sprinklernotes
Decorative Roof Features
You have asked the following question: “We have a project where several small
structures are built on top of the roof. These structures are completely
separated from the main building and sit on a finished roof. The small
structures are made with combustible materials and are uninsulated. There are
no penetrations into the main building from these structures. The project team
is calling the small structures dormers or decorative elements. We believe this
does not qualify as a decorative element as it is part of the roof structure
and it exceeds 160 cubic feet. We believe sprinkler protection would be
required in these structures. Could these structures be considered a decorative
element? Could sprinklers be omitted in these spaces? In response to your
question, we have reviewed NFPA 13, 2016 edition as the applicable standard.
Our informal interpretation is sprinkler protection is required.
In this situation, Section 8.15.1.2.18.1 has to be reviewed and it states:
Sprinklers shall be permitted to be omitted from within combustible soffits,
eaves, overhangs, and decorative frame elements that are constructed in
accordance with 8.15.1.2.18.2 through 8.15.1.2.18.5.
Since Section 8.15.1.2.18.1 states “8.15.1.2.18.2 through 8.15.1.2.18.5” all
four conditions listed have to be met. With the small structures being on top
of the roof structure Section 8.15.1.2.18.2 does not apply because the 4 ft.
maximum width in Section 8.15.1.2.18.2 is directed at limiting the impact of
combustibles beneath overhang type features. With that being said, this
allowance is not limited to just features on the exterior wall such as
overhangs. It also applies to features on the roof, as indicated by Section
8.15.1.2.18.4 dictating separation by walls or roofs of noncombustible
construction. Next, Section 8.15.1.2.18.3 is requiring these spaces to be less
than 160 cu. ft., which they are not. Since the structures do not meet Section
8.15.1.2.18.3, this alone removes the possibility of applying Section
8.15.1.2.18.1 to omit sprinkler protection. Continuing on to Section
8.15.1.2.18.4, the structures are required to be separated from the main
building interior by walls or roofs of noncombustible or limited-combustible
construction. To be considered noncombustible or limited-combustible the
structural members have to be noncombustible not just the exposed finish
material. If the structural members are combustible, Section 8.15.1.2.18.4 also
removes the possibility of applying Section 8.15.1.2.18.1 (to omit sprinkler
protection). Finally, Section 8.15.1.2.18.5 requires no openings or unprotected
penetrations directly into the building, which there are none. As stated, all
of the conditions listed in Section 8.15.1.2.18.1 to omit sprinkler protection
must be satisfied and two of the four are not met in this situation. Thus,
sprinkler protection is required in the structures. With that being said, there
are other ways to omit sprinklers in these spaces per NFPA 13 if sprinkler
protection is undesirable due to possible freezing and maintenance issues. The
most commonly used section to omit sprinkler protection from a combustible
concealed space would be Section 8.15.1.2.7, which requires the space to be
filled entirely with noncombustible insulation. There are other conditions in
Section 8.15.1.2 that could be used as well in this situation to omit sprinkler
protection, Section 8.15.1.2.7 is more commonly used.
