Does roof cleaning brighten the color of the tile?

Concrete roof tile gets its color in one of two ways, and which one a roof has decides most of what a cleaning can reveal.

The Tile Roofing Industry Alliance (TRI Alliance) puts the two methods in one sentence in its Roof Maintenance Guide: “Tiles are normally colored by either adding pigment into the body of the tile during the mixing stage (integral colored) or by applying a concentrated slurry coat of pigment to the tile surface following extrusion and forming.” Integral color runs all the way through. A slurry coat is a layer of concentrated pigment on the face of the concrete body.

The guide then says how each one ages. “Slurry-coated tile can oxidize and turn chalky before gradually wearing down to the concrete base.” And: “Integral-colored tile may show some surface lightening, but will retain its base color indefinitely.” That is the oxidation and chalking the glossary defines, and they are changes to the tile, not deposits on it. A chalky look in depth is its own question, taken up under why a roof looks chalky.

Which of the two a particular roof carries is not something to guess from the ground. The tile maker, or a roofing contractor looking at the tile, can say. The instructions each maker publishes for its own tile are gathered under cleaning by roof type.

What darkens a tile roof is mostly not the tile. TRI Alliance writes that mildew, algae and moss grow on the dust and organic material that settles on tile, not on the tile directly.

A cleaning removes that layer, and TRI Alliance describes the result with care: “While this growth can result in a dull surface appearance, it can be treated to restore the original look.” The original look is the tile without the growth on it. It is not a promise about pigment, and it does not reach a slurry coat that has already chalked or worn thin. How a light roof goes dark in the first place is covered under why a white tile roof turns black.

The shingle side of the trade chooses its verb just as carefully. ARMA's technical bulletin on algae discoloration says that discoloration “may be lightened” by a solution of household bleach and water. Lightened is ARMA's word, written about asphalt shingle, and restore the original look is TRI Alliance's, written about growth on tile. Brighter is the reader's word, and neither document uses it for what a cleaning does.

Whether the roof as a whole will look new once the film is gone is a wider question, answered under whether a roof looks new after cleaning. The color question is narrower: a cleaning uncovers color, and the tile decides how much is there.

Two more facts shape what a clean roof looks like: clay ages differently from concrete, and concrete tile of one color still varies from piece to piece.

On clay, TRI Alliance writes two sentences that belong together. “In general, clay tile doesn't fade in the sun.” And: “Color softening will occur, but the results are subtle.” Fading in the sun is the change the glossary files under UV degradation. TRI Alliance says clay generally resists it, and the color softening it does expect, it calls subtle.

On concrete, Eagle Roofing Products' Florida limited warranty text, as archived, explains that a single-color roof shows a variation in hue from one tile to another because the tiles are made from natural raw materials that vary in color. “As the roof ages, the variation tends to be less noticeable.” The same document states: “Eagle does not warrant color due to the tile exposure to the elements.”

So on a single-color roof, a shade difference from one tile to the next comes from the tile's raw materials, by Eagle's account, and not from the cleaning. Why some tiles read darker than others after a wash has its own answer under why some tiles look darker after cleaning.

The documents do describe a way to add something back to concrete tile, and it is not a cleaning.

TRI Alliance writes that, unlike most other roofs, a concrete tile roof can be recoated, and that a clear coat of 100 percent acrylic sealer “may be applied to renew the roof's original luster.” It recommends a professional with experience for any work on a concrete tile roof, and elsewhere it pairs periodic cleaning with resealing when it writes about the surface finish of tile. Whether a tile roof should be sealed after it is cleaned is argued under sealing a tile roof after cleaning.

Florida draws the line on that coat. Florida Statutes 489.105(3)(e) places coating in the roofing contractor's trade “except when coating is not represented to protect, repair, waterproof, stop leaks, or extend the life of the roof.” A clear coat sold as any of those five things is roofing contractor work, and a question about recoating a roof belongs with a roofing contractor.