How deep should old mortar be raked out before tuckpointing for a lasting repair on a GTA home?

Old mortar should be raked out to a minimum depth of 20mm (about 3/4 inch) before tuckpointing — anything shallower than this will fail within a few GTA winters.

This 20mm minimum isn't arbitrary. New mortar needs sufficient depth to develop mechanical strength and bond area within the joint. A shallow scrape of 5-10mm gives the new mortar almost no purchase, and the first serious freeze-thaw cycle — of which Toronto sees 50 or more per winter — will pop it right out. The new mortar plug simply can't grip the sides of the joint deeply enough to resist the expansion forces of ice forming behind it.

The standard method is to use an angle grinder with a tuckpointing blade, an oscillating multi-tool, or a cold chisel and hammer to cut or chip the deteriorated mortar out cleanly. The goal is square, clean sides to the joint — not a tapered or V-shaped groove, which gives even less mechanical grip. After raking, blow or brush out all dust and loose particles. The joint must be clean and slightly damp (not wet, not dry) before new mortar goes in.

Depth matters even more on older GTA homes. Pre-war brick homes in neighbourhoods like Cabbagetown, Leslieville, Roncesvalles, and the Annex were built with soft, handmade brick and lime-based mortar. The mortar in these joints was intentionally softer than the brick — it acts as the sacrificial element, absorbing freeze-thaw stress so the brick doesn't spall. When you're repointing heritage brick, you need to rake to 20mm and then fill with a lime-based mortar (Type O or a lime-putty mix), not modern Type S Portland cement mortar. Type S is harder than the brick itself, and water and frost will damage the brick face rather than the joint. This is one of the most common and costly mistakes made on older Toronto homes.

For post-war concrete block or modern brick homes across Scarborough, North York, Etobicoke, and the inner suburbs, Type S mortar is the correct choice — it's weather-resistant, strong, and appropriate for the harder masonry units used in that era.

A few practical things to check during the raking process. If you're finding that mortar crumbles out easily beyond 20mm — say, 30-40mm or more — that's a sign of significant moisture infiltration and extended deterioration. In those cases, the joint may need to be fully cleared and the repair mortar packed in two lifts (layers), allowing the first lift to firm up before applying the second. Packing too much mortar in one deep lift can cause it to slump or crack as it cures. Also, if you're finding soft, powdery mortar throughout the joint all the way to the back, that's worth flagging to a mason — it can indicate chronic water infiltration that a surface repointing won't fully solve.

Curing is just as critical as depth. New tuckpointing mortar must be kept moist for 3-5 days after application. In GTA summer heat, mist the joints twice daily and shade the wall if possible. In cooler fall weather, protect the work from frost — mortar placed when temperatures drop below 5°C at night won't cure properly and will be weak and crumbly by spring. The safe tuckpointing window in the GTA runs roughly mid-April through mid-October.

Tuckpointing done right — 20mm depth, correct mortar type, clean joints, proper curing — lasts 25-40 years. Done wrong, it's a recurring expense every few winters. If you're dealing with more than a few isolated joints, or working on a heritage brick home where mortar selection is critical, it's worth having a professional mason assess the work. Toronto Parging can match you with an experienced local masonry contractor for a free estimate — reach out anytime.