? The outside? Would this be advisable, since I’d be installing a perfect condensing material where it shouldn’t go (NC climate)? I’ve only seen metal strapping used once (a while ago), and the builder used fiberboard sheathing.
IRC mentions 1/2″ Drywall can be used as bracing. This may be a stupid question, but does it count if it’s applied to the inside? I’m too young and work for cheap builders to know of any other interior cladding (aka plaster). If interior drywall counts, why don’t builders use even thinner ext. sheathing than 7/16″?
Replies
Sheathing, let-in bracing, or metal straps are the only three ways I'm much aware of. I'm sure there are others. Can't help you with the 1/2" drywall part.... I can't see it helping with the racking forces a houses is under during high winds, but I could be wrong. Maybe it helps, but geez.... I'd hate to be relying on my sheetrock to keep my family safe in the event of the inevitable hurricane, earthquake, or tornado.
Here in coastal Alabama, while we are under the IRC in my county, we also have to design for "maximum 100-MPH fastest wind speed." All exterior walls have to be sheathed with min. 15/32 ply or 7/16 OSB all 'round, nailed 2" OC on all panel edges and 3" OC in the field using 1/2"x 1 3/4" sheathing staples.
Beyond code, with vinyl siding what you need to think about if you live in a tornado or hurricane prone area is the impact resistance of the siding and sheathing material. JLC had an article a few months ago on what kind of damage happens due to tornadoes. It made the damage from Ivan look mild, if not more widespread.
BTW, they're still using foamboard to sheathe homes built right on the Gulf, while we 40 miles inland have to use all plywood. Makes ya wonder...Jason Pharez Construction
Framing & Exterior Remodeling
I see the same thing Jason. I'm an hour from the coast but, literally, everything I've built for as long as I can remember has been totally sheathed in 1/2" ply or OSB. Our nailing schedule isn't as strict or monitered as closely as yours, but still... we sheathe the whole building.