Efflorescence is the white, chalky, powdery deposit you see on brick and masonry, and it’s caused by water carrying natural salts out of the masonry to the surface, where the water evaporates and leaves the salt behind. It’s usually cosmetic, not structural, but it’s a signal that water is moving through your brick, and that underlying moisture problem is what actually needs fixing. Wiping off the white residue without addressing the water just guarantees it returns.

What Efflorescence Actually Is

Brick, mortar, and concrete all contain naturally occurring soluble salts. When water gets into the masonry, whether from rain, ground moisture, or a leak, it dissolves those salts, travels to the surface, and evaporates. The salt can’t evaporate, so it’s left behind as a white crystalline film. You’ll see it most on north-facing and shaded walls, near grade, and after wet weather. It’s extremely common on Philadelphia rowhomes, and on its own it doesn’t mean your wall is failing.

Why It Matters Even Though It’s Cosmetic

The white powder itself is harmless and easy to remove. The reason to pay attention is what it tells you: water is getting into your masonry. In Philadelphia’s freeze-thaw climate, water inside brick is the root cause of the real problems, spalling, cracked brick, and failing mortar. So efflorescence is best understood as an early warning. Treat the moisture now and you avoid the expensive damage later.

Common Sources of the Moisture

• Failing or cracked mortar joints letting rain into the wall, the most common culprit.
• Poor drainage or grading that pushes ground water against the foundation and lower brick.
• Leaking gutters and downspouts dumping water onto the masonry.
• Missing or damaged flashing and caps, especially on chimneys and parapet walls.
• New construction moisture, which causes a one-time bloom that fades as the masonry dries out.

How to Remove Efflorescence

Removal is the easy part. The right approach depends on how heavy the deposit is:

1. Dry brushing. For light deposits, a stiff (non-metal) brush often knocks it right off.
2. Water and scrubbing. Plain water and a brush handle most cases, though you want to let the wall dry fully afterward so you don’t redissolve and resettle the salts.
3. Specialized masonry cleaners. Heavy or stubborn deposits may need a proper cleaning solution applied correctly. Harsh acid washes can damage brick and mortar if misused, so this is best left to someone who knows the material.

Pressure washing and acid should be used cautiously, if at all, on older Philadelphia brick. Aggressive cleaning does more harm than the efflorescence ever would.

How to Stop It From Coming Back

This is where the real fix lives. Stopping efflorescence means stopping the water:

• Repoint failing mortar joints. Fresh, properly matched mortar seals the most common entry point for water. Our repointing work is the single most effective fix for recurring efflorescence.
• Fix drainage and grading so water flows away from the wall, not toward it.
• Repair gutters, downspouts, and flashing so roof water stays off the masonry.
• Address chimney caps and crowns where water enters from the top, part of our chimney work.
• Consider a breathable masonry sealer only after the moisture source is fixed, never as a substitute for it. Sealing wet brick traps moisture and makes things worse.

When to Call a Mason

If the efflorescence keeps coming back, covers a large area, or shows up alongside crumbling mortar, spalling brick, or damp interior walls, the water problem is significant and worth a professional look. A mason can trace the moisture to its source and fix the cause, not just the symptom. See our restoration and brickwork in the gallery.

Stop the Water at the Source

Frequently Asked Questions

What causes the white powder on brick?

That white, chalky deposit is efflorescence. It forms when water moves through brick and mortar, dissolves naturally occurring salts, carries them to the surface, and evaporates, leaving the salt behind. It signals that water is getting into the masonry.

Is efflorescence on brick a serious problem?

The white residue itself is cosmetic and harmless, but it’s a warning that water is entering your masonry. In Philadelphia’s freeze-thaw climate, that moisture is what eventually causes spalling, cracked brick, and failing mortar, so the water source should be addressed.

How do I remove efflorescence from brick?

For light deposits, a stiff non-metal brush or plain water and scrubbing usually works; let the wall dry fully afterward. Heavy deposits may need a proper masonry cleaner. Avoid harsh acid and aggressive pressure washing on older brick, which can do real damage.

How do I keep efflorescence from coming back?

Stop the water. Repoint failing mortar joints, fix drainage and grading, repair gutters and flashing, and address chimney caps. A breathable sealer can help only after the moisture source is fixed, never as a substitute for it.