Mortar Between Bricks Crumbling: What It Means for a Chicago Building
Published October 8, 2026 · More articles
You brush against the side of the building and sand trickles out of the joints. Maybe there are gaps you can fit a key into, or you've found little piles of grit along the foundation. You're wondering if the wall is falling apart.
The Problem
Mortar is the part of a brick wall that's meant to wear out. It's softer than the brick on purpose, so it takes the stress and the weather instead of the brick. But it only lasts so long. When the mortar between bricks starts crumbling, the wall loses its first line of defense against water.
That's the part that worries owners, and it should. Chicago's winters bring dozens of freeze-thaw cycles. Water gets into open joints, freezes, expands and pushes the gap wider each time. A wall that looks a little rough this fall can have loose bricks by spring. Bungalows in Portage Park and Jefferson Park, two-flats in Logan Square and Pilsen, and greystones and courtyard buildings across the North Side are mostly decades old, and a lot of them are due.
Why Mortar Crumbles
Age and weather
Lime-based mortar in older Chicago buildings slowly washes out over time. South- and west-facing walls take the most rain and sun. Parapets and chimneys take the worst of it because they're exposed on both sides.
Water from somewhere it shouldn't be
Leaking gutters, failed flashing, missing coping stones on a parapet or a downspout dumping against the wall will wear out mortar fast in one area. If the damage is concentrated, look up for the water source.
The wrong mortar in an earlier repair
Hard, high-cement mortar used on soft Chicago common brick is a common mistake. It doesn't flex with the brick, so the brick edges crack and the joints break loose. If someone "patched" your wall with gray mortar that looks different from the rest, keep an eye on it.
Settling and movement
Cracks that step diagonally along the joints, or run through bricks, can point to movement rather than simple wear. That's worth having looked at.
Signs You're Past Wear and Into Damage
- Joints recessed more than about a quarter inch, or gaps you can see daylight through
- Sand or mortar pieces collecting at the base of the wall
- Bricks that feel loose or move when pushed
- Water stains, peeling paint or damp plaster on the inside of the wall
- White, chalky staining (efflorescence) on the brick face
- Brick faces flaking or popping off. If you're thinking "my bricks are crumbling," not just the mortar, water is already doing damage. See brick repair.
What You Can Safely Check Right Now
- Walk the building and note which walls are worst. Take photos from the ground.
- Scratch a joint with a key or screwdriver. If mortar turns to powder easily, it's spent.
- Look up. Check gutters, downspouts, parapet caps and chimney flashing for obvious water sources.
- Check inside along exterior walls for damp spots, stains or bubbling paint, especially after rain.
- Don't smear new mortar or caulk over the joints. Surface patches trap water and make the eventual repair harder.
- Stay off ladders on tall walls and keep people clear of any loose brick overhead.
When to Call Instead
Call if bricks are loose, if water is getting inside, if the crumbling is on a chimney or parapet, or if more than a few joints are open. Those are the places where waiting turns a mortar job into a rebuild. Loose brick at height can also become a falling hazard over a sidewalk or gangway.
The fix for worn joints is tuckpointing: grinding out the failed mortar to a consistent depth and repacking the joints with a mortar matched to your brick. Our tuckpointing page explains how it's done right and what to ask when comparing contractors.
The Plan
- Call (773) 389-2576 or send the form. Tell us which walls are affected and whether you see any leaks inside.
- We inspect the masonry. We look at the joints, the brick, the water sources and any signs of movement, and tell you what's wear and what's damage.
- You get a clear price before any work starts. The scope is written out so you know exactly what's being repointed or repaired. Tuck point repair cost depends on the square footage, height, access and how deep the damage goes. Our tuckpointing cost page breaks down what drives the price.
The win: tight, weather-sealed walls, a dry interior, and a building that's protected for years instead of wearing out one winter at a time.
Frequently Asked Questions
Is crumbling mortar a structural problem?
Can I just patch crumbling mortar myself?
How long does tuckpointing last?
What time of year is best for tuckpointing in Chicago?
Stop Water Before It Gets Behind the Brick
Crumbling mortar lets water in, and Chicago's freeze-thaw winters do the rest. Tell us what you're seeing. Call (773) 389-2576 or send the form.
- Inspection first, with photos of what needs work
- Written estimate before anything starts
- Serving Chicago & Chicagoland