Replacing Windows in a Brick House: The Masonry Work That Should Happen First

The Short Answer

Before new windows go into a brick house, four things should be checked and corrected: the steel lintel above the opening, the sill below it, the mortar joints around it, and the perimeter sealant joint. Window installers install windows — they do not repair masonry, and they are not looking at your lintel. A new window set into an opening with corroding steel above it or a cracked, back-sloped sill beneath it will leak, and the fix afterward costs more because it means working around brand-new units.

Emerald Masonry LLC inspects and repairs window openings across Chicago and the Chicagoland suburbs — family-owned, licensed and insured, 40+ years of experience. Free on-site estimates: (708) 288-1696.

Why This Goes Wrong So Often

Window replacement is the single most common exterior project on an older Chicagoland home. It is well marketed, it has an obvious payback in comfort and energy, and it is usually the first big-ticket item an owner takes on.

The trouble is that a window opening in a masonry wall is a masonry assembly, and the window is only one component of it.

The opening has to be spanned by something — a steel lintel, a stone lintel, or a brick arch. It has to be closed at the bottom by a sill that sheds water away from the wall. It has to be sealed at the perimeter with a joint that can move. And it sits in a field of mortar joints that are the wall's first defense.

A window installer's scope starts at the window frame and stops there. So a homeowner can spend a considerable sum, get excellent new units correctly installed, and still have water coming in around them — because the leak was never in the window.

The Four Things to Check First

1. The lintel above the opening

Brick cannot span an opening by itself. In most Chicagoland masonry, a steel angle lintel carries the brick above each window, bearing on the masonry at both ends.

Steel is entirely reliable until it gets wet. Then it corrodes — and rust occupies several times the volume of the steel it replaced. Inside a rigid wall there is nowhere for that expansion to go, so it pushes up and out, lifting the courses above the opening. That is rust jacking.

Look for:

• Orange or rust-colored staining running down from the top corners of the window
• A horizontal crack in the mortar joint directly above the opening
• Brick above the opening that looks lifted, stepped or out of line
• Visible rusted, flaking or scaling steel at the head of the opening
• A window that has started sticking as the opening distorts

The single most important detail, and the one almost never discussed: a replacement lintel needs through-wall flashing above it. The old steel rusted because water was reaching it. Installing new steel without changing anything about the water simply restarts the clock. Flashing above the new lintel, with end dams, catches water inside the wall and directs it back out through weeps.

2. The sill below the opening

The sill's entire job is to throw water clear of the wall beneath it. It does that with slope and, ideally, with a drip edge — a groove or projection on the underside that stops water tracking back against the brick.

Sills fail in specific ways:

| Sill condition | What it causes | |---|---| | Cracked through | Water enters the wall directly beneath the window | | Spalled or delaminating stone | Loss of slope; surface holds water | | Back-sloped from settlement | Water runs toward the wall instead of away | | Missing or clogged drip edge | Water tracks under the sill onto the brick below | | Open joint at sill ends | Water enters at the corners, the most common leak point |

Limestone sills are extremely common on Chicago bungalows, greystones and two-flats, and they are layered stone — which means they can delaminate along their bedding planes after decades of freeze-thaw. Full replacement is not always necessary; a matched dutchman repair, where the failed portion is cut out and a matched stone insert is set in, is often the right answer. We cover this in why limestone sills and lintels fail.

3. The mortar joints around the opening

Openings are stress concentrators. Wall movement, thermal cycling and settlement all find the corners of windows and doors first, which is why brick cracks around windows and doors so predictably.

If joints around the opening are recessed, crumbling, or you can rake them with a fingernail, water is already getting into the wall regardless of what window you install. Repointing the perimeter — and typically the whole elevation, since the rest of the wall is the same age — belongs in the same project.

4. The perimeter sealant joint

The gap between a window frame and the masonry is a movement joint, not a crack to be filled. Masonry and window frames expand and contract at different rates, so the joint has to flex.

Done properly, that means backer rod sized to the gap, then an elastomeric sealant tooled to the correct hourglass profile, at a width-to-depth ratio that lets it stretch. Done improperly, it means a thin bead of caulk pressed into a deep gap, which will split within two seasons, or rigid mortar packed into a joint that needs to move, which will crack.

More detail in masonry sealants: silicone, urethane and hybrids.

Reading the Leak: Where the Water Shows Tells You Where It Came From

| Where you see water or damage | Most likely source | |---|---| | Staining at the top of the window, interior | Lintel corrosion, or open joints above the opening | | Damp at the corners of the opening | Perimeter sealant joint, or open joints at the jambs | | Wall damp directly below the sill | Cracked, back-sloped or drip-less sill; open sill end joints | | Efflorescence on brick beneath the window | Sustained water movement through the wall at that point | | Condensation between panes | The window unit itself — this one really is the window | | Sticking sash, distorted opening | Structural movement, usually lintel rust jacking |

That last row matters. It is the one case where the window is genuinely the problem — a failed insulating glass seal. Everything else on the list is masonry.

