IFC 317.3 - "Combustible vertical surfaces" and rooftop gardens

[Harrison Staab]

IFC 2015. No local amendments. Somewhere in Colorado, USA, Earth. Multi-family (R-2) Type VA construction, sprinklered. Roof is entirely class A rated assembly, with TPO membrane over gypsum coverboard.

IFC 317.3 Rooftop structure and equipment clearance. For all vegetated roofing systems abutting combustible vertical surfaces, a Class A-rated roof system complying with ASTM E108 or UL 790 shall be achieved for a minimum 6-foot-wide continuous border placed around rooftop structures and all rooftop equipment including, but not limited to, mechanical and machine rooms, penthouses, skylights, roof vents, solar panels, antenna supports and building service equipment.

Does "combustible vertical surfaces" refer to combustible finish materials (a la IBC section 1406) or of a combustible construction type?

Does the 6-foot-wide continuous border requirement include parapet walls?

May a vegetated roof be located closer than 6' to a wood-framed penthouse wall with noncombustible stucco finish?

May a vegetated roof be located closer to 6' to a wood-framed parapet wall that is entirely covered with a class A roof covering assembly?

 

[steveray]

Poorly written section to me but I have never dealt with it, I say it is the "surface/ finish" not the construction type.....But the Class A roofing is probably combustible....

 

[cda]

Have not read this yet

 

[Lorenbb]

Poorly written section to me but I have never dealt with it, I say it is the "surface/ finish" not the construction type.....But the Class A roofing is probably combustible....

I had one local AHJ say that combustible framing is the key issue, so we had to move green roof away from a wood-framed penthouse.
At the same time, an abutting City's AHJ said, no, it's just the finish/cladding that matters, so if the penthouse is clad with fibercement, we're happy.

 

[Yankee Chronicler]

It says "... abutting combustible vertical surfaces ..."

To me that says the exterior cladding material.