Paver Patios

What actually holds a paver patio up

Pavers don't carry load the way a slab does. Each unit rides on a bed of sand over a compacted aggregate base, and the whole field acts as one surface only because the units are wedged tight against each other and against a restraint at the perimeter. Take away the base or take away the restraint and the field spreads, the joints open, and the patio starts eating itself.

That's the whole job. It's all in the base. The pavers are the part you look at. The base is the part that decides whether you're still looking at it in fifteen years.

Excavation

We dig to the full section, not to whatever the shovel felt like giving up. The section is the sum of three things: base depth, bedding depth, and paver thickness.

• Pedestrian patio: 6 inches of compacted base is the working minimum on stable subgrade. On Front Range expansive clay we routinely run 8 inches.
• Driveways and anything a vehicle touches: 10 to 12 inches of compacted base. A car is not a patio chair.
• Bedding: 1 inch. Always 1 inch.
• Paver: typically 2⅜ inches (60mm) for pedestrian, 3⅛ inches (80mm) for vehicular.

Do that math and a standard backyard patio is a 10-to-11-inch excavation before a single paver comes off the pallet. Anyone quoting a 4-inch dig is quoting you a repair job with a delay fuse.

The excavation runs about 6 inches wider than the finished patio on every side. You need room to build and compact the base past the edge — a base that stops exactly where the pavers stop has nothing supporting the perimeter row, which is precisely the row that fails first.

The subgrade, and why clay changes the plan

Much of the Denver metro sits on expansive clay. It swells when it takes on water and shrinks when it dries, and it will move a poorly built patio around like it's a hobby. We proof-roll the subgrade, cut out soft spots, and lay a woven geotextile separation fabric between the clay and the aggregate. That fabric isn't decoration — it stops the fine clay from pumping up into the base and turning your engineered aggregate into mud. Once the base is contaminated, it's done compacting and done draining.

Base: Class 6, compacted in lifts

We use CDOT Class 6 aggregate base course — a dense-graded crushed product with fines that lock up under a compactor. Not pea gravel. Not "recycled fill." Not screened topsoil the last guy left in the yard.

It goes in in lifts of 3 to 4 inches, and every lift gets compacted before the next one goes down. This is the single most-skipped step in residential hardscape, and it's the one that costs you the patio. A plate compactor only densifies a few inches of material. Dump 8 inches of base in one shot and run the plate over it and you have a firm crust sitting on loose rock. It will look perfect on install day and settle for the next three years.

Compact each lift in passes at right angles to each other. The base gets lightly moistened if it's bone dry — Class 6 needs some moisture to compact properly, and Colorado air pulls it right back out.

Slope and drainage

Every patio gets built to fall away from the house at roughly ¼ inch per foot — a 2 percent grade. That's the standard, and it's not negotiable. Over 20 feet that's 5 inches of drop, which sounds like a lot until you stand on it and feel nothing.

The slope is built into the base, not into the bedding sand. Sand is not a grading material. If your base is out of plane and someone is "fixing" it by piling sand in the low spots, that sand will consolidate under load and the low spot will come right back.

Bedding and setting

One inch of coarse concrete sand — ASTM C33 washed sand, or #8/#9 chip — screeded to a uniform depth off rails. Never walk the screeded bed. Pavers get laid from the field forward, off the set pavers, so nobody is standing in the bedding course.

Cuts get made with a wet saw and set full-thickness, not filled with mortar or slivers. A cut narrower than about a third of a paver is a cut that pops out.

Edge restraint — the part nobody sees

The perimeter is where a paver field either holds or spreads. We restrain every free edge with a rigid restraint — spiked polymer or aluminum edging driven with 10-inch spikes into the compacted base, or a poured concrete toe where the geometry calls for it.

Then joint sand gets swept in and the field is compacted with the plate (on a protective pad) to seat the units and drive sand into the joints. Polymeric sand gets a second sweep, a light misting per the manufacturer, and time to cure.

Interlock — the thing that makes a paver field behave like a single surface — comes from three places: vertical (the bedding and joint sand), rotational (the joint sand), and horizontal (the edge restraint). Skip the restraint and you've got a pile of bricks.

Repairability

The best argument for pavers on the Front Range isn't the look. It's that when the ground does something you didn't plan for, you pull twenty units, fix the base, and reset them. Nobody can tell. Compare that to a cracked slab.

Read more on what good base prep actually looks like, or on why Colorado patios heave. If you're still deciding on material, we laid out pavers vs. flagstone vs. concrete honestly.