Paver Calculator

Paver failures are almost never paver failures. The units themselves are concrete blocks that will outlast the house. What fails is the base, and the base fails because it was too shallow, not compacted, or not wide enough.

Base depth is decided by the load, not the look

The base is compacted crushed aggregate, and the depth follows what will drive or walk on it:

• 4 inches for a garden path carrying nothing heavier than a wheelbarrow.
• 6 inches for a patio, which is the common residential case.
• 8 to 12 inches for a driveway, because a car concentrates a considerable load on four small contact patches.

Soil type overrides all of that. Clay holds water, swells when it freezes and offers little bearing capacity, so it wants more base than sand does, sometimes half as much again. In cold climates the frost depth matters too: an installation that traps water below the pavers will heave every winter until the surface is visibly uneven.

The base must also extend beyond the paved area, usually by 6 to 12 inches on each side. A base that stops at the edge has nothing supporting the outer row, and that row is where movement starts.

Compaction, and why volume estimates run short

Aggregate compacts by roughly 20 percent as it is plated. Order the loose volume the geometry gives you and the finished base will be short. The calculator adds that 20 percent, which is why the tonnage looks higher than the simple depth-times-area figure suggests.

Compact in lifts of no more than 3 to 4 inches with a plate compactor. Dumping 8 inches and running the plate over the top compacts the top two inches and leaves the rest loose, which produces a surface that looks perfect for one season and then dips.

Bedding sand is exactly one inch

The screeded sand layer between base and pavers should be one inch, and it should be uniform. This is the single most common place where a good base gets ruined.

Thicker bedding sand is used to fix an uneven base, and it does fix it, briefly. Then the pavers consolidate into it unevenly over the first freeze-thaw cycle and the surface becomes wavy. Correct the base, then screed a consistent inch.

Use coarse concrete sand rather than fine masonry sand. Fine sand holds water and migrates; the industry specification for bedding is a washed, well-graded concrete sand.

Pattern decides the waste

Cutting is where the pavers go. The pattern, not the installer, determines how much:

• Running bond, roughly 5 percent. Cuts only at the two ends of each row.
• Basketweave, around 8 percent.
• Herringbone at 45 degrees, 10 to 15 percent. Nearly every perimeter paver is cut on an angle, and the offcut is rarely reusable.
• Circular or fan patterns, 20 percent or more.

Herringbone is worth the waste on a driveway. The interlocking pattern resists the twisting force of turning wheels far better than a running bond, which is why it is the standard for vehicle traffic in the segmental paving industry.

Edge restraint is not optional

Without a restraint, the outer row of pavers spreads outward under load, the joints open, and the spread works inward row by row. Plastic or aluminium edging spiked into the base is the usual solution, and the spikes must go into the compacted base rather than into soil beyond it.

Concrete edging works too and lasts longer, but it is far harder to alter later.

Joint sand, and why polymeric is worth it

Joints are filled after laying, and the fill locks the pavers into each other so they act as a surface rather than as loose blocks. Plain sand works and washes out over a few years. Polymeric sand contains a binder that sets when wetted, resists washing out, and suppresses weeds and ants.

Polymeric sand has to be installed dry, swept fully into the joints, the surface blown completely clean, and then watered exactly as the instructions say. Residue left on the paver faces sets into a haze that is genuinely difficult to remove.

Slope, which is easy to forget

Water has to leave. A minimum fall of about one eighth of an inch per foot, away from any building, is the usual guidance, and a quarter inch per foot is safer on a patio against a house wall. Level looks right on paper and produces standing water and, in winter, ice.