Building 24x24 metal building and need firewall.

[carcrazyguy]

I am having a 24x24x12 metal (web truss design) building built behind my house. City code requires a 1 hour firewall on he side near the property line. I was planning to use a fire retardant spray foam, however the spray foam company is saying it would be much cheaper to build a frame and Sheetrock style firewall. Spray foam for that 28 feet, 24 foot wall plus 2 foot of front and back wall, was over 1700 alone.

Anyway, it got me to thinking. If the frame is all metal, rebar and the exterior is metal sheeting, how would that ever burn? So why would a 1 hour firewall be any better than actual metal, in preventing a fire from spreading?

 

[readhead]

Metal burns. That's how a cutting torch works. More accurately if there was a fire in the building it would cause the metal to deflect and collapse. I'm actually more puzzled by how you got a permit without this detail already worked out on the plans. Are you protecting your building from a fire at the neighbors or are you protecting the neighbors property? Makes a difference. How close is the building to the fence? Did the building company say we don't do that and you are on your own? I would suggest you talk to the building department and find out what they expect to see before you proceed. This could turn into a huge can of worms.

 

[wssix99]

There are actually "brochures" for this. Just pick out the option you want: http://www.usg.com/content/dam/USG_...ire-resistant-assemblies-catalog-en-SA100.pdf

 

[jaysberman]

check you local codes. The let me use tow layers of 5/8 drywall for a fire wall. Pa.

 

[pmiranda]

I'm guessing the firewall is to protect your neighbors from your garage. I'd consider myself lucky if I were even allowed to build that close to the property line.
The drywall is cheaper, but I'm guessing the fire-rated spray foam would also be a great insulator and maybe over the long run it's worth it up-front expense if you're going to keep the building cool/warm (where are you?)