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A few months ago I put in a 9ft x 9ft x 6in slab for a hot tub. It turned out great but there isn't a lot of room to walk around it. I want to build a concrete path around the existing slab. The new path will be 42 inches wide and wrap all four sides.

Should I keep the new concrete isolated from the existing slab? The path will be 4 inches thick and I'm planning to put down 4 inches of gravel underneath it.

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    I'm not an expert by any means, but I'd think that the different thicknesses would lead one to having them be completely separate.
    – FreeMan
    Jul 13, 2021 at 17:19
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    Or use pavers.... Jul 13, 2021 at 17:31
  • @FreeMan, see "thickened-edge" patio home slabs. They have integrated footings of different thickness than the interior of the slab. There are plenty of other situations where thickness varies. It's more about substrate uniformity, etc.
    – isherwood
    Jul 13, 2021 at 18:38

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Concrete is a lot of work & expense. That is necessary to support a hot tub. It generally is not necessary for a walkway. I'd look into using pavers instead. They are available in brick, concrete and stone. You still need a gravel base, plus sand, but the overall process is much more forgiving than concrete - you don't have to get it all done in one pour, and you can much more easily DIY than with concrete.

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    Exactly my thinking. You don't need the support that the hot tub requires... you're not gonna land the space shuttle on it. :-)
    – JACK
    Jul 13, 2021 at 17:34
  • I have a company nearby that delivers concrete and it's not that expensive. Jul 13, 2021 at 17:53
  • I agree with the suggestion, but this doesn't answer the question.
    – isherwood
    Jul 13, 2021 at 18:40
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Yes, you should keep the new sidewalk isolated. I would not connect the two as they're likely to settle differently due to time and varying substrate. If you were to engage the original slab with rebar connections, and the new walkway settles differently, you'll have cracking and tilting. Better to let it settle in a more level way.

Whether you need expansion joints (compressible strips) is a matter of the overall design. If you're wrapping more than two sides, I'd put a thin (1/4") buffer of sill seal foam or similar between to prevent damage due to expansion.

Note that 4" of gravel may be inadequate if there's 12" of organic soil or soupy clay there now. More important than thickness is what the gravel rests on. That's why thickness matters.

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