DIY Garden Room Base

[MontyVeda]

Gravel grid does look like an interesting alternative to a concrete slab. It'd still need something substantial beneath it though. (?)

 

[Jameshow]

Gravel grid does look like an interesting alternative to a concrete slab. It'd still need something substantial beneath it though. (?)

Not really as the weight would be uniformly distributed.
Unless your building a brick building you don't really need substantial foundations.