How to Use This Tool
Enter the patio and the paver, pick a pattern and a base depth. The paver count is the easy half; the base is the half that decides the budget and the weekend.
What actually goes under a patio
A paver surface is a flexible pavement. The pavers themselves carry very little — the compacted aggregate base spreads the load and drains the water, and the thin sand layer only sets the level. Skimp on the base and the surface settles, no matter how good the pavers are.
12 x 16 ft patio = 192 sq ft, 4 x 8 in pavers, herringbone
pavers 192 / 0.2222 = 864, +15% waste = 994
base 192 x (6/12) = 96.0 cu ft = 3.56 cu yd
x 1.25 for compaction = 4.44 cu yd
x 1.4 tons per cu yd = 6.2 tons
sand 192 x (1/12) = 16.0 cu ft = 0.59 cu yd
edging perimeter = 56 ft
Base depth is a soil question
Four inches suits foot traffic on firm, well-drained ground. Six is the usual patio figure. Eight or more is for driveways, soft ground or clay that holds water and heaves when it freezes. Depth scales the material linearly, so going from 6 to 12 inches doubles the delivery and doubles the compaction work.
Compaction means ordering more than the hole
Aggregate arrives loose and is installed compacted, losing roughly a quarter of its height as the fines are driven into the voids. Ordering the finished volume leaves the base short of depth. The base must also be compacted in lifts of no more than about four inches; dumping six inches and running a plate compactor over the top compacts the surface and leaves the bottom loose.
Edge restraint holds everything together
An unrestrained paver field spreads. The perimeter units creep outwards under load, the joints widen, sand escapes and the failure works inwards from the edges over a couple of seasons. Plastic or metal edging spiked into the base is cheap and not optional, and the base should extend six inches beyond the paver edge to support it.
Two different sands
Bedding sand is coarse and angular so it locks up under the pavers. Joint sand is finer, and polymeric joint sand contains a binder that sets. They are not interchangeable: bedding with fine sand gives a surface that keeps moving, and using bedding sand in the joints leaves them to wash out in the first heavy rain.
