Walk any block in Skokie, Niles, Morton Grove, Lincolnwood, or the older neighborhoods of Evanston and you will see them: the solid, one-and-a-half story brick homes built between roughly 1910 and the late 1930s that define Chicago’s residential streetscapes. The Chicago bungalow. There are an estimated 80,000 of them across the metropolitan area. They were built to last, and most of them have. But they were built with materials that require a specific approach to repair, and that approach is widely misunderstood.
The most common masonry mistake on Chicago bungalows is also the most preventable: repointing with the wrong mortar. This guide explains the physics of why it matters, how to identify what you are dealing with, and what correct repair looks like.
The Original Material System
Soft Common Brick
The brick used on Chicago bungalows was not the hard, dense brick produced by modern manufacturing. It was common brick: a softer, more absorbent material fired at lower temperatures. This brick was produced locally and regionally, often with significant variation in density and composition between batches. The result was a material that is more porous than modern brick, has lower compressive strength, and is more susceptible to surface damage from hard abrasives or incompatible mortars.
Soft common brick is not a design flaw. It was the standard material of its era, and when used with the appropriate mortar system, it creates a wall assembly that has now stood for over 100 years in one of the most punishing climates in the country.
Lime-Based Mortar
The mortar used with soft common brick was lime-based: a mixture of lime putty or hydraulic lime, sand, and sometimes a small amount of Portland cement. This mortar has a compressive strength well below that of modern Portland cement mortar. That softness is intentional and critical.
Masonry walls move. They expand and contract with temperature changes, they settle with the soil beneath them, and they absorb and release moisture seasonally. Every one of these movements creates stress in the wall. In the original lime mortar system, those stresses are accommodated by the mortar joint. The mortar is the sacrificial element in the system. It cracks and flexes so the brick does not have to. Over decades, lime mortar slowly erodes and requires periodic repointing. That is the expected maintenance cycle.
The key relationship to understand is this: in any masonry system, movement stress travels through the path of least resistance. The mortar joint is designed to be that path.
The Portland Cement Problem
What Happens When Hard Mortar Meets Soft Brick
Modern Portland cement mortar has a compressive strength of 2,500 to 3,000 psi or higher, depending on the mix. The soft common brick on a Chicago bungalow may have a compressive strength of 1,500 to 2,500 psi. When hard mortar is applied to soft brick, the material relationship inverts. The mortar is now harder than the brick. When the wall moves, stress can no longer travel through the mortar joint. Instead, it transfers into the brick itself.
The result is spalling: the fired face of the brick separates and breaks away. Early spalling looks like fine surface crazing or thin flaking at the mortar joint edges. As the process continues, concave depressions form where the brick face has fractured along the boundary between the outer fired layer and the softer interior material. Eventually, the brick loses structural integrity and requires replacement.
Spalling caused by incompatible mortar is irreversible on the damaged brick. The brick face cannot be restored once it has spalled. The only options are living with the damaged appearance or replacing the affected brick, which is expensive and never perfectly matches the original.
For a detailed explanation of spalling causes and identification, see What Causes Brick Spalling and How to Prevent It.
Why This Problem Is Common
Portland cement mortar became the default repointing material in the mid-20th century because it is strong, widely available, and relatively easy to work with. Many contractors who are competent at general masonry work are not specifically trained in historic masonry compatibility. A contractor who repoints modern commercial brick all day with Type S mortar and then repoints a 1920s bungalow with the same mix is not being negligent in any obvious way. They are applying a material that works well on most of the jobs they do. The compatibility issue is not visible on the day of installation. It shows up three to five years later as progressive spalling that accelerates with each freeze-thaw season.
If your bungalow has had tuckpointing done in the past 20 years, and you are now seeing spalling concentrated at mortar joint edges, there is a reasonable chance it was repointed with incompatible mortar. Spring is the season when this damage is most visible, as brick that absorbed water the previous winter shows new surface failure.
Identifying What You Are Working With
Reading the Existing Mortar
Before any repointing work, the existing mortar should be assessed. Lime mortar can be identified by several characteristics:
- Color: Lime mortar is typically buff, cream, or light gray. It often varies in color across the wall as original batches mixed differently.
- Texture: Lime mortar has a slightly granular texture when examined closely. It is not smooth like a Portland cement mix.
- Hardness: A light scratch with a nail or key on a clean joint face will crumble lime mortar. Portland cement mortar resists scratching much more firmly.
- Depth of weathering: Original lime mortar on an unrepaired wall will be recessed naturally, sometimes 1/4 to 3/8 inch, from decades of slow weathering.
A masonry professional performing a proper assessment will compare mortar hardness directly to brick hardness, examine previous repairs for evidence of incompatible material, and check the extent of any existing spalling before recommending a repair approach.
Reading the Brick
Soft common brick has visual characteristics that distinguish it from modern brick:
- Surface variation: The faces are not uniformly smooth. There is often subtle texture, slight warping, and color variation within a single brick from the firing process.
- Color depth: Colors tend toward buff, cream, rose, and red-brown tones with more variation than modern extruded brick.
- Dimensional variation: Pre-war brick was not manufactured to the same tight tolerances as modern brick. Brick thickness, width, and length vary across a single wall.
If you are unsure what you have, a professional assessment is the appropriate starting point before any repair work begins. Attempting to repoint without knowing the mortar specification risks permanent damage to the brick.
