I’m going to do the soil test for sure, but how deep? I live on a hillside, and my lawn is turf with a lot of clay in the first four or five inches, then a very hard gravel sand underneath. My theory is that I should go with the turf roof layer, but I’m not sure about the hard sand (it is not very absorbent). Water will seep horizontally to some degree, and I can’t count on the hard sand for water-holding capacity since my lawn slopes both back to front and left to right, and seems to pool in the bottom right corner below the root level.
