Creating storage room in carport roof space

[max_depth]

Hi
I am planning to create a store room by flooring the roof space of my carport.
The car port is quite substantial, breeze block construction, more like a garage but no doors.
Its 5m wide by 6m deep.
The roof joists run across the 5m span, ie the joists are 5m long, 600mm apart, and 75mm deep by 38mm thick.
I plan to use 18mm chipboard for the floor.
I just want somewhere to put all those boxes of junk nobody ever uses but which I'm not allowed to throw away
Nothing too heavy.
How can I calculate whether the joists need strengthening?
Thanks

 

[pieman]

will of course depend on how heavy your stuff is!
you will find the building regs structural sizes tables here
(the actual documents are PDFs)

or suck it and see? if it really is bulky light weight items like cardboard boxes, packaging, broken flymo grass boxes, Ronco 'Buttoneers' etc. then nail some boards up and do an ad hoc thing?

If it is an open carport, I presume there is no ceiling, and the joists you refer to are actually ties - they'd be very small at a 15 metre span to support even plasterboard.

I'd be very wary of doing anything which looked like you might be able to walk on it with such tiny timbers...

 

[masona]

75mm deep by 38mm thick.

Are they gang nail roof trusses ?

What sort of roof ? lean-to or pitch etc.

Do you have ceiling joists ?

 

[max_depth]

Hi Masona
You are correct of course, they are roof trusses. I understand it now.
So the reason they seem too flimsy to be used as floor joists is because they aren't floor joists. The horizontal members are in fact part of a triangulated structure, and therefore much stronger than unsupported beams or joists of the same size.
Does 'gang nail' mean the individual timbers of each truss are joined using galvanised steel plates? If so then yes, these are gang nail.
Its a pitch roof, trusses every 600mm and fully cross-braced. It seems very well-built and adequately strong now I understand the structure.
I have done a 'proof test' by hanging off one of the trusses right in the middle and there was no noticeable deflection. So I think that they will be fine for storage.
Thanks
Hi Pieman
Thanks for the link, but I guess it doesn't apply since these aren't actually isolated joists. My mistake