I would like a raised flower bed against a new building that is slightly downhill. Once sided I would like rocks and dirt up the siding about 12 inches. Now putting something in front of the siding is possible but I would rather seal behind the siding right into the ground to keep water away. The actual wood of the building right now is above the ground about 6 inches with a slab underneath but the slab is back 4 inches because the building is cantilevered past the slab edge. So in effect there is a space under the building 6 inches high by four inches deep that I would like to keep empty to prevent water getting on top of the slab or into the wood. All the wood under the overhang is heavily tarred as is the slab.
I'm not explaining this very well but I think I need a waterproof long lasting membrane to go from the ground up the wall about 12 inches behind the siding just to be safe. I was considering that rubber ice/water proof roof membrane because I have a half a roll.
Any thoughts