Duplex condominium separated by storage area require fire rated walls

[Ralph]

I am working on two single family houses that are considered condominiums because of shared building lot, septic and well. The two buildings are attached by a shared storage room between them. The storage rooms are completely enclosed but not insulated and only accessible from the exterior. The distance from each building across the storage rooms is 10'. The drywall contractor has questioned if the walls adjoining the storage rooms should be fire rated.

The drawings by the architect don't show that any fire rating is required. I have asked them this question but have not yet received answer. Does the unfinished storage room between the two units make them attached and require a fire rated wall? Will we have to fire rate both exterior walls or only one? The exterior walls have 4" of foam on the exterior. Will installing 5/8 drywall over the foam cause issues with the fire rating?

Thanks,

 

[Mr. Inspector]

If the plans were appoved during the plan review I would just go by the plans. You could ask your inspector what they require.

 

[Ralph]

The plans were approved but it does seem like the walls should be fire rated. It's always good to get some sense of the answer before I approach the building inspector.

 

[Plumb-bob]

Not sure what code you are under, but where I am the walls would be required to be rated for both fire and sound. I would assume all codes would require the same.

 

[steveray]

Welcome and nice to see another CT person (especially a contractor).....IRC 302 is where you need to look, and here is one piece of the CT amendment.....

(Amd) R302.3 Two-family dwellings. Dwelling units in two-family dwellings shall be separated from each
other and from common spaces serving both dwelling units by wall or floor-ceiling assemblies having not
less than a 1-hour fire-resistance rating when 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 to the underside of the
roof sheathing. Fire-resistance-rated assemblies shall be supported to the foundation by construction with
the same fire-resistance rating as the assembly supported.
Exceptions:
1. 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.
2. Wall assemblies need not extend through attic spaces when the ceiling is protected by not less than
⅝-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 ½-inch (12.7 mm) gypsum
board or equivalent.

I've been thinking about this lately (for connected garages) and really, the garage is not the dwelling unit, but.....I would say put the 1hr wall where the garages (or in your case the storage rooms are connected (for a garage might already be 5/8" drywall and already 1hr by default....)

Any chance you can post a floor plan??

 

[Ralph]

Welcome and nice to see another CT person (especially a contractor).....IRC 302 is where you need to look, and here is one piece of the CT amendment.....

(Amd) R302.3 Two-family dwellings. Dwelling units in two-family dwellings shall be separated from each
other and from common spaces serving both dwelling units by wall or floor-ceiling assemblies having not
less than a 1-hour fire-resistance rating when 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 to the underside of the
roof sheathing. Fire-resistance-rated assemblies shall be supported to the foundation by construction with
the same fire-resistance rating as the assembly supported.
Exceptions:
1. 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.
2. Wall assemblies need not extend through attic spaces when the ceiling is protected by not less than
⅝-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 ½-inch (12.7 mm) gypsum
board or equivalent.

I've been thinking about this lately (for connected garages) and really, the garage is not the dwelling unit, but.....I would say put the 1hr wall where the garages (or in your case the storage rooms are connected (for a garage might already be 5/8" drywall and already 1hr by default....)

Any chance you can post a floor plan??

Steveray

Thanks for the replay. This is exactly the information I was looking for.

Welcome and nice to see another CT person (especially a contractor).....IRC 302 is where you need to look, and here is one piece of the CT amendment.....

(Amd) R302.3 Two-family dwellings. Dwelling units in two-family dwellings shall be separated from each
other and from common spaces serving both dwelling units by wall or floor-ceiling assemblies having not
less than a 1-hour fire-resistance rating when 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 to the underside of the
roof sheathing. Fire-resistance-rated assemblies shall be supported to the foundation by construction with
the same fire-resistance rating as the assembly supported.
Exceptions:
1. 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.
2. Wall assemblies need not extend through attic spaces when the ceiling is protected by not less than
⅝-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 ½-inch (12.7 mm) gypsum
board or equivalent.

I've been thinking about this lately (for connected garages) and really, the garage is not the dwelling unit, but.....I would say put the 1hr wall where the garages (or in your case the storage rooms are connected (for a garage might already be 5/8" drywall and already 1hr by default....)

Any chance you can post a floor plan??

 

[Ralph]

Steveray

Thanks for the replay. This is exactly the information I was looking for.

I have attached a copy of the floor plan and elevation

 

[steveray]

That layout gets weird as you would have to "zig-zag" the rating around/through the storage rooms....

 

[Ralph]

That layout gets weird as you would have to "zig-zag" the rating around/through the storage rooms....

The storage rooms are separate so my thought is to just rate the exterior wall of each unit. The problem is that the walls and the roof are complete. The existing walls have 4" of foam on the exterior so I am not sure if I can just add 5/8 rock upto the roof line of the storage room or if I should remove the foam insulation first.

 

[steveray]

The one hour wall needs to be a listed assembly and constructed "exactly" in accordance with the listing instructions....I wouldn't wing it if the money is going to be yours...

 

[Ralph]

The one hour wall needs to be a listed assembly and constructed "exactly" in accordance with the listing instructions....I wouldn't wing it if the money is going to be yours...

Now we can see what the answers are from the architect. Thanks for your help

 

[steveray]

Can I ask who the architect is? Or PM me?