Spanning 6m

[jason121]

No steel spray foamed with 4 inches of insulation

 

[Earthstore]

Maybe Tritec would have a solution?

 

[Gavin A]

No steel spray foamed with 4 inches of insulation

What I think you probably need here is for the structural engineer to factor in the strengthening associated with actually bolting an additional steel / aluminum Ibeam or equivalent (ie big solar rail designed to span 3m) at eg 600mm intervals along the length using 8mm bolts.

I suspect that the increased strength given to each by being bolted together in this way would be sufficient to allow for the additional loading without actually having to bridge the full 6m. The 2 combined and tied together in this way should be stronger than the sum of each would be individually.

Then what the impact is of doing this but also using cruciform mounting to create an incredibly strong lattice covering the entire roof.

But that might be something best asked to a specialist such as sunfixings or hilti.

 

[Worcester]

Simple enough for any graduate stuctural engineer to design something using off the shelf materials. You should be able to get the whole design done including checking the support loadings and full design drawings with full bom and materials specifications that would satisfy any insurer for less than £1k