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Duplex separation with different stories

O

Otter

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Joined
Jan 12, 2021
Messages
15
Location
Montana
Hi all,
When looking at a side-by-side duplex with different story heights - a 2 story butted up to a 1 story, does the required 1 hour separation need to go all the way up to the top of the higher unit or stop at the top of the lower one?
2018 IRC, no sprinklers required
Thanks for looking
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If it is a two family dwelling, then no, it does not.

The IRC requires separation of the dwelling units. As there is not a portion of the dwelling unit adjacent to the Unit A upper floor, separation is not required.

R302.3 Two-Family Dwellings
Dwelling units in two-family dwellings shall be separated from each other by wall and floor assemblies having not less than a 1-hour fire-resistance rating where tested in accordance with ASTM E119, UL 263 or Section 703.3 of the International Building Code. Fire-resistance-rated floor/ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend from the foundation to the underside of the roof sheathing.
Exceptions:​
  1. A fire-resistance rating of 1/2 hour shall be permitted in buildings equipped throughout with an automatic sprinkler system installed in accordance with NFPA 13.
  2. Wall assemblies need not extend through attic spaces where the ceiling is protected by not less than 5/8-inch (15.9 mm) Type X gypsum board, an attic draft stop constructed as specified in Section R302.12.1 is provided above and along the wall assembly separating the dwellings and the structural framing supporting the ceiling is protected by not less than 1/2-inch (12.7 mm) gypsum board or equivalent.
That said, some AHJ may tell you that you need to treat the wall as an exterior wall and require 1-hr construction given the lack of fire separation distance. This stance may be tough to counter, but you can attempt to sway them with the via the forthcoming 2021 code language. See this Building Journal Article by ICC and/or the ICC Significant Change Summary.
 
classicT said:
If it is a two family dwelling, then no, it does not.

The IRC requires separation of the dwelling units. As there is not a portion of the dwelling unit adjacent to the Unit A upper floor, separation is not required.

R302.3 Two-Family Dwellings
Dwelling units in two-family dwellings shall be separated from each other by wall and floor assemblies having not less than a 1-hour fire-resistance rating where tested in accordance with ASTM E119, UL 263 or Section 703.3 of the International Building Code. Fire-resistance-rated floor/ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend from the foundation to the underside of the roof sheathing.
Exceptions:​
  1. A fire-resistance rating of 1/2 hour shall be permitted in buildings equipped throughout with an automatic sprinkler system installed in accordance with NFPA 13.
  2. Wall assemblies need not extend through attic spaces where the ceiling is protected by not less than 5/8-inch (15.9 mm) Type X gypsum board, an attic draft stop constructed as specified in Section R302.12.1 is provided above and along the wall assembly separating the dwellings and the structural framing supporting the ceiling is protected by not less than 1/2-inch (12.7 mm) gypsum board or equivalent.
That said, some AHJ may tell you that you need to treat the wall as an exterior wall and require 1-hr construction given the lack of fire separation distance. This stance may be tough to counter, but you can attempt to sway them with the via the forthcoming 2021 code language. See this Building Journal Article by ICC and/or the ICC Significant Change Summary.
Click to expand...
My imediateimpression is: Seems like the fire wall height ( I know it isn't directly referenced) of what 30" or 36" above 1st floor roof should or could be FR plywood as a minimum to insure the integrity of the Rated Assembly.
 
Genduct said:
My imediateimpression is: Seems like the fire wall height ( I know it isn't directly referenced) of what 30" or 36" above 1st floor roof should or could be FR plywood as a minimum to insure the integrity of the Rated Assembly.
Click to expand...
And maybe the horizontal 4ft on the 1st floor roof as well?

Just seems vulnerable
 
Greetings, I have an empty basement in 2 unit apt that I was in the process of converting the basement to a basement apt using fire rated ⅝ sheetrock on walls and ceilings and everywhere the eye could see. The basement is a walk out and so was moving forward with renovations and plumber and electrician work mostly finished and paid when the inspector mentioned that it might need to be sprinklered. I don't think it was a hard must and mentioned it in pushing mostly to cover himself in case ge neded to change his mind later. Where did that come from and is there a rebuttal in code I can comply with as is and proceed? Really appreciate the look. Thanks!
 
Clean … you should start a new discussion, especially since you are off-topic in this one. You will get better exposure.
 
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