Importance of Repointing Brick & Stone Structures

What is Repointing? 

Newly Repointed Sandstone Chimney

Repointing, also known as tuckpointing, is the process of repairing cracks or deteriorated mortar joints in brick and stone wall systems. This repair work is critical for maintaining a water-resistant masonry system. 

Why Does Mortar Crack & Erode?

Freeze-Thaw Cycles

Weathering over time will cause mortar to deteriorate. Our harsh Ottawa winters coupled with frequent freeze thaw cycles in the shoulder seasons can be hard on masonry systems especially near the ground or in the horizontal plane like flagstone and window sills. These mortar joints are frequently exposed to moisture penetration. When the weather is warm it's not a problem as brick/stone units are breathable and the moisture evaporates off. But in the colder months, wetting from rain or melting snow accumulates moisture in masonry that freezes causing the mortar to crack or pop due to the expansion. 

Movement Cracking

Cracking caused by garage steel angle lintel

Mortar joints can crack on new homes caused by settlement in the new foundation or if a foundation cracks due to water ingress or hydrostatic pressures. Steel angle lintels spanning doorways and windows are notorious for causing cracks if not maintained. The steel begins to rust if not painted which causes expansion and puts pressure on the stonework. Lentils covering large spans like garage openings are also susceptible to some bowing over time and the difference of expansion rates between steel and masonry can cause cracking at the ends of the steel lintel. A well built arch is often the better option for longevity. For more info on steel lintels vs. arches see our post comparing the two. 

Repointing Process 

-In most cases, damaged mortar joints or cracked mortar should be cut out to a depth of 25mm or 1 inch from the face of the brickwork. This is typically done with a segmented diamond blade grinder or with a proprietary tungsten/carbide oscillating saw. 

-For stone or on masonry systems where the mortar joints are much bigger, in order to protect the stone arris and remove mortar efficiently, a groove is scored into the middle of the mortar joints to relieve the joint. The scoring is then followed by a pneumatic chisel to chip the old mortar into the relief groove. 

-The cut out joints are then cleaned out with a dust extractor, or blown out with compressed air removing any loose debris. 

-The clean mortar joints are then misted with water to allow for good bonding to the masonry and to prevent the new mortar from drying out too fast. In hot weather and on heritage brick buildings, the walls can be so dry that the moisture in the new mortar is almost immediately sucked out causing the new mortar to “flash” which is an improper cure and will fail rapidly.. 

-New mortar is prepared using a recipe as close to the original prescribed masonry as possible and is applied using a slicker and trowel. It is critical that the new mortar be compressed into the mortar joint adequately so there are no voids. 

-Newly repointing joints are then tooled typically with a barrel jointer or a wheeled-rake jointer to match the original brick/stonework as close as possible.

-On heritage mortars (lime-dominant mortars), damp curing may be required to slow down the curing process to prevent shrinkage. This is typically done by covering the pointed work with a wet sheet of burlap and covering the burlap with a plastic sheet to prevent evaporation. 

Getting it Done Right

-Repointing typically needs to be done once every century on a well built home. Areas where masonry is exposed to extreme weather like chimneys, window sills and stone walkways, may need to be done at much more frequent intervals. A repointing project carried out properly should last 50-100 years before any maintenance is required.

-Repointing is very tedious work that requires a great level of detail and focus in order to not damage the masonry units or stain the work. 

-The use of new mortars that are harder than the original mortar can cause detrimental effects to masonry systems, particularly heritage stone foundations. If done properly, newly repointed walls will enhance the integrity and aesthetic of the structure. 

Hiring a Professional 

For these reasons, all repointing should be carried out by a licensed masonry contractor to ensure the right tools and methods are used for the job. It is critical that the prescribed mortar for the job is the same as what was removed or it can cause further structural or moisture issues to occur over time. 

If you are in the Ottawa or surrounding area and are interested in getting brick/stone cracks repaired or repointing work done, please feel free to contact us on the Request a Quote page. All of our repointing projects are carried out by a Red Seal Licensed Journeyman mason. Bring vitality and beauty back to your masonry and choose Kavanagh Masonry for your restoration project.