Basement at Property Line (Zone 6A)
We’ll be building an infill townhouse in Toronto with a basement.
It’s a secondary building at the back of the property (accessed from a laneway), and there are no existing buildings at the back of the neighbouring properties.
If a typical basement treatment includes rigid insulation, dimple mat, granular backfilling and sloping the surface away from the building, the last two are not feasible since the building sides are at the property lines with the neighbours.
We expect to be able to work with the neighbours to organize access from their properties for construction, but it doesn’t solve the issue of keeping away and draining underground water near the building.
Ideally, the neighbours will do similar infill projects on their properties in the future, eliminating the problem altogether, but there is no guarantee it would happen soon, or ever.
What would be the best approach?
Is there a standard practice for these conditions that I’m missing?
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> If a typical basement treatment includes rigid insulation, dimple mat, granular backfilling and sloping the surface away from the building, the last two are not feasible since the building sides are at the property lines with the neighbours.
Maybe the neighbors would be amenable to granting you an easement to install drainage that's over their property line but below grade.
Failing that, I suspect you'll have to rely on interior side drainage only. Lots of buildings are retrofitted this way, so it's not the end of the world, but not preferable.
Hi Patrick, thanks for the advice.
For a solution with interior side drainage, would you recommend any changes to the design of the basement wall and/or slab?