Joined: July 2004
||Posted: 07 Sep. 2019,21:23
The best guide can be found here for rigid/bound construction.
For a driveway, I'd look for minimum 100mm of DTp1 to give a firm sub-base, then bed the setts in 75-100mm of ST1 or C7.5 concrete. You could use the 4:1 grit sand mortar if you prefer, but a concrete bulks up the bedding with gravel/coarse aggregate and can save a few quid. It also provides better support for heavier setts (and 1t 150-175mm depth, they *will* be heavy!) over the first 24 hours.
The downside is that a concrete mix is a little more awkward to, compact, more resilient, but you should soon get a 'feel' for the ideal surcharge that gives just enough upstand to allow the setts to be properly bedded-in without having the wallop them too much.
No real need for a waterproofer unless you have vulnerable sub-surface structures, such as cellars or vaults.
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