Chicago Common Brick: Why the City's Oldest Brick Crumbles and How It's Repaired

Chicago Common Brick: The City's Other Brick

Chicago common brick is the soft, porous, salmon-and-buff colored brick made from local clay that sits behind and beside the face brick of nearly every pre-1940 Chicago building. It formed the inner wythes of solid masonry walls, and it faces the side walls, rear elevations, alley walls, coach houses and garages that nobody was expected to look at. It was never designed for weather exposure — and where it is exposed, it deteriorates far faster than the face brick on the front of the same building. Emerald Masonry LLC restores this masonry across Chicago and the Chicagoland suburbs. Family-owned, licensed and insured, 40+ years of experience, free on-site estimates. Call (708) 288-1696.

If you own a Chicago brick bungalow, two-flat, worker cottage, greystone or courtyard building, you almost certainly own a large quantity of this brick, whether you knew it or not. And if the side or rear wall of your building is crumbling while the front looks fine, this article explains exactly why.

Where It Came From

Chicago sat on a very large deposit of clay. From the 1870s through the 1930s, brickyards along the Calumet and elsewhere in the region turned that clay into staggering quantities of cheap utility brick. After the Great Chicago Fire drove the city toward masonry construction, demand for brick was effectively unlimited, and common brick was the material that met it.

Common brick was fired at lower temperatures than face brick, produced with less consistency, and priced accordingly. It came out soft, sandy, and in a color range from pale salmon and buff to pinkish orange, with a good deal of variation between and within batches. Builders used it wherever appearance and exposure did not matter:

• The inner wythes of solid masonry walls, hidden behind face brick
• Side walls on narrow city lots, often within a few feet of the neighboring building
• Rear elevations and alley-facing walls
• Coach houses, garages and outbuildings
• Party walls, foundations above grade, and chimney interiors

The front of the building got hard, dense, uniform face brick — often shipped in from other regions and selected for color and durability. This is why a Chicago bungalow can present a crisp, sound front elevation and a badly deteriorating side wall in the same year of the same weather.

Common Brick vs. Face Brick

| | Chicago common brick | Face brick | |---|---|---| | Firing | Lower temperature, less vitrified | Higher temperature, dense fired skin | | Absorption | High — drinks water readily | Low — sheds water | | Color | Salmon, buff, pink, highly variable | Uniform, selected for appearance | | Intended use | Interior wythes, hidden elevations | Exposed, visible facades | | Weather tolerance | Poor when directly exposed | Designed for exposure | | Repair mortar | Soft, lime-rich, matched | Type N or S per era | | Failure mode | Rapid surface loss, crumbling, spalling | Slower spalling, usually joint-driven |

Why Chicago Common Brick Crumbles

The mechanism is straightforward, and it is entirely about water.

Common brick is highly absorbent. Without a hard vitrified outer skin, it takes water in through the whole face rather than shedding it. A rain event that a face brick wall sheds in an hour will leave a common brick wall saturated for days.

Chicagoland freezes and thaws relentlessly. It is not the depth of cold that destroys masonry — it is the number of times the temperature crosses freezing with water present in the material. We get dozens of those crossings each winter, plus more in the shoulder seasons. Water inside the brick expands about nine percent when it freezes, and in a soft, saturated unit that expansion breaks the surface apart in layers.

The joints made it worse. Common brick was laid in soft lime mortar, which has now been in service for eighty to a hundred and fifty years. Once those joints recede and open, water enters faster and stays longer, and the deterioration compounds.

The exposure was never planned for. Countless common brick walls became exposed by accident — a neighboring building demolished, leaving a party wall standing in the weather; a rear addition removed; a coach house that always faced the alley. Brick chosen precisely because it would never see direct weather ended up doing exactly that for a century.

The result is the familiar Chicago sight: a wall where the brick faces have crumbled back a quarter inch or more, joints are washed out, surfaces are sandy to the touch, and the brick itself sheds material when rubbed.

The Signs, in Order of Severity

• Sandy residue on the ground or at the base of the wall, and brick that leaves grit on your hand.
• Receded, washed-out mortar joints you can rake with a screwdriver — the screwdriver test works the same here as anywhere.
• Efflorescence — white powdery bloom — showing water is moving through the wall.
• Surface crumbling and spalling of the brick faces themselves, often in patches following water paths.
• Deep pitting, where units have lost a substantial fraction of their depth.
• Step cracks running diagonally through joints.
• Loose brick that can be moved by hand.
• Bulging or bowing in the wall plane — a structural condition requiring immediate professional evaluation, not a maintenance item.

Water paths concentrate the damage: below a leaking gutter, under a failed sill, at grade where splash-back keeps masonry wet, and along the shaded north elevations that never fully dry.

How Chicago Common Brick Is Properly Repaired

This masonry is repairable — very repairable — but it punishes the wrong approach severely. Three things determine whether a repair protects the wall or destroys it.

1. The mortar must be softer than the brick

This is the entire ballgame. A masonry wall is designed so the mortar is the sacrificial element, absorbing movement and moisture stress so the brick does not have to. With common brick, which is already soft, the mortar must be softer still — a lime-rich or lime-modified mix matched to the original.

