| How to Remove Portland Mortar Before Repointing | | | | attention because the grinder is harder to control when |
| The biggest challenge in restoring masonry walls and | | | | removing very hard material. Center-cutting the joints |
| buildings is replacing Portland-cement-based mortars | | | | relieves the pressure that the hard mortar puts on the |
| with a natural lime mortar. The difference between the | | | | faces of brick and stone. |
| two is easy to determine. Using a pointing chisel to | | | | The second step is to hand chisel the joints out. Usually |
| remove lime mortar is quite easy; the mortar is soft | | | | the best method is to place a flat chisel right where |
| and breaks easily in front of the chisel. Portland-based | | | | the mortar meets the edge of the brick or stone, |
| mortars are quite hard, and hand-chiseling takes many | | | | aiming toward the center groove that was cut with the |
| blows from the hammer to remove just a couple | | | | grinder. A pointing chisel can also be used to go |
| inches of joint. | | | | across. Pick a 2"or 3" section of joint and aim the |
| This hard mortar is very damaging for brick and soft | | | | pointing chisel toward the area that has already been |
| stone. One reason they are so damaging is that | | | | removed. The chisels will break the bond between the |
| Portland-based mortars (Type N, Type S, and most | | | | Portland-based mortar and the brick or stone. |
| mortars available today) are not water permeable, so | | | | Usually the repointed joints are less than an inch deep, |
| they do not allow moisture to escape from the wall. | | | | so removal is safe as long as care is taken with the |
| Also, Portland-based mortar is not flexible, but brittle, so | | | | faces of the masonry units. Remove mortar at least |
| the masonry units are stressed by freezing | | | | 2x the height of the joint. A 3/8"-wide joint should be |
| temperatures and imperceptible building movements. | | | | chiseled back to at least 3/4". This will ensure an |
| This can take the faces of brick right off of buildings | | | | adequate bond between the new mortar and the brick |
| that should be preserved and protected. Natural lime | | | | or stone. |
| mortar will wick moisture away, and flex with the small | | | | Once the mortar is removed, the joints should be |
| movements of temperature changes and settling that | | | | vacuumed, or blown out with compressed air. A low |
| occurs in every building over time. | | | | pressure jet of water, such as from a nozzle on a |
| To remove Portland-based mortars efficiently, a | | | | garden hose, can also be used. If the joints are |
| grinder should be used to cut a groove in the center of | | | | vacuumed or blown out, it is a good idea to dampen |
| the joint. Usually a thin blade works better than a thick | | | | the wall before applying the new mortar. |
| one, and a 4" blade will cut through the Portland-based | | | | Never use a pressure washer on soft brick or stone. |
| pointing back to the original lime-based mortar. Cutting | | | | High-pressure water can damage walls of even hard |
| the center of the mortar joints prevents slipups from | | | | stone (like granite), so the nozzle should be kept well |
| damaging the original brick or stone. Special care | | | | back from the face of the stone. Pressure washers |
| should be taken on head (vertical) joints to cut only as | | | | often remove the beauty of the weathered faces of |
| deep as the grinder can without cutting into the | | | | stone, including the green moss that can make a |
| masonry units. This can take strength and focused | | | | building look old. |