Tuckpointing and masonry.

Why River Forest brick is different

Most of the brick between Thatcher and Harlem was laid between 1900 and 1940 with mortar made of lime and sand. Portland cement existed, but in small proportions or not at all. That mortar was deliberately softer than the brick. When the wall moved with the seasons, the mortar gave and the brick did not.

The brick itself is often Chicago common on the sides and back, a soft, porous brick fired unevenly, and a harder face brick on the front. Both are softer than modern brick. Both were made to work with soft mortar.

Modern masons carry Type N or Type S mortar, which is mostly Portland cement. It is stronger than the old brick. Pack it into a 1925 wall and the next hundred freeze-thaw cycles have to go somewhere. They go into the brick face, which pops off. That is spalling, and once you see it on a Lathrop Avenue Tudor, you know the tuckpointing was done in the 1990s with the wrong mix.

What tuckpointing actually is

Mortar joints weather. The surface erodes, water gets in, and eventually the joint is recessed or crumbling. Tuckpointing, called repointing in most of the country, means cutting the failed mortar out to a set depth, cleaning the joint, and packing new mortar in, in layers, then tooling it to match the original profile.

It is not a coating and it is not a skim. A crew that smears new mortar over old joints without grinding is doing a job that fails in three winters. The grind is the work.

Full tuckpointing means every joint on an elevation. Spot tuckpointing means the failed joints only. Both are legitimate; the estimate should say which.

Lime versus Portland, in plain terms

Mortar is sand plus a binder. The binder is where the argument lives.

Lime mortar, or a lime-rich mix such as Type O or a restoration blend, cures slowly, stays slightly soft, and lets water vapor pass through it. It is what your house was built with. It sacrifices itself so the brick does not.

Portland-based mortar, Type N or S, cures hard and fast, is nearly waterproof, and is stronger than old brick. On a 1990s house it is correct. On a 1925 house it traps moisture in the brick and concentrates stress at the brick face.

The rule masons who work on old houses use: the mortar must be softer than the brick. For pre-war River Forest brick, that means a lime-rich mix, often Type O or a specified lime-Portland ratio, and never straight Type S.

A contractor who says "we use the same mortar on everything" is telling you they do not do old houses. It is the most useful sentence you will hear during the estimate.

Reading the estimate, row by row

Line these rows up across every estimate you collect. Where two of them differ, that is where the price difference usually lives.

Areas and square footage. Which elevations, and how much. "Front" means different things on a corner lot.

Mortar type and depth of grind. The type by name, the grind depth in fractions of an inch, and whether the color will be matched to a test patch.

Brick replacement. How many, from where, and matched how. Salvage yards carry Chicago common; face brick is harder to match.

Lintels and sills. The steel over each window and the stone under it. Covered below.

Cleaning and sealing. Method and pressure. Sealer is usually a red flag, not a feature, on old brick.

Grind depth, and why a quarter inch is not enough

New mortar needs something to hold onto. The standard is to grind to at least twice the joint width, typically three quarters of an inch on a three-eighths joint, and to a square back so the new mortar keys in. A quarter-inch skim has no purchase and pops out in a few winters.

Grinding is also where brick gets damaged. A crew in a hurry with a wide blade widens every joint and chips every arris. Ask what blade width they use and ask to see a section they did last year.

Mortar goes in in lifts, each packed and allowed to set before the next, then tooled to match the original joint profile. Concave, flush, raked, grapevine: the profile changes how the wall looks from the street, and the original is usually still visible somewhere under a porch roof.

Matching brick and color

New mortar the wrong color is the most visible mistake in masonry, and it is visible from the Metra platform. Color comes from the sand as much as the binder, and matching means sampling the original, sourcing a similar sand, and doing a test patch that cures for a week before anyone judges it. Wet mortar is always darker.

Brick matching is harder. Common brick can be had from salvage yards around Chicago. Face brick from a particular 1920s plant often cannot, so a good mason will pull brick from an inconspicuous spot on your own house to fill a visible one, and use the closest match where it will not show.

Lintels, sills and the structural line

Above every window in a brick wall sits a steel angle, the lintel, carrying the brick over the opening. After ninety years it rusts, and rusting steel expands, which cracks the mortar above the window in a stair-step pattern and eventually lifts the brick. That is rust jacking, and it is the most common structural item on a River Forest masonry estimate.

The fix ranges from scraping and priming the exposed face, to cutting out the brick above and replacing the lintel. The estimate should say which. Under each window, the stone sill cracks and tips, letting water into the wall below; sills get reset or replaced.

Bulging sections, wide vertical cracks, and cracks that keep growing are not tuckpointing. They are structural, and they call for a mason experienced in rebuilds or, for anything large, an engineer. Chimneys have their own page, because they fail in their own ways.

Cleaning, sealing and what not to do

Old brick is cleaned with low pressure and, where needed, a masonry-specific cleaner. High-pressure washing drives water into the wall and erodes soft brick faces. Sandblasting is never appropriate on historic brick and is prohibited in most preservation guidelines.

Sealers are the tempting mistake. A clear sealer on old brick traps moisture that used to breathe out through the wall, and the freeze-thaw damage moves inside the brick. Most masons who work on pre-war houses will decline to seal them. If yours wants to, ask why.

What drives the price

Square footage and access. A full-house tuckpointing on three stories with pipe scaffold is a five-figure job because of the time and the scaffold; the mortar is a rounding error. Lime-rich mortar costs more than Type N and takes longer to work, and that shows up, but it is hundreds on a job of thousands.

Lintel work and brick replacement are the swing items. Two lintels scraped and primed is a few hundred dollars. Two lintels cut out and replaced with the brick above rebuilt is several thousand.

Red flags

• "Same mortar for everything," or no mortar type on the page.
• No grind depth stated.
• A sealer included as a feature.
• Power washing at pressure, or any mention of sandblasting.
• Lintels not mentioned on a house with stair-step cracks over the windows.
• No permit line. Tuckpointing requires one here.

Questions to ask

• What mortar type will you use on my house, and why?
• How deep do you grind, and with what blade width?
• Will you do a test patch and let it cure before we approve the color?
• Which lintels and sills are included, and what is the fix for each?
• Where does replacement brick come from?
• How do you clean the wall when you are done?
• Can I see an elevation you did five years ago?

The short list

Lime-rich mortar named on the page. Grind depth in inches. Test patch before the elevation. Lintels and sills itemized. No sealer. Permit included. Six things, and you can tell a mason who works on old houses from one who does not before the ladder comes off the truck.

Permits, programs and the Village