Should Chicago brick be sealed the same way as other pavers?

The answer turns on a date. “The last Chicago common brickyard closed in 1981,” WTTW's Chicago history column records, and with that yard went the one party the Brick Industry Association tells a brick owner to ask first.

WTTW traces it to the blue clay under the city, high in lime and iron, fired in a kiln. What the brick is, and how it got its name, is defined under Chicago brick in the glossary.

Fired clay is the fact that matters for cleaning and coating. The Brick Industry Association's Technical Note 20, dated August 2018, says in its abstract that it addresses cleaning of brickwork and brick pavements, so a reclaimed clay brick patio falls under BIA's guidance and not under the concrete paver documents. The name alone does not settle the material, though: Tremron, a Florida paver maker, sells concrete units under the name brick pavers. How to tell clay from concrete, and why each has its own cleaning rules, is covered under whether clay brick can be cleaned like concrete pavers.

What is sold as Chicago brick today is reclaimed. WTTW puts it simply: “When old buildings are torn down in Chicago, the bricks are salvaged, cleaned and resold”.

That history removes a step. BIA's coating note tells the reader to “Consult the brick manufacturer prior to the selection of a coating,” and its cleaning note caps water pressure unless the brick manufacturer permits more. For a reclaimed brick whose yard closed in 1981, there is no manufacturer to consult and no one who can permit anything beyond BIA's general guidance.

The Brick Industry Association's Technical Note 6A, Colorless Coatings for Brick Masonry, is dated August 2008, and its abstract describes a discussion of coatings on above-grade brick masonry. Its summary still names paving directly: “Application is not recommended on newly constructed brick veneer or cavity walls or on new or existing pavements using clay pavers.” A patio of reclaimed clay brick is a clay brick pavement, the case that line addresses.

Where a coating is considered anyway, the note sets conditions of its own, and it warns that stains and salts that occur under a coating “may be difficult or impossible to remove.” BIA's full position on clay paver pavements, from breathable coatings to slip resistance, is set out under whether brick pavers can be sealed.

With no manufacturer, what remains is the general guidance BIA writes for clay brickwork and brick pavements. On coatings, that is the 2008 note's line against coating clay paver pavements. On cleaning, Technical Note 20 says not to use water pressures higher than 400 psi measured at the nozzle tip unless the brick manufacturer permits more, calls high pressure, above 800 psi, not appropriate for brick, rules out unbuffered muriatic and hydrofluoric acid, and asks for the gentlest effective method. The unless-permitted exception is the one part reclaimed brick cannot use.

That 400 psi is a clay brick figure and travels nowhere else. The Natural Stone Institute publishes no pressure figure for stone, a gap explained under whether there is a PSI limit for pressure washing travertine, and the concrete paver range belongs to ICPI. The three materials side by side are on the paver cleaning page's rulebooks for concrete pavers, travertine and clay brick.

None of this lets a sealer maker's label stand in for the missing brick manufacturer. BIA's instruction names the brick maker, and for reclaimed Chicago brick that party no longer exists. The words used here, from efflorescence to PSI, are defined in the paver and stone glossary.