I’m putting a paver walkway next to a concrete walkway. When I dig the hole for the gravel base, I have to believe some of the gravel under the concrete walkway will come falling out. How should I handle this? Do I just fill the recess with the gravel base I will use for the pavers? I want to make sure there is no path for the gravel base and/or sand to disappear into.
Any other tips for putting a paver walkway next to a concrete walkway would be appreciated.
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This will serve mainly to bump your question up towards the top of the list. I, myself, never saw gravel used under a concrete sidewalk, but perhaps you could use some metal edging like is used between lawns and flower borders--drive it in at the edge of the sidewalk and maybe put a couple stakes in, then dig out for your pavers. Puty in the gravel and then remove the edging before putting in the pavers. I don't really have a good answer.
Maybe a little will trickle out, but it won't be of any consequence. The concrete is strong enough that if an inch or so of the edge is not so solidly supported it won't break off unless you run something very heavy (like a truck) over it.
The pavers should be laid on a compacted stone base. When you compact the base it will shore up under the concrete sufficiently enough so you will not have any problem.
For a walkway on all but the softest ground about 4 or 5 inches of compacted stone is enough. The stone should be crushed stone in mixed sizes up to about 3/4" or 1". The sharp and varied sizes of crushed stone lock together well. Don't use round stone or stone with sand, it will never compact and lock. Wet it enough to wet the stone all the way down but not enough to soak the subsoil, and compact it with a jumping jack style compactor. Don't use a vibratory plate compactor, it would be insufficient. Expect about 25 to 30% reduction in thickness upon compaction. The top of the compacted stone should allow for the thickness of the pavers plus about 1" of stone dust.
When ready to place the pavers use some straight sticks or plumbing pipe to create screeds, put in a layer of stone dust, screed it smooth, remove the screeds, and fill in the grooves from the screeds with more stone dust. You want to lay a layer of about 1¼" uncompacted, nice and smooth. Lay the pavers, and the edging on the side away from the concrete, and compact with a vibratory plate compactor, beginning on the side away from the concrete and work towards it. Spread DRY sand on top and vibrate more to work as much sand as possible into the cracks. You could put the dry sand on before compacting to reduce the amount of scratch marks the compactor will make on the surface of the pavers.
In place of stone dust under the pavers you can use mason sand, but stone dust will be more solid and will not attract ants like sand will. Don't use beach sand because it will not compact.
There are lots of books in the stores that have good pictures of the process.