A 3-in-12 pitch to a ceiling or overhang might not appear that dramatic, but I came across a reminder again this past week as to the importance of paying attention to ceiling and overhang slopes.
We had a project with a corridor that had a high roof where routing pendents would be impractical. The slope of the corridor was 3 in 12 (3 inches vertical for every 12 inches horizontal), and so we evaluated use of sidewall sprinklers to protect the corridor.
Here's where there's three important points to remember came into play that offered a good refresher for us:
Sidewall sprinklers are required to have the deflector aligned parallel to ceiling or roof slopes (NFPA 13 2002-2016 Editions Section 184.108.40.206), and, where the slope exceeds 2 in 12 the sprinkler must be located at the high point of the slope and be positioned downward (NFPA 13 2002-2016 Editions Section 220.127.116.11.2). Additionally, as with all slopes, the sprinkler coverage is measured along-the-slope, not in floor area (NFPA 13 2002-2016 Editions Section 18.104.22.168.2).
Those can be easy-to-miss rules and I probably didn't pick up on them for longer than it should have taken when I first started designing fire sprinkler systems.
Other considerations that often pop up in these scenarios include:
(1) Use of extended coverage sprinklers may have specific limitations on how dramatic of a slope they can handle,
(2) Sidewall sprinklers must be listed for use when they are lower than 6 inches down from the ceiling or roof (NFPA 13 2002-2016 Editions Section 22.214.171.124.1.2). This listing often involves different required pressure and coverage. Reference the product data sheets to be sure installations match their listings.
(3) Sidewall sprinklers can't be located more than 6 inches from the wall on which they are mounted (NFPA 13 2002-2016 Editions Section 126.96.36.199.2.2)
What issues do you look for with sloped ceilings? Post in the comment section below.
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Joseph Meyer, PE, is a Fire Protection Engineer in St. Louis, Missouri. See bio on About page.