Draft stop or not?

[ICE]

The duct chase runs the length of a new church. There is one on each side of the building. Ca code based on the 2009 IBC. There is a fireblock where the chase meets the wall. Is a draft stop required in line with a floor joist that divides the chase at 10' intervals?

Oops I put this in the wrong forum.

 

[Francis Vineyard]

The 10 ft. interval is for walls; soffits are floor/ceiling. Does the volume from the free space in the soffit interconnecting to the space between each floor joist to the blocking exceed 1,000 sf?

717.3.3 Other groups. In other groups, draftstopping shall be installed so that horizontal floor areas do not exceed 1,000 square feet (93 m2).

Francis

 

[ICE]

This is as close as I can get to a yes.

717.2.2 Concealed wall spaces. Fireblocking shall be provided in concealed spaces of stud walls and partitions, including furred spaces, and parallel rows of studs or staggered studs, as follows:

1. Vertically at the ceiling and floor levels.

2. Horizontally at intervals not exceeding 10 feet (3048 mm).

 

[mtlogcabin]

Is this a sprinklered building? The volume of the soffit and floor joist together may not meet the exceptions for non-sprinklered concealed spaces is my thought. Don't have an NFPA 13 at home.

 

[KZQuixote]

This is as close as I can get to a yes.717.2.2 Concealed wall spaces. Fireblocking shall be provided in concealed spaces of stud walls and partitions, including furred spaces, and parallel rows of studs or staggered studs, as follows:

1. Vertically at the ceiling and floor levels.

2. Horizontally at intervals not exceeding 10 feet (3048 mm).

That's not a concealed wall space. There are fire blocks at the soffit/ceiling level. A better technique would have been to apply drywall to the wall or ceiling before the soffit framing was installed. Look at the midspan solid blocking:

1000 SQ FT draft stop limitation.

FogHorn

 

[ICE]

Is this a sprinklered building? The volume of the soffit and floor joist together may not meet the exceptions for non-sprinklered concealed spaces is my thought. Don't have an NFPA 13 at home.

Yes the building is sprinklered.

 

[Francis Vineyard]

717.3.3 Other groups. In other groups, draftstopping shall be installed so that horizontal floor areas do not exceed 1,000 square feet (93 m2).

Exceptions:1. In other than Group A, E, H, I, L and R-2.1 occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, draftstopping is not required in buildings equipped throughout with an automatic sprinkler system in accordance with :Next('./st_ca_st_b200v10_9_sec003_par061.htm')'>Section 903.3.1.1.2.

In Group A, E, H, I and L occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, where an automatic sprinkler system in accordance with :Next('./st_ca_st_b200v10_9_sec003_par061.htm')'>Section 903.3.1.1 is installed, the area between draft stops may be 3,000 square feet (279 m2) and the greatest horizontal dimension may be 100 feet (30 480 mm).

Aside from the sprinkler exception; let's clarify the communication between the horizontal duct chase (soffit) opened to the ceiling joists; do you see this configuration the same as a drop ceiling for draftstopping?

Francis

 

[ICE]

do you see this configuration the same as a drop ceiling for draftstopping?

No I don't. I do see a concealed space that would allow the free passage of fire from one end of the building to the other end. In the recent past (20 years or so) has there been a code that would have required a draftstop in a concealed space such as this? If this were two parallel walls, there would be a requirement for a draftstop. What if one of the parallel walls stopped short of the floor by 2"? Or 10' as in this case? Code requires the fireblock where the soffit meets the wall but it seems counterintuitive to have a chase the length of the building without draftstopping.

Could somebody with 007 power move this thread to commercial building?

 

[KZQuixote]

By my calc that construction would only be a concern if it exceeded 166 feet in length.

FogHorn

 

[mtlogcabin]

Yes the building is sprinklered.

Then if you do not do fire sprinkler inspections call the FM and ask him/her if the cubic feet of the length of soffit and all of the floor joist space meets the limited combustible space exceptions in the NFPA 13 or the soffit may require sprinklers or be filled with insulation.

I will check on monday if some one else does not comment.