Brick Repointing and Tuckpointing: Mortar Repair Technique

When Repointing Is Needed

Mortar is recessed 1/4 inch or more behind the brick face. Mortar is crumbling or sandy when scraped with a key. Mortar has fallen out of joints leaving open gaps. Water is entering the wall through joints (visible as damp patches on the interior wall, or as efflorescence — white salt deposits on the brick face).

Repoint when you notice these signs, not when the wall is obviously failing. Waiting until joints are wide open allows water deep into the wall, where freeze-thaw cycles crack the bricks themselves. At that point, you are replacing bricks, not just mortar.

Mortar Matching

This is the most important step and the one most people get wrong. Modern mortar (Type N or Type S Portland cement mortar) is much harder than the lime-based mortar used in pre-1930 construction. Using hard mortar on soft old bricks traps moisture in the brick and causes spalling — the face of the brick pops off in sheets.

For buildings constructed before 1930: use a lime-based mortar mix (Type O or a custom lime/sand mix). For buildings from 1930-1960: Type N mortar is usually appropriate. For buildings after 1960: Type N or Type S depending on the original specification.

The color of the mortar matters aesthetically. Take a sample of the existing mortar to a masonry supply store. They can match the sand color and aggregate to produce a close visual match. Hardware store pre-mixed mortar rarely matches existing joints.

Joint Raking (Removal)

Remove deteriorated mortar to a depth of at least 3/4 inch (twice the joint width for standard joints). This gives the new mortar enough depth to bond properly. Shallow repairs — packing a thin layer over the old mortar — fail within a year.

Use a grout rake, cold chisel and hammer, or an angle grinder with a diamond blade for removal. An angle grinder is fastest but aggressive — it can cut into bricks if you are not careful. A grout rake is slower but safer for delicate old brick.

Work carefully at brick edges. Chipping the corner off a brick is easy to do and impossible to undo. If a brick is already damaged, note it for possible replacement.

Brush out loose debris with a whisk broom. Rinse the joints with water to remove dust. Damp joints (not soaking wet) help the new mortar bond by preventing the old masonry from sucking moisture out of the fresh mix too quickly.

Mixing and Applying Mortar

Mix mortar to a stiff but workable consistency — it should hold its shape on a trowel when turned sideways. Too wet and it shrinks and cracks as it dries. Too stiff and it will not bond to the joint walls.

Load mortar onto a hawk (flat handheld board) and press it into the joints with a pointing trowel. Pack the horizontal (bed) joints first, then the vertical (head) joints.

Work in thin layers if the joint is deep — 3/8 inch per layer, letting each layer firm up before adding the next. Packing a deep joint in one pass traps air and leaves voids that hold water.

Work in manageable sections. Mixed mortar is workable for about 90 minutes depending on temperature and humidity. Do not re-temper (add water to) mortar that has started to set — it weakens the final strength.

Tooling the Joints

After the mortar firms up (30-60 minutes depending on conditions — it should resist a light thumb press without smearing), tool the joints to compress the surface and match the existing joint profile.

Common joint profiles: concave (most common and most weather-resistant — pressed with a round jointing tool), flat/flush (scraped level with the brick face), and raked (recessed with a flat surface — looks sharp but holds water and is less durable).

Tool horizontal joints first, then vertical joints. Use a jointer that matches the joint width. A consistent tooling depth and pressure produces clean, professional-looking joints.

Brush off excess mortar crumbs after tooling with a stiff bristle brush. Do this after the mortar is firm enough not to smear — typically an hour after tooling.

Curing

New mortar needs to cure slowly to reach full strength. Mist the repaired area lightly 2-3 times per day for the first 3 days. Cover with damp burlap or plastic if the weather is hot, dry, or windy.

Do not repoint in direct hot sun, freezing temperatures, or heavy rain. Ideal conditions: overcast, 50-80°F, moderate humidity. Temperature extremes during the first 72 hours weaken the mortar bond permanently.

Lime-based mortars take longer to cure than Portland cement mortars — up to several weeks to reach full hardness. Be patient and keep them damp.

Tools for Repointing

Grout rake or cold chisel and hand sledge for mortar removal. Pointing trowel (narrow, flat blade). Hawk for holding mixed mortar. Jointing tools matched to your joint profile and width. Stiff bristle brush for cleanup. Spray bottle or garden sprayer for misting.

For large projects: a mortar mixer saves arm fatigue. For precise removal: an angle grinder with a 4-inch diamond tuckpointing blade, plus safety glasses and a dust mask rated for silica dust.

Frequently Asked Questions