Walk the exterior of any commercial building in the Chicago suburbs that's more than 20 years old and you'll likely find at least a few brick faces that have popped or cracked off, leaving rough craters in the wall. In the trade this is called spalling, and in Illinois it's almost always caused by the same predictable sequence of events.

Understanding what causes spalling tells you more than just what went wrong. It tells you where to look for damage before it's visible from the street, and it tells you whether a simple brick replacement will hold or whether the same damage will recur.

The Mechanism: Freeze-Thaw Cycling

Brick is porous. Water enters brick faces and mortar joints, penetrates into the material, and sits there. In a climate like Chicagoland's — with 30–40 freeze-thaw cycles per winter, where temperatures swing above and below freezing dozens of times between November and March — that trapped water freezes.

When water freezes, it expands approximately 9% in volume. In a confined space — inside the pore structure of a brick — that expansion creates pressure. A single freeze-thaw cycle doesn't destroy a brick. But after years of repeated cycling, the cumulative expansion fractures the material from the inside. Eventually the outer face of the brick separates from the body: that's spalling.

The key variable is how much water is in the brick. Dry brick doesn't spall regardless of temperature. Saturated brick that freezes repeatedly will always eventually spall.

What Lets Water In

Spalling doesn't happen in isolation. It follows from one or more water entry points that have been active for years before the visible damage appears. The most common sources:

Failed Mortar Joints

This is the leading cause of brick saturation in commercial buildings. Mortar joints fail before brick does — mortar is intentionally softer and more porous than brick, so it deteriorates first. Once joints crack open or recess more than ½ inch, water runs directly into the wall with every rain event. The brick on either side of failing joints absorbs that water. After several winters of freeze-thaw cycling, spalling begins adjacent to the worst joints.

This is why tuckpointing — replacing failed mortar joints — is the most important preventive maintenance for brick buildings. It stops the water entry that eventually causes brick damage.

Improper Mortar from a Previous Repair

This is a less obvious but extremely common cause of spalling, especially in Chicago's older building stock. Portland cement mortar that's too hard — Type S or M used on pre-1960 soft brick — doesn't flex with thermal movement. Instead of absorbing movement in the joint, the stress goes into the adjacent brick face. The brick cracks and spalls along the joint line within a few years of the repair.

If you're seeing spalling that closely follows repointed joint lines — especially if a previous contractor did "repairs" — this is likely the cause. The fix isn't more repointing with the wrong mortar. It's removing the incompatible mortar and replacing it with a softer, lime-based mix that matches the original construction.

Compromised Coping and Parapet Caps

On flat-roof commercial buildings, the parapet top is the most direct water entry point. Cracked or shifted coping units let water pour into the top of the parapet wall with every rain event. Parapet brick saturates from above and spalling works its way down from the parapet into the upper section of the wall.

This pattern — spalling concentrated in the top 4–8 feet of an exterior wall, below the parapet — is diagnostic. The coping needs to be addressed first; replacing the spalled brick without fixing the coping means replacing the same brick again in 5–10 years.

Failed Window Sills and Lintels

Cracked or separated masonry sills allow water to run back toward the wall instead of draining away. Corroding steel lintels expand, crack the surrounding brick, and create pathways for water entry. Both conditions cause localized brick saturation and eventual spalling concentrated around window and door openings.

What Spalling Looks Like in Practice

Early-stage spalling: small chips on the brick face, surface crazing (fine crack networks), areas where the face looks slightly separated. This stage is easy to miss from the street.

Active spalling: brick faces visibly popped off, rough clay or aggregate exposed, sections that crumble when touched. The brick is structurally compromised.

Advanced spalling: multiple courses of brick with severe face loss, structural wall integrity affected, potential for dislodged material to fall. At this stage, adjacent areas need assessment for stability.

On commercial buildings, spalling at the parapet level presents a falling hazard and should be inspected and addressed with some urgency.

The Saturated Brick Problem

Here's what complicates brick repair: a brick that looks intact from the outside may be fully saturated inside. When you replace visible spalled units without addressing the water source, the adjacent "intact" brick is still wet — and it will spall in the next few winters.

The correct approach is to address the water entry point first, then replace the spalled units. In some cases, the surrounding brick should also be tested for saturation before completing the repair.

A simple field test: tap brick faces with a metal object. Solid brick returns a sharp ring. Saturated or delaminating brick returns a dull thud. Experienced contractors use this to map out the extent of damage beyond what's visually obvious.

Repair Options

Individual unit replacement is appropriate when spalling is limited to a small number of units, the water source has been addressed, and surrounding brick is sound. Spalled units are cut out, replacement brick is sourced to match, and new units are set in compatible mortar.

Section repair is used when a concentrated area has multiple spalled units in adjacent courses. The section is cut out to sound brick on all sides, the underlying cause is addressed, and new brick is laid to match the original coursing and bond pattern.

Full wall rebuilding is rare but necessary when spalling has progressed to the point where multiple courses are structurally compromised across a wide area. This involves removing all affected courses, installing new lintels if needed, and relaying brick from the substrate up.

In all cases, the repair mortar must be specified to match the existing masonry. Using the wrong mortar type on a repair causes the spalling pattern to repeat.

Prevention

The best prevention for brick spalling in Illinois is a consistent masonry maintenance program:

Repoint joints before they fail to the point of water entry (typically every 20–30 years for commercial buildings)
Maintain coping and parapet caps in good condition
Replace failed caulk at window perimeters and penetrations on a 7–10 year cycle
Inspect parapet condition every 5–7 years using a lift — ground-level inspection misses parapet deterioration

Most commercial brick buildings in the Chicago suburbs that we see with significant spalling damage have one thing in common: deferred mortar maintenance. The damage was preventable.

Emerald Masonry LLC handles brick repair, spalling assessment, and full masonry restoration for commercial properties throughout Chicagoland. Call (309) 323-9959 or request a free estimate.

Also see: Brick Repair services | Tuckpointing | Masonry Restoration

What Causes Brick to Spall in Illinois — And How to Stop It