There is a 17 story high rise hotel that is being remodeled. On the first floor, a new wood ceiling was installed approximately 24” below the existing concrete deck. The wood ceiling planks are 6” apart with a 1/4" gap between each plank. The total area of the ceiling is approximately 1,373 square feet. The combined area of the opening is approximately 57.25 square feet. The concern the AHJ has is that the ¼" gap between the wood planks will not allow the heat to adequately collect at the ceiling level and will instead filter through the gaps and collect above the ceiling at the concrete deck, delaying activation of the sprinklers. The spacing between each sprinkler head is approximately 15 feet since the area of coverage is 225 square feet. No sprinkler heads were installed above the ceiling. The question we have is this, do the ¼” openings between the 6 inch wide wooden planks fall into the category of “small openings” as mentioned in section 188.8.131.52.1.1 not requiring protection above the ceiling? Or, do the gaps between the ceiling planks need be adjusted so that a minimum width between the gaps is 2 feet as per section 184.108.40.206 and Table 220.127.116.11?
Code referenced is NFPA 13 (2016 Edition).