Smoke detector spacing with low height ceiling and beams.

[DavidCR]

Hello.
A question on smoke detector spacing/location.

Case:
Intermediate floor with low ceiling.
Ceiling height: H=2m (6.7´)
Beam height: h=0.38m (15")
Beam distance: L=1m (3.3´)

For smoke detectors: since h>0.1H, and L>0.4*H >them each beam space is a pocket so I need a @#%& lot of detectors.

On "beam reduction rules" as per NFP72, or an manufacturers rules is there a consideration for low ceilings?.
Do reduction rules on detector spacing apply the same if the ceiling is relatively low?

 

[cdafd]

What kind of business are they going in??

Why are they required?

 

[DavidCR]

Client requirement. Used for storage of working materials, temporary storage of tools, access to other areas.In the sketch I describe.

(not on scale).
Following NFPA 72, I interpret the upper level shall be considerd a different case.
The detector spacing looks fine for the high ceiling area, but in the upper level the size of beams lead me to a detector in each beam pocket.

 

[cdafd]

A little beyond my little knowledge.



I do not think you can get a reduction for low ceiling, unless some engineering analysis is done?



Waiting for Scott to answer you.



From the 2013 edition, does this help you::





Looks like you fall between a solid joist and a beam.



If all else fails, can they sheetrock the area?? And make it smooth? would it be cheaper in the long run?







17.6.3.3* Beam Construction.



17.6.3.3.1 Spacing.



17.6.3.3.1.1 A ceiling shall be treated as a smooth ceiling if the beams project no more than 4 in. (100 mm) below the ceiling.







17.6.3.3.1.2 Where the beams project more than 4 in. (100 mm) below the ceiling, the spacing of spot-type heat detectors at right angles to the direction of beam travel shall be not more than two-thirds of the listed spacing.







17.6.3.3.1.3 Where the beams project more than 18 in. (460 mm) below the ceiling and are more than 8 ft (2.4 m) on center, each bay formed by the beams shall be treated as a separate area.









17.6.3.3.2 Location. Where beams are less than 12 in. (300 mm) in depth and less than 8 ft (2.4 m) on center, detectors shall be permitted to be installed on the bottom of beams.