How do I remove old caulking that someone used instead of proper mortar in the brick joints on my foundation?

Removing caulk from brick mortar joints requires patience and the right tools, but it's definitely a DIY project that most GTA homeowners can tackle successfully. The key is removing all the caulk without damaging the brick faces, then properly repointing with appropriate mortar.

Start with a sharp utility knife or caulk removal tool to score and slice through the caulk. Work the blade along both edges of the joint to separate the caulk from the brick faces. For stubborn sections, a oscillating multi-tool with a narrow blade works exceptionally well — the vibrating action cuts through caulk without the lateral pressure that can chip brick edges. Heat guns can soften old caulk, but use caution around heritage brick which can be damaged by excessive heat.

For deeper caulk removal, use a narrow chisel and hammer to carefully chip out remaining material. Work slowly and angle the chisel along the joint, not toward the brick faces. Wire brushes help clean out the final residue, and a shop vacuum removes all loose debris. The goal is to clear the joint to a minimum depth of 20mm — deeper than the caulk likely penetrated, but necessary for proper mortar adhesion.

GTA climate makes this repair especially important because caulk in mortar joints creates a moisture trap that accelerates freeze-thaw damage. Unlike mortar, which is porous and allows moisture to evaporate, caulk seals moisture into the joint where it freezes and expands, causing the surrounding brick to spall and crack. This is particularly problematic in Toronto's clay soil areas where foundations experience constant moisture exposure.

Once the caulk is removed, repoint with appropriate mortar — not more caulk. For most GTA foundation brick (1920s-1960s era), use Type S mortar mixed to match the original joint colour. Heritage homes (pre-1920) may require softer lime-based mortar to prevent brick damage. Mix small batches to a peanut butter consistency, pack firmly into the joints with a pointing trowel, and tool smooth with a jointing tool when the mortar begins to firm up.

Timing matters significantly in the GTA — repointing must be done when temperatures are consistently above 5°C day and night for at least 7 days. Spring through early fall is ideal. Keep newly pointed joints damp for 3-5 days by misting lightly if temperatures exceed 25°C.

Hire a professional if you discover extensive brick damage, structural cracks, or if the foundation has heritage brick that requires specialized lime mortar. Professional masons can assess whether the caulk application caused underlying damage that needs addressing beyond simple repointing. For large areas (more than 10-15 linear feet of joints), professional repointing ensures consistent colour matching and proper mortar curing across the entire repair area.