Drafty Brick House? What Failed Mortar Joints Do to Your Heating Bill

Do Failed Mortar Joints Make a House Drafty?

Yes, they contribute — but they are rarely the biggest leak in the house, and anyone selling tuckpointing primarily as an energy upgrade is overstating it. Air moves through open and deteriorated mortar joints, and on an older Chicago brick house with widespread joint failure that becomes a genuine leakage path spread across a very large surface. Emerald Masonry LLC repoints masonry across Chicago and the Chicagoland suburbs — family-owned, licensed and insured, 40+ years of experience, free on-site estimates. Call (708) 288-1696.

We want to be straight about this one, because it is a topic where the trade sometimes oversells.

Repointing is a water repair first. Reduced air movement is a real but secondary benefit. If your primary goal is a lower heating bill, there are cheaper places to start — and we would rather tell you that than take the job under a false premise.

That said, on an older masonry house the joints genuinely do belong on the list, and they are almost always the item nobody checked.

How Air Actually Moves Through a Masonry Wall

A brick wall is not a monolith. It is thousands of units in a matrix of mortar, and the mortar is the continuous element.

When joints are sound, that matrix is essentially closed. When mortar has receded behind the brick face, cracked through, or turned sandy, the wall develops a distributed network of small openings. No single one matters. A hundred linear feet of them across an elevation does.

Two things drive air through those openings:

Wind pressure. Wind on the windward face pushes air in; suction on the leeward face pulls it out. On an exposed elevation this runs continuously.

Stack effect. Warm air rises and escapes high in the building, drawing cold air in low to replace it. In a two- or three-story Chicago house that pressure difference is meaningful all winter, and it pulls through whatever openings exist near the base of the wall.

Where the Bigger Leaks Usually Are

Honest ranking, for most older Chicagoland houses:

| Leak path | Typical significance | Cost to address | |---|---|---| | Attic plane — top plates, penetrations, hatch | Usually the largest | Low to moderate | | Rim joist / sill plate at the basement | Usually large | Low | | Window and door perimeters | Concentrated and significant | Low | | Open chimney flue with no cap or damper | Often surprisingly large | Very low | | Failed mortar joints across the wall field | Moderate, spread over a big area | Moderate | | Weep holes on veneer | Negligible — and must stay open | N/A |

Air-seal the attic and rim joist first. They are cheaper and usually more effective. Then window perimeters. Then the masonry.

That ordering is not us talking ourselves out of work — it is what an energy auditor would tell you, and a blower door test will rank your specific house rather than leaving you guessing.

The Chimney Draft Nobody Fixes

Worth calling out because it is cheap and commonly ignored.

An uncapped flue, or one with a failed or missing damper, is an open shaft from your living space to the sky. It drives stack effect all winter, and on a chimney that is no longer used for anything it is pure loss.

A chimney cap and a functioning damper cost very little relative to what they stop — and a cap also keeps rain, snow and animals out of the stack, which is the masonry reason to install one anyway. See chimney repair.

Cold Wall vs. Drafty Wall — Not the Same Problem

Worth separating, because the fixes differ entirely.

A cold wall is a thermal issue. Solid masonry has very little insulating value by modern standards, so an uninsulated brick wall in a Chicago January will feel cold whatever condition the joints are in. Repointing does not change that.

A drafty wall is an air-movement issue — you can feel air moving, or see curtains stir, or the room never quite holds temperature. That is where joints, perimeters and penetrations matter.

Most older houses have some of both. Knowing which one is bothering you tells you what to spend money on.

A Real Caution About Insulating Solid Masonry

If you are considering adding insulation to the inside of a solid brick wall, get advice specific to your wall before proceeding.

Here is the risk in plain terms. A solid masonry wall currently stays warm enough, from the inside, to dry out. Add interior insulation and the masonry gets colder, because you have stopped heating it. Colder masonry holds more moisture, dries more slowly, and is more vulnerable when the temperature crosses freezing — which in Chicagoland happens dozens of times each winter.

Done thoughtfully, with attention to where moisture will condense, it can work. Done as a straightforward "add foam to the interior face," it has caused real freeze-thaw damage in this climate.

Whatever you decide: fix the joints and the water sources first. A wall that is taking on water is the worst possible candidate for being insulated.

