sprinklernotes
Obstructions and the Three Times Rule
You asked the following questions: “In regard to NFPA 13 section 8.6.5.2.1.3,
the main requirement includes a reference to columns; subparagraph (B)
indicates that for columns the maximum clear distance does not apply. Is it the
intent that the three times rule apply to columns, if the sprinkler is more
than 24-in away from the face of the column, but less than the three times
requirement? Is the column still an obstruction requiring sprinklers on the
obstructed side?” In response to your question, we have reviewed NFPA 13, 2016
edition as the applicable standard. Our informal interpretation is that if the
sprinkler is located at least three times the width away from the column, it
meets the intent of the standard.
Section 8.6.5.2.1.3 specifies that sprinklers shall be positioned away from
obstructions at a minimum distance of three times the maximum dimension of the
obstruction (e.g., truss webs and chords, pipe, columns, and fixtures). For
example, if you have an 8-in column, you must be at least 24-in away (8 x 3 =
24). If you have a 10-in column, you have to be 30-in away (10 X 3 = 30). The
sprinkler shall be placed at an appropriate distance away from the obstruction,
a column in this application, where sprinklers are able to spray on either side
of the column. A shadow area may exist behind the column and may not apply an
even coat of water on the floor. This is acceptable since a sprinkler is
located on both sides and sprinkler systems are designed to control the fire to
allow time for the responding fire service to finish the job. In previous
editions to the 2016 NFPA 13 there was a 24 inches maximum distance from the
obstruction.
