Hi I’m thinking of installing a 8ft by 6ft shed in the garden, I have one jumbo bag of sand and lots of old bricks lying around, can I use these bricks as a base and compact with sand, do I have to break the bricks down first or use them whole? Then put a membrane and 4inch layer of concrete, or can I leave the concrete and put slabs on top of compacted sand? The shed is gonna be those metal or plastic ones.