How to Repair Mortar Joints

Step 1: An overview

Brick is one of the most prized exteriors for homes because it's so attractive and easy to maintain. Yet over the years, water, ice and seasonal expansion and contraction all attack the solid mass of a brick wall at its most elastic (and weakest) point: the mortar joints.

Mortar joints deteriorate wherever water can soak them—under windows and walls, around chimneys, behind downspouts, at ground level and at any exposed wall top.

Repairing eroding and cracked mortar joints is called pointing, repointing or tuckpointing. We'll show you the proper tools and techniques to repair and restore cracked and worn-away mortar joints to make them solid, durable and good looking. To keep them that way for the long run, you have to stop water from getting into your bricks and foundation.

Repointing brick is slow, painstaking work that requires few special skills but a lot of patience. Using the steps we show in Photos 1 – 8, you can expect to repoint about 20 sq. ft. of brickwork a day. However, if you rush and do careless work on a highly visible area, the results will stick out like graffiti. Brick is durable; bad results will bother you for a long time! If you don't have pointing experience, consider hiring a pro for:

• Larger-scale pointing jobs, such as a whole wall that needs repair.
• Chimney and wall repair requiring setting up and moving scaffolding.
• Areas with a lot of loose or missing brick requiring rebuilding walls or corners.
• Color-matching new mortar to existing mortar in highly visible areas.

Step 2: Tools and materials

Home centers and well-stocked hardware stores carry the tools and materials needed for pointing brick. Anything they don't have can be bought from retailers that sell to contractors. Look in the Yellow Pages under “Brick” or online.

Cleaning out old mortar joints requires basic tools: hammer, flat utility chisel (Photo 2), safety glasses, dust mask and whisk broom. Filling the cleaned-out joints requires masonry tools: brick trowel (Photo 5), 3/8-in. pointing trowel (Photo 5), a special tool for contouring the joints (Photo 7) and waterproof gloves.

If you do tackle larger jobs or encounter hard mortar that can't be easily chiseled out, we recommend that you rent or buy an angle grinder fitted with a diamond blade (Photo 1). Select a grinder with a 4-1/2 in. blade diameter; larger grinders are harder to control and cut the mortar too deep.

Step 3: Break out the old mortar

Break out old mortar using a hammer and cold chisel or a flat utility chisel that's narrow enough to fit into the joints (Photo 2). Wear safety glasses and a dust mask and remove 3/4 to 1 in. of old mortar (more if needed) until you reach a solid base for bonding the new mortar. If the mortar is so soft that the bricks are loosening up, you'll have to remove and properly reset them. If the cracked mortar is harder, make a relief cut down the center of the mortar joint using the pointed edge of the chisel and then gently chip out the mortar that contacts the brick.

If the removal work is going really slowly, use an angle grinder to make the relief cuts (Photos 1 and 2). Exercise care here; the grinder can easily nick and chip the bricks, so don't use it to clean out the mortar contacting the brick. To avoid nicking the bricks, cut the vertical joints before cutting the horizontal joints. Once the old mortar is removed, dust out the joints (Photo 3). Prepare the joints to receive new mortar by misting them lightly with a garden hose sprayer.

Step 4: Mix the mortar just right

Using only the amount of water specified by the manufacturer, mix the mortar until it's the consistency of peanut butter and sticky enough to cling to an overturned trowel (Photo 4). It should be stiff but not crumbly. Allow the mortar to “rest” for 10 minutes as it absorbs the water, then remix it using your brick trowel. Don't try to revive mortar that's drying out by adding more water to it. Mix a fresh batch instead.

Step 5: Filling the mortar joints

Follow the pointing techniques shown in Photos 5 and 6 and these additional tips:

• Pack the mortar tightly with no voids for the strongest, most water-resistant joints.
• Fill deeper joints (those greater than 3/4 in.) in two stages. Allow the first layer to partially harden (until a thumbprint barely leaves an indentation) before adding the second layer.
• In hot weather, work in shaded areas first (if possible) so the sun won't dry the mortar too fast. Mix smaller batches of mortar.
• Don't work in temperatures below 40 degrees F.

Step 6: Match new joints with the old

Buy the mortar finishing tool you need to match the contour and depth of your existing mortar joints (Figure A). We recommend that you repoint brick sills (Photo 1) and other horizontal brick surfaces (ledges, wall tops, etc.) with flush joints (Figure A) to promote drainage—regardless of the type of mortar joint in your vertical walls. Allow the mortar to cure to “thumbprint” hardness before you finish the joint. Shape the vertical joints before working the long horizontal joints.

Use a soft-bristle brush as shown in Photo 8 to remove mortar chunks on the brick face before they harden. The brush keeps the mortar from smearing. If you do smear mortar onto the brick, you'll have to go back later and use a chemical cleaner.

Prevent water from entering and damaging your brickwork by applying color-matched polyurethane caulk where stucco, wood and other materials meet brick.