Nittan EVCA-P - Page 7

DW1500110 Rev.K1
Sep 18 2015
7
6.2.5 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 3: Smoke detector spacing — solid joist construction (side view)
Figure 4: 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.
CEILLING SECTION
Less than 91cm (3 ft.)
Less than
10cm (4 in.)
Smoke detector
Solid joist
1
3
S
2
3
S
2
3
S
2
3
S
1
3
S
1
2
S
S
1
2
S
Solid joist Smoke detector