Why are my pavers sinking and spreading at the edges, and how are they fixed?

What is actually under a paver

A paver walkway or patio is only as good as what you cannot see. Under the pavers sits a thin bedding course of coarse sand, and under that a base of compacted crushed rock, typically four to six inches for foot traffic and more for driveways. At the perimeter an edge restraint, usually a plastic or aluminum edging spiked into the base or a concrete curb, holds the whole field tight so the pavers cannot creep apart. Joint sand locks the pavers to each other.

When any of those is skipped, the pavers move. Thin or uncompacted base settles into low spots. No edge restraint lets the outer rows drift, joints open, sand washes out and the whole surface loosens. Water running across or under the field carries fines away and leaves voids.

Reading the pattern of movement

The pattern tells us how much of the field needs to come up. A local fix for a sprinkler washout is a few hours; a patio with no edge restraint and a thin base usually needs the whole surface reset.

• A dish-shaped low spot in the middle: base settled or washed out, often where a downspout or sprinkler soaks the area.
• Outer rows tilting outward and joints widening: missing or failed edge restraint.
• A straight line of sunken pavers: a trench for irrigation or a utility that was backfilled without compaction.
• A hump with pavers tilting up: a tree root, or expansive clay heaving in wet weather.
• Pavers rocking underfoot but level: joint sand gone, usually from pressure washing or ants.

How a proper re-leveling is done

We mark the area, lift the pavers and stack them in order so the pattern goes back as it was. The bedding sand comes out, and the base below is inspected. If it is thin or soft, we add crushed rock in lifts and compact each with a plate compactor until it is firm and at the right depth. Screed rails set the new bedding course at a uniform thickness, sloped so water sheds away from the house. The pavers go back, are tapped level, and the whole area is compacted again through a protective pad so the pavers seat into the sand.

At the edges, new restraint is spiked in before the final compaction. Joints are filled with sand, or with polymeric sand that hardens when wetted and resists washout and weeds, then the surface is swept clean. The side-yard walkway we re-edged against a new retaining wall in North County went through this process, with the slope above regraded so soil no longer washed onto it.

Fixing the cause, not just the surface

Re-leveling pavers without fixing what moved them is a repeat appointment. A downspout that discharges onto the patio gets a drain line or a splash extension. A sprinkler head spraying the walkway is moved or converted to drip. A slope washing onto the pavers gets a low wall or a swale. Expansive clay under a patio may call for a thicker base or a geotextile layer between soil and rock so the two do not mix.

Roots are their own topic; our answer on tree roots lifting pavers goes into what can be done without harming the tree.

When a reset is not worth it

If pavers are cracked, spalled or badly faded, or the field was laid directly on dirt with no base at all, resetting the old pavers over a new base is still possible but the result looks tired. In those cases it may be time for new pavers, or a different surface altogether. Levi gives a straight opinion either way, and because the base work is the same, choosing new pavers at that point adds material rather than labor.

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