How deep should the base be?
The Interlocking Concrete Pavement Institute gives a minimum compacted base of 4 to 6 inches for walks and 6 to 8 inches for driveways. Belgard gives 4 to 6 inches for walkways and patios and 8 to 12 inches for driveways; Unilock gives 6 to 10 inches and 8 to 14 inches. ICPI’s reason for the spread: base thickness depends on the strength of the soil, drainage, climate and traffic. Your installer’s or maker’s plan for your soil comes first.
Bedding sand goes on top of the compacted base, 1 inch thick in ICPI’s guide.
Order extra for compaction
These depths are finished, compacted layers. Loose stone compacts when it is laid and rolled, so you need more than the finished volume. Ask your supplier how much extra loose stone its product needs to reach the compacted depth, and enter that as the allowance. Maine’s gravel road manual, for comparison, multiplies the volume by about 1.11, which is 11 percent extra.
What goes on top
Count the pavers with the paver calculator and the joint sand with the polymeric sand calculator.