new verandah - beam & foundation questions

Dear All,

I'm planning on building a verandah out the back of my house, with Bluescope Trimdeck steel roof, glass wool insulation, and some sort of ceiling (timber or strawboard, etc, if possible). I've attached a plan (not to scale). I've got no experience with construction, but my neighbour is a builder, and dad is a handyman, both of them are helping, thank God. I've been down to the local Hyne timber yard, and the guy used his computer program to determine that I could use 190 x 45 mgp 10 timber for the beams and rafters. Oddly enough the treated H3 timber is cheaper than the untreated, so I'll use that. Anyway I've got two quesions:

1. beams: I've been told that I can use these 190x45's for a long single span 5.4m ... however its at the top limit of the allowable deflection; I'll be getting a downwards bend 17.9mm. I'd like to reduce that if possible.

I've been thinking that I'd like to support this large section with an additional beam at 3.3m, straight along from the other beam that is supporting the short part of the verandah. However, of course I guess it will have to be below the rafters. So what size should that support beam be? Does it have to be another 190x45, or could it be a smaller size? Or would a metal rod or beam be more affordable, or better somehow (perhaps I could drill holes in the rafters and have it internal, I don't know if that is ever done?)

2. foundations: I've been told I should pour big 450mm cubic blocks for the post foundations, and I'll do that at the end of the big rafter spans, where the posts go down to bare ground. However at the short ends, for the beam at the end of the 3.3m rafters ... can I just bolt the posts down into the existing slab?

I don't believe its as thick as a house slab; i'd guess its only 3 inches or so. However, currently I have there a Spanline verandah roof that has been attached down that way for years, and it's never been ripped up by updrafts or anything. This leads me to believe that I'd be fine to do the new verandah roof that way also (way easier, & cheaper too). Whaddya reckon, OK ... or should I just go ahead dig out a big hole and pour a deep foundation?

Any advice on verandah issues would be appreciated!

thanks,
Charlie

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