What's the proper joint profile for tuckpointing — concave, V-joint, or flush — on a GTA foundation?

For GTA foundations, concave (tooled) joints are the proper profile for tuckpointing, as they shed water most effectively and withstand freeze-thaw cycling better than V-joints or flush joints.

The concave joint profile creates a slightly recessed, curved surface that directs water away from the mortar joint rather than allowing it to pool or penetrate. This is critical in the GTA where over 50 freeze-thaw cycles per winter can destroy improperly profiled joints within 2-3 seasons. The curved profile is created using a jointing tool (concave jointer) when the mortar reaches "thumbprint hard" consistency — firm enough to hold the profile but soft enough to tool without tearing.

V-joints should be avoided on GTA foundations because they create a water collection point at the bottom of the V. Water pools in this groove, freezes, expands, and cracks the mortar joint from the inside out. V-joints are sometimes used on interior decorative masonry where freeze-thaw isn't a concern, but they're inappropriate for exterior foundation applications in Toronto's climate.

Flush joints (where mortar is simply cut flush with the brick face) provide no water-shedding profile and leave the joint vulnerable to direct water penetration. They're the weakest option for GTA foundations and typically fail within 5-10 years compared to 20-25 years for properly tooled concave joints.

Proper tuckpointing technique for GTA foundations requires grinding out deteriorated mortar to a minimum depth of 20mm (twice the joint width), cleaning out all loose debris, dampening the joint, applying new mortar in layers, and tooling to a concave profile when the mortar reaches the correct consistency. The mortar type must match the existing — typically Type S mortar (2,500 PSI strength) for modern foundations or Type O lime-based mortar for heritage brick foundations built before 1945.

Timing is critical in the GTA — tuckpointing should only be done when temperatures will remain above 5°C for 7 consecutive days after completion. The best window is typically May through September, avoiding the extreme heat of July-August when rapid drying can cause surface cracking.

For foundation tuckpointing projects covering more than 50 square feet or involving heritage masonry, hire an experienced mason who understands GTA climate requirements and proper joint profiling techniques. Improperly profiled joints will fail prematurely and require expensive re-pointing within a few years.