Interpretation #6871

Published December 16, 2011

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Original Request

Code Version
2007
Code
BUILDING
Code Description
Building
Chapter
7
Section
705.5
Topic
non-combustible exterior sheathing

Question

Is it the intent of FBC 705.5 exception 3 to use non-combustible exterior sheathing with combustible exterior finishing if the building is sprinklered?

Answer Published 12/16/2011 at 12:02 PM

No. 705.5 exeption #3 allows the removal of the 18”
extension in a building with automatic sprinkler protection
(on both sides of the Fire Wall) if the Fire Wall
terminates at the interior side of noncombustible exterior
sheathing. It is silent on the combustibility of additional
exterior finish.

Commentary

If the 7/16" OSB is sheathing or siding and the fire wall will terminate at the sheathing or siding, the answer is yes, a one hour fire resistance rating is required for 4 feet on either side of the fire wall. The requirements of protection on the sides are governed by the requirements/conditions of 705.5.1.