"Sand has smaller particles..." Well, can't say where Ink buys his stone dust, but here in Massachusetts, stone dust is by far the smaller particle. Perhaps Canadian dust is larger than sand, or sand up there is extremely small...:-) Around here, the dust is the smallest. Sand in these parts varies in size based on where it's mined and how it's processed (if at all), but always has a larger grain size than the dust. " As you don't want water draining THROUGH your patio but over it the drainage capability of sand/stone dust is a moot point." Not necessarily so. A well designed and constructed hard surface of pavers, or stone, depends on slope to evacuate rainwater, and the material within the joints if slopes are minimal. And most patios will have minimal slopes. It should be pointed out that the reason many patios fail is not due to poor surface drainage, it's due to poor subsurface and base preparation that doesn't allow for water in the soils to drain away from the area. Water draining through the joints should be able to do just that.., drain through a well prepared base and beyond. Stone dust is a commonly used material in both commercial and residential applications as a base material. Depending on the loading requirements of the surface, it can be used directly over a well compacted gravel base, or over a well compacted crusher run (processed stone) base. And a very important key to good base preparation is good drainage. If stone dust were impermeable, it wouldn't be used around here to the extent that it is. Just thought you'd like to know...

How about plants? Gravel? Place some chunks of the grey stuff (concrete" that cover the gap and a bit of the edging too? I don't think your border is going to move much, except for the inevitable frost heaving. If you re-set anything that has shifted in the spring, you won't have the big rebuild effort.

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Excellent point above!! I can't tell you how many of my clients ask me to expand the dinky little builder's patios that seem to be SOP for any new construction. And if new builds, I always suggest that they increase the size they were thinking about by at least half....often as much as double. Few people ever complain their patio is too big........too small is always the problem! And unless your landscaper is a very skilled mason (few are) I would never contemplate laying pavers over an existing concrete patio. There are just too many obstacles for this to be done correctly and effectively and join smoothly with the extension. It would be a lot less expensive and with greater opportunities for more creative shaping to just use concrete. Both the existing concrete pad and the new extension can be stained if you prefer a different color.