Two Family Dwelling Fire Seperation

[Chip O'Brian]

In attic seperation between town houses new build. Does this fire retardant sheathing meet the requirements of separation?

[Jerry McCarthy]

No.... refer IRC 317 - Dwelling Unit Separation.

[Rick Sabatino]

I would say NO. The seperation is as much for fumes as it is anything. I had a manager working for me who died in his sleep because the wack job in the next townhome decided to off herself running the car in the garage. She died, her husband and it almost killed her daughter. This is not something to take lightly.
Rick

[Jerry Peck]

Chip,

That's a complicated question you've raised there ... "Two Family Dwelling " ...

*IF* it is a "two family dwelling" instead of a "townhouse" (there *IS* a difference), then the separation requirements are as follows:

From the 2004 FRC.
- R317.1 Two-family dwellings.
- - Dwelling units in two-family dwellings shall be separated from each other by wall and/or floor assemblies having not less than 1-hour fire-resistance rating when tested in accordance with ASTM E 119. Fire-resistance-rated floor-ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend to the underside of the roof sheathing.
- - - Exception: A fire resistance rating of ½ hour shall be permitted in buildings equipped throughout with an automatic sprinkler system installed in accordance with NFPA 13.
- - - R317.1.1 Supporting construction.
- - - - When floor assemblies are required to be fire-resistance-rated by Section R317.1, the supporting construction of such assemblies shall have an equal or greater fire-resistive rating.

You will notice that for "two family dwellings" the roof is not required to be protected, unlike they are for townhouses.

However, let's review your photos for problems with either "two family dwelling" or "townhouse".

First photo:

First and foremost, the roof sheathing (in a "townhouse" would be required to be either fire retardant treated (as your second photo shows it is) for a minimum distance of 4 feet to each side of the fire rated separation wall *measured from each face of the wall*, not measured from the center of the wall. From looking at your photo, that does not appear to be the case - the first two trusses look closer together, meaning that it is unlikely that the roof sheathing is fire retardant rated for 4 feet from the wall.

Also, I don't see where the roof sheathing has been staggered, which is required for all roofs, two family dwellings or townhouses, or any other type.

Now, though, there is yet another problem, and it affects both two family dwellings and townhouses, but it affects both differently.

*IF* the roof sheathing was required to be fire retardant treated (or otherwise protected), then *no openings are allowed with that first 4 feet* ... which includes ... *NO RIDGE VENT OPENINGS*.

That said, however, *IF* that is a two family dwelling, no fire retardant treatment is required, so the ridge vent opening is not a problem ... EXCEPT for where the opening crosses the separation wall.

Now, for two family dwellings, that wall is required to have a 1 hours fire resistance rating, and drywall on one side as that one was constructed only serves as a draft stop wall, it *is not* a 1 hour fire rated wall. Townhouses also require fire rated walls, except that the fire rated wall is now a 2 hour fire rated wall.

Now, for those outside Florida (Chip is in Florida), the IRC applies in most areas (and the FRC is based on the IRC). The IRC is similar, but different.

From the 2006 IRC.

- R317.1 Two-family dwellings. Dwelling units in two-family dwellings shall be separated from each other by wall and/or floor assemblies having not less than a 1-hour fire-resistance rating when tested in accordance with ASTM E 119. Fire-resistance-rated floor-ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend 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 when the ceiling is protected by not less than 5/8-inch (15.9 mm) Type X gypsum board and an attic draft stop constructed as specified in Section R502.12.1 is provided above and along the wall assembly separating the dwellings. The structural framing supporting the ceiling shall also be protected by not less than 1/2 -inch (12.7 mm) gypsum board or equivalent.
- - R317.1.1 Supporting construction. When floor assemblies are required to be fire-resistance-rated by Section R317.1, the supporting construction of such assemblies shall have an equal or greater fire-resistive rating.

[Chip O'Brian]

Jerry it is listed as a Townhouse, One continuous roof and appears continuous ridge vent. Approx 6 units two story. As to sheathing not stagered it appears not inthe plywood to OSB. Trusses 24 inch

Where is stated on stagering sheathing? And continuous ridge vents.

[Jerry Peck]

Chip,

As soon as you go from two units to three units, the one- and two-family dwelling parts no longer apply. Townhouses are defined as three or more, thus the townhouse parts apply.

That means the *2 hour* fire rated wall now may either: a) extend to the roof and the roof is protected for 4 feet to each side of that 2 hour fire rated wall, or, b) the 2 hour fire rated wall extends at least 30 inches above the roof.

If the roof is to be protected to 4 feet to each side of the wall, how can you do that with any openings in there? No plumbing vents, no exhaust vents, no dryer vents, no ridge vents.

Staggering roof sheathing ...

I've always seen it specified to be staggered, however ...

From the 2004 FRC. (underlining is mine)
- R803.2.3 Installation.
- - Wood structural panel used as roof sheathing shall be installed with joints staggered or nonstaggered in accordance with Table R602.3(1), or APA E30 for wood roof framing or with Table R804.3 for steel roof framing.

Thus, it depends on the engineering, I've just never seen any which allowed for "nonstaggered".

I know the trusses are 24" o.c., however, it is common for the first trusses next to the separation wall to be less, which means it takes two spans plus (meaning 3 spans) to make 4 feet.

[Chip O'Brian]

Jerry nice call on the open ridge vents. Yu saved my and a familys bacon. Thumbs Up!! Called the locals are informed and agree.

Ply extends out 4 ft went back and measured. They squeezed a truss closer at 3rd truss out from wall note pic.

Sheathing was not staggered, although it appears not required Darn good idea Imagine a 300lb man walking that OSB at 24 on Center. Oh MY!!

Where was the code # for the roof seperation in IRC?


Chip