I was recently ask can you install fire dampers in a wood floor joist system. The building is old and is having a change of occupancy that requires the floors to be rated between the 1st and 2nd floor. The membrane is 3/4" plaster on the ceiling side.

This is a big "it depends" answer.

You first need to make sure the whole floor assembly is a rated assembly. If it is without upgrades, you should be able to install the fire dampers in the floor if that specific fire damper has been rated by UL to be installed horizontally in a UL rated floor assembly.

My experience with fire dampers is that as long as it is UL rated in the way you want to use it, there are no issues. This may require extra framing around the opening, but that shouldn't be a huge deal.

I really think your biggest issue is the fire rating of the existing floor construction. You may need to add fire rated drywall to get the fire rating you need.

You might consider red-flagging this one an re-posting in the NFPA (fire) Code Issues forum. There are some experienced inspectors who prowl that forum.

Good on ya,

Goober Dave

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In my experience, installation in rated wood assemblies are accomplished by using radiation dampers in lieu of fire dampers. Much less of a hassle installing them in thin assemblies.

In my experience, installation in rated wood assemblies are accomplished by using radiation dampers in lieu of fire dampers. Much less of a hassle installing them in thin assemblies.