duh Wrote:
>
> I was thinking the same thing. I think townhouses
> once had to have a masonry wall between
> them....but, new ones I've seen being built don't.
> They just nail up 4X8 sheets of, I'm sure, very
> special (and cheap) "fire resistant" stuff.
> I wonder how many junkets the developers sent the
> County Board on to get them to approve that shit!
None. It's a double-layer of 1" thick fire resistant drywall mounted in metal tracks. This provides at least a 2-hour fire rating. This is the same stuff used to line stairwells and elevator shafts in office buildings.
In addition, the framing of the house is attached to the firewall with metal brackets that will melt in the event of a fire. The firewall is otherwise completely independent of the framing. This prevents a collapsing house from pulling down the firewall.
See
http://www.nationalgypsum.com/literature/gypsumconstructionguide/H_StudArea.pdf for more than you ever wanted to know about this type of construction.