sprinklernotes
Sprinklers Under Intermediate Landings
You have asked the following questions: "I have a noncombustible stair shaft,
and the AHJ is requiring sprinklers under the stairs going from the first floor
to the intermediate landing and also under the stairs going from the
intermediate landing to the second-floor landing. This is in addition to the
sprinkler under the first intermediate landing required by 8.15.3.2.1. Are the
sprinklers under the stairs required? Would section 8.15.3.2.3 be considered in
this situation? 8.15.3.2.1 does not say anything about sprinklers under
stairs." In response to your question, we have reviewed NFPA 13, 2016 edition
as the applicable standard. Our informal interpretation is that a sprinkler
should be in one of the noted locations but not both.
The base requirement in Section 8.15.3.2 indicates that in noncombustible stair
shafts having noncombustible stairs with noncombustible or limited-combustible
finish sprinklers shall be installed at the top of the shaft and under the
first accessible landing above the bottom of the shaft. The concern is the
storage of materials in stairwells under the first landing or a large landing
at the top of the stairs. As such, sprinklers are required at these locations.
For stairs that have an intermediate landing, a sprinkler would be located
under this landing. The area under the first intermediate landing is used quite
often for storage. Some buildings provide walls or other types of barriers
installed to prevent storage under the first landings where sprinkler
protection would not be necessary. This is explicitly stated, starting with the
2013 edition of NFPA 13, in section 8.15.3.2.3.1: Sprinklers shall be permitted
to be omitted from the bottom of the stairwell when the space under the stairs
at the bottom is blocked off so that storage cannot occur. In defining where to
place the sprinklers, Section 8.15.3.2.3 explicitly says to sprinkler beneath
the landings OR the stairways where the area can be used for storage. Beneath
the stairways often require protection, but not in both locations provided the
spacing limitations have not been exceeded to the wall under the landing. Even
though a portion of the area beneath the landing may be shielded, it would not
negatively affect the ability of the sprinkler in controlling a fire. NFPA 13
allows shadowing of the sprinkler discharge, and with a single sprinkler
operating you will have an over-discharging situation due to the excess
pressure available. Additionally, with the sprinkler over-discharging, you will
have water that could reach the shadowed areas due to bouncing off the other
surfaces in the area reaching the fire indirectly.
