Can clay brick be cleaned like concrete pavers?

Start with a Florida paver maker. Tremron sells “brick pavers,” and it specifies its pavers to ASTM C936, the standard specification for interlocking concrete paving units. The word brick in a product name does not tell you the unit is fired clay.

That matters because the material, not the trade name, decides which cleaning rulebook applies. Fired clay has one, written by the Brick Industry Association. Concrete has another, written by the Interlocking Concrete Pavement Institute. The installer or the supplier who provided the units is the reliable source for which one was laid.

The edge of the unit will not settle it either. BIA says clay pavers can have edges that are square, round, beveled or relieved, and ICPI's glossary defines a chamfer on concrete units as a 45 degree beveled edge, so a beveled edge turns up in both documents.

The Brick Industry Association's Technical Note 20, “Cleaning Brickwork,” dated August 2018, states its reach in its abstract: “This Technical Note addresses cleaning of brickwork and brick pavements.” It covers clay brick paving, not concrete pavers.

Its governing instruction is a method, not a machine: “Select the gentlest effective cleaning method.” Its other paving-relevant limits sit beside that line.

• Pressure: “Do not use water pressures higher than 400 psi (2800 kPa) as measured at the nozzle tip unless permitted by brick manufacturer.”
• High pressure defined: greater than 800 psi, which BIA says is not appropriate for brick and may damage the brickwork.
• Acid: “Do not use unbuffered muriatic (hydrochloric) or hydrofluoric acid.”
• Match and approve: “Match the cleaning method and cleaning solution to the type of brick,” and verify that the brick manufacturer approves both.
• Test first: a trial cleaning on a 20 square foot sample area before the whole surface.

The number in those limits is a clay brick number, measured at the nozzle tip, and it means nothing for another material without that material's own document; what the unit measures is under PSI, pounds per square inch.

ICPI Tech Spec 5 describes professional cleaning of interlocking concrete pavers with a high pressure sprayer applying cleaner and water between 1,000 and 4,000 psi. That range is written for concrete pavers, and ICPI pairs it with a nozzle and an angle chosen to keep the joint sand where it is.

ICPI's reasoning is about the joints: “A nozzle that creates a wide spray enables a large area to be covered efficiently and prevents sand from being washed from the joints.” Its cleaners are typically a mix of detergent and acid, and it warns that “Cleaners with strong acids will change the color of the pavers slightly,” which is why a small test area comes first on concrete too.

A concrete paver maker adds its own line for its own product. Tremron, on its own concrete pavers, says muriatic acid will damage the surface of the pavers and cause pitting. Each line belongs to its owner. The limits for concrete pavers, travertine and clay brick sit side by side in one table under cleaning limits by paver material.

Put the two documents next to each other and pressure washing clay brick the way concrete pavers are washed runs into BIA's limits on every line that matters.

The joints row deserves a second look. BIA notes that “acid-based cleaning solutions may not be appropriate for pavements containing joint sand stabilizers or polymeric sand,” and recommends verifying the compatibility of the cleaner with the paver manufacturer before selecting a solution for brick pavements. A brick pavement with joint stabilization puts two approvals in play, not one. What buffering an acid changes is explained under buffered acid and paver cleaners.

Three decisions sit with people other than the cleaner: which material the unit is, an answer for the installer or supplier; whether the brick maker approves the method and the solution, under BIA's note; and whether the cleaner suits stabilized or polymeric sand joints, which BIA sends to the paver manufacturer.

That chain assumes a brick maker still exists to ask. Reclaimed brick from a brickyard that has closed breaks it, a case set out under reclaimed Chicago brick and the missing maker. Whether clay brick should be coated after cleaning is a separate question, answered under whether brick pavers can be sealed.