Need 2 hr rating for old 2x6 wood floor-clg assembly

[Yikes]

I have an old (circa 1950s) unsprinklered building at a private college where downstairs (daylight basement) is a small library (B occupancy), and upstairs was/ once - and is now again becoming - housing (R-2). The owner has agreed to make the floor-ceiling assembly comply with current fire code for a 2-hour occupancy separation.

We initially assumed that multiple layers of type X could be added to the underside to achieve the rating, but problem is, the existing floor-ceiling assembly is 2x6 joists (with a very short span) and all the prescriptive assemblies that I find assume a minimum 2x10 joist. We don't have enough headroom in the library to "sister" 2x10 joists alongside the 2x6s.

Does anyone know of a 2 hour wood-framed floor-ceiling assembly that can work with 2x6 joists?

 

[ADAguy]

Humm, can you use a combination of gyp and fire resistant paint, the type that expands?
No fire sprinklers?

 

[RLGA]

Do you need to have an occupancy separation? Can the building qualify for height and area using the nonseparated occupancies method? If so, then all you need is the 1-hour separation required for dwelling units.

 

[Yikes]

Thanks, RGLA! Believe it or not, in my 30+ year career, I've never had to utilize 508.3, and I'd forgotten that it existed as an option.

 

[Paul Sweet]

Try Gypsum Association GA5406. The double layer of 5/8" type X provides one hour fire protection for framing.

 

[Yikes]

Thanks, Paul. RGLA's suggestion worked, and to rate it solely for one hour dwelling unit separation we are likely going with CBC Table 721.1(3) item 21, which is even simpler than GA5406.