The Correct Repair Approach
Mortar Specification
Lime-based repointing of original bungalow masonry uses a mortar formulated to be softer than the brick it contacts. Common specifications for this work include:
- Type N mortar: A moderate-strength blend of Portland cement, lime, and sand. Compressive strength around 750 psi. Appropriate for above-grade, non-load-bearing applications where some compatibility with soft brick is needed.
- Type O mortar: A lower-strength blend with a higher lime-to-cement ratio. Compressive strength around 350 psi. Better compatibility with very soft brick.
- Lime putty mortar: Pure lime putty and sand with no Portland cement. The most historically compatible option, with very low compressive strength and high flexibility. Requires longer curing time.
The right specification depends on the specific brick hardness, the location on the building (above-grade vs. below-grade, exposed vs. protected elevations), and the condition of the existing wall. A mason experienced in historic masonry will match the new mortar to the existing system rather than defaulting to a standard modern mix.
For more on why mortar color and composition matching matters beyond just aesthetics, see The Importance of Mortar Color Matching in Tuckpointing.
Joint Preparation
Correct preparation of the joint before repointing is as important as the mortar specification. Existing mortar must be removed to a minimum depth of 3/4 inch to 1 inch to ensure the new mortar has enough depth to bond. Removal must be done carefully to avoid damaging the brick arrises (the sharp edges where the brick face meets the joint).
On soft brick, angle grinders are a high-risk tool. The abrasive disc can easily slip and abrade the brick face, permanently damaging it. Hand chisels and oscillating tools are preferred for detailed work. For longer runs of straight joint, a tuckpointing grinder with a vacuum attachment and careful technique can be used by an experienced mason, but requires more care on soft brick than on hard modern brick.
The goal of joint preparation is clean mortar removal to depth without touching the brick. Any tool contact with the brick face on soft common brick leaves a mark that does not go away.
Curing and Timing
Lime mortar cures differently from Portland cement mortar. It does not set by a chemical hydration reaction in the same way. Lime mortar cures through carbonation, a slower process that requires moisture management. New lime mortar joints should be kept slightly damp during the first week of cure to prevent premature drying. In hot, dry, or windy conditions, misting the joints is appropriate.
For timing purposes, spring and early summer are the best seasons for mortar work in Illinois. Temperatures consistently above 40 degrees F support proper cure. Avoid repointing in conditions below 40 degrees without supplemental heat because lime mortar is particularly sensitive to freezing during cure.
What Bungalow Owners in Skokie, Niles, and the North Shore Should Know
The bungalow belt extends through communities across Chicago’s north and northwest suburbs. Skokie, Niles, Morton Grove, and Lincolnwood have significant concentrations of 1920s and 1930s brick bungalows that are now reaching the age where original mortar requires attention. Evanston and Des Plaines have their own substantial bungalow stock with similar maintenance needs.
For most of these homes, the masonry has either never been repointed or has received one or more repairs at some point in the past 50 years. The state of those past repairs determines the urgency and approach of any work today:
- Original lime mortar in good condition: Monitor annually. Repointing becomes necessary when joints are recessed more than 1/4 inch, crumbling, or missing.
- Previous Portland cement repointing with no visible spalling: Assess carefully. The repointing may have been done with a moderate mix that has not caused damage. Or damage may be developing. A professional assessment distinguishes between these.
- Previous Portland cement repointing with spalling at joint edges: This is the most common problem scenario. The incompatible mortar needs to be removed, damaged brick assessed, and replacement done with a compatible specification.
- Previous lime mortar repointing: This is the best scenario. Assess joint condition and repoint with matching material as needed.
A proper spring inspection will identify which category your home falls into. See our spring masonry inspection checklist for a guide to what to look for.
Common Bungalow Masonry Problems Beyond Mortar
Efflorescence
White crystalline deposits on bungalow brick are a common spring appearance. They indicate water is cycling through the masonry. On a bungalow, the most common sources are failing mortar joints on the north-facing elevation (the most exposed side), window sill drainage concentrating water at the brick below, and any point where the original lime mortar has eroded to the point of allowing direct water infiltration. For a detailed explanation of what efflorescence tells you, see Efflorescence and White Staining in Spring.
Lintel Rust
Steel lintels over window and door openings on bungalows are approaching 100 years old. Corrosion is common. When steel corrodes, it expands, cracking the mortar above the lintel and eventually cracking or displacing the brick above it. Look for horizontal cracking in the mortar joint directly above window openings and rust staining on brick below.
Foundation Transition
Many bungalows have a transition between the above-grade common brick and the below-grade foundation, which may be concrete block, poured concrete, or a different masonry material. This transition point is a common water entry location. Check the parging coat on the foundation exterior for cracks or delamination, and look for efflorescence streaking below the water table line.
Scheduling Repairs
Tuckpointing and brick repair on a Chicago bungalow should be treated as planned maintenance, not emergency response. The repair is straightforward when caught at the mortar joint level. It becomes significantly more complicated and expensive when brick replacement is required or when water has entered the structure and caused interior damage.
For homes in the bungalow belt communities of the North Shore and northwest suburbs, scheduling a professional assessment in spring, while the seasonal damage from winter freeze-thaw cycles is fully visible, is the right approach. Spring and early summer also provide the optimal temperature window for mortar work.
If you are seeing crumbling mortar, spalling brick faces, or efflorescence on your Chicago bungalow, call (847) 713-1648 or contact us online to schedule a free masonry assessment. We work with historic restoration specifications and carry lime-compatible mortar specifications for the bungalow-era housing stock across the North Shore and northwest suburbs.