Expert: Dan Griffin - 11/16/2009

Question
DAN, I NEED TO BUILD A TWO HR. FIRE WALL TO SEPERATE FLAMM. GAS FROM  NON-FLAM. GAS. ASIDE FROM 10" BLOCKS, IS DRYWALL MADE W/ A TWO HR. RATING  ???/ THANK YOU IN ADVANCE.....JIM  ( EXT. DRYWALL)

Answer
Jim, there are many ways to comply with a two hour wall.  I have the UL directory of tested assemblies as of 2001.  It is a 3 volume set and the one dealing with wall assemblies is over 1,000 pages.  There are far too many to even begin to share.  It makes a lot of difference on whether this wall is a fire separation wall or a fire rated assembly.  It also makes a difference whether this wall is bearing or non-bearing.

You can make the 2 hour rating with wood studs, metal studs, CMU, etc.  As I glanced through, most will require 2 layers 5/8 firecode rock both sides, 1 1/8 core board, or 3/4 rock both sides - most had mineral wool insulation in the stud chamber.

Your best answer would be to contact a local commercial drywall house, discuss your problem.  Find a rated assembly that you know how to assemble - go to your AHJ and ask if this assembly will meet their requirements.  They will want to see a UL rated assembly, so have a photostat of the assembly.  Make sure you read the details as to dimensions, fastening, and assembly so that your installation meets all the criteria.  Also be aware there are very stringent rules about conduit and electrical outlets in a fire separtation wall and very specific rules about penetrations.  The local fire marshall has final jurisdiction.