Planning a new shed

[CmdrBond]

I am planning to replace my existing shed and intend to build rather than buy a new one.

Chances are, due the cost of building (or buying for that matter) a shed of the size I am considering, this will be a long term project.

My existing shed is 8'x10' with a pent roof standing at 7'2" and dropping to 6'6" over the 8' side.
aStanding next to this, is a 6'x6' wooden glass house that has seen better days. I plan to remove this and extend the shed over where it used to be. the one issue here is that the shed's base is about 10" higher than the glass house.

The shed is on solid concrete and the glass house on shingle of some sort.

What I propose to do is, rather then have 2 separate sheds, to make then new shed split level.

With that in mind I have a few questions:

I plan on using either 63x38 or 47x47 for the main carcass. Are these sufficient.

Do I put any cladding around the step? Or do I have exposed concrete in the shed?

Should I clad in thick T&G or slim OSB + T&G? I don't plan on insulating.

 

[CmdrBond]

Comments and criticisms please?

I have drawn up a basic plan in sketchup to try an illustrate what I am trying to achieve.

To make life easy I have opted to make 2 separate frames (rather than 1 big frame), and then bolt them together.

The corner posts, door frame and lintel are 75x75 and the rest is 38x63.

The vertical supports are at 600mm centres and the floor joists are spaced |500|500|400|500|500|, the doorway aperture is 700mm.

The larger part of the carcase stands 2.0m tall and the smaller part stands 2.2m tall.

This allows me a further 0.3m for the roof line as it is within 2m of a boundary and therefore the maximum height before planning permission is required is 2.5m.

I have included an "exploded" view to show how I intend to joint it together.

I have not drawn the roof line yet, because I am undecided. I plan on using Onduline or similar corrugated bitumen.

If I stick with a pent roof, I will only have a pitch of ~7º. If I change to an apex roof I can get a pitch of 14º.

Onduline is capable of both, but the lower pitch requires solid decking or close boarding whereas the higher pitch only requires purlins.

I will clad the outside of the area adjacent to the concrete, and then probably cover in shingles just for a little added protection. Obviously I will leave an air gap (not shown in the plan).

Your thoughts please?