Repairing Brick Stairs in Cold Weather

Cut through the mortar joints surrounding the damaged bricks in the stairway, or through the damaged mortar lines, using a 4 1/2-inch angle grinder containing a diamond blade. Make the cuts about 1-inch in depth to allow you to force a chisel into the joint to remove the remaining mortar.

Push the blade of a chisel into the joint at an angle and then strike the head of the chisel to chip out the remaining mortar from the joint until you reach the base of the bricks.

Clear the debris from the joint with a nylon brush and then pry out the damaged brick, if you’re replacing the brick, with a prybar.

Mix the mortar in a large bucket. Use high early strength Portland cement to create a concrete that achieves its strength as quickly as possible, and dry hydrated lime to reduce the water contained in your concrete mixture. Add an antifreeze admixture to the water, following the admixture instructions for mix ratio to prevent the mortar from freezing once in place. Use hot water for the mortar mix to prevent the mortar from developing ice crystals during the mixing and placement process. It’s also best to reduce the amount of water used in the mix itself, creating a stiffer mix with less water content to freeze. Use a mix ratio of seven parts sharp sand to one part cement and one part lime. Mix with an electric drill containing a grout mixing attachment.

Spread a 1/2-inch layer of mortar onto the bottom of the replacement brick with a trowel and then place the brick back into the open area of the stair where you removed the damaged brick. Press down on the brick until it's level with the bricks to either side. Place a mound of the mortar onto the flat surface of a concrete hawk. Position the hawk alongside the open mortar joints, and then push the mortar into the joints with the tuckpointing trowel filling them to within 1 1/2-inches of the surface of the brick.

Mix a second batch of mortar to serve as the finish layer within the joints using six parts sand, 3/4-part Portland cement and one part lime. Fill the rest of the joint with the finish mixture.

Shape the mortar in the joints with a brick jointer with a head the same shape as the mortar joints surrounding the replacement brick. Make the new mortar lines the same depth as the surrounding ones.

Cover the stairs with a weather-resistive membrane to protect it from rain or snow during the first 24 hours of curing time.