[Ropster]

I am in the process of siting a green house in my garden and wonder what the best base is for it.
it will be going behing my Garage and there are already 2 rows of slabs that one side will sit on, the ither side is lawn

Should I slab all the way under it
or slab under the uther wall and gravel in the middle ?

any thoughts ?

[tode]

Which way does it face ?

[Ropster]

the side( which isnt against the garage) faces South, door facing West

[NigelB]

Yes indeed slab it all round.. Having one side sink into the ground could spell disaster, structurally speaking.
Also, you may want to consider sitting the whole thing on bricks too. Mine sits atop three courses of bricks, which gives me so much more room inside. No having to stoop or finding there's not as much space as you'd like, and plenty of space for shelving and still having room to move about.
Good luck with it, whichever way you choose to erect it.