Adding one more spec most homeowners never ask about — drainage slope. On any hardscape within 6 ft of a foundation it needs to run ¼" per foot (≈2%) minimum, away from the house. Anything flatter and meltwater pools in late March, refreezes overnight, and erodes the bedding course from below. Combine that with an underbuilt base and you’re not just heaving, you’re getting joint spall by year four.
Two more adds for clay-heavy lots — and a lot of Scarborough, Markham, Pickering sits on clay till:
- Excavate an extra 2–4" under the Granular A and lay a drainage core of clear ¾" stone (no fines) wrapped in non-woven geotextile. Gives hydrostatic pressure somewhere to go.
- Watch the timeline. A proper residential patio install with correct lifts is 2–3 working days, not a one-day job. Any quote that pencils out to single-day install, walk it.
Quick cross-refs for anyone shopping patio quotes right now:
- How to Vet a Contractor Before Signing Anything — pairs well with the 4 base-depth questions above.
- 2026 Ontario Home Renovation Savings Program — permeable interlock can tie into stormwater/insulation rebate bundles.
- Most Commonly Asked Questions for newer folks.
Answering my own Q1: driveway at my own place, 2019 build, 14" of base (Granular B below, Granular A above). Seven winters in, still flat.