Last Updated on October 20, 2026 by Umar Farooq
Pavers sinking behind retaining wall blocks usually trace to one of two things: soil behind the wall that was never compacted properly, or water getting into it. The first check costs nothing. Look at the shape of the dip. A strip that runs along the wall points at compaction right beside the blocks. A bowl that grows after rain points at water. Check that the wall itself is not leaning or bulging before you lift a single paver, because if the wall is moving, the paving is only reporting it.
Pavers sinking behind retaining wall: read the shape of the dip
I read the long-running forum threads on this, and the questions are strikingly alike: the ground behind the wall sinks, someone fills it, it sinks again, and by the third fill the poster is asking whether the wall company did something wrong. The thread's regulars usually split the cause into two: soil that was not compacted, or water collecting behind the wall (a downspout, a leaking pipe, surface runoff). That is only forum opinion, but it matches what the engineering guidance says, below.
Use the shape to sort it:
| Shape of the dip | Most likely cause | First thing to check |
|---|---|---|
| Narrow strip right along the wall, roughly 3 to 4 feet wide | Backfill or base next to the wall compacted in thick lifts or with a tiny tamper | How the strip was built, and whether the strip is as wide as the zone in the next section |
| Bowl or trough that deepens after rain | Water entering behind the wall or under the pavers | Downspouts, irrigation, the drain outlet at the foot of the wall |
| Slump with the wall face leaning or bulging | The wall is moving | Level the wall face; stop and read "When it is an engineer's job" |
| Low patch with soil stains or holes at the wall joints | Fine soil washing through the wall | Look at the face and the ground below the wall for soil trails |
This is my own sorting of the sources I read, not a published test.
Why the strip next to the wall is hardest to compact
The NCMA Segmental Retaining Walls Best Practices Guide says hand-operated compaction equipment is generally used within 3 feet of the back of the wall units, about 4 feet measured from the face, and that the loose lift may need to be thinner there to reach the specified density. It also says compacted lifts should never exceed 8 inches, that retained soil is compacted in no more than 8 inch lifts to 95% of standard Proctor, and that stacking two or three courses before placing and compacting the fill is not a recommended practice (NCMA Best Practices Guide).
Put that together and you see the weak spot. Soil is not shy about telling you when it was rushed. The strip along the wall is the one place where the big plate cannot work and the small tamper has to do the job, and where thick lifts hide the most air. My inference: if your dip is about that wide, the likely culprit is compaction in that strip, not the pavers. The guide describes engineered walls and your block maker's manual governs a small garden wall, but the mechanism is the same.
Here is my opinion: spend the day on the strip. A few extra passes beside the wall cost nothing, and a dip along a wall comes back every time if the lifts are thick and the tamper is small. (A wall does not care how nice the pavers look. It cares what is behind it.)
Check the wall before you touch a paver
Hold a long level or a straight board against the wall face, and sight along the top. You are looking for a lean outward, a belly in the middle, or blocks stepping out of line. A contractor page on this says a wall that is tipping, bowing or stepping out of line is telling you about water pressure or foundation movement, not about the blocks, and that resetting the face of a wall that is failing because water has nowhere to go "buys a season" (HD Landscape). It is a contractor opinion, so weigh it, but it is the right order of operations.
If the wall is straight, carry on. If it is moving, stop: fixing the paving first would just bury the evidence.
Find the water before you dig
Rochester Concrete Products lists the usual sources of excess water: downspouts that discharge near the paving, grading that sends water toward it, irrigation that saturates one spot, and open joints. It adds that runoff collects against retaining walls, steps and foundations (Rochester Concrete Products). Walk the wall during rain, or run a hose along the top, and watch where water goes.
- Downspouts. If a downspout lands on or beside the strip, extend it past the paving. Downspout drain under patio covers piping it away.
- Sprinklers. A head that waters the same patch behind the wall saturates the base.
- The drain outlet. A drain pipe at the foot of the wall only works if its outlet is clear. If you cannot find an outlet at all, that is information.
