A paver patio is decided by what is under the pavers. Across the Ozarks, the usual trouble starts in the base: too little crushed stone, poor compaction, no slope to drain it, or nothing holding the edges.
The ground in southwest Missouri is thin and rocky over heavy clay. A patio built on it can look fine for a while. Then a couple of winters pass, water works into the clay, freezing and thawing move it, and low spots, uneven edges and open joints start to show around the outside.
What Is Under a Properly Built Paver Patio?
A foot-traffic patio has pavers on about 1 inch of bedding sand, washed concrete sand rather than mason or play sand, over a compacted base of crushed stone. The usual base is 4 to 6 inches, and that assumes ground that drains. On clay it runs deeper, 6 to 8 inches.
Where vehicles drive, the base goes to 8 to 12 inches.
From the bottom up:
- Compacted soil
- Geotextile fabric over clay, so the stone and the clay stay separate
- Compacted crushed-stone base
- About 1 inch of washed concrete sand as bedding
- Pavers
- Joint sand between the pavers
- Edge restraint around the outside
A common mistake is using the bedding sand to level the patio. Bedding sand is a thin setting layer, about an inch, screeded flat and left loose until the pavers are down. If the stone base under it is uneven or soft, extra sand on top only gives the pavers room to move.
Why Ozarks Patios Are Harder on the Base
Across most of the Ozarks the topsoil is thin and cherty over a dense clay subsoil, with limestone below. Rain goes through the top layer fast and then sits on the clay.
Clay holds water, and water that freezes in the ground under a patio can heave it. A base that might get by in sandy ground has less room for error here.
A sinking patio seldom fails all at once. Two winters in, it may look like this:
- A dip where water sits after rain
- Pavers that no longer meet evenly in one section
- Open joints near an outer edge
- An outside row beginning to spread
- A low area that was not there when the patio was new
The pavers themselves are usually fine. They are riding on a base that settled or held water.
The Base Has to Be Compacted in Lifts
This step is invisible once the pavers are down, and it is where settling starts.
The crushed stone goes in and gets compacted in lifts, layers about 4 inches deep, each one run with a plate compactor before the next goes down.
You cannot dump the full depth in one pile, run a compactor over the top once, and expect the bottom to be compacted. The surface may feel firm that day with soft material still below it. Later, those soft spots show up as dips in the patio.
If you are comparing patio bids, ask this directly: "How deep is the base, and are you compacting it in lifts?"
Slope: The Patio Has to Shed Water Away From the House
The finished surface should fall away from the house at least 1/4 inch per foot. That is the 2 percent the residential code asks for on hard surfaces within 10 feet of a foundation (section R401.3), and it moves water without making the patio feel tilted.
The slope is built into the compacted base and carried up through the bedding sand to the pavers. It cannot be fixed once the pavers are down, and a patio that looks level can still send water toward the foundation.
On a larger patio, or one that meets a porch, steps or an existing slab, the slope has to work with the elevations already there.
Edge Restraint Is What Keeps the Patio From Spreading
Pavers lock together only while the outside edge is held in place. That is the edge restraint's job.
Plastic or concrete edging, or a border course set in concrete, keeps the outer row from moving outward. Plastic edging holds only when its spikes go into compacted base, so the base should run 6 inches or more past the pavers. Without restraint, the joints open first around the perimeter, and once the outer row spreads, the rest of the field has room to shift.
"Paver patio installation" on a proposal says nothing about this. Ask what holds the edges and how the perimeter is finished.
Joint Sand, and Why It Has to Go in Dry
Once the pavers are laid, a plate compactor with a pad on it runs over the whole surface to seat them in the bedding sand. Then polymeric sand is swept into the joints, the surface gets another pass with the compactor to settle it, the joints are topped off, and the loose sand is swept and blown off the face of the pavers. Only then is it wetted. Once it sets, it resists washout and weeds far better than plain sand.
The pavers and the sand have to be dry when it goes in, and it needs dry weather after it is wetted; the bag gives the hours. This is the step that gets rushed when rain is coming or the patio is still damp, and a rushed job leaves a haze on the pavers or joints that wash out.
Build the Things Underneath Before the Pavers Go Down
If you want a fire pit, an outdoor kitchen, a pergola or landscape lighting, bring it up before the base is finished. Their footings, bases and conduit go in at the base stage, before any pavers are set. Cutting into a finished patio later is work nobody needs to do if the plan is known at the start.
The same goes for a patio built into a slope. Where part of it is cut into a hillside, a small retaining wall or seat wall does the holding, and that wall needs gravel backfill and a drain outlet behind it like any other retaining wall.
We build outdoor fireplaces and kitchens, landscape lighting, pergolas and decking with our patios, and we plan them with the patio, not after it.
Is a Paver Patio a DIY Job?
A small, simple patio is a fair DIY project for a homeowner willing to do the base work carefully: call 811 before digging, then the excavation, the slope, the compacted lifts and the edge restraint.
A patio against the house, cut into a slope, with a wall, or with footings and conduit for other features is work for a pro.
Before you sign a patio bid, make sure it states the base depth, whether the stone is compacted in lifts, how the patio slopes away from the house, and what holds the edges.
For patio work anywhere from Springfield to Branson, call Ozarks Custom Hardscaping at (417) 861-3462.