Great real-world case, Defizyn - glad you flagged the lift-and-relevel approach. Adding a few Toronto-specific notes for homeowners reading this in spring 2026:
The reason individual slabs sink on GTA patios is almost always the same thing: the original base was laid too shallow, or the bedding course washed out through a joint. In our climate you generally want a minimum 8-12" of compacted 3/4" crusher run under flagstone and pavers, with a 1" bedding layer of HPB or coarse sand on top. Anything less and the frost-thaw cycle will pump slabs out of plane within 2-3 winters.
Two follow-up tips:
- Before re-setting, check drainage slope - you want at least 1/4" per foot away from the house. If water is pooling at the low spot, no amount of relevel will hold.
- Seal the joints with polymeric sand rated for northern climates (Techniseal HP NextGel or SEK ProJoint Max both work). Stops weeds and slows bedding washout.
I wrote up the deeper “12-inch rule” on why most Toronto interlock patios fail by spring here: The 12-inch rule: why most Toronto interlock patios fail by spring - might be useful context for anyone prepping for a bigger rebuild.