Masonry on Canadian heritage buildings spans a wide range of brick types, stone species, and mortar formulations — each tied to the era of construction and the regional materials available at the time. A building erected in Toronto in 1895 used a different brick hardness and lime-to-sand ratio than one built in Montreal in 1910 or Victoria in 1920. That specificity matters, because a mortar that is harder than the surrounding brick will cause the brick face to spall, not the mortar joint, over repeated freeze-thaw cycles.
This guide covers the standard sequence followed by conservation specialists when approaching original masonry on a designated or pre-1930 building: condition assessment, mortar analysis, removal of failed joints, and repointing with a compatible material.
Condition Assessment Before Any Work Begins
The first step is a systematic visual survey of the entire facade, ideally from a scaffold or elevated platform that allows close inspection at each course. What you are looking for falls into a few categories:
- Open joints — mortar has shrunk or eroded, leaving a gap between mortar and masonry unit. Water enters here and begins the deterioration cycle.
- Spalling brick faces — the outer layer of the brick detaches in sheets or chips. This is almost always caused by moisture trapped behind an incompatible mortar or a surface coating that prevents evaporation.
- Efflorescence — a white salt deposit on the surface, indicating that water is moving through the wall and carrying soluble salts to the face.
- Cracks — distinguish between settlement cracks (typically diagonal, through mortar and brick) and movement cracks (often horizontal or following the mortar joint pattern).
- Missing or replaced units — brick patches installed with a different material alter the visual character and often signal previous failed repairs.
Document everything photographically before touching anything. Heritage review panels in Ontario and BC expect a condition report as part of any alteration application.
Mortar Composition Analysis
The single most consequential decision in a masonry restoration project is the mortar mix. Heritage brick — particularly the soft, lime-fired brick common in pre-1920 Canadian construction — requires a mortar that is weaker than the masonry unit itself. When mortar is too hard (high Portland cement content), expansion and contraction stresses are transferred to the brick face rather than the joint, and the brick spalls.
The standard reference in Canada is the Historic Places Canada guidance on mortar compatibility, which recommends petrographic analysis of a mortar sample before specifying a new mix. A petrographic report typically identifies:
- The binder type (lime putty, hydraulic lime, natural cement, or Portland cement)
- The aggregate type, gradation, and colour
- The approximate original mix ratio
- Any later patching materials that have been applied over the original
For most pre-1930 buildings in Ontario and Quebec, the original mortar was a Type O or Type K equivalent — very weak by modern standards, with compressive strengths in the range of 1–2.5 MPa. The current ASTM standard mix types go down to Type K (0.5 MPa), but matching the original often requires a custom formulation using a lime-rich binder such as NHL 2 (Natural Hydraulic Lime).
Rubble limestone masonry, common in Ontario's pre-Confederation structures, requires a particularly soft lime mortar with a coarse aggregate matched to the local stone colour.
Removing Failed Mortar
Failed mortar must be removed to a depth of at least 19 mm (¾ inch) to give the new mortar adequate bearing area. The method of removal is as important as the depth:
Hand Raking
Preferred for soft brick and narrow joints. A hand-held plugging chisel or a purpose-built raking tool is worked along the joint without contacting the brick arrises. Slow, but causes the least damage.
Oscillating Multi-Tool
Faster than hand raking and controllable. An oscillating blade follows the joint line without the rotational torque of an angle grinder. Suitable for medium-hardness brick with joints 10 mm or wider.
Angle Grinder
Generally discouraged on heritage buildings. Even experienced operators damage brick arrises. If used, it should be restricted to straight horizontal joints where the wheel can be guided by the brick course. Never use on vertical joints or on soft brick.
A common error is cutting too deep or too wide, which enlarges the joint beyond its original dimensions and creates a visual anomaly that is difficult to reverse. The removed joint profile should match the original.
Repointing: Application and Tooling
New mortar is applied in two or three thin layers for joints deeper than 19 mm, allowing each layer to stiffen before the next is applied. Forcing a single thick application leads to cracking as the mortar dries unevenly.
After the final layer reaches the correct stiffness (it should indent slightly under thumb pressure but not smear), it is tooled to match the original joint profile. Common profiles on Canadian heritage buildings include:
- Flush — mortar is struck level with the brick face. Common in Ontario's commercial buildings.
- Weathered (rodded) — a slightly concave joint that sheds water efficiently. Frequent in residential construction.
- Beaded — a convex or half-round joint, more decorative, found on higher-quality Victorian facades.
- Recessed (raked) — the mortar is pushed back from the face. Historically accurate for some stone construction but should not be introduced where not original, as it holds water.
Match the mortar colour by testing the mix on a small patch of wall and allowing it to cure for several weeks before assessing the final colour. Mortar darkens significantly during curing, and a sample that looks correct when wet will often be lighter when dry.
Spalling Brick Repair and Unit Replacement
Where individual bricks have spalled beyond repair, replacement with a matching unit is preferable to applying a surface consolidant. Consolidants can change the appearance and moisture behaviour of the brick face and are rarely as durable as replacing the unit.
Matching replacement brick requires attention to:
- Colour — old brick oxidizes over decades; new brick of the same clay body may look noticeably brighter
- Texture — wire-cut, hand-made, and sand-mould bricks have different surface characters
- Size — imperial bricks (pre-metrication) have different nominal dimensions than modern units
- Hardness — select a brick with a similar absorption rate to the surrounding units
Several Canadian suppliers stock reclaimed and reproduction heritage bricks. The Ontario Heritage Act does not mandate specific suppliers, but provincial conservation officers maintain informal lists of tested material sources.
Flemish bond — alternating headers and stretchers — was widely used in Ontario townhouses built between 1850 and 1900. Replacement units must replicate the header dimension, which is the full depth of the brick.
Surface Cleaning
Cleaning heritage masonry is often necessary before restoration, but it carries significant risk. The wrong cleaning method can etch stone surfaces, dissolve mortar, or drive contaminants deeper into the substrate.
The generally accepted hierarchy, from least to most aggressive:
- Low-pressure water wash (cold, then warm)
- Soft-bristle scrubbing with water
- Poultice cleaning for specific staining (biological growth, metallic staining)
- Chemical cleaners matched to the substrate and contaminant type (never generic acid on limestone or marble)
- Low-pressure abrasive cleaning as a last resort, only by experienced contractors with a masonry conservation background
Sandblasting is not an acceptable method on heritage brick or stone. Even low-pressure systems remove the hard outer surface of the brick, exposing the more porous inner core to accelerated moisture absorption.
Documentation and Heritage Approvals in Canada
In Ontario, any alteration to a designated heritage property's character-defining elements — including repointing — requires a Heritage Permit under Section 42 of the Ontario Heritage Act. The permit application must include a description of the existing conditions and the proposed materials and methods. Municipal heritage staff review the application; timelines vary from 4 to 12 weeks depending on the municipality.
In British Columbia, the Local Government Act and the Community Charter provide the legal framework for designation. Alteration permits are required in most designated districts, and the approval process mirrors Ontario's in structure.
Before beginning any work on a designated building, confirm the permit requirements with the municipal heritage planner. Undertaking work without a permit can result in orders to reverse the changes at the owner's expense — and reversal of mortar work is considerably more expensive than the original project.
