Hi all, I plan to build a 15ft x 9ft shed with thermalite blocks but am unsure about footing/base do I lay a 3 or 4 inch slab made from concrete then brick up from that or lay some sort of perimeter footings ( what depth ) and then brick up from that then lay concrete floor ? ( what depth ) also are thermalite blocks strong enough , I am building off an existing garage and two sides will be built as tight to perimeter fence and the exposed side clad with shiplap any advice welcome thanks guys