Rafter support replacement

[gnomeo]

First post so here goes.....

This is my man cave and vehicle storage facility.
https://lh4.googleusercontent.com/-B4FPKEA2Xss/TtmbnYsljsI/AAAAAAAAAE0/8stFFIhc9E8/s640/1449.JPG

The shed was built in the 1960’s by the original owner of the property. It’s all hardwood frames and clad in fibro. The roofing material is second hand trimdeck. The shed is shown on the house plans to have council approval but the roof could never have passed an inspection. To give you a bit more of an idea. Here's a mud map of the shed
87262

And here are a few pics of the offending beam if you could call it that. (Dont mind the mess, it's usually cleaner than that)
87263872648726587266

When we bought the place in 1993 the building report we paid for noted the shed roof as being suspect structurally. In the near future I’d like to put solar PV panels on it so we need to fix the problem.

What I need to know is if I were to replace the centre beam with a C purlin or timber beam what sizes I would need to make the roof structurally sound. I’d also be replacing the roof cladding with new custom orb as the old trimdek is lapped and starting to leak in places.

Any help would be appreciated.

[TermiMonster]

Definitely dodgy building practice, but let's face it, it's still standing after 50 odd years. It's nearly as old as me. Ya gotta love OBHW......F8.....compare that to the "F7" pine you buy now.:doh:
TM

[ringtail]

I'd be looking at a I beam (engineered timber) with the metal support trussing. A traditional beam, timber or steel would be huge to clear span that distance. Then add the weight of the solar panels. You will need to know how many panels and their weight before sizing a beam. A post in the middle would make life a lot easier but would probably stuff up the space.

[gnomeo]

Definitely dodgy building practice, but let's face it, it's still standing after 50 odd years. It's nearly as old as me. Ya gotta love OBHW......F8.....compare that to the "F7" pine you buy now.:doh:
TM
You ought to try driving a nail into it :o

[gnomeo]

I'd be looking at a I beam (engineered timber) with the metal support trussing. A traditional beam, timber or steel would be huge to clear span that distance. Then add the weight of the solar panels. You will need to know how many panels and their weight before sizing a beam. A post in the middle would make life a lot easier but would probably stuff up the space.

I'd rather not put a post in the middle of the shed.

The custom orb roofing would weigh ~210kg for 36m². I'd be looking at 16 panels weighing ~240kg in total.

[Compleat Amateu]

Whaddya mean I can't hang me chain block off it? Great timberwork ... I'd never walk on the roof!