Why are my interlock pavers sinking in certain spots?

Sinking pavers are almost always caused by inadequate base preparation or water infiltration that has compromised the foundation beneath your installation. In Metro Vancouver's wet climate, this is unfortunately one of the most common interlock problems, and it typically gets worse over time if not properly addressed.

Base Preparation Issues

The most likely culprit is insufficient base depth or poor compaction during the original installation. Residential patios and walkways require a minimum 6-8 inches of compacted granular base, while driveways need 10-12 inches to support vehicle loads. If your installer cut corners and used only 3-4 inches of base material, or failed to compact it properly in 2-inch lifts, the pavers will inevitably settle into the subgrade soil below.

In Metro Vancouver's clay-heavy soils — particularly common in Surrey, Richmond, Delta, and Langley — inadequate base preparation is even more problematic. Clay expands when wet and contracts when it dries, creating movement that transfers directly to the pavers above. Without sufficient granular base acting as a stable platform, pavers follow every movement of the clay subgrade beneath.

Water and Drainage Problems

Metro Vancouver receives over 1,200mm of annual rainfall, and water infiltration is the second most common cause of sinking pavers. If water is pooling beneath your installation due to poor surface drainage, blocked drain pipes, or roof runoff concentrating on the paver area, it saturates the base material and softens the subgrade soil. This creates a cycle where traffic loads on wet, unstable base material cause progressive settling.

Look for signs like standing water on the paver surface after rain, moss or algae growth in the affected areas, or pavers that feel spongy underfoot when wet. These indicate that water is not draining properly through or away from your installation.

Root Intrusion and Soil Movement

Tree roots within 3-5 metres of your paver installation can cause differential settling as they grow and shift the soil structure. Large trees like maples, cedars, or Douglas firs are particularly problematic. Additionally, if the original excavation disturbed utility lines, septic systems, or underground drainage, settling along these disturbances can create localized sinking.

Repair Solutions

Small areas (10-20 pavers) can often be relevelled by lifting the affected pavers, adding or removing bedding sand to correct the grade, and relaying them. However, if the sinking is widespread or recurring, the problem lies deeper in the base preparation and requires professional repair.

Professional repair typically involves excavating the affected area down to the subgrade, installing proper geotextile fabric if missing, rebuilding the base to correct depth with proper compaction, and reinstalling the pavers. For a 100 sq ft area, expect repair costs of $1,500-$4,000 depending on how much base reconstruction is needed.

When to Hire a Professional

If more than 25% of your paver installation is affected, if the sinking is near your foundation or affecting drainage away from your house, or if you're seeing recurring settlement after previous repairs, this requires professional assessment. A qualified hardscape contractor can determine whether the issue is localized base failure or a more serious subgrade problem requiring engineering solutions.

Don't ignore sinking pavers — they create trip hazards, allow water infiltration that worsens the problem, and become significantly more expensive to repair as the affected area spreads to adjacent pavers.

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