Repointing common brick with a hard Portland-heavy mortar inverts that relationship. The joints become the strongest part of the wall, and every freeze-thaw cycle drives the stress into the brick faces instead. The result shows up within three to eight winters as widespread spalling — a repair that actively destroys the building. Standard modern Type S mortar on Chicago common brick is a mistake we are called to undo regularly.

2. The joints must be prepared gently

Aggressive power grinding on a soft wall widens joints permanently, chews the edges of the brick, and can do more damage than the deteriorated mortar did. On common brick, joints are raked by hand or with carefully controlled tools, to a sound depth, without cutting into the units.

3. Replacement units must be salvaged and matched

New Chicago common brick is no longer manufactured. Replacement comes from salvage — reclaimed brick from demolished Chicago-area buildings — which is why restoration masons keep salvage sources. Salvaged common brick matches in size, in the soft salmon-buff color range, and critically in hardness and absorption, so the repair behaves like the wall around it.

The process, start to finish

1. Assessment — determine whether the wall is solid multi-wythe masonry or veneer, how deep the deterioration runs, whether the wall is plumb, and where water is entering.
2. Fix the water source first — gutters, downspouts, sills, coping, flashing, grade. Repairing masonry while leaving the water in place guarantees a repeat.
3. Gentle joint preparation — hand raking to sound depth.
4. Soft matched mortar — lime-based, color- and sand-matched, tooled to the original profile.
5. Unit replacement — cut out and replace deteriorated brick with salvaged matches.
6. Section rebuilding where required — for walls that have lost cohesion or gone out of plane, rebuilt with salvaged brick and proper detailing.
7. Breathable protection only — if the wall is sealed at all, with a vapor-permeable product. Never paint. Never a film-forming coating.

The Two Things That Destroy Common Brick Fastest

Sandblasting and high-pressure washing. Common brick has little protective skin to begin with; abrasive blasting and high pressure remove what there is and open the porous body directly to the weather. A blasted common brick wall can be visibly deteriorating within a couple of winters. This is irreversible.

Paint and film-forming sealers. Homeowners paint deteriorating common brick constantly, and it is an understandable impulse — it looks better immediately. But this brick must dry outward. Trapped moisture behind paint or a waterproof coating freezes inside the unit and spalls the face off from behind, and once brick is painted, removing the paint without further damaging the soft face is difficult and expensive. Painted brick traps moisture, and on common brick it accelerates exactly the failure it was meant to hide.

Where This Comes Up in Chicagoland

• Bungalow side walls. The classic case: a hard face brick front on a Chicago brick bungalow and common brick on the sides, deteriorating along the shaded north elevation.
• Two-flat and three-flat rear elevations. Rear walls, rear porches and alley-facing masonry, all common brick, all fully exposed.
• Greystones. Limestone front, common brick sides and rear — the same contrast in a more dramatic form. See historic masonry restoration.
• Coach houses and garages. Entirely common brick, minimally maintained, and typically the first structure on a property to need real work.
• Exposed party walls. A neighboring building comes down and a wall built to be hidden spends the next fifty years in the weather.
• Courtyard and vintage apartment buildings. Property managers and condo associations deal with this on light courts and rear elevations constantly.
• Suburban pre-war stock. The same brick appears in Berwyn, Cicero, Oak Park, Evergreen Park, Beverly, Mount Greenwood and the older parts of the near suburbs.

Maintenance That Keeps It Standing

• Keep water off it. Clean gutters, extended downspouts, grade sloping away, splash controlled. This matters more for common brick than for any other masonry on your property.
• Repoint on schedule with soft matched mortar, and spot-repoint early rather than waiting for a whole elevation.
• Repair sills, crowns, coping and flashing the moment they stop shedding water.
• Inspect annually, especially north and rear elevations and anything above an alley or walkway.
• Never blast it, never pressure wash it, never paint it.
• Use breathable products only if sealing after repointing.

Related Services

Work on this masonry usually involves brick repair, brick replacement, tuckpointing and repointing, historic masonry restoration, chimney repair and masonry sealing.

The Bottom Line

Chicago common brick is a hundred-year-old material doing a job it was never designed for, and the fact that so much of it is still standing is a testament to how it was laid. It is not fragile in the sense of being beyond saving — it is fragile in the sense that it demands the right materials and the right hands.

Soft mortar. Gentle preparation. Salvaged matches. Water managed. Do those four things and a crumbling common brick wall goes back to being a sound wall for another few generations. Do the opposite — hard mortar, a pressure washer, a coat of paint — and you can lose in a decade what survived a century.

Emerald Masonry LLC is a family-owned, licensed and insured masonry contractor serving Chicago and the Chicagoland suburbs with 40+ years of experience in tuckpointing, chimney repair, brick repair and replacement, lintel and parapet repair, foundation and limestone/sill repair, caulking, sealing, and commercial, residential and historic masonry restoration. We work on Chicago's oldest masonry the way it needs to be worked on.

Free on-site estimates. Call (708) 288-1696 or request an estimate.