On 10/01/2019 13:29, Bill Wright wrote:
Well, it isn't really gravel. It's limestone, mostly one inch lumps. The
limestone is a couple of inches deep, then there's six to nine inches of
rubble underneath. There's 187 sq metres. In places moss has grown. I've
killed the moss but under it the stone has a lot of soil mixed in,
somehow. I'll have to scrape all this off and put new stone down, but
how can I stop this happening again? I was wondering about waiting until
the dry weather and getting some sort of blow torch thing? Ideas?

The moss is there because of poor drainage. Soil will invariably find
its way into the gravel by being wind borne dust and also breakdown of
leaves that fall on the path and get run over by vehicles.

Around 4" layer of limestone might be deep enough to drain cleanly. It
is much worse if the area is north facing and so stays wet for longer.

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Regards,
Martin Brown