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Well, he's wrong on the drainage issue in that when properly designed and coordinated with the adjacent landscape and landform, runoff will mostly find its way on the surface with little impact on the base below.

Now, there are many ways to skin a cat, and there are just a many ways to set pavers. The concrete base thing is most often used in high traffic commercial areas where snow plowing is also a consideration. Public spaces is where you might find a lot of that design. The concrete base will be set on a well compacted free draining gravel sub-base about 8-12" thick. The concrete will be a minimum of 4" and a maximum of 6" thick and will be reinforced with (usually) welded wire fabric set at the mid-depth of the slab (heavier reinforcing steel might be used where vehicular traffic is a concern). In that scenario, the pavers are usually set on a mud (mortar) bed on top of the concrete. Sand can be, and is, used frequently, but there will be the weed problem in the joints between the pavers. Sometimes crusher run (crushed and processed stone) is used, but not often.

Without the concrete base, pavers can be successfully set on a 6-8" sand base that is well compacted with a vibratory plate compactor. In commercial work there are fairly rigid specifications on exactly how tight the compaction should be, and they even have methods of testing the compaction prior to setting the pavers. But this is residential. No such white glove approach is necessary, but the sand should be well compacted. Better than sand here is that crusher-run or processed crushed stone. It has a coarser aggregate than stone dust, and almost appears to be concrete-like when correctly compacted with the vibratory plate. But it still drains, like sand. But unlike sand, which will loosen with time and load, the crusher-run holds its firmness and stability. On top of the compacted crusher run, a thin levelling course of stone dust can be laid for adjusting the pavers, if desired. Or, the pavers can be simply laid on the compacted base, and stone dust swept into the joints.

[This message has been edited by treebeard (edited April 28, 2003).]