Maximum span of flat roof joists

[wakey77]

Hi can anyone tell me the maximum span of a 9 x 2 joist used on a flat roof

 

[RNReindeer]

With access for maintenance and repair only or unlimited access?

Imposed load 0.75 kN/m2, 1.0kN/m2 or 1.5kN/m2?

Strength Class C16 or Class C24?

Dead loads (kN/m2) excluding self-weight of joist of less than 0.5, 1.0 or 1.5?

Spacing of joists 400, 450 or 600mm?


nearest available size will be 47 X 220mm.

 

[noseall]

Aboot 4.5m at 400m c/c using C16.

 

[wakey77]

Thanks for your reply
400 centres the span is 5200 I was hoping to get away with using joists rather than dropping in a steel to split the span
What size joists would I need for that span and at what centres

 

[wakey77]

Access for maintenance only

 

[wakey77]

Would a 9 x 3 work

 

[wakey77]

ok just been looking at the strada tables for flat roof joists
its saying the maximum span for a 47 x 220 joist at 400mm centres for maintenance and repair only is 5.34 m
as my clear span of joist is 5150mm according to this table a 47 x 220 is sufficient
does anyone else go by these tables and are they reliable?

 

[freddiemercurystwin]

They are fine to use.