45min fire rating wall assembly
I am not really understanding some feedback from our building inspector regarding sheathing requirements.
I’m building a small shop in the corner of our city lot in BC, Canada. I require a 45 min wall along the property lines.
According to our code, this means an acceptable sheathing and cladding combination, WRB, 2×4 studs, rockwool, and type x drywall.
I has assumbed I could use hardie panel and battens over WRB, directly attached to the studs. inspector tells me I need sheathing to meet the fire rating, but I can’t find where it says what this sheathing needs to be.
I am assuming its gypsum based..
our limiting distance is 0.8m
If it is a 12.7mm gypsum sheathing, what are people using? Densglass? I don’t seem to be able to source it here locally. Everyone is out of stock.
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Replies
You typically need to use one of the tested assemblies for a fire rated wall. The most common example would be a typical 1 hour wall, which would be 5/8" drywall on both sides, with wood or metal studs between.
Has your inspector given you any guidance as to what the city wants to see here? Fire rated walls are usually built in specific ways, not using just any handy combination of materials.
Bill
"You typically need to use one of the tested assemblies for a fire rated wall. "
Or have some guy with a bunch of letters after his name put his stamp on your plans.
Even that doesn't work. Ours needs a ULC listed assembly specifically called out.
Most are easily searchable one line (ie ULC W302). This generally does mean either 1/2" gypsum sheathing (a couple out there besides densglass) or brick veneer over plywood on the outside and 1/2 type C on the interior. Lot of times 5/8" type X is the same price as the type C and easier to get.
Hardie panel is non-combustible but it does not have a fire rating. It can be used for assemblies that require non-combustible cladding but you need something else to provide the fire resistance.
I would also doublecheck with the building department, lot of times for garages you only need fire rating on one side.
Hmm, I have never seen drywall on the exterior of a wall... but in these tight lot line situations, I usually see densglass or securock, or similar in Canada. Not sure where you source it from though.
J. Murray,
I've used exterior gypsum behind brick veneer on multi-family buildings which were tight to a lot line.
densglass is commonly available from commericial building supply houses. It's a commonly used product for exterior details in commercial buildings. Most of the "unusual" (non paper faced) gypsum board products are more easily sourced from commerical-oriented supply houses than residential places (box stores), since residential sites use almost exclusively paper-faced gypsum products.
Bill
My local box store stocks 1/2" denseglass and the local lumber yards have both 1/2" and 5/8".
I wish mine did. Here we have a vast selection of paper faced drywall, but zero selection of anything else in the box stores. I just go to my commerical suppliers so it's not really a problem for me, but it would be nice if some of the box stores carried at least a little of the less common stuff.
Bill