My stone slab stair started rocking back and forth this spring. How can I properly fix it? Obviously it's very heavy, so lifting/moving it is a challenge. I'm in Ontario, Canada (in case it matters because the issue might have been caused by water freezing).

Here's the photo, the top stair is rocking:

enter image description here

  • 2
    Which bit is rocking? Longterm repair varies with that. A short term fix would be slamming a plastic shim into whatever gap you find when it moves. Commented Apr 5, 2017 at 18:47
  • Is there any existing mortar between the stone slabs?
    – Ed Beal
    Commented Apr 5, 2017 at 18:48
  • 2
    My other question is, how much water is coming through that downpipe? Half a roof? Only a little? Water saturation impacts soil heaving. You might consider moving the pipe away. Commented Apr 5, 2017 at 18:48
  • @AloysiusDefenestrate: Top stair is rocking back and forth (parallel to the house), about 1/16" of an inch or so. The downpipe drains away from house (via that white pipe, underground), about 10 feet away from the stairs, and down the slope, so I don't think it has any effect.
    – haimg
    Commented Apr 5, 2017 at 18:52
  • 1
    I am thinking when it froze there may have been enough space between the blocks for some dirt or small pebbles to get in causing the top to rock on the pivot point. Heavy stone like these keeps its shape and since it Did not wobble before it is probably something small between them. I would try using a flat crow bar like a wonder bar to slip between the stones and step on it to lift the top stone while spraying a water hose or compressed air to blow the debris out then remove the bar and see if that helped or moved the pivot point.
    – Ed Beal
    Commented Apr 5, 2017 at 21:42

1 Answer 1


One approach is to pry up one of the tottering edges up slightly and inject exterior construction adhesive (some are rated for stone/masonry) a few inches in and staying well away from the outside edges. Then lower the stone and let it dry undisturbed.

When dry, this creates an adhesive wedge. Its sticking power is less important than its shape.

Obviously, if rearrangement or removal of the stone is someday needed, this makes it a bit more difficult, but not impossible.

However, if you think the problem is progressing, you need to address the underlying erosion problem before taking this step.

  • To "pry up" as with a pry bar, or did you mean something else? I'm afraid to chip the stone while wedging or prying it up...
    – haimg
    Commented Apr 5, 2017 at 19:41
  • 1
    Yes to a small pry bar. Stone is usually fairly resistant to chipping if done carefully. If it makes you nervous, you could tap in a wooden shim(s) until the gap is big enough to get the tip of your adhesive tube well into the gap.
    – bib
    Commented Apr 5, 2017 at 19:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.