How to Clean Chicago Brick Without Damaging It

The safe way to clean old Chicago brick is the gentlest method that works, tested first on a spot nobody sees, after the water causing the stain has been fixed. Most of the brick damage we get called to repair after cleaning was not caused by dirt. It was caused by the cleaning.

Brick that has stood on a Chicago street for a hundred years is not the same as brick made today. This article covers what to clean, what not to, and what to ask a contractor who offers to "wash" your building.

First: is it really a cleaning job?

Many "dirty brick" calls are something else. Sort it out before anyone touches a hose.

• White powder. That is efflorescence, salt carried out of the wall by water. Scrubbing without stopping the water brings it back. See how to remove efflorescence from brick and is efflorescence bad for brick.
• Flaking or sanding faces. That is spalling, not dirt. Cleaning it removes more brick. See can you fix spalling brick without replacing it.
• Missing or crumbling mortar. That is a tuckpointing job. Chicago requires masonry joints to be kept weather resistant and water tight (City of Chicago, 14X-3-303). Clean after the joints are repaired, not before.
• Paint. Removing paint from old brick is its own project. See below.
• Black soot, green algae, rust or drip streaks. These are surface stains, and they are the cases where cleaning is the job. Rust stains and streaks under windows can also point to a failing lintel, so look at the cause.

What can go wrong when you clean old brick

We do not have a number for you. The honest answer is that old brick is softer than modern brick, and the way to avoid damage is to start gentle and to test.

Things to be careful with:

• High-pressure water. BIA refers readers to its Technical Note 20 for water washing, which is the place to start for method (BIA Brick Brief on repointing). Ask any contractor what pressure they will use and how they will test it.
• Abrasive blasting of any kind. Ask what they use and what it does to the face of this brick.
• Acid and chemical cleaners. NPS says cleaning efflorescence with some methods can liberate additional salts (NPS Preservation Brief 2). Chemicals also need rinsing, protective gear and the manufacturer's instructions.
• Soaking a wall that is already wet. Water in the wall is the source of most problems. Trapped moisture and salts can crystallize inside soft brick and push the face off (NPS Preservation Brief 2).
• Sealing right after cleaning. NPS cautions that water-repellent coatings are appropriate only after a building is made watertight and dried (NPS Preservation Brief 1). A coating over wet brick traps moisture.

How to clean old brick safely

For a light, surface-level cleaning job, this is the sequence we would follow:

1. Look at the wall first. Photograph it. Note flaking brick, missing mortar and where water is staining.
2. Fix the water. Gutters, downspouts, flashing, copings. Cleaning a wall that is still taking in water is wasted effort.
3. Repair the mortar. Clean after repointing, so you do not wash water into open joints.
4. Start with the gentlest method. Plain water and a soft natural bristle brush on a small hidden area. Stop if the brick surface changes or comes away on the brush.
5. Test before you scale up. If a stronger method is needed, test it in a hidden spot, and let it dry before you judge the result.
6. Dry before sealing, and think twice about sealing. If anything is applied to the brick, a professional should recommend it.

Cleaning paint off brick

Stripping paint is not light cleaning, and one issue comes before any method: lead. EPA's RRP rule requires anyone paid to disturb painted surfaces in homes built before 1978 to be lead-safe certified and to use certified renovators. It generally does not apply to homeowners working on their own home, but it does apply to landlords, rentals and house flippers (EPA). Many Chicago brick buildings are older than that.

Ask whether your building is a rental. Whatever method is used, the paint comes off in dust, chips or sludge, and it needs to be handled.

For brick that is painted and needs mortar work, see can you tuckpoint painted brick.

Dust, silica and what happens on the ground

Cleaning is messy, and some of the messy work is regulated:

• Silica dust. Grinding mortar throws silica dust. OSHA requires tuckpointing grinders to have a shroud and dust collection, plus respirators for the crew (OSHA).
• Dust control. The City notes that masonry grinding may need a Chicago Department of Public Health air quality permit, and that lead-safe practices, asbestos notification and dust control apply regardless of permit exemptions (City of Chicago).
• The sidewalk. Scaffolding or materials on the sidewalk need a separate public way permit from CDOT. Cleaning the front of a building at the lot line almost always touches the sidewalk. Confirm with the City.

Confirm current rules with the Department of Buildings before work starts.

What to ask before you hire

1. What method will you use, at what pressure, and why is it right for this brick?
2. Will you test a hidden spot first, and let me see it?
3. Will the mortar joints be repaired before or after cleaning?
4. Do you handle lead-safe work if the wall is painted?
5. Will anything be sealed or coated, and who recommended it?
6. Who handles the sidewalk and any permits?

If you want a mason to tell you whether the wall needs cleaning, repair or both, our masonry crew can look at it. The Chicago brick and masonry guide covers the whole system.

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.