# Fire rating lathe and plaster ceiling



## adianz (Apr 13, 2007)

I could use some advice about obtaining a fire rating between two occupancies in the same building.

My customer is opening a small theater on the first floor of their building, while 4 apartments occupy the second floor.

Code says that there needs to be a 2-hour seperation (1 hour in each direction, so to speak) unless they sprinkle the entire building.

The main goal in this converstion is to not displace the tenants or destroy the apartments by ripping up the hardwood floors and installing a new, approved fire-rated floor system.

The secondary goal would be to NOT destroy the ceiling of the 1st floor since the owner just hung 5/8ths drywall over the old plaster/lathe at some expense.

The standard code would require rippnig everything off the top of the joists and replacing with plywood and a topping coat AS WELL AS ripping off all of the new drywall and old plaster and lathe on the ceiling and then re-install a dual layer of 1/2" drywall with steel furring strips between.

I'm hoping that we can be creative and avoid as much of that as possible.

SO... i'm wondering if anyone has any suggestions.

One idea was to figure out what the fire rating of archaic materials are. A co-worker suggested that there might be acceptable fire ratings for plaster/lathe and the flooring above... just not in current code books. 
Ideas on that?

Another idea was to fill the cavities between the joists with a fire-proofing foam of some kind, allowing us to obtain the fire-rating without trashing either the finished ceiling or beautiful hard-wood floors of the apartments above.

Any suggestions would be greatly, greatly appreciated.

Thanks in advance.


----------



## mdshunk (Mar 13, 2005)

Fire ratings of existing materials are covered in the UL "Orange Book", _"Fire Resistance Directory, Volume 1"._

_http://www.constructionbook.com/ul-listing/_


----------



## Tscarborough (Feb 25, 2006)

Keep adding ****rock to the ceiling until you achieve the rating. Maybe 2 more layers?


----------



## adianz (Apr 13, 2007)

*problem with adding*

Well... the joke is that the ceiling already has plaster, lathe and a layer of 5/8ths drywall.

But code calls for ripping that all out and installing two layers of 1/2 inch in a very specific way using specific screws and metal furring strips between the two.

Granted, there is a chance that the inspector who shows up won't know the difference.
But... if busted, i'm sure that they will be sticklers that it be done right.

So i'm looking for an alternative to ripping down and starting from scratch.


----------



## AustinDB (Sep 11, 2006)

it make make the most sense to tear off the new layer of 1/2", then install the two layers as instructed, on top of the plaster. If the first 'new' layer is 5/8"-is it the fire code rated drywall? If so, your inspector may allow you to install the furring strips and an additional layer on the surface of the existing 5/8" drywall. You don't have direct access to the lathe, so treating it w/ fire retardant material is not an option. You'll notice an orange coloring to wood which is treated w/ fire retardant. 

Are you sure about the 1/2" requirements for the drywall-does it call for 5/8"? I've seen similar systems in engineered lumber books where the ceiling system is designed to provide a stronger floor (for above it) which increases the pounds per square foot of loading.


----------

