Brick is one of the world's oldest building materials and one of the most enduring. It is fireproof as well as pest and weather resistant. Because brick does not require painting and never warps, rots or fades, brick homes built hundreds of years ago are still standing and with some maintenance they can look as attractive as the day they were built.
There are two components to brick structures: the brick itself, and the mortar. Brick is made mainly from clay with the addition of small stones, seashells, lime and other secondary ingredients such as colouring. The clay mixture is molded into shapes and fired at very high temperatures (1,000 degrees Celsius or more). Mortar is made from a mixture of sand, lime, pigment and cement. Although the composition of the mortar and the clay used to make the bricks will vary slightly depending on the region, the results are generally long lasting. The Great Wall of China demonstrates the durability and strength of mortar. In the 1300’s, during the Ming Dynasty, part of the wall was rebuilt using a special mortar made of clay, lime and rice flour. The wall is still sound to this day.
If you have a brick home or would like to own one, it is reassuring to know that compared to many other building materials such as wood and stucco, brick requires little maintenance. When maintenance is required, however, it can be costly and time-consuming. The bricks themselves can typically last for centuries if the hard fired exterior is not damaged. The main concern with brick construction tends to be the mortar, which usually only lasts between 50 and 100 years. Unfortunately, not all mortar is as durable as that used in the Great Wall!
Over time, mortar begins to deteriorate becoming cracked, eroded and in places separating from the brick. To test the strength of the mortar, gently scrape a knife across a seam. If mortar crumbles or flakes off, it is advisable to repair it promptly before further deterioration occurs. Once moisture is able to penetrate the wall through eroded or cracked mortar, it can do damage to the interior structure of the building. A common problem in older homes occurs when moisture reaches the interior walls, weakening the walls and creating an ideal habitat for unhealthy molds.
There are a number of important considerations when repairing mortar. If you plan to do the work yourself rather than hiring a professional company, be careful to use the proper mortar and to mix it with water in the correct proportions. If your proportions are wrong, the mortar may not expand and contract as it should with temperature fluctuations. As a result, the pressure of expansion may cause the old brick to crack. Also the mortar used a hundred years ago or more tended to have a higher lime content and did not expand to the same degree as modern products. If you have an old home, you may wish to consult a professional regarding the best type of mortar.
Another step that requires caution is the removal of the deteriorating mortar. You can use a chisel or old screwdriver to carefully scrape off the crumbling mortar. Only remove the top 12mm to 18mm of mortar. If you use a power grinder to remove mortar you may find it removes too much too quickly and can chip the bricks. In general, power grinders should be left to experienced professionals.
Painted brick poses other challenges. In order to create a firm seal, a new layer of mortar must be applied to the existing mortar. If the old mortar is covered by paint, the new layer will not bond properly. Most likely, the paint will have to be removed. Before removing the paint consider its age. According to Health Canada, exterior paint manufactured before 1980 most likely contains lead. During removal of the paint you may be exposed to dangerous levels of lead. It is highly recommended that you consult a professional paint-removal company. If you are sure that the only paint on the bricks was manufactured after 1992, there is no need for concern about lead. By that time, all consumer paints produced in Canada and the U.S. were virtually lead-free.
Taking all these factors into consideration you may be ready to repair your mortar. The first step is to remove the top 12mm to 18mm of deteriorating mortar. As mentioned above, hand tools are the best way to avoid damage to the bricks. After scraping, brush out the mortar dust. When you are ready to apply the new mortar, wet the seam and the bricks to prevent too much water being absorbed too quickly from the new mortar. Apply the mortar firmly to the seam with a pointed trowel. Trim off the excess. Use a damp cloth to remove excess from the brick faces; mortar can stain the brick. As it dries, use a small stone to shape the mortar to match the original. Mortar is often slightly recessed in a rounded hollow. It is best to work in small sections completing them as you go rather than scraping the entire building then applying new mortar.
Once you have repaired the mortar you may be planning to seal it will a water repellent as is done with wood. This is strongly inadvisable. Sealing the mortar and bricks would trap moisture inside and lead to decay. It is far better for the health of the building to allow the bricks to breathe.
Doing a little preventative maintenance on a brick building will ensure that it lasts for many years to come.