Joined: July 2004
||Posted: 17 Nov. 2018,18:38
It's always something of a gamble re-using an existing driveway sub-base - best to do a couple of trial holes to check depth, compaction and aggregate type - but patio sub-bases are notorious for being what we might call "short-changed".
Too many patio sub-bases are litle more than a blinding of chippings or cruher run material. I have so-called professionals telling me they never have any problems using just 50mm of Type 1 - how the hell do you get 50mm thickness of an aggregate that has a a upper size of 37.5mm, anyway?
I'd put in a couple of trial holes to see what we have. As long as there's at least 100mm of well-compacted Type 1 or Type 2 aggregate, you might be able to follow Sean's suggestions, but remember, because block paving has no bound bedding or jointing, it *must* have an adequate sub-base, or it "will* fail.
If in doubt: dig it out!
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