What Repointing Actually Does

1. Free on-site assessment — joint condition on every elevation, plus gutters, downspouts, grade, sills, lintels and chimney.
2. Mortar matching — color, sand and, critically, hardness. The governing rule is that mortar must be softer than the brick it holds, so joints take the stress instead of the brick faces. Type N for most post-war walls; Type O or a custom lime blend for soft pre-1930 brick.
3. Grinding or raking failed mortar out to a sound depth, typically two to two and a half times the joint width.
4. Cleaning the joints so fresh mortar bonds to clean masonry.
5. Repointing in lifts, packed and compacted so no voids remain behind the face — which is the part that actually closes the wall.
6. Tooling to the original joint profile.
7. Proper cure and protection.

That fifth step is the one that matters for air movement. Mortar smeared over the face of old joints looks repaired and leaves the voids behind it intact.

Where Veneer and Solid Masonry Differ

The two wall types behave differently here, and it changes what is worth doing.

Solid multi-wythe masonry — most pre-1940 Chicago buildings — is several courses of brick thick with no cavity. Air moving through it has to pass through the full depth of the wall, and the mortar matrix is the continuous path. Repointing genuinely closes that path, because there is nothing behind the joints but more masonry. This is where joint condition matters most for air movement.

Brick veneer — most post-war construction — is a single decorative layer with an air cavity behind it, then flashing, weep holes, and a separate backup wall. That cavity is intentionally vented to the outside. Air passing through a veneer joint enters the cavity, not your living space; whether it reaches the interior depends on the air barrier on the backup wall, which is a different assembly entirely.

The practical consequence: on veneer, repointing does very little for drafts. If a veneer house is leaky, the problem is almost certainly the backup wall's air sealing, the window and door perimeters, the rim joist, or the attic — not the brick joints. Chasing drafts by repointing veneer is spending masonry money on a framing problem.

Repointing veneer is still worth doing when the joints have failed — for water, which reaches the ties and lintels in that cavity. Just do not expect it to change how the house feels.

The Real Argument for Repointing

Not the heating bill. Water.

Open joints let water into the wall, where freeze-thaw spalls the brick faces, corrodes the steel lintels and ties inside, saturates the chimney and eventually loosens masonry. That escalation is expensive, and repointing is the cheapest rung on the ladder that prevents it.

Reduced air movement comes along with closing the wall. Treat it as a bonus, and judge the job on the water.

What Homeowners Usually Feel, and What It Actually Is

Translating common complaints into likely causes, because the symptom rarely names the source.

"The room above the porch is always cold." Usually the floor cavity over an unheated space, not the walls. Air sealing and insulating that cavity does more than any masonry work.

"I feel a draft along the baseboard." Very often the rim joist or sill plate at the top of the foundation, which is a framing detail rather than a brick one.

"The wall itself is cold." A thermal issue — solid masonry has little insulating value. Repointing will not change it.

"Cold air comes down the fireplace." An open flue with a failed or missing damper. Cheap to fix, and commonly ignored.

"It's worse on windy days." That points at genuine air leakage rather than a thermal problem, and wind-driven infiltration is where joint condition, window perimeters and penetrations all contribute.

"One corner room is always worse." Corner rooms have two exterior walls, more window perimeter and often more exposure — usually additive small leaks rather than one large one.

Chicagoland Context

The region's older housing stock — brick bungalows, two-flats, greystones and worker cottages built between 1890 and 1940 — is largely solid multi-wythe masonry with no cavity and no insulation, laid with lime mortar that is now at or past a century old. Post-war ranches and Georgians add another sixty to seventy years of Portland-based mortar reaching the end of its service life.

Combine that with dozens of freeze-thaw crossings per winter, real wind exposure across open suburban lots, and three-story stack effect in city two- and three-flats, and joint condition genuinely matters here in a way it would not in a mild climate.

Maintenance That Helps Both Problems

• Keep water off the wall — gutters clear, downspouts extended, grade sloping away, splash controlled.
• Repoint on schedule with matched mortar, before spalling starts.
• Recaulk window and door perimeters when sealant splits or pulls away — cheap and effective on both fronts.
• Cap unused flues and confirm the damper closes.
• Never seal weep holes on veneer.
• Never paint brick or use a film-forming sealer — trapped moisture spalls the face from behind.
• Get a blower door test if drafts are a real complaint, and let the results set your priorities.

Related Services

Tuckpointing and repointing, caulking and joint sealant, chimney repair, brick repair, masonry sealing and historic masonry restoration.

The Bottom Line

If your brick house is drafty, the mortar joints are worth checking — but check the attic, the rim joist, the window perimeters and the chimney flue first, because those are usually larger and always cheaper.

And when you do repoint, do it for the right reason. Closing the wall against water is what justifies the work. The fact that it also stops air moving through a hundred feet of open joint is a genuine benefit, just not the headline.

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 will tell you when the fix is not masonry.

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