What Happens Under a Paver Patio

Every paver failure we get called out to repair traces back to the same place: what happened below the pavers, not the pavers themselves. Concrete pavers are extraordinarily durable products—they routinely outlive the installations they sit on. When a patio sinks, waves, or spreads at the edges, the base failed.

Here's what a correctly built paver installation looks like from the dirt up, and why each layer matters in Arizona soil specifically.

Layer 1: Excavation and Subgrade

We excavate to a depth that accounts for the finished paver thickness, the bedding course, and the full aggregate base—typically 8 to 10 inches total for a pedestrian patio and considerably more for driveways. Cutting corners here is the single most common shortcut in the industry, because it's invisible the day the job finishes.

Arizona subgrade brings its own complications. Caliche layers—naturally cemented calcium carbonate—can be rock-hard and irregular. Expansive clay pockets swell when wet and shrink when dry. We proof-roll and compact the exposed subgrade before any aggregate goes down, and where we find soft spots, we over-excavate and replace rather than build on top of a known weakness.

Layer 2: Aggregate Base

Type 2 / Class 2 aggregate base is the structural heart of the system. It's a graded mix—not a single stone size—so the fines lock the larger aggregate into a dense, interlocked matrix that distributes load and resists movement.

Two details separate a real base from a nominal one:

• Lift thickness: We compact in lifts of 3-4 inches maximum. A plate compactor cannot densify 8 inches of material in one pass no matter how many times it's run over the surface. The top compacts, the bottom stays loose, and the patio settles a year later.
• Moisture content: Aggregate compacts properly only within a narrow moisture window. Bone-dry base material in July simply will not reach density. We water the base to condition it before compaction.

Our target is 95% relative compaction or better, verified as we go rather than assumed.

Grading Within the Base

Slope is built into the base, not into the pavers. We establish a minimum fall of roughly 1/8 to 1/4 inch per foot away from the house and toward the intended discharge point. Getting this right during base construction is straightforward; trying to fix it by varying bedding sand depth is not, and it produces exactly the soft, uneven spots that cause settling.

Layer 3: Bedding Course

A one-inch, screeded layer of coarse concrete sand sits between the base and the pavers. Its job is narrow: to give the pavers a uniform setting bed. It is not a leveling layer, and it is never compacted before the pavers are placed.

The most common amateur mistake here is using too much sand—two or three inches—to smooth out a poorly graded base. That sand consolidates under traffic, and the surface goes wavy within a season.

Layer 4: Edge Restraint

Pavers work by interlock. Remove the perimeter restraint and the field will creep outward, joints will open, and the whole assembly loses its structural behavior. Edge restraint is not optional and it is not decorative.

Depending on the design we use:

• Concrete edging: A troweled concrete haunch against the outside face of the perimeter course. Our default for turf and gravel transitions.
• Rigid plastic or steel restraint: Spiked into the compacted base beyond the paver edge, then buried. Clean and fast where the finished grade allows.
• Soldier course set in mortar: Where the design calls for a visible border with maximum rigidity.

Finishing: Compaction and Joint Sand

Once the field is laid and cut, we run a plate compactor with a protective pad over the surface. This seats the pavers into the bedding course and forces sand up into the joints from below. Joint sand goes down next—we specify polymeric sand on most residential work because it resists washout during monsoon downpours and suppresses weed growth and ant activity in the joints.

"A paver patio is a structural assembly that happens to be beautiful. Treat it as decoration and it fails; treat it as structure and it outlasts the house's original roof."

What This Costs You in Practice

A properly built base adds real cost—material, machine time, and labor hours that a homeowner never sees. It's also the difference between a patio that still looks new in year fifteen and one that needs to be pulled up and reset in year four. When you're comparing bids and one is dramatically cheaper, the base depth and compaction standard is almost always where the difference lives. Ask about it specifically.