- Patios rarely fail because of the pavers. They fail because of the base.
- Soft and organic soil must come out before base goes in.
- Base aggregate should be compacted in thin layers, not dumped and run over once.
- Edge restraint and a planned slope for drainage are not optional.
We rebuild a lot of patios that someone else installed. The stories are similar: it looked great the first summer, then low spots appeared, pavers shifted at the edges, and puddles formed. When we pull the pavers up, the cause is almost always under them.
A patio is mostly what you can't see
A paver patio is a layered system. From the bottom up, a properly built one includes:
- Compacted subgrade: firm native soil, shaped to drain.
- Geotextile fabric where needed, often recommended over clay to keep base stone from mixing into the soil.
- Base aggregate: crushed stone compacted in layers. Industry guidelines commonly call for at least four inches for patios and walkways, more over clay or poorly draining soil, and considerably more for driveways.
- Bedding layer: about an inch of screeded sand or fine aggregate.
- Pavers, compacted into the bedding.
- Joint sand, often polymeric, swept in and set.
- Edge restraint holding the perimeter in place.
Every layer has a job. Skip or shortchange one and the patio fails, usually within a couple of years.
Failure #1: building on soft soil
Topsoil, roots, and loose fill compress over time. If they're left under a patio, the patio sinks with them. Excavation should go down to firm, undisturbed soil, even when that means hauling away more material than expected. In Northeast Georgia, that often means digging through a layer of fill on newer lots.
Failure #2: base dumped, not compacted
This is the most common shortcut. Base aggregate gets spread to full depth in one pass and run over with a plate compactor once. The top inch gets tight; everything below stays loose. Proper compaction happens in thin lifts, a couple of inches at a time, each compacted before the next goes down. It takes longer. It's also the main reason a patio is still flat ten years later.
Failure #3: no plan for water
A patio should slope gently away from the house so rain runs off instead of soaking in at the foundation, commonly around a quarter inch per foot or a bit less. Water also needs to drain out of the base. On clay, water that gets into the base can sit there, soften the subgrade, and contribute to heaving and settling. That's why patio projects often include drainage work like a catch basin or a swale at the low edge.
Failure #4: no edge restraint
Pavers stay locked because they're held tight on every side. Without a solid edge restraint, the outer rows creep outward under foot traffic and furniture, joints open, and the whole field loosens. Plastic edging spiked into clay, or no edging at all, is a common culprit.
Failure #5: joints left open
Joint sand transfers load between pavers and keeps them from rocking. Ordinary sand can wash out in summer storms. Polymeric sand, installed correctly, sets firm and resists washout and weeds.
Questions to ask any installer
- How deep will you excavate, and what happens if you hit soft fill?
- How thick is the base, and how many lifts will you compact it in?
- Will you use fabric over our clay?
- Which way will the patio slope, and where does the water go?
- What edge restraint will you use?
- What kind of joint sand?
A good contractor answers all of these without hesitation. If the answers are vague, so is the base.
Can a sunken patio be fixed?
Usually, yes. Pavers can be lifted, the base corrected and recompacted, and the same pavers reset. Poured concrete is harder; cracked and sunken slabs often need replacement or an overlay. For help choosing materials for a new project, see pavers vs. flagstone vs. concrete.