A paver patio fails from the bottom up. The pavers themselves are usually fine after twenty years. What gives out is the base underneath, and no amount of releveling the surface fixes that.
What actually went wrong
When a patio sinks, tips or rocks, one of a few things happened when it was built:
- The aggregate base was too thin for our soil and frost depth.
- The base was dumped in one lift and compacted once, rather than built up in layers and compacted at each stage.
- There was no edge restraint, so the field spread outward and the joints opened.
- The grade was wrong from the start, so water sat on the patio and washed out the bedding sand.
Drainage comes first
Before anything else, we work out where the water is going. A patio should shed water away from the house at about an eighth of an inch per foot. It is a slope you cannot really see but it makes the difference between dry basement walls and a foundation that gets soaked every storm.
More than a few of the patios we rebuild were actually pitched back toward the house. Fixing that is often worth more to the homeowner than the new surface.
The rebuild
Pavers come up by hand and get stacked for reuse. The old base comes out. We excavate to depth, put in compacted aggregate in lifts, screed a bedding layer, and relay the pavers on the original pattern. Edge restraint goes in around the perimeter, and polymeric sand gets swept and set into the joints to lock the field together and keep weeds and ants out.
The result should sit flat, drain correctly, and stay that way through the freeze-thaw cycles rather than needing attention every spring.
Signs you need this work
- Pavers that have sunk, lifted or tipped
- Water pooling on the patio or running toward the house
- Weeds and ants coming up through the joints
- Wobbling or rocking underfoot
- Edges spreading outward and joints opening up
- A patio that sits lower than it used to against the foundation
What's included
- Careful lift and salvage of existing pavers where they are reusable
- Excavation to proper depth and removal of the failed base
- Compacted aggregate base built in lifts, not dumped in one go
- Grading set to fall away from the house
- Polymeric sand swept into the joints
- Edge restraint installed so the field cannot spread
- Site graded and cleaned, debris hauled away
How we do it
- 1
Assess the base
Sunken pavers are a base problem, not a paver problem. We dig a test area and find out what is under there.
- 2
Lift and excavate
Pavers come up and get stacked for reuse. The failed base is dug out to proper depth for our soil.
- 3
Rebuild the base
Aggregate goes in and gets compacted in layers, which is the step that gets skipped on nearly every patio we rebuild.
- 4
Relay and lock
Pavers go back on screeded bedding sand, edge restraint is installed, and polymeric sand locks the joints.
Common questions
Why did my patio sink?
Almost always an inadequate base. If the aggregate was too thin, was not compacted in layers, or was laid over soft soil, the patio settles as the ground moves under it. Chicago clay and frost make this worse.
Can you reuse my existing pavers?
Usually most of them. Concrete pavers hold up well; it is the base under them that fails. We typically reuse 80 to 90 percent and source replacements for the rest.
How deep should the base be?
For a patio in our soil, six to eight inches of compacted aggregate. For a driveway, ten to twelve. Anything less and you are rebuilding it again in five years.
What about drainage?
This is the part that matters most. A patio should fall roughly an eighth of an inch per foot away from the house. We reset the grade as part of every rebuild, because a patio pitched toward the foundation is a wet basement waiting to happen.
Do you do new patios as well as rebuilds?
Yes. New patios, walkways, steps and sitting walls, built on the same base detail.