How to Repair Brick and Block Walls

Adjust the blade of a 4-inch grinder to cut the mortar to about one-half its depth. With the rear of the grinder guard on the face of the brick, turn the grinder on, and ease the blade into the joint.

Brush the loose mortar from the joint with an old paintbrush. You can also blow out the dust on a small area with an air hose. In all cases, wear eye protection. After cleaning, mist the joint with a sprayer.

Replace the mortar in the joint by sliding it off the face of a flat trowel and into the recess. Use a narrow trowel or a thin piece of scrap wood to put mortar into the joint and not on the brick. Press the mortar into the joint until it's solidly filled—mortar will start oozing at the edge of the tool when the joint is full.

Let the mortar set until it's fairly stiff and you can just dent it with pressure from your thumb. Then tool the joints with a striker that matches the profile of the original joints. Tool the horizontal joints first, then the vertical joints.

To remove a damaged brick, drill several 1/4-inch holes in its center. Next chip out the old mortar with a plugging chisel and small sledge. Using a brick set, break the brick into pieces and remove them. Brush away debris, blow out the dust, and dampen all surfaces of the cavity.

Mix latex-fortified mortar, tinting it with pigments if necessary to match the existing color. Using a pointing trowel, apply a 1-inch-thick layer of mortar to the bottom side of the recess.

Butter the top and ends of the replacement brick with mortar and set the brick on a pointing trowel. Slide the new brick off the trowel and into the recess, holding the trowel on the mortar in the cavity to keep it as undisturbed as possible. Pry the brick as necessary to make the joints evenly thick. Set a straightedge on the brick and push it level with the wall.

When the mortar has stiffened slightly, scrape away any excess with a masonry trowel and brush the area with a stiff brush. Let the mortar set up until it's fairly stiff and you can just dent it with pressure from your thumb. Then tool the joints with a striker that matches the profile of the original joints. When the mortar dries to a crumbly surface, brush it again.

Use a masonry drill to drill holes into the cores of the block. Then chip out the mortar around the block with a plugging chisel and small sledge, being careful not to damage the surrounding blocks. Set a cold chisel in the holes and break out the front face of the cores.

Using a cold chisel, chip out the block face just enough to leave all but the front 2 inches of the webs. This provides a bonding surface for the replacement face. Chip out the mortar on the sides of the recess also.

Using a circular saw with a masonry blade, cut through the side webs at the thickness of the face and score the top and bottom of the center web. Then cut away the face from the center web with a cold chisel. Apply an inch of mortar to the perimeter of the new block face, as well as to the center and edges of the rear surface. Set the new face in place, slipping it in with a pointed trowel.

Center the block face in the opening by driving wood wedges in the mortar. Let the mortar set up and remove the wedges. Then mortar the holes left by the wedges, and strike the joints.

One of the most common brick problems is efflorescence, a powdery white residue that forms on the surface. The culprit: salts in the brick or mortar that rise to the surface.

Recently placed mortar is particularly prone to developing efflorescence, especially if it rained while the wall was under construction. This type of efflorescence usually goes away on its own within a year.

Poorly finished (or maintained) mortar joints and poor seals that allow water in around moldings and flashings cause the efflorescence on older structures.

If efflorescence is found near the ground, the problem may be due to poor drainage in the soil around the foundation of the structure. Before treating the efflorescence, deal with its cause. Make sure the wall dries completely between rains.

To remove efflorescence, start by wetting down the entire surface with a garden hose. Then loosen the deposits with a stiff-bristle brush. Don't use a wire brush—it will leave metal marks on your masonry. Follow with a strong rinse from a power washer.

If the efflorescence continues to reappear, scrub the surface with a solution of 1 part muriatic acid and 12 parts water. Muriatic acid is a diluted form of hydrochloric acid. Handle it with care. Wear old clothes, safety glasses, and rubber gloves. Always pour acid into water to dilute it, don't pour water into the acid. When water is poured into the acid, it causes a reaction that produces heat. This reaction can make the solution expand rapidly, creating a large acid bubble that can burst up and out from the container and splash onto you, possibly causing burns. Rinse acid-washed surfaces thoroughly to dilute the acid and flush it away. Store the acid in its original, marked container. Rinse with a power washer. On concrete blocks, use only water; acid can damage them.