Markham’s housing spans several generations — and each comes with its own waterproofing challenge.
• Aged weeping tile — Homes in Unionville, Markham Village, and Milliken Mills were built in the 1970s–80s. The original clay weeping tile around those foundations is now 40–50 years old, collapsed or clogged, leaving nothing to redirect groundwater away from the foundation.
• New build soil settlement — In Cornell, Cathedraltown, Berczy Village, and Boxgrove, backfill soil around newer foundations is far more permeable than undisturbed ground. Water concentrates there and presses against the foundation — causing leaks within five to ten years of construction.
• York Region clay — The expansive luvisolic clay across Markham shrinks when dry and swells when wet, putting repetitive lateral pressure on foundation walls year-round.
• Freeze-thaw cycles — Water enters hairline cracks in autumn, freezes, expands, and widens them over winter. By spring snowmelt, those cracks are actively letting water in.
• Rouge River watershed — Properties in eastern and northern Markham near Rouge National Urban Park sit in a high-groundwater zone that stays elevated well into spring, overwhelming even functional drainage systems during peak season.
