The construction is almost identical to the OGR garden rooms, 4 x 2 joists for the floor (although on Patio, thjat's overkill), OSB3 on top of that, then for a finish, T&G wooden flooring (as that was in the clearance section at the timer yard!).
Interior walls are cladding (log lap), roofing battens, breathable waterproof membrance, OSB3, 3 x 2 treated timber (unnecessary, but that's all they had!), insulation, aluminium tape for the joints, vapour barrier and plywood to finish.
I repruposed the french doors we had ripped out for the rear extension, the builder got them quite dirty, but they where only 2 years old, so serviceable, the guy installing the windows/doors for the house fitted it for £100.
Inside before insulation:
Insulation added: (that was around £600 I think for 50mm and 75mm for the roof (8 x 3 joists)
For the roof I just copied OGR with the EPDM and exact trims he uses.. super easy to install following his video, same wood glues, same everything!
The only difference is because it's a lean to and attached to the house, I did add the correct flashing that the roofing company sell..
And because it's a shed and not a garden room, I went with loglap cladding, it looks neat enough, better than an average shed, but affordable, and no side windows, as the french doors and LED lighting work really well..
This allowed me to use our old IKEA kitchen units and old racking from the garage:
I did the electrics myself, but did get the sparky doing his inspection to get the extensions signed off to include the shed just in case...
I've since added guttering and will be building a small corner uninsulated summer room in the garden for the bike/lawnmower and other things to claim some space back and make this more of a workshop (most of the racking will go..)