My patio covered with slate has sunk a little, as indicated by the bowed line on the left. The patio is up on the level indicated by the arrow in the image on the right.

My question is: if I were to have the slate reset, is it just going to start sinking again? It seems that because of its location, there is some erosion issue that would need to be addressed first. Or is this something that happens no matter what?

enter image description here


While I'm not an expert, typically you can pull up slates, re-level the sand underneath them, and then re-lay them.

It is entirely possible that the slates were put on too-thin a layer of gravel and sand, and that the underlying soil has compressed a bit since they were laid. This is different from erosion.

It is also possible that they were laid in order to promote drainage and avoid puddles.

  • So, once I lift them, should I add sand, gravel (modified, I assume), or both? – Wynne May 22 '20 at 23:37
  • I think you want to talk to an older stonemason. The traditional way to do this is to pitch them away from the house -- you don't want water pooling up and going through the bricks or the door. there's a technique that uses pins and string to set an overall pitch, and then adjusts the sand under each stone so that the whole patio looks good, but not something I'd try as my first project :) – gbronner May 24 '20 at 5:02

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