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Brick Repair - Niles, IL

Brick Repair - 1938 Brick Two-Flat, Wrong Mortar Damage

September 7, 2025 | near Milwaukee Avenue

Before: Brick Repair - 1938 Brick Two-Flat, Wrong Mortar Damage Before
After: Brick Repair - 1938 Brick Two-Flat, Wrong Mortar Damage After
Location Niles, IL
Service Brick Repair
Scope 19 spalled bricks replaced, surrounding joints repointed with Type O
Mortar Type Type O lime-rich
Duration 3 days
Building 1938 brick two-flat

The Problem

The owner of a 1938 brick two-flat in Central Niles noticed crumbling brick faces along the second-floor front facade. Chunks of brick face were accumulating on the first-floor window ledge and the front stoop. Nineteen bricks on the second-floor front had lost significant face material, exposing the soft inner core to direct weather.

The cause was a previous tuckpointing job done roughly eight years earlier. The contractor had repointed the entire front facade with Type S mortar - a Portland-heavy mix designed for structural load-bearing applications. On this 1938 two-flat, the original mortar was lime-rich Type O. The switch to hard mortar trapped moisture inside the soft pre-war brick rather than allowing it to breathe through the joints. Freeze-thaw cycles over several winters did the rest, popping face sections off brick after brick.

Our Solution

We removed all nineteen damaged bricks carefully, cutting the mortar bed on each side with a hand chisel rather than an angle grinder to avoid damaging the soft adjacent brick. Each cavity was cleaned of loose mortar debris and dampened before setting replacement brick.

Replacement brick was sourced from a demolition salvage supplier who stocks 1930s-era common brick from Chicago-area teardowns. We tested three samples against the existing wall in natural light before selecting the closest color match - a warm red with tan aggregate that reads within a shade of the original.

All replacement bricks were set in Type O lime-rich mortar, the correct specification for this era and brick hardness. We also removed the incorrect Type S mortar from the twenty-six joints immediately surrounding each replaced brick and repointed with Type O. Leaving hard mortar adjacent to soft brick would continue the moisture trap pattern on neighboring bricks.

The Result

All nineteen bricks were replaced and the surrounding joints repointed correctly. The mortar change stops the spalling mechanism. Moisture that enters the wall assembly can now migrate out through the joints rather than through the brick face.

The salvage brick has aged naturally and blends with the existing facade. The building’s two units are protected from water infiltration that was working its way toward the wall cavity behind the second-floor front bedroom.

Related: Brick Repair Services | Niles Service Area

Questions About This Project

Why did the previous mortar cause brick spalling on a pre-war two-flat?

Pre-war brick from the 1930s and earlier is soft common brick, typically with a compressive strength around 1,200 PSI or lower. Type S and Type N Portland-heavy mortars can exceed 1,800 PSI compressive strength. When mortar is harder than the brick, moisture that enters the wall cannot migrate out through the joints. It migrates through the brick face instead, and freeze-thaw cycling pops the face off. The mortar should always be softer than the brick.

What is Type O mortar and when is it the right choice?

Type O is a low-strength mortar with roughly 350 PSI compressive strength, using a lime-heavy mix with minimal Portland cement. It is the correct specification for soft pre-war brick, interior non-load-bearing walls, and any masonry where flexibility and vapor permeability matter more than compressive strength. On a 1938 two-flat with original common brick, Type O or Type N lime-rich is the appropriate choice.

How do you match replacement brick color on a building this old?

We source period salvage brick from demolition suppliers who catalog brick by era, region, and manufacturer. For 1930s Chicago-area construction, the original brick is typically a warm red-orange common brick made by regional producers. We test samples against the existing wall in morning and afternoon light before purchasing. An exact match is rarely possible, but salvage brick from the same era and region gets close enough that the repair blends within a few years of weathering.

Project Location

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