If a site has poor grading, with sand (some gravel) as the top layer and clay underneath, is it enough to do proper grading on top of the sand or should the sand be moved/removed and grading done from the clay layer up?
Where are you located? What is your climate? Are talking the driveway, the yard, the entire building site?
IMO, in a heavy rainfall area, sand on top of clay would be a nightmare. Need more precise info for an opinion of any merit.
I am in Edmonton, Canada. I would not consider it a heavy rainfall climate, although spring snow melt is considerable.
This grading issue is only on one side of the house (back yard). There is a ground level deck over this area. Water can be seen pooling in some areas, I assume this is because the sand layer is saturated and it can’t get through the clay layer underneath.
The sand should be removed and the drainage issue addressed from the clay up. If they want to install sand back on top have them install black plastic or landscape fabric under it first to keep it draining properly. I would recommend rock before sand in my opinion as the sand retains moisture.
That is my concern that the sand allows the water to drain without retaining it, and then it all sits on the clay layer below, which probably isn’t level. Is the grade level, sloped, sloped away from the home? Another concern is that the deck FOOTINGS are actually below the frost line, and not just resting on top of the clay. Do you see any signs of movement?
Q: Is this a new build, or old established home?