Spring’s the season my phone starts ringing about patios that heaved over the winter. Pavers tilting, flagstone rocking underfoot, joints opened up an inch wide. Homeowner got a “great price” two summers back and now it looks like a skate park.
Nine times out of ten the failure has nothing to do with the pavers themselves. It’s what’s underneath.
The physics nobody explains when they quote you
GTA sits in Zone 5b/6a. Our frost line runs about 3.5 to 4 feet down. Every winter the soil below your patio swells when water in it freezes, then thaws unevenly come March/April. If the base under your stone can’t drain and can’t absorb that movement, the whole surface rides the heave up and settles back down crooked.
A proper base for a walk-on patio in Toronto is roughly 6 inches of compacted ¾" crushed gravel (Granular A works) under 1 inch of bedding sand or HPB, with filter fabric between native soil and the gravel. For a driveway or anywhere that’ll see vehicle load, you’re looking at 10 to 12 inches of compacted base. Compacted in 2 to 3 inch lifts, each lift plate-tamped before the next goes on. Skip the lifts, skip the compaction, and you’ve got a cushion, not a base.
What the “great price” quotes are actually skipping
I’ve seen quotes in the $10 to $15/sqft range for interlock installs in the GTA this month. All-in, legitimate Toronto work is sitting at $25 to $60/sqft this season, closer to $30 to $45 for a straightforward backyard patio, more if you’re adding steps, sitting walls, or proper drainage.
The gap between the cheap quote and the real one is usually:
- 3 to 4 inches of base instead of 6 to 12
- No geotextile fabric between native soil and gravel
- No edge restraints, or plastic ones spiked with 6" nails instead of 10"
- Polymeric sand skipped, or the bargain bag instead of a real one
- Pavers rated for appearance (no CSA A231.1 spec) instead of the freeze-thaw rating you actually need here
Any one of those shortcuts will cost you inside five years. Two or more and you’re rebuilding by year three.
Four questions to ask before you sign anything
Put these on every quote, in writing:
- How many inches of base are you installing, and is it measured compacted or loose?
- Which polymeric sand are you using for the joints?
- What’s your settlement guarantee, in years, in writing?
- Are you installing geotextile fabric between native soil and gravel?
If they dodge any of them, move on. A 10-year written guarantee with a real base behind it is worth paying 40% more than the quote that doesn’t mention base depth at all.
Salt, while we’re here
Ontario homeowners love rock salt. Concrete pavers that aren’t rated for de-icers will spall on the top surface within 2 to 3 winters. If your patio will ever see salt tracked from a driveway, spec pavers rated for freeze-thaw AND de-icer resistance, or switch to full-depth clay pavers or natural flagstone (granite, basalt) in those zones.
Over to you
Three questions for the thread:
- If you got a patio installed in the last 5 years, what base depth did your contractor actually install? Did you ask?
- Anyone running permeable interlock in Toronto, how’s it holding up through our freeze-thaw?
- Trades lurking here, what base-prep failure are you seeing most often on rip-and-replace jobs this spring?
Pass this along to anyone shopping patio quotes right now. If you’re newer to the forum, the most commonly asked questions thread has the primer on contractor vetting too.