About those "Fire Rated" ceiling light cans.

NCLopez

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So this is something we've been catching more of lately with the rise of attached garages being converted into ADUs and Jr ADUs. If they have a separate occupancy above them, the ceiling/floor assembly is required to be fire rated, The plans usually call out a 1hr fire rating with a detail on how they will achieve such rating. Everybody want the recessed lights, but that's a penetration into the fire rated assembly, so in order to maintain that fire rating they buy the bright red luminaires or cans that have that 2 hr Fire rated sticker. The problem is how they achieve that rating and what assemblies they are rated for.

So far that I've seen, they have this sticker listing what classifications they are rated for.

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A quick search on the internet finds that most of these assembly designs aren't feasible for existing dwellings. The ones that are call out for things like 3 layers of drywall with resilient channel, which no contractor wants to deal with. We've started recommending they purchase the regular lights and prelim them: 1 layer of 5/8ths type x on 5 sides with fire caulk (not foam!) on all corners, edges, and penetrations. This essentially maintains the ceiling membrane around the lights, as long as they have room for any insulation required on the plans. We ask for 2 layers if we see Wood I-joists with osb webbing.

As an inspector I don't appreciate that most of the suppliers either don't know this or leave it out of their literature for these cans. The first time the contractors hear about this is at Electrical rough when I have to tell them that they spent way too much on their lights, or they're going to have to spend too much to match the listing. I have made it a point to bring these up as early as possible in the project to keep them informed.

Who's at fault here? The manufacturer, UL, supplier, the contractor, the local authority, or some combination of them?
 
Location
California, United States
The 2-3 layers of drywall sounds like what is needed for a 2-hr rating. They sell 1-hr rated fixtures that only require 1-layer. I would want my plan checkers to call this out in their review and not rely on the inspector to catch it in the field.
 
I agree that this would be easier to catch in plan check, but electrical plans are only required for systems over 400 amps. Most ADUs and J-ADUs aren't going to reach near that large.

Most junction boxes with fire padding are sufficient to maintain the 1 hour fire rating required, but I'm seeing more people use recessed lights instead of surface mounted to keep protrusions to a minimum. I understand the aesthetic but if there is a separate occupancy above, the fire rating needs to be maintained, and, unless exceptions are listed on the device's UL listing, the design needs to meet one of the listed standards.

The design criteria I was referencing (L505) requires minimum 2x10 joists 16" OC, Resilient Channels 24" OC, and two layers of 5/8ths Gypsum (not 3, my mistake). However, this only has a finished Rating of 75 minutes.

It is a subject I am continuously learning about and gaining more information to present to my jurisdiction so we can keep well informed, but I am still researching as I go so any input is more than welcome.
 
We require electrical plans for all ADU's, JADU's, SF additions, new SFRs and even kitchen/bath remodels, so it is easy for us to catch prior to permit issuance.
 

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