The process of refurbishing and strengthening the mortar joints in a brick-based structure is called brick repointing. Repointing is a necessary part of maintaining masonry or concrete surfaces. However, it is also done as a part of finishing a newly-laid or repaired brick surface.
This is because joints between bricks are subject to many elements that can cause weathering, such as moisture and chemical vapor seepage. This compromises the overall stability of the brick configuration and makes it more susceptible to large-scale water seepage. More water entering any masonry or concrete surface also means greater deposition of water-soluble salts or minerals. The debris further weakens the structure along with making it vulnerable to weather induced patterns like freezing and thawing.
Repointing is a rather simple procedure, and it can be easily done using basic household tools and the information listed below.
Brick Repointing Basics
The word "repointing" does indicate handling some sort of a pointed surface or sharp edging, but this isn't so. The word "repointing" has gained prominence since the pointed end of a trowel is used extensively in this project. The pointed edge of the trowel is repeatedly used to insert the freshly-mixed mortar between the brick joints that have been prepared for repointing. Furthermore, the excess mortar is scraped-off using the blunt side of the trowel.
Choosing Surfaces for Brick Repointing
Among older surfaces, identifying brick repointing areas is much easier as the older mortar begins to crumble. The real challenge lies in brick repointing as a part of finishing a freshly-mortared surface. It should be noted that the entire, repaired, or newly-built brick surface doesn’t need to be repointed. You need to mark-out the joints that need repointing.
If you are not sure about how to do this, it is better to repoint brick joints that are along the base of the structural element and around the edges since these are most susceptible to moisture seepage and pressure induced by nearby surfaces. Similarly, if any of the mortar-covered bricks are along zones/areas with a history of moisture seepage, ensure that you repoint such bricks.
Criticality of Cleaning Old/Previously-laid Mortar
This is perhaps the most tedious part of the project, but it is very important. The old mortar joints that you have marked for repointing should be cleaned thoroughly. This means using tools like paint-scraper, hammer and chisel to remove lines of old mortar to the extent that a thin cavity is formed.
It is vital that you chisel deep into the old mortar joints. Among residential surfaces, the depth of the chiseled lines should be around 1/2 inches. You should use a wire brush to clean the mortar lines. This process becomes even more demanding when the bricks have been joined by a more durable material like Portland cement. To loosen such mortar joints, you need a motored masonry blade or power-driven chisel.
Choose Repointing Materials with Care
Apart from the cleaning equipment and trowel, the most critical component of this project is the mortar-mix. The chosen material should be largely similar to the original mortar. This is because each kind of mortar presents a different level of compressive integrity, level of permeability and extent of thermal expansion.
Presence of different mortar layering within the same structure can induce unwanted imbalances between the brick layers, making them weaker. Thus, if the original mortar was a lime-based material, you cannot use a more advanced material like Portland cement. The chosen brick repointing material should have some amount of soft lime.