A homeowner in Sandy Springs called us last spring about a patio that was two years old. The pavers were a good product, laid in a neat herringbone, and the color had held. There was also a dip the size of a dinner plate three feet out from the back door, deep enough to hold water for a day after rain, and one corner had dropped about half an inch away from the step. Nothing was wrong with the pavers. Everything was wrong with what had been put under them.
That job is the reason this post exists. When you hire somebody to build a paver patio, almost all of what you are paying for is buried by the time you see it. The pattern and the color are the cheap part. What decides whether the patio still looks like that in ten years sits six or eight inches down, finished and hidden before most homeowners come out to look.
What is supposed to be under a patio
There is a published standard for this, so the answer is not a matter of opinion. The Concrete Masonry and Hardscapes Association, formerly the Interlocking Concrete Pavement Institute, publishes the specification good installers work to. The short version, for a patio or walkway that only ever carries people:
- Four to six inches of compacted crushed aggregate base, more if the soil underneath is soft or the patio will take vehicle weight.
- That base compacted in layers of four to six inches at a time, not dumped in one lift and run over once. Density of at least 98 percent standard Proctor for a patio or a residential driveway.
- One to one and a half inches of bedding sand, screeded to an even thickness. Not two inches. Not three. Bedding sand is there to seat the paver, not to make up for a base that was never leveled.
- An edge restraint with at least an inch of vertical face against the side of every paver. Without it the outside course walks outward, the joints open, and the pattern unravels from the edge inward.
- At least two passes with a plate compactor to seat the pavers, then joint sand, then two or three more passes until the joints are packed full.
None of that is exotic. It is a day of unglamorous work with a compactor, and it is the first thing a cheap bid takes out, because nobody can see it afterwards.
Five questions worth asking, and the answers you want
How deep is the base going, and how will you compact it? A straight answer with numbers in it is a good sign. Four to six inches, compacted in lifts, with a plate compactor sized for the job. An installer who says “we’ll get it solid” and moves on is telling you something.
How much sand are you screeding? You want to hear an inch, maybe an inch and a half. If the answer is “however much it takes to get it flat,” the base is doing none of its job and the patio will print every soft spot in your yard within two winters.
Which way does the water go, and where does it end up? This is the question that separates people. A patio needs to fall away from the house, and the fall has to go somewhere that is not a flower bed against the foundation. On a flat lot in Dunwoody or Brookhaven that often means tying the patio into a drain line or a swale, and that is a conversation to have before anything is dug, not after.
What are you doing about the clay? Most of metro Atlanta sits on red Piedmont clay that swells when it is wet and shrinks when it dries. Under a patio that matters less than it does behind a wall, but it still means the base needs a separation layer in wet ground so the clay does not pump up into the aggregate and turn it to mud. A geotextile between the two is cheap insurance, and we wrote about which fabric belongs where if you want the detail.
Can I see one you built four or five years ago? Anybody can show you a patio finished last month. A patio that has been through four Atlanta summers and four sets of winter freezes is the only reference that proves anything. Walk it. Look along the surface from a low angle for dips. Press on the outside course with your foot and see if it moves.
The things that go wrong, in the order we see them
Settling near the house comes first, and it is almost always backfill: the soil within a few feet of a foundation was dug out when the house was built and put back loose, so the patio sinks exactly where you walk most. Then pitch, where somebody builds a level patio because level feels like good work and the water is left with nowhere to go. You want roughly a quarter of an inch of fall per foot, enough that a puddle drains and not enough that a table rocks. Then edges: with no restraint, or plastic restraint pinned into uncompacted ground, the outside course goes first, the joint sand washes out of the next course in, and it works its way toward the middle.
Where sustainability actually shows up
It is not in the brochure language. It is in two practical choices.
The first is permeable paving. A permeable patio uses an open-graded stone base and wider joints filled with small chip rather than sand, so rain goes down through the surface and sits in the stone instead of running across the yard to your neighbor’s fence line. On a lot where the downspouts already overwhelm the back garden, that can do more good than a drain. It costs more to build and it has to be kept clear of silt, so it is not right everywhere, but on the wrong lot a standard patio is just a new roof over your soil.
The second is less obvious: building it properly the first time is the sustainable version. A patio rebuilt after six years means a second set of pavers, a second load of aggregate quarried and trucked, and the first set in a dumpster. The greenest patio on any street is the one nobody has had to take apart.
What we would do in our own yard
Spend the money underground and show restraint above it. Pick a simple pattern in a paver made near enough to truck without an ocean in between, get the base and the fall right, and put what you saved on fancy banding into a proper drain for the water coming off the patio. October is one of the best stretches of the year for this work in north Georgia: the ground is still warm and dry, the leaf drop has not started in earnest, the crew is not fighting July heat, and the patio is settled before the first freeze.
If you are weighing a patio for this fall, two other pieces of ours are worth reading alongside this: how to choose the paver itself, and, if your yard already holds water, whether you need a french drain or regrading. The rest of our writing is collected on the guides page.
And if you would rather just have somebody stand in the yard with you and say what they would do, get in touch and we will come out and look.
And if you are still at the stage of deciding whether to build at all, what hardscaping does for a property is the piece to start with.
Base, bedding and compaction figures in this post are from the Concrete Masonry and Hardscapes Association technical notes on the construction and application of interlocking concrete pavement.
