Can You Fix Spalling Brick Without Replacing It?

Can you fix spalling brick without replacing it? Sometimes, yes. If the brick has only lost a thin outer layer and the wall is otherwise sound, the fix is not a patch on the brick. It is stopping the water and the mortar problem that are causing the face to pop off. If the damage is deep, or the brick is crumbling or loose, replacing that brick is the honest answer. A mason has to look at it, because the same photo can describe a ten-minute fix and a wall that needs to come down.

What is spalling, and what causes it?

Spalling is when the face of a brick flakes, peels or pops off, leaving a rough or pitted surface. It is not a type of brick. It is what happens to a brick that took on more water or stress than it could handle.

The National Park Service and the Brick Industry Association name two causes (NPS and BIA): salts crystallizing inside the brick, which creates pressure that makes the outer surface spall or delaminate, and freeze-thaw cycling of brick that is saturated with water. Chicago winters supply plenty of the second. Either way, water has to be in the brick for it to happen. The brick is the victim, not the cause.

Why does the mortar matter so much?

A brick wall is supposed to move water out through its weakest, most replaceable part, which is the mortar joint. The NPS says the new mortar must be softer and more vapor-permeable than the brick, and the joint is the sacrificial element: stress in the wall should be relieved by the mortar, not the brick (National Park Service).

When someone repoints soft old brick with a hard, dense modern mortar, that logic flips. Moisture and dissolved salts can no longer leave through the joint, so they move out through the brick. Salt then crystallizes inside the brick and the face spalls or delaminates (National Park Service). The NPS calls mortar that is stronger than the masonry a cause of cracking and spalling of the units that cannot be easily repaired (National Park Service).

That is how a freshly tuckpointed wall ends up losing brick faces a few winters later. The mortar job was the cause of the spalling.

When can you leave spalled brick in place?

You can often leave a brick that has lost a thin face, as long as three things are true:

1. The wall is sound. No bulging, no stair step cracking, no movement.
2. The brick is stable. It does not crumble, flake further when scraped, or sit loose in its bed.
3. The cause is fixed. The water source is stopped and the joints around it are not hard, failing mortar.

If those three are true, fixing the cause protects the brick you have. That means addressing the water path first. The BIA lists where flashing belongs: through-wall flashing at the base of walls, sills, heads of openings, tops of walls, parapets and chimneys (BIA). It also says caps and copings are meant to channel water away, and brick caps with many mortar joints can be a poor choice at the most exposed spot (BIA). A parapet cap that leaks or a chimney crown that is cracked will keep feeding water to the brick below no matter what you do to the face.

Then the joints. If the mortar around the spalled brick is the wrong type, it has to come out and be replaced with mortar that is softer and more permeable than the brick. The NPS advises removing old mortar to a depth of about two to two and a half times the joint width, with hand chisels the traditional method (National Park Service). The tuckpointing side of this is in our tuckpointing guide.

When do you have to replace the brick?

Replace it when:

• The face is gone deep, not just the thin outer layer.
• The brick crumbles or powders under a scrape.
• It is loose, cracked through or no longer bonded to the wall.
• It is part of a larger failure, such as a bulging section or a parapet.

Loose masonry is also a code issue. Chicago's code requires the exterior to be maintained in good repair and structurally sound, and lists masonry joints that are not weather resistant or water tight, and facings that are not properly anchored, as unsafe conditions (City of Chicago). A brick that can fall is a brick that has to be dealt with, and how it is done is covered in replacing spalled bricks. If bricks on your building are shedding pieces onto a sidewalk, see are spalling bricks dangerous.

Can you patch, coat or seal over spalling brick?

This is what people usually try first, and it is usually the wrong first move. A coating or sealer that does not let the wall breathe can trap moisture in the brick, and trapped moisture is what pops faces off in the first place. The NPS cautions that water-repellent coatings are appropriate only after a building is made watertight and dried, and it makes the point in the context of very soft, early American brick, not Chicago common brick specifically (National Park Service). The safe reading is the same: fix the water first, then talk about coatings. We cover the question in can you paint or seal over spalling brick.

Does fixing spalled brick need a permit?

It depends on what the repair is. The City exempts in-kind replacement of up to 50 square feet of masonry on residential buildings up to four stories (City of Chicago). Repointing, which is how you correct a mortar problem, is listed on the Express Permit masonry page as permitted maintenance work (City of Chicago). If your repair mixes both, check with the Department of Buildings so you pull the right one. For the full rules, see do you need a permit to repair brick.

What should you do next?

Start by figuring out whether the brick is stable and where the water is coming from. A photo from the ground will not tell a mason everything, but you can help by noting which bricks are affected and where, and whether it gets worse after rain or after the freeze-thaw cycle. For the larger picture, our Chicago brick and masonry repair guide covers causes, repair options and what to ask a contractor. When you want a mason to tell you which bricks stay and which go, our masonry crew can look at it and write it up.

Common questions

This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.