So, my build is progressing slowly, i’ve now built my mini retaining wall and backfilled, started leveling off preping for a raft slab. Initial plan was 300mm around the edges with double mesh for the walls and 200mm with single mesh for the floor. I’m finding it a headache to create the form for the difference in height and was thinking could i not just put a 200mm slab down and double the mesh for the walls and single for the floor ❓ A slab of one thickness would make it much easier. My garage is to be within permitted development, 100mm block, single storey, approx 25 sq Mts, flat roof and may get to see a car in it.

cheers

To be fair 200 mm is massively over engineered for a garage slab. However I do like the idea of a thickening around the perimeter! The thickening can easily be created by levelling the whole area as you have done, then go back and dig an extra 100 mm x 400 mm of ground out where the slab perimeter will be! You then (and if you still want a 200 slab), get 200 mm depth timbers to use as shutters. These will sit flush with the outside edge of your over dig therefore creating your 300 mm depth. Personally I’d have gone for a couple of strip footings and utilised the rw as the garage wall after you’d gone to all that previous effort. Also if you do go down the route of 2 layers a193 is plenty strong enough, place the bottom layer in, don’t forget your lap an make sure the top layer covers the slab and into the thickening!
God I’m dull!
Good luck!