Underpinning in Leslieville and Riverdale: Why the Foundation Itself Is Older

Leslieville and Riverdale carry some of the oldest housing stock in the city, Victorian and Edwardian workers' cottages and rowhouses built from the 1880s through the early 1900s on lots that are often narrower than even East York's semis, and a meaningful share of those original foundations are rubble stone or fieldstone rather than poured concrete. That changes the underpinning conversation before lot width or party walls even come up.

The foundation material is the real story here

Most of Toronto's underpinning stock, the 1920s-to-1950s bungalows and semis further out, sits on poured concrete or block foundations. Leslieville and Riverdale's oldest rowhouses predate that. A lot of them were built on rubble stone or fieldstone footings, sometimes with a brick foundation wall above, because that was the standard construction method before poured concrete became typical in the city.

That matters for underpinning because rubble stone does not behave like poured concrete. It is not a uniform, engineered material, it is stacked and mortared stone that has settled and shifted over more than a century, and an engineer assessing it has to treat each section on its own rather than assuming consistent bearing capacity across the whole wall. The underpinning sequence, working in short alternating sections with new concrete footings poured beneath the old wall, is the same basic method described on the process and timeline page, but the pre-work assessment on a rubble stone foundation is a genuinely different, more careful process than assessing a 1940s poured wall.

Narrower lots than the rest of the east end

Riverdale and Leslieville rowhouses commonly sit on lots narrower than the semi-detached stock in East York or Leaside, sometimes in the range other neighbourhoods would consider a driveway width. Some are true rowhouses sharing a wall on both sides, not just one, which means the party-wall sequencing discussed on the East York and Leaside page can apply twice over on a mid-row unit rather than once on a semi. End units and semis in the neighbourhood have it closer to the East York situation, one shared wall instead of two.

Rear access is the other constraint. A number of these streets have laneways or narrow rear yards rather than a side-yard path to the backyard, which affects how excavated soil and materials move in and out. It is a real planning question for scheduling and equipment, not a cost promise, since every lot and laneway is different.

What stays the same

The Toronto-wide rate on the cost page, $500 to $750 per linear foot, still applies here, and a narrow rowhouse generally means a shorter perimeter to underpin than a wider detached house, which tends to work in the total's favour even with the added foundation-assessment complexity. Run your own footprint through the cost calculator rather than estimating from a neighbourhood average.

The City's permit process is also identical citywide, covered on the permits page: the same review window, the same staged inspections, and the same requirement for a licensed engineer's stamped drawings before any digging starts. On a rubble stone foundation, that engineering step is doing more work than it would on a newer poured wall, which is exactly why it is not a step anyone should skip or rush.

Benching on a rubble stone foundation

Benching, which reduces basement width rather than extending under the existing footing, is sometimes discussed for older stone foundations because it avoids disturbing the original wall as extensively. Whether that trade-off, less headroom width in exchange for touching less of a century-old foundation, makes sense for a specific rowhouse basement is exactly what the decision tool is built to walk through, alongside a real engineering opinion on the foundation itself.

Common questions