Why is my paver patio sinking or heaving after a NB winter?

Paver patios that sink, heave, or become uneven after a New Brunswick winter are almost always the result of an insufficient gravel base that fails to prevent frost heaving — NB's deep frost penetration (4-6 feet in inland areas) demands a more robust base than many contractors and DIY installers provide. The freeze-thaw cycles typical of Maritime winters, where temperatures can swing from -20°C to +5°C within days, create enormous upward pressure as soil moisture freezes and expands beneath an inadequate base.

The minimum base depth for paver installations in New Brunswick should be 12-16 inches of compacted gravel (3/4-inch crusher run), depending on your location and soil type. Many failed patios in NB were installed with only 4-6 inches of base — sufficient for milder climates but completely inadequate for New Brunswick's frost conditions. Clay soils, which are common in the river valley areas around Fredericton, Woodstock, and the Miramichi, are particularly prone to frost heaving because clay holds moisture that expands dramatically when frozen. Sandy coastal soils near Moncton and Saint John drain better and are somewhat more forgiving, but still require a proper base depth.

Sinking typically occurs when the base material was not properly compacted during installation, or when water pools beneath the patio and erodes the base over time. Poor drainage — where water from downspouts, roof runoff, or grading directs water toward or under the patio — accelerates this problem. Heaving, where individual pavers or sections push upward, results from water trapped beneath the pavers freezing and expanding. Both problems worsen with each successive NB winter.

For minor issues affecting less than 20% of the patio area, targeted repair is usually practical. Remove the affected pavers, excavate the base material, add and compact additional gravel to the proper depth, re-level the bedding sand (1 inch of coarse concrete sand), and re-lay the pavers. This costs approximately $500-1,500 depending on the area involved. For heaved sections, check for tree roots growing under the patio — maple and willow roots in NB can lift pavers significantly and the roots must be addressed or the problem will recur.

If more than 30-40% of the patio is affected, a complete rebuild with a proper base is usually more cost-effective than repeated spot repairs. This means removing all pavers, excavating to the proper 12-16 inch depth, installing compacted gravel in 4-inch lifts (each lift compacted individually with a plate compactor), adding the bedding sand layer, and re-laying the pavers. Budget $15-25 per square foot for professional paver repair and relevelling in NB. When rebuilding, also address drainage by ensuring a minimum 2% slope away from your home's foundation and installing perforated drain pipe at the base if the area has chronic water issues. A reputable NB landscaping company should guarantee their base work against frost heaving for at least 3-5 years.

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