Flat roof conservatory/ balcony/ veranda

Hiya,
I have an existing "lean to" conservatory that needs replacing, I am considering replacing it with a double glazed upvc one, however i would also like to have a flat roof on it that would be able to be used as a balcony accesable from a first floor bedroom
I'm currently just trying to get my head around how this would need to be built,
The "room" would be approx 6 x 12 ft and ideally full height glazed units with a double door on on side.
I assume that i will need structural uprights on the two outer corners and a "ring" sat on this to support a floor
Can anyone answer the following:-
How big would the vertical supports need to be? - i would like to keep them to a minimum to reduce the amount of "non-glazed" parts
How big would the "ring beam" have to be? - again i would like to keep the thickness of the floor structure to a minimum
What could the floor be made from? would a timber construction be advisable? - i would like to put a number of small "sun tubes" through the floor to allow light in to the conservatory
What type of final finish could the external floor be made of? - it would obviously have to be hard wearing and anti slip
I hope these questions make sense!!! and please be aware that i'm just investigating the options and have no intention of attempting this build myself!!!
Cheers
D
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I have a roof terrace which is a suspended plywood floor covered in asphalt with lightweight 'promenade' tiles on top of that. Done some 20 years ago and so far so good.
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*If you must choose between two evils, pick the one you've never tried before

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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