Repair Loose Bricks
This page covers replacing bricks that have come loose on small walls and steps and other minor masonry structures. You can use a drywall mud pan and putty or joint knife for this jobs.
If you don't have the original brick to replace, you should try to find one that closely matches or the difference may be distracting. If the brick structure you want to repair was build before the late 1800's, don't use modern mortar and bricks to repair it. Because modern masonry is much harder than old brick and mortar, the patch will crush the surrounding older bricks as the structure moves naturally over time. Also don't make repairs to older brick structures if freezing temperatures are likely for a few days.
Soak the replacement bricks in a bucket of water for a couple of hours before replacing them. This will encourage a strong, permanent bond between the new mortar and the bricks. This is the most important thing you can do to make sure the replaced bricks stay put. If you're repairing older bricks, especially noticeably soft bricks, don't soak them as long or they may absorb excess water
Also soak the wall where the brick will be inserted. Use a spray bottle or a hose to soak the wall or steps repeatedly. The more water the wall brick absorbs the more likely the repair will be a success.
If the replacement brick has old mortar on it, try a cold chisel to chip it off. Also clean mortar off the wall where you are replacing the brick. Soaking the brick in water overnight may help to loosen the mortar making it easier to remove. Use a hammer and chisel blade joint knife to get as much of the old mortar off as possible. The more you can remove the better the repair results.
If the bricks to be repaired are new, you can use a bag of pre–mixed mortar to make this repair. If you have an older brick structure built after the Civil War you can use a mortar mix of using 1 part lime, 1 part portland cement and 6 parts sand. Mix the lime and cement before adding the sand. For structures older than 150 years or so, use a lime mortar for repairs to avoid damage to the original masonry. A general lime mortar mix is one part lime and 3 parts sand.
After mixing your dry ingredients add water slowly and mix to get a mud that scoops easily and holds it shape on the side of a brick. Heap the mixed mortar onto the replacement brick and the wall, on all sides that make contact. Press the replacement brick into the mortar and shift it back and forth until it settles into it's original position. Scrape the excess mortar as it oozes out. Use the edge of the knife or a mortar pointing tool to level the mortar joint to a little below the brick face. Wipe any mortar off the face of the brick with a wet rag of sponge before it sets. Be careful not to disturb the mortar between the bricks.
Lay all the missing bricks in this manner and let the mortar set for about 24 hours. If the replaced brick is held in place by the new mortar alone, support it with a board or something else that will hold it in place until the mortar can set. Be careful not to disturb the brick and setting mortar while doing this.
