Brick Mortar Repointing: When and How to Restore Masonry Joints

Exterior Renovation Services

Deteriorating mortar joints are one of the most common and most overlooked sources of water damage in Ontario brick homes — repointing at the right time prevents structural problems.

Mortar joints between bricks are the first part of a masonry wall to deteriorate. Mortar is intentionally designed to be softer than the brick itself — it's the sacrificial element that absorbs thermal movement, freeze-thaw stress, and moisture cycling, protecting the harder brick faces from fracturing.

Planning Your Project

Joints that are recessed more than 6 mm from the brick face, that are crumbling or soft when pressed, or that show open gaps or cracks need repointing. At this stage, water is entering the wall cavity, beginning a deterioration cycle that can extend to wood structure behind the brick if left unaddressed.

Repointing requires removing deteriorated mortar to a depth of approximately 20 mm using an angle grinder or oscillating tool, thoroughly cleaning the joint of dust and debris, then packing new mortar in controlled layers. Attempting to fill over existing mortar without removal produces a cosmetic repair that fails within 1 to 2 seasons.

Working With D&D Exterior Finishing

Mortar mix selection is critical. Modern Portland cement-rich mortars are harder than historic lime-based mortars and can cause spalling and fracturing of soft, historic brick when used for repointing. Older brick homes — particularly pre-1950 construction in Kitchener's heritage districts — require a softer, lime-based mortar mix for correct repointing.

The appearance of the repointed joint — flush, slightly recessed, or struck at an angle — affects both aesthetics and water shedding. A slightly recessed, weather-struck joint that pitches outward sheds water more effectively than a flush-filled joint and is the standard for exterior repointing.