steel beam size?

[martin68]

Hi guys, i'm needing advice as to the size of an "I" beam I want to use for a roof apex.

This does not involve building regs as its for an out building and the roof covering will be light weight poly-carbonate panels as a conservatory type roof, with 4x2 timber rafters between the panels which are 2.4m long before resting on an existing brick wall on the other end.

So given the light weight of the roof, I want an "I" beam that is thin enough but strong enough not to sag at a 4.5m span, to use as an apex support for the polycarbonate panels.

I could use timber, possibly 9x2" at 4.5m long, but im prefereing something thinner and stronger.

Any suggestions?

 

[Ian H]

I’d guess a 203x133.

 

[Notch7]

Is this a gable ended building.

Is the roof vaulted and you want a structural ridge?

You could do it in timber and have the rafters finish below the top of the ridge -that way not so much will be visible inside and externally the ridge could be used to wrap lead over.

If you use an I beam you will need to put timber in the webs for something to fix the rafters to.......making for a bit more complication

 

[martin68]

The gable ends are in fact the existing walls of a house on one side and a block built shed on the other, so i want to fix the steel beam between the two walls.
Its a courtyard shape area between the house and the shed, where i want to build a conservatory type of covering.
I want the beam to take the load of the polycarbonate as the wall on the other end of the sheets where the gutter goes is a 4" block wall and i'm worried it would spread and push on the wall in a sideways direction if the gable is not solid and strong to hold the trusses and sheets downward pulling direction.
see attached drawing.

 

[^woody^]

7x4

 

[noseall]

7x4

=28?