You can put paint or sealer over spalling brick, but it does not stop the spalling. The brick is failing because of moisture and salts, and a coating over that damage leaves the cause in place. The National Park Service advises that water-repellent coatings are appropriate only after a building has been made watertight and dried. Fix the water source, repair or replace the damaged bricks, then decide on a coating with a mason.
Short answer: you can, but it will not fix anything, and it can hide a problem that keeps growing. Spalling is a symptom. Paint and sealer treat the look of the symptom.
Why paint or sealer does not fix spalling
Spalling happens when water gets into the brick and either freezes or carries salts that crystallize inside it. Salt crystallizing inside a brick creates pressure that can make the surface spall or delaminate, and freeze-thaw of saturated brick is another cause (NPS and BIA guidance). Paint or sealer on the face does nothing about where that water is coming from: a bad gutter, open mortar joints, a failed cap or coping, a leaking roof edge.
The National Park Service is cautious here. Its brief on coatings says soft, incompletely fired early brick can become so porous that a coating may be considered, but that water-repellent coatings are appropriate only after a building is made watertight and dried (NPS Preservation Brief 1). That brief speaks about early American brick in general, not Chicago common brick specifically, so treat it as a caution, not a rule for your wall. For the related problem of white salt deposits, the Brick Industry Association says to find and fix the moisture cause first and that coatings alone are not recommended (BIA Technical Note 23A).
What about filling or mortaring over the spalled face?
Troweling mortar or patching compound over a spalled face has the same problem, plus another one. The repair material tends to be harder than the soft brick under it, and NPS guidance is that mortar should be softer and more permeable than the brick, because stress should be relieved by the mortar and not the units (NPS Preservation Brief 2). A thin skim coat also has nothing solid to hold onto when the face behind it is already letting go.
A common pattern on older Chicago brick is a wall that was painted or coated to "stop the flaking," and a few winters later the paint is peeling off in sheets with the brick face coming away behind it. The coating hid the problem, and the water kept working underneath.
What to do instead
- Find the water. Check gutters, downspouts, roof edges, caps and copings, and open joints above the damage.
- Repair the joints and the source. Mortar that is cracked or missing lets water in. See signs your brick needs tuckpointing.
- Deal with the damaged bricks. Depending on how deep the damage is, that can mean leaving it alone, repairing it, or replacing the bricks. See can you fix spalling brick without replacing it and how to replace spalling bricks.
- Only then talk about a coating. If you still want a water-repellent or a color coat, ask a mason whether the wall is dry and sound enough to take one. Our note on sealing brick after tuckpointing covers the timing question.
If the brick is already painted and the job involves scraping or removing paint on a building built before 1978, the EPA's lead-safe rule applies to paid contractors (EPA).
Got a wall that is flaking and you want a straight answer on what it needs? Our masonry crew will look at it, and the brick repair guide explains the whole sequence.
Common questions
Not by itself. Spalling comes from moisture and salts working inside the brick, and a coating on the face leaves that cause in place. The water source has to be found and fixed first, then the damaged bricks repaired or replaced.
The National Park Service says water-repellent coatings are appropriate only after a building is made watertight and dried. Sealing brick that is still taking on water or already breaking down is not a repair. Ask a mason to check the wall first.
It is not a good fix. A patch over a face that is already letting go has little to bond to, and a hard repair material on soft brick can cause more damage. The better approach is to repair or replace the damaged brick and use mortar that is softer than the brick.
Sources
- National Park Service: Preservation Brief 1: Cleaning and Water-Repellent Treatments for Historic Masonry (PDF)
- Brick Industry Association: Technical Note 23A: Efflorescence, Causes and Mechanisms (PDF)
- National Park Service: Preservation Brief 2: Repointing Mortar Joints in Historic Masonry Buildings (PDF)
Facts last checked: October 7, 2026.
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.