How it works

How Tuckpointing Works, Step by Step

Good joint work is mostly removal. Here is what happens between the grinder and the finished joint, and why a skim of fresh mortar over failed joints never lasts.

Two words for nearly the same thing

Strictly speaking, repointing means removing deteriorated mortar and replacing it. Tuckpointing originally described a decorative technique, a contrasting fine line tucked into a wider joint to fake the look of very fine brickwork. In practice homeowners and contractors here both use tuckpointing to mean joint replacement, and everyone knows what is meant.

What matters is not the word. It is whether the failed mortar comes out or merely gets covered. Those two things get sold under the same name, and the price difference tells you which one you are being offered.

It starts as a removal job, not a filling job

Roughly three quarters of the labor in joint work happens before any new mortar exists. The old mortar has to come out, cleanly, to a consistent depth, without chewing the edges of the brick.

The tool depends on the wall. On modern brick with tight, hard joints, a small angle grinder with a diamond blade cuts the horizontal beds fast, followed by hand chisels on the vertical head joints where a spinning blade cannot go without nicking brick. On soft older brick a grinder is often the wrong choice entirely and the work goes back to hand chisels and patience. The tool decision is made by the wall, not by the schedule.

• Beds cut first, head joints cleaned by hand where the blade cannot follow
• Loose material raked out and the joint blown or brushed clean of dust
• Cracked or spalled brick pulled and replaced while the joint is open
• The wall dampened before new mortar goes in, so the brick does not drink the water out of it

Depth is the whole job

The rule of thumb the trade works to, and the one in the Brick Industry Association's technical literature, is that a joint gets cut back to roughly two and a half times its width, or until sound mortar is reached, whichever is deeper. On a standard three eighths inch joint that is close to an inch of removal.

The reason is mechanical. New mortar packed into a shallow scratch has almost no surface area to grip and no depth to resist water freezing behind it. That matters here, because a Rutherford County winter crosses the freeze point and comes back again and again rather than settling below it, and every crossing works at shallow work. Cut to proper depth, the new mortar becomes a wedge locked between two brick, and it behaves like part of the wall.

This is why a quote that promises a whole house in a day should be read carefully. Correct removal is slow, dusty and loud. If the neighbors in a Smyrna or La Vergne subdivision never hear a thing, very little came out.

Matching mortar, which is not the same as strong mortar

The instinct is to use the strongest mix available. That instinct is wrong, and on older walls it is destructive. Mortar is supposed to be the softest component in the assembly so that movement, moisture and salts are relieved through the joint rather than through the face of the brick. A joint that is harder than the brick around it turns the brick into the sacrificial part. On the soft nineteenth century brick around the Murfreesboro square that trade is visible, with hard modern repairs standing proud of brick faces crumbling behind them.

Matching runs across four properties, and color is only one of them. Compressive strength has to sit at or below the brick. Vapor permeability has to let the wall dry. Texture and aggregate size have to read the same from six feet away. Color comes last, and it comes mostly from the sand rather than pigment.

Good practice is to mix small test batches, trowel them onto a hidden section, and let them cure for several days before choosing. Wet mortar is always darker than cured mortar. Choosing a color off a wet sample is how walls end up with a stripe.

Packing the joint in lifts

New mortar does not get dumped into a deep joint in one pass. It goes in as thin layers, each pressed hard into the back of the joint with a pointing tool, each allowed to stiffen before the next. On a joint cut back an inch that is commonly two or three lifts.

The reason is shrinkage and voids. A single thick placement traps air pockets, shrinks unevenly as it cures, and pulls away from the brick at the edges. Those hairline gaps at the brick face are exactly where water enters, and water in a joint in January is how the whole problem started.

Tooling, and why the profile is not just a look

When the mortar has stiffened to thumbprint hard, the joint gets tooled. A concave jointer, a rounded bar or a flat slicker is run along it under pressure. That compaction densifies the surface and closes the pores, which is the cheapest thing anybody can do to make a joint shed water.

The profile also has to match what is already on the wall. A concave joint on a wall of weathered struck joints looks wrong from across the street. On historic buildings the original profile is part of the character of the wall, and changing it changes the building.

After tooling the wall gets brushed at the right moment, too early and the joint smears, too late and dried mortar has to be scraped off the brick face. Then it is kept damp for a few days so the mortar cures rather than dries out. That misting step gets skipped constantly and it costs joints years of life.

Why a skim coat over failed joints always fails

There is a cheap version of this work. A crew arrives, mixes a soupy batch, and slathers a thin veneer of fresh mortar over the existing joints without removing anything. It looks transformed on the day. The photographs are excellent.

It fails for three reasons at once. There is nothing for the new material to key into, so it is bonded to a crumbling surface. It is only a few millimeters thick, so a single freeze cycle behind it lifts it away. And it seals a joint that was already letting water in, so the water that gets past it, and it will, now has nowhere to leave. Walls treated this way are usually worse off two winters later than if nobody had touched them.

The way to tell before you sign is one question. What tool is cutting the joints out, and how deep is the cut? A mason who does this work properly has an immediate answer and will show you a test section on your own wall.

Related services: Brick Masonry · Stone Masonry