SWMBO and I are the initial back-of-an-envelope stage of planning a Big Shed (approx. 16' x 16', not-quite-square to fit the corner of the garden behind some trees, replacing a pair of 8x8 sheds, one on a concrete raft, one on piers) which I hope may end up accomodating a Proper Lathe (in the ton to ton-and-a-half weight range) so could use some advice regarding the floor - I'm pretty sure I'll need more than the 4" of concrete on scalpings/sand blinding/DPM, is a 6" pad with steel reinforcement at 2" and 4" going to be inadequate, adequate or overkill? would it be wise to go for 8" with 4" of concrete between the reinforcement to get a bit more stiffness? The shed itself probably will be of wood construction with a cut roof (possibly mansard to allow some more storage above) with a couple of brick pillars (braced with brick buttresses) to support an RSJ for lifting, I hope. Fortunately I can get away with a few feet of extra height by taking my "highest point of the surrounding terrain" reference from the neighbour's garden the other side of a dwarf wall (on my side of the boundary)... So ridge height could be as much as 14' above the base! At this size am I likely to need to add a trench foundation in addition to the raft I've envisaged? The neighbour has a couple of tall (approx 30' cypressus (sp?) close to the boundary, will they need their roots dealing with if they're below the level of the scalpings etc.?
Thanks in Advance,
Dave H.