How to repair mortar joints

Brick is one of the most prized exteriors for homes because it’s attractive and easy to maintain. Yet over the years, water, heat 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 downpipes, 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, you can expect to repoint about two square metres. of brick work a day. However, if you rush and do careless work on a highly visible area, the repointing brickwork will stick out like graffiti. Brick is durable; bad results will bother you for a long time! If you don’t have repointing brick 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.

Colour-matching new mortar to existing mortar in highly visible areas.

Read on to learn how to repoint brick.

Tools Required

Angle grinder

Dust mask

Flat chisel

Hammer

Rubber gloves

Safety glasses

Trowel

Tuckpointing tool

Whisk broom

Materials Required

Mortar mix

Cleaning out old mortar joints requires basic tools: hammer, flat utility chisel, safety glasses, dust mask and whisk broom. Filling the cleaned-out joints requires masonry tools: brick trowel, 10mm pointing trowel, a special tool for contouring the joints and waterproof gloves.

If you do tackle larger jobs or encounter hard mortar that can’t be easily chiselled out, we recommend that you rent or buy an angle grinder fitted with a diamond blade. Select a grinder with a 115mm blade diameter; larger grinders are harder to control and cut the mortar too deep. To begin, cut grooves 20-25mm deep in cracked or deteriorating mortar using a 115mm angle grinder fitted with a diamond blade. Push the blade into the joint until the grinder head contacts the brick, and make a single pass along the centre of the joints.

Learn how to build and render a brick wall.

Break out old mortar using a hammer and cold chisel or a flat utility chisel that’s narrow enough to fit into the joints. Position a flat utility chisel at the edge of the brick and drive it toward the relief cut to fracture and remove the mortar. Wear safety glasses and a dust mask and remove 20-25mm 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 centre of the mortar joint using the pointed edge of the chisel and then gently chip out the mortar (brick grout) that contacts the brick.

If the removal work is going really slowly, use an angle grinder to make the relief cuts. 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.

DIY Basics: Check out our essential guide to grinders, files and rasps.

Once the old mortar is removed, dust out the brick cavity joints using a whisk broom or compressed air. Prepare the joints to receive new mortar by misting them lightly with a garden hose sprayer.

This is how to clean a brick paved area.

Using only the amount of water specified by the manufacturer, gradually add in the water and mix the mortar in a cement boat until it’s the consistency of peanut butter and sticky enough to cling to an overturned trowel. 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.

These are the 12 most common mistakes when pouring concrete.

The basic steps for how to mortar brick start like this: Load mortar onto an overturned brick trowel, hold the trowel under the horizontal joint – tight to the brick – and sweep 6mm slivers of mortar into the cavity using a 10mm wide pointing trowel. Fill the horizontal joints first. Avoid getting mortar on the brick face. Follow these additional tips for filling mortar joints:

• Pack the mortar tightly with no voids for the strongest, most water-resistant joints.
• Fill deeper joints (those greater than 10mm) 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 4 degrees C.

Learn how to build and pour your own modern concrete patio.

Load smaller amounts of mortar onto the back of the brick trowel, hold the trowel tip along the vertical joints and above the horizontal joints – tight to the brick – then sweep and pack the mortar into the cavity using the pointing trowel.

Discover how to repair cracked concrete.

Before finishing the mortar joint, determine which joint matches your existing joints using Figure A above. Next, buy the mortar finishing tool you need to match the contour and depth of your existing mortar joints. We recommend that you repoint brick sills and other horizontal brick surfaces (ledges, wall tops, etc.) with flush joints 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. These are the most common mortar joint profiles:

Raked joint: Formed by removing mortar to 6mm deep with a raking block.

V-Joint: Formed by a brick jointer, it has a concave, “V” look.

Flush joint: Formed by cutting off the mortar with the edge of a brick trowel.

Concave joint: Formed by the curved end of a brick jointer.

For this project, we used a raked joint mortar profile. To make your own raked joint tool, drive a 6d box nail into a short 1×2 board so that it matches the depth of the existing joints. To “rake” joints, hold the board perpendicular to the bricks and move it back and forth, first along the vertical joints and then the horizontal joints. Other joint profiles require other shaping tools.

Use a soft-bristle brush to remove mortar chunks on the brick face before they harden and to sweep loose mortar from the finished joints. 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 colour-matched polyurethane caulk where stucco, wood and other materials meet brick. Mist the new mortar twice a day for two days using a hand pump sprayer or a light mist from a garden hose to help it harden.

Sign up here to have Handyman’s favourite stories delivered straight to your inbox.

Source: Family Handyman