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Fire Blocking at flush baseboard trim

R

rentastic

Registered User
Joined
Feb 16, 2017
Messages
4
Location
San Francisco
Hello - We're working on a modern design 4-unit R-2 building. We'd like to do a flush baseboard trim or 'museum' 3/4" z-mold trim at the base. With these two trim types, we're unable to extend our fire-rated gyp. bd. down to the floor, thus breaking our fire stop. Has anyone dealt with this type of detail before in a fire-rated wall, and if so how did they accomplish the fire-rating? Does a fire-rated z-mold exist? We might have to default to an applied baseboard, but we'd like to do something crisper if possible. Any insight would be great!

Thanks
 
^Agreed. This is only a problem on the walls common with adjacent units, right? It is not fireblocking, rather a non-continuous fire barrier. The only solution would be to install 2 layers of drywall.
 
The double layer of drywall in the UL assembly is because it is for a 2-hour wall. You'll need an engineering judgement from the manufacturer to reduce that down to 1-hour using only one layer of gypsum board.

Below is a system from the same manufacturer with 1- and 2-hour assemblies with only a 3/4-inch gap (the one I posted above can go up to 4 inches). If the 3/4-inch gap works (i.e., the trim piece doesn't require more than 3/4 inches between the edge of the gypsum board and the floor), then this system will work:
http://database.ul.com/cgi-bin/XYV/...n=versionless&parent_id=1073995560&sequence=1
 
After looking at Ron's assembly, that does look like something that might work IF the OP can find a system that works with his construction type....
 
rentastic said:
Hi RLGA -
This is great, I think this will work. Based on the Clark Dietrich intumescent strip channels, I'm also looking into just using intumescent strips taped onto the framing (such as this STI product - https://www.stifirestop.com/products/ssw-intumescent-wrap-strips/). It's Type V-A wood-frame construction. Thanks for pointing me in the right direction.
Click to expand...
This might work, but the building official will likely require a tested assembly. The tape you linked to is for wrapping plastic pipe and not as a fire-resistant joint system for a wall.
 
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