DW1401831 Rev.K1
Sep 18, 2015
15
8.3.5
Exposed solid joists
Exposed solid joists may impede the flow of smoke to detectors. A joist is defined as greater than 10 cm (4 in.) in depth
and spaced less than 91 cm (3 ft.) apart. The detectors must be mounted on the bottom of the joists.
Figure 14: Smoke detector spacing
—
solid joist construction (side view)
Figure 15: Smoke detector spacing
—
solid joist construction (plan view)
Note:
Joists less than 10 cm (4 in.) deep are considered flat ceilings. Smoke detectors can be mounted on ceilings or
on the bottom of joists.
