sprinklernotes Obstructions Against the Wall
You asked the following question: “In the 2016 ed. of NFPA 13, Figure 8.6.5.1.2(c) shows an obstruction against the wall that when no more than 24 in. deep, the bottom of it has no maximum distance below the ceiling. It shows no minimum required separation from the face of the obstruction. Is this the intent?” In response to your question, we have reviewed NFPA 13, 2016 edition as the applicable standard. Our informal interpretation is that only the standard 4 in. minimum separation applies. Allow me to first say that Figure 8.6.5.1.2(c) has some mistakes that were addressed by a tentative interim amendment (TIA 17-7). The figure that was originally published showed the maximum distance from the wall as “S” and that the bottom of the obstruction must be at least 18 in. below the deflector. The distance to the wall was changed to the standard ½ S. This is measured to the wall behind the obstruction in order to account for the floor area beneath it. The 18 in. minimum to the bottom of the obstruction was deleted. It now just says “no maximum.” For example, the bottom of the obstruction can be 4 ft. below the plane of the deflector and no protection is required beneath the obstruction. This allowance is not like the beam rule where the closer you are to the side of the obstruction, the closer the plane of the deflector must be to the bottom of the obstruction. What isn’t stated but understood is that the face of the obstruction is also treated like a wall when it comes to Section 8.6.3.3 and the minimum 4 in. separation from walls. This addresses the heat at the corner of ceilings and walls and the associated impact on activation of the sprinkler. The bottom line is that because these obstructions are only 24 in. deep, the water cascading down the front of it will contain a fire beneath it.
