sprinklernotes
Cloud Ceilings
You have asked the following questions: “There is a new Table for determining the Maximum Sprinkler Protection area based on the width of both the Ceiling Clouds and openings between the clouds (Table 8.15.24.1). The formula provided within this table is hard to interpret. Math formulas are not our challenge, just interpreting what the formula actually is from the narrative is confusing.” In response to your question, we have reviewed NFPA 13, 2016 edition as the applicable standard. Our informal interpretation is the Table is applied as follows. This is a really confusing issue partly because all of the criteria is new for the 2016 edition of NFPA 13. To start off, note there are other requirements on this issue in other sections. Per the definition of cloud ceilings in Section 3.3.5.4, this section cannot be applied if the clouds are tilted. Another remote requirement is in Section 8.15.1.2.1.2 where the openings cannot exceed 20% of the total area of the ceiling and where the length is greater than 4 ft you cannot have a depth greater than 8 in. The good news is the limitation on the length and depth have been removed for the 2019 edition. Also keep in mind Section 8.15.24.2.2 limits the ceiling height to 20 ft. The intent of Section 8.15.24 is to give us a sprinkler spacing based on the ceiling height and the gaps or spaces between the cloud ceiling panels. Table 8.15.24.1 gives us four items we have to consider. The first item is the minimum width or least dimension of the cloud ceiling. For example, if the cloud ceilings were 4 ft by 8 ft we would have to choose the 2.5-4 ft line. The second through fourth columns allow us to determine our area of coverage based on the ceiling height and opening width or gaps between ceiling panels. The bigger the gap, the lower the area of coverage. Only one of the columns will apply depending on your circumstances. For example, take a ceiling located at 12-ft with 4 ft by 8 ft ceiling clouds. The second column tells us we can have a maximum of 0.5 in. of space between panels for every foot of the ceiling height. With a 12 ft. ceiling the clouds need a 6 in. or less gap between the clouds (12 ft. x 0.5 in. = 6 in.) in order to apply the 225 sf. area of coverage. If the gap is bigger than 6 in, we move to the next column. This column states a maximum of 0.75 in. of space between panels for every foot of ceiling height, allowing a gap up to 9 in. (12 ft. x 0.75 in. = 9 in.). With a 9-in. gap, the maximum sprinkler spacing would then be 120 sf. If the gap is bigger than 9 in., we refer to the final column. The final column states we can have a maximum 1 in. of space between panels for every foot of ceiling height, allowing a gap up to 12-in. (12 ft. x 1.0 in. = 12 in.). With a 12-in. gap the maximum sprinkler spacing would then be 70 sf. If the gap is larger than 12 in. (for a 12-ft. ceiling height), then sprinkler protection would be required above the cloud ceiling.
