2 hour fire wall between townhouses

[Jmeng1026]

I have been asked to design a townhouse unit that will be constructed on the rear side of an existing townhouse building.

I have designed townhouses before with a 2-hour firewall between units but that was all new construction.

Is there a way to get a 2-hour firewall without having to redo the existing rear wall of the existing unit?

Basically a one-sided firewall.

 

[dik]

Not likely, if it's a code requirement. This is a life safety issue. The firewall has to stand independent of either part of the two buildings.

 

[Greenalleycat]

Can you do it in masonry block? A 20 series block would easily provide that and could be built from one side while providing protection to both sides

 

[dik]

Can you do it in masonry block?

It requires lateral support in the event either half of the building burns down.

 

[Greenalleycat]

It requires lateral support in the event either half of the building burns down.

Just design it to cantilever? Super easy for single story. Two story would be a bit niggly as you'd need midfloor support on the existing building side - may be tricky to attach. The post fire load here is only 0.5kPa though so they're pretty small loads