After finishing the front yard, there was a small project around back at the Thyme House. This step up onto the back deck had caved in over the course of its short life (less than ten years.) The exposed paint edge shows how much it had settled.
Removing the step tread revealed this interesting arrangement. The riser stones are snapped square, so set well, they’re unlikely to shift, but they still seem too thin to me. The bigger problem being that there’s no back edge to support the step, or prevent the fill from trickling out. Dried leaves are not an effective backfill. Don’t look too closely or you’ll see the leathery corpse of a rat, again, not recommended backfill.
The real problem revealed itself as I dug further. The step rested on a patio that sat on twelve inches of shifting sand. Sand is great for leveling under flagging, but I don’t suggest it as a structural fill. Other parts of the flagging have been compromised by moles burrowing through the sand. Immediately behind the step, under the deck, the ground slopes away quickly, giving the sand a place to slump towards. Gravity won and the whole thing relaxed.
I neglected to photo the small underground retaining wall I built to support the flagstone patio, that then supported the new step. I decided to stack stone instead of re-using the snapped edging. I did use a couple of pieces as tie stones, reaching toward the center of the step.
The old step made new again.