Laying a new garage slab, plan was 5" hardcore with 5" concrete. Problem is now the old garage has been removed I can see the true extent of the slope it's on. One side is fine but on the edge next to my property boundary the ground level is already 9" below the finished level. What's the best way to sort this? Dig deeper and do 5"hardcore and 9" concrete at that edge? I also have two 8 x4 inch concrete lintels spare, could these be used as a retaining wall at that edge, ie dig them in 4 inch then have 5inch concrete on top of them at that edge?
Thanks in advance
Thanks in advance