GA 4490 / Horizontal Dwelling Unit Separation

[Grimace]

Can GA 4490 be used for 1 HR Horizontal Dwelling Unit separation in Type IIIB or VB construction - for R2 multistory construction?

 

[walker.t]

Can GA 4490 be used for 1 HR Horizontal Dwelling Unit separation in Type IIIB or VB construction - for R2 multistory construction?

Gypsum Association FC 4490 is two layers of 5/8” Type X wallboard over metal floor joists, it has a 1-hour rating. IBC 711.2.4.3 (Dwelling Units and Sleeping Units) requires a 1-hour horizontal assembly between dwelling units, so the 1-hour rating is good. Type IIIB and Type VB construction allow combustible interior framing, you might considering looking for a different detail using wood but you’re allowed to use metal in the combustible types of construction if you want.

The exception under 711.2.4.3 allows you to use a 1/2-hour horizontal assembly in IIB, IIB, and VB if the building is sprinklered with an NFPA 13 sprinkler.

 

[Yankee Chronicler]

From the Gypsum Association Manual:

Ceiling Openings
Many fire-resistance rated floor-ceiling systems have
been tested with openings through the ceiling
membrane for air ducts, electrical outlets, and lighting
fixtures.
Building codes permit air duct openings in most
ceiling systems when the air duct openings are
protected with approved ceiling dampers.
Building codes also permit membrane penetrations in
maximum two-hour fire-resistance-rated horizontal
systems by steel outlet boxes that do not exceed 16
square inches in area provided the aggregate area of
such penetrations does not exceed 100 square inches
in any 100 square feet of ceiling area and the annular
space between the ceiling membrane and the box does
not exceed 1 /8 inch.

What you are describing is a membrane penetration. The GA 4490 listing doesn't state that any openings are allowed, so the vents/grills would have to be fire dampers.

But GA 4490 is for light gauge steel framing. Does not apply to IIIB or VB construction.

 

[redeyedfly]

From the Gypsum Association Manual:



What you are describing is a membrane penetration. The GA 4490 listing doesn't state that any openings are allowed, so the vents/grills would have to be fire dampers.

But GA 4490 is for light gauge steel framing. Does not apply to IIIB or VB construction.

What penetration was described? And why can't you use CFMF in IIIB or VB?