Spans are calculated based on the following applied loadings, any additional loadings will reduce the maximum spans shown:

Top chord (live) - 750 N/m² (Snow Load)
Top chord (dead) - 685 N/m² (Roofing Covering Materials)
Bottom chord (dead) - 250 N/m²
Flat Roof Total Load - 1685 N/m² + 900N Man Point Load at Centre of Span + Wind Loads

Depth	WS200 - 195mm		WS200 - 219mm		WS250 - 254mm		WS300 - 304mm		WS400 - 417mm
Spacing	400	600	400	600	400	600	400	600	400	600
72mm	4820	4210	5670	4890	6370	5500	7360	6370	8210	7650
97mm	5340	4630	6240	5390	7010	6040	8030	7000	8380	7900
122mm	5780	4960	6710	5790	7540	6490	8250	7530	8770	8200
147mm	6120	5290	7110	6130	7990	6880	8580	7980	9650	8250
Width	Approximate Maximum Span (mm)