Chicagoland Makes All of This Worse

Freeze-thaw. The Chicago area crosses the freezing point dozens of times each winter — far more than the annual-average temperature suggests. Every crossing that catches saturated masonry expands the water inside it by roughly nine percent. Openings are where water most reliably gets in, so openings are where that cycling does the most work.

The housing stock. Chicago bungalows, greystones, two-flats, three-flats and worker cottages were built with steel angle lintels over essentially every opening and limestone sills below them. That steel and that stone are now 80 to 120 years old.

Original detailing. Much of the pre-1930 stock predates the routine use of through-wall flashing over lintels. In a large number of these houses, there was never anything directing water away from the steel.

Later suburban stock. Post-war ranches and 1970s-onward brick veneer homes have their own version: precast or cast-stone sills, veneer ties, and a drainage cavity that depends entirely on weep holes staying open. See solid masonry vs. brick veneer repair.

The Right Sequence

1. Masonry assessment before you order windows. Every opening looked at from outside, ideally from a ladder for upper floors. You want to know what you are dealing with before the budget is committed.
2. Correct the water sources. Gutters, downspouts, coping, failing joints above the openings.
3. Lintel work. Shore the masonry above, remove the courses over the lintel, replace or treat the steel, install through-wall flashing, rebuild the brick with salvaged and matched units.
4. Sill work. Dutchman repair or full replacement, set with correct slope and drip edge, joints properly detailed.
5. Repointing. The opening perimeter and, in most cases, the elevation — joints cut back to sound mortar, matched for hardness first, then color, sand and texture, packed in lifts and tooled to the existing profile.
6. Windows installed.
7. Perimeter sealant last, with backer rod, so the joint seals against finished masonry and a finished frame.

Step 7 is the one most often done out of order. Sealing before the masonry is finished means cutting it out again.

What Drives the Cost

There is no meaningful per-window number, because two openings on the same house can require entirely different work. What actually drives it:

• Number of openings, and whether they can be done in one mobilization — the second opening is meaningfully cheaper than the first once staging is set
• Span width — a storefront or wide picture window versus a bedroom window
• Height — ground floor versus second or third story, and whether staging is required
• Extent of brick removal above the lintel
• Steel condition — treatable surface rust versus full section loss requiring replacement
• Whether flashing is being installed, which means opening the wall properly rather than patching around it
• Sill material and repair type — dutchman versus full matched replacement
• Brick matching, since pre-1930 units usually require salvage
• Access — gangway width, landscaping, protecting a neighboring property

We assess in person and itemize by opening, so you can see the number per opening and phase the work if that is what makes sense. See what a masonry estimate should include.

DIY vs. Hiring a Mason

Repointing a few joints around a window with correctly matched mortar is genuinely within reach for a careful, patient homeowner willing to learn the joint-preparation depth and the tooling.

Lintels and sills are not.

Lintel replacement requires temporarily supporting the masonry above the opening while the steel comes out. That is not a step you improvise. Sill replacement requires matched stone, correct bedding and correct slope, and a mis-sloped new sill actively directs water into the wall.

There is also the mortar-hardness trap that catches nearly every well-intentioned DIY masonry repair: mortar must be softer than the brick it holds. Modern bagged Portland-heavy mixes are considerably harder than century-old Chicago brick. Use them on a bungalow and the joints stay perfect while the brick faces spall off around them, within a handful of winters. See Type N vs. Type S mortar and lime vs. Portland mortar.

After the Work: Keeping Openings Sound

• Walk the openings each spring. Look for rust streaks, hairline cracks above openings, and gaps at sill ends.
• Check perimeter sealant every few years. It is a wear item; a joint that has split is doing nothing.
• Keep gutters and downspouts working. Overflow at the eave runs down the wall and finds openings.
• Do not caulk weep holes. On veneer walls they are the drainage path.
• Watch interior corners below and beside windows for the first sign of staining.
• Address one opening's rust staining promptly — the others on the house are the same age.

Related Services

• Lintel repair and replacement
• Limestone and sill repair
• Tuckpointing and repointing
• Brick repair and brick replacement
• Caulking and joint sealant
• Residential masonry restoration

The Bottom Line

New windows are a good investment in a Chicagoland brick home. They are also the moment when the masonry around every opening is more accessible, and more worth looking at, than at any other point in the building's life.

Spend an hour on a masonry assessment before you spend the window budget. If the lintels and sills are sound, you will know it, and you can proceed with confidence. If they are not, you will have found out at the one moment when fixing them is straightforward — instead of two winters later, looking at stains on the wall beneath windows you just paid for.

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.

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