Will the roof look new after cleaning?

Split a stained roof into two layers and the question mostly answers itself: the growth sitting on the surface, and the tile underneath that growth.

The left column is what the cleaning documents describe a cleaning acting on. The Tile Roofing Industry Alliance puts the growth on settled dust and organic matter rather than on the tile itself, and ARMA's technical bulletin for asphalt shingle chooses its verb carefully: “Discoloration may be lightened by applying a solution of liquid household bleach (sodium hypochlorite) and water.” Lightened, not removed, and not returned to new. What the black streaks on a roof are covers the growth itself.

TRI Alliance's sentence about appearance is also about the left column. It writes, “While this growth can result in a dull surface appearance, it can be treated to restore the original look.” The subject of that sentence is the dullness the growth causes. It says nothing about the pigment in the tile, and the right column is where the tile's own story sits.

TRI Alliance explains that concrete tile gets its color in one of two ways, pigment mixed through the body of the tile or a concentrated slurry coat of pigment laid on the surface, and the two age differently.

A slurry-coated tile, in TRI's description, can oxidize and turn chalky before it gradually wears down toward the concrete base. An integral-colored tile may show some lightening at the surface but keeps its base color indefinitely. Neither change is a stain. A cleaning that takes the growth off a chalked slurry coat shows the chalked slurry coat, and whether roof cleaning brightens the color of the tile goes further into what that looks like.

Clay gets a shorter entry. TRI Alliance writes, “In general, clay tile doesn't fade in the sun,” and in the same passage, “Color softening will occur, but the results are subtle.” Both halves belong together: clay holds its color well, and it still changes a little.

Even a roof that was one color on installation day was never exactly one color. Eagle Roofing Products' Florida warranty text, as archived, says single-color concrete tile roofs show hue variation from tile to tile because the natural raw materials vary, adds “As the roof ages, the variation tends to be less noticeable,” and states “Eagle does not warrant color due to the tile exposure to the elements.” A patchy look after a wash has several possible reasons, and why some tiles look darker than others after cleaning sorