Why Do Pavers Shift and Sink?

Paver shifting and sinking is one of the most common landscape complaints we hear from homeowners who had a patio installed by a contractor who cut corners. Here's what actually causes it — and how to prevent it.

The Root Causes

1. Insufficient Base Depth

The most common cause. Chester County's clay soils expand during freeze cycles. A paver base that doesn't extend below the frost depth (approximately 24–30 inches in Chester County) will move with the frost, displacing the pavers above it.

ICPI-standard base depth for Chester County residential patios: 8–12 inches of compacted aggregate, plus the leveling course. Most cut-rate installations use 4–6 inches.

2. Inadequate Compaction

Aggregate placed and not properly compacted will settle over time as it consolidates under load. Each 3-inch lift of aggregate must be compacted with a vibratory plate compactor before adding the next lift.

3. Drainage Failure

Water that gets into the aggregate base and saturates it can migrate the fine particles, eroding the base material from under the pavers. This causes settlement in specific areas — typically the lowest point of the patio where water accumulates.

The fix: geotextile fabric between native soil and aggregate (prevents fines migration), plus positive drainage slopes that move surface water away from the patio rather than letting it accumulate.

4. Edge Restraint Failure

Without rigid perimeter edge restraints, pavers at the edges of the patio gradually migrate outward under traffic load. This creates gaps at the perimeter and a domino effect of paver movement inward.

5. Joint Sand Loss

The polymeric sand filling paver joints stabilizes each paver against lateral movement. If joint sand erodes (usually from water washout), pavers become unstable and shift under foot traffic.

Prevention

ICPI-standard installation prevents all of these failures:

• Proper base depth (8–12 inches in Chester County)
• Compacted base in 3-inch lifts
• Geotextile fabric between soil and aggregate
• Positive drainage slope on all surfaces
• Rigid edge restraints on all perimeter edges
• Polymeric sand in all joints

Learn about our ICPI-certified installation standards | See our hardscape services

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JHL Landscape Design | PA HIC #PA035784 | ICPI Certified | Licensed & Insured West Chester: 701 S Franklin St, Suite 101, West Chester, PA 19382 Newtown Square: 12 Smedley Ln, Suite 101, Newtown Square, PA 19073 HBA Member | BBB A+ Rating