Why Is the Mortar Between My Bricks Crumbling? When You Need Tuckpointing

You run your finger along a joint and it comes away gritty. Maybe there’s a little pile of sand on the sill, or a few joints look sunken compared to the brick face. Crumbling mortar between bricks is one of the most common things building owners notice in the fall, and it’s usually the first visible sign that a wall needs attention.

The good news: it’s almost always fixable. The real question is which fix you need, and whether you can get it done before the ground freezes.

Why Is Mortar Crumbling Between My Bricks?

Mortar is designed to be the weak link in a brick wall. It’s softer than the brick on purpose so it absorbs movement and lets moisture escape. The National Park Service’s Preservation Brief 2 on repointing says new mortar should be “softer (measured in compressive strength) than the masonry units.” That means mortar wears out first, and it’s meant to be replaced every few decades while the brick lasts much longer.

The usual causes of mortar crumbling are:

• Age. Older joints simply erode from rain and wind over time.
• Freeze-thaw cycles. Water soaks into the joint, freezes, expands, and breaks the mortar apart from the inside. We cover this in detail in our post on how Illinois weather destroys brick.
• Water from somewhere else. Clogged gutters, failed flashing, and leaking downspouts keep one section of wall wet all the time. That’s why damage often shows up in patches.
• Wrong repair materials. Past patches made with hard, cement-heavy mortar can trap moisture and push damage into the surrounding brick.

Does Crumbling Mortar Always Mean I Need Tuckpointing?

Not always, but most of the time. If you can scrape mortar out with a key or screwdriver, if the joints are powdery when you rub them, or if they’ve receded so you can see a shadow line under the brick edge, the mortar has failed. Tuckpointing, which means grinding out the old joint and packing in fresh mortar, is the standard fix for deteriorating mortar joints.

Hairline cracks in otherwise solid mortar are different. Those may just need monitoring. A quick masonry inspection can tell you which category you’re in.

Can You Just Fill or Patch the Missing Mortar?

This is the most common question we hear, and the short answer is that patching rarely holds. Smearing new mortar or caulk over old joints leaves a thin layer sitting on top of weak material. It has nothing solid to bond to, so it pops out after a winter or two.

Proper repair means removing the old mortar to a real depth first. The NPS brief recommends removing it to “a minimum depth of 2 to 2-½ times the width of the joint to ensure an adequate bond.” For a standard joint, that’s well past what a surface patch reaches.

Small spot repairs are fine when the problem is limited to a few joints. Just make sure they’re done as true tuckpointing, not a skim coat, and with a mortar that’s matched in strength and color. Our post on mortar color matching in tuckpointing explains why that second part matters for how the wall looks afterward.

How Can I Tell If the Damage Is Localized or Across the Whole Wall?

Walk the building and compare elevations. A few things to check:

• Is the damage clustered? Crumbling mortar under a window, beside a downspout, or below a parapet usually points to a water source. Fix the source and repair that area.
• Is it on the weather side only? Walls facing prevailing wind and rain often wear faster. One elevation may need full tuckpointing while the others need spot work.
• Is it everywhere? If joints are soft and recessed on every side, the mortar has reached the end of its life and a full facade repoint makes more sense than chasing patches.

For commercial and multi-unit buildings, a documented scope helps you budget in phases. Our commercial masonry maintenance guide covers how owners plan this work over several seasons.

What If the Brick Is Crumbling Too?

Then you’re past a mortar problem. Bricks that are flaking, popping their faces off, or turning to powder are spalling, and tuckpointing alone won’t fix them. Those units need to be cut out and replaced as part of a brick repair job.

Spalling often happens next to failed joints because water that gets past the mortar ends up inside the brick. See what causes brick spalling for the full picture. If you also see bulging, leaning sections, or long stair-step cracks, call a professional before any work starts. Those can signal structural movement that needs to be assessed first.

Can Crumbling Mortar Let Water Into the Wall?

Yes. Open and recessed joints are the easiest path for water into a masonry wall. Once inside, it can soak interior plaster, rust steel lintels, rot wood framing in older buildings, and show up as damp spots or efflorescence (white salt staining) on the brick face.

If water is already getting in, tuckpointing should be paired with checking the through-wall flashing and drainage. Repointing a wall that still has a failed flashing above it just puts new mortar in the path of the same leak.

What Happens If I Leave Crumbling Mortar Through a Chicago Winter?

It gets worse, and usually faster than owners expect. Every freeze-thaw cycle pushes water deeper into open joints. Mortar that was soft in October can be missing by April, and bricks that were fine can start to loosen or spall.

Timing matters on the repair side too. Mortar needs above-freezing temperatures to cure properly, so most masonry crews stop exterior tuckpointing once nights stay cold. If you’ve noticed crumbling joints this fall, getting an inspection on the calendar now gives you the best chance of finishing before the weather closes the window.

How Much Does It Cost to Repair Crumbling Mortar?

Costs depend on how much wall is affected, access, and whether bricks also need replacing. Based on Delta’s published pricing ranges:

Larger commercial facades, parapets, and buildings that need lift access are priced by scope. For a deeper breakdown, read our tuckpointing cost guide for Chicago.

The cheapest repair is almost always the one done early. A few hundred dollars of tuckpointing now can prevent brick replacement and interior water damage later.

Get Crumbling Mortar Fixed Before Winter

If the mortar between your bricks is crumbling, falling out, or turning to powder, the wall is telling you it’s time. Delta has handled tuckpointing and masonry repair for homes and commercial buildings across the North Shore and Chicago suburbs since 1987. Contact us for a free inspection and written estimate, and we’ll tell you plainly whether you need a spot repair, full tuckpointing, or brick replacement.