I am looking to build a blockwork outbuilding/workshop (~6.5x4m, 2.5m total height) down at the bottom of my garden, where there are currently several leylandii trees. My intention is to remove these trees and as much of their roots as possible using a stump grinder.
I am concerned that after removing the roots, the ground may not be suitable for a footing of normal depth to support the structure (soil is clay) so I was looking for feedback on the possibility of using some variant of raft foundation to spread the load over a wider area (entire building footprint). Is this feasible? My thoughts were something along the lines of 6"deep concrete slab reinforced with steel mesh... (sitting on 4" of sub-base).
Any thoughts or feedback would be much appreciated.