Sunken or uneven pavers: why they drop and how relaying fixes them

Short answer: pavers sink because something under them has moved, usually water softening the ground, a trench that was never compacted properly, or an edge that has let the pavers spread. In most cases they do not need replacing. The fix is to find and fix the cause, lift the affected pavers, rebuild and compact the base, re-screed the bedding to the correct level and fall, then relay the same pavers and lock them in with joint sand.

If you skip the "fix the cause" step, the dip comes back. Here is how to work out what is going on, and what a proper relay involves.

The usual reasons pavers sink

Water getting under the paving

A downpipe that discharges onto the paving, a leaking pipe, a blocked stormwater line or paving that falls toward a low corner will all keep the ground underneath wet. Wet base material loses strength and the bedding sand washes away through the joints, so the pavers drop. If the dip is next to a downpipe, tap or pit, start there.

A trench that was not compacted

This one is common. Pavers get lifted so a plumber or electrician can run a new downpipe, pipe or cable, then the trench is backfilled loosely and the pavers are put straight back on top. Loose fill settles for months, and the pavers settle with it. A recent enquiry we had was exactly this: a section of backyard pavers lifted for a new downpipe, put back without proper re-bedding, and several had sunk.

Reactive clay moving

Much of Adelaide sits on reactive clay that swells when wet and shrinks when dry. Adelaide University research published on 9 September 2026 found that shrinkage cracks in these soils can reach more than a metre deep and act as pathways for water. Uneven wetting, such as one corner that always gets the downpipe water, makes the ground move unevenly, and paving shows it first.

No edge restraint

Pavers hold each other in place through friction in the joints. Without a solid edge, such as a concrete haunch, a kerb or a wall, the outer rows creep outward, the joints open up and the pavers near the edge drop and rock.

A thin or poorly compacted base

If the original base was too shallow for the load, or was not compacted in layers, the whole area slowly ruts. On driveways this shows up as tyre tracks. In this case a patch repair only buys time and the honest answer may be to relay the area on a new base.

Tree roots

Roots lift pavers rather than sink them, but they often cause a hump on one side and a dip on the other. The root may need to be dealt with before the paving can sit flat again.

How a proper relay works

1. Find the cause. Check downpipes, pits, taps, trenches and edges, and where the water goes when it rains.
2. Lift the pavers. Lift past the dip into the sound paving around it, and stack the pavers to reuse.
3. Fix what is underneath. Dig out soft or wet material, re-compact trench backfill, and add base material, compacted in layers.
4. Set the level and fall. Re-screed the bedding so the relaid area sits flush with the surrounding paving and still sheds water away from the house.
5. Relay and lock in. Relay the same pavers, cut in any that were broken, compact, and sweep joint sand in so they lock together.
6. Sort the water. If a downpipe was the cause, it needs to be connected to the stormwater system. That part is a plumber's job, and it is worth doing before we relay.

Next to the house, the relaid paving still needs to fall away from the building. The National Construction Code's housing provisions set a general minimum of 50 mm of fall over the first metre from a slab-on-ground home, unless a lower figure applies to your site (ABCB Housing Provisions, Part 3.3.3). We explain the full rule in paving fall and drainage next to your house.

If the repair means digging deeper than the existing base, for example to find a leaking pipe, check for underground services first through Before You Dig Australia, which is a free service.

Relay, or replace?

Relaying is usually the right call when:

• the problem is a patch or a strip, not the whole area
• the pavers themselves are in good condition
• the cause is local, such as one downpipe or one trench

A larger rebuild makes more sense when:

• the whole area is rutted or rocking because the base was never built for the load
• the paving sits too high against the house and has to come down
• many pavers are cracked, or the range is discontinued and you want a fresh look anyway

A lot of paving around Gawler does not need replacing. It needs lifting and relaying where it has sunk or spread. We will tell you which one your job needs. See our paving repairs and restorations service, our paving in Gawler page, or send us photos for a free quote.