- Soil trails. NCMA says fine soil can migrate into the gravel fill and through the wall face, which is why a filter fabric is considered where the backfill is fine-grained. Dirt stains or holes at the joints are a sign that is happening, and it is an engineer's question, not a paver one.
Fix it from the top down, cheapest first
- Stop the water. An extension, a moved sprinkler head or a cleared outlet costs almost nothing and removes the most common cause.
- Measure the dip with a string line, then lift the pavers in the strip and one full row beyond it, the same lift-and-relay method as how to fix sunken pavers.
- Dig out the soft base down to firm material, working carefully near the wall. Do not undercut the blocks.
- Rebuild with crushed stone in thin lifts, compacting each one with a hand tamper or a small plate, with extra passes along the wall. How to compact gravel has the lift and pass pattern.
- Relay with 1 inch of loose bedding sand, set the pavers 1/8 to 1/4 inch high for settlement (CMHA), compact and re-sand.
If you find soft soil more than a few inches below the base, that is the backfill itself failing, and the fix gets bigger.
What will not work
- Filling the low spot with soil and tamping the top. The forum thread where the poster filled the dip three times is the cautionary tale. Filling treats the surface, not the cause.
- More bedding sand. CMHA says not to use sand to fill depressions in the base.
- Resetting only the wall face when the wall is under water pressure. The contractor page above says it buys a season.
- A big plate right against the wall face. NCMA specifies hand-operated equipment in that zone, and that is a good reason to follow it.
When it is an engineer's job
Call a pro, or at least a local engineer, if the wall leans or bulges, is taller than about 3 to 4 feet, has a driveway, building or steep slope above it, or if the settlement keeps coming back. Our paver retaining wall guide covers the 4 foot permit line and what counts as surcharge: a patio full of furniture sitting above the wall counts. Rochester's guide also lists recurring settlement near a retaining wall as a reason for a pro. Photograph the wall and dips with a tape in the frame, and write down when the dips grow.
Build the next one so the strip stays put
If you are building new, the plan is NCMA's: backfill as you go, never stack two or three courses first, keep lifts to 8 inches or less, and hand-compact within 3 feet. Use a clean, free-draining gravel column at least 12 inches deep behind the units, with no more than 5% fines. A landscape fabric on top keeps topsoil out of the gravel. And lay the paving only once the backfill is done. For a raised patio built on a wall, see raised paver patio.
Compact the strip by hand, drain the water and call someone if the wall moves
Most dips behind a retaining wall are local, fixable and cheap once you know whether they are compaction, water or movement. Sort the shape, check the wall, stop the water, then rebuild the strip with thin lifts and patience. And if the poster on the forum tells you to fill it a fourth time, thank them kindly and rent the tamper instead.
FAQ
Why does the ground behind my retaining wall keep sinking?
Usually because the backfill was not compacted in thin lifts, or because water is getting into it. NCMA says compacted lifts should never exceed 8 inches. Filling the dip from the top does not fix either cause.
Is it normal for soil behind a retaining wall to settle?
A little settling in new fill happens. A dip that keeps returning, or keeps growing, is not normal and points to weak compaction, water or a wall that is moving.
How wide is the area behind a retaining wall that needs hand compaction?
NCMA says hand-operated equipment is generally used within 3 feet of the back of the wall units, about 4 feet from the face. Your block maker's manual is the final word for a small wall.
Can I put pavers on top of backfilled soil behind a retaining wall?
Yes, if the backfill is compacted in lifts and drained, and the pavers sit on a proper stone base. A patio above a wall counts as extra load, so check the wall height and your local rules first.
How long should I wait before laying pavers behind a new retaining wall?
I could not find a published waiting time. What the guidance stresses is compaction lift by lift as the wall goes up, so the fill is firm before the pavers go on.
When is a sinking patio behind a wall a structural problem?
When the wall leans, bulges or steps out of line, when it is taller than a few feet, or when there is a driveway or building above it. Get an engineer to look.
