Roof Beams

[rosinante]

Hi All
Can anyone advise me on how to make and size roof beams to span a nominal 6 metres, the roof is the insulated box profile steel/PVC stuff and is lightweight, the roof is flat,I am thinking about a timber/plywood "I" beam but am at a loss as to size and materials,would a 4x2 top and bottom of the I and the upright of the I 6 " of 3/4 ply set into routed grooves fixed with glue and screws be ok?
I dont want to use a solid beam as the ones I have already have bowed and twisted so need an engineered solution, all help/ advise welcome

Cheers
Chris

 

[Dee J]

"upright of the I 6 " of 3/4 ply " So the whole beam will be about 9" tall by 4" wide over a 20' span, on a virtually flat roof? I know you're in kent, but snow loading is worth bearing in mind.... As you're aready using box steel roofing, wouldn't some ready made steel Z purlins be more predictable.
Dee

 

[Racers]

Hi, Chris

How about these http://www.donaldsontimberengineering.c ... php#ibeams I know its not DIY solution but seems like a quite important task the beams have to do so safety is a consideration

Pete