Limit on fixtures in a rated floor/ceiling assembly

[Ryan Schultz]

With certain UL listed floor/ceiling assemblies, there's limits with how many light fixture penetrations you can have per a certain SF.

Generically, does this limit apply even if the fixture has an equal rating as the assembly?

That is, if you have an 1hr rated floor/ceiling for example, can you put as many 1hr rated light fixtures as you want, or are you still limited to the UL listing's fixture/sf ratios?

Thanks, Ryan

 

[cda]

Not my area, so check on this section 2015 IBC

The OneFrame™ junction box reduces installation costs significantly because it eliminates the requirement to create boxed-out cavities at the time of construction by utilizing one of the exceptions provided by subsection 714.5.2:
Ceiling membrane penetrations of maximum 2-hour horizontal assemblies by steel electrical boxes that do not exceed 16 square inches (10,323 mm²) in area, provided the aggregate area of such penetrations does not exceed 100 square inches (44,500 mm²) in any 100 square feet (9.29 m²) of ceiling area, and the annular space between the ceiling membrane and the box does not exceed 1/8 inch (3.2 mm).

https://www.dmflighting.com/fire-rated-assemblies/

 

[steveray]

Is the assembly a fire wall, fire barrier, fire partition, or horizontal assembly? Most have there own unique quirks for allowable penetrations....

 

[RLGA]

The IBC does not limit the number of penetrations that comply with a tested UL assembly. It does limit the number of non-tested penetrations via several exceptions. What you're describing is most likely a membrane penetration in a horizontal assembly, which is covered in Section 714.4.2 of the 2015 IBC. It essentially points back to the through penetration section regarding either a penetration tested with the horizontal assembly or tested as a separate firestop system per ASTM E814 or UL 1479 having F and T ratings equal to or greater than the horizontal assembly.

If the light fixture has been tested as described above and installed per the tested assembly, then the number of light fixtures would not be limited (unless the tested assembly description provides a limitation).

 

[Ryan Schultz]

For example, the following UL restricts 24 sq ft (of 2x4 fixtures) per 100 sq ft of ceiling area.

https://iq.ulprospector.com/en/profile?e=14281

Am I to assume, if the fixture is not rated, but has 'fixture protection' to cover it as outlined in the UL listing above, than the fixtures would be limited to 24 sq ft per 100 sq ft of ceiling area?

If, however, the fixture has a 1hr rating, than there's no limit to the number per 100 sq ft of ceiling?

 

[RLGA]

Am I to assume, if the fixture is not rated, but has 'fixture protection' to cover it as outlined in the UL listing above, than the fixtures would be limited to 24 sq ft per 100 sq ft of ceiling area?

Yes

If, however, the fixture has a 1hr rating, than there's no limit to the number per 100 sq ft of ceiling?

Yes, provided the horizontal assembly has a 1-hour rating.

 

[Ryan Schultz]

Thanks everyone. Per this conversation, ff anyone's interested, added a few floor/ceiling UL assemblies to our open source Revit template
https://github.com/OpeningDesign/OD_Library/blob/master/BIM/OD_Revit_Template.rte