Exterior brick walls are subject to a variety of stresses. Both the mortar and the brick expand and contract with changes in temperature, and any cracks that form in either widen with moisture penetration. The result is that mortar eventually cracks and crumbles, while brick cracks or spalls. Repair jobs for exterior brick walls may have to address either problem or both. Thankfully, the basic masonry skills used in these tasks are within the reach of any do-it-yourselfer.
Remove loose mortar from the joints between the bricks with a wire brush. Chip out the cracked, but largely solid, mortar with moderate blows from a hammer and chisel. Take care to not chip or crack the adjacent bricks.
Make a batch of mortar in a bucket by adding water, as directed by the product's label. Pour the mortar into a masonry bag.
Insert the masonry bag's nozzle into the hollow joints between the bricks, and force mortar to fill the gaps by squeezing the bag. Set the trowel flush against the wall and scrape downward, removing any excess mortar that may have oozed out of the joints.
Shape the wet mortar with a trowel so it matches the old mortar.
Loosen cracked or spalled bricks by removing the mortar around them with the hammer and chisel. Once it is loose enough, pull the brick out of the wall.
Brush debris out of the hollow in the brick wall with the wire brush.
Trowel mortar into the hollow, spreading it out on the bottom to create a bed that matches the old mortar in thickness.
Butter the ends and top of the fresh brick with mortar, making these coats a little thicker than the old mortar gaps contained.
Force the brick into the hollow. This squeezes a little mortar off the top and sides, but also ensures a snug fit.
Set the trowel flush against the wall and scrape downward, removing any extra mortar that dripped out of the joints. Shape the wet mortar with a trowel so it matches the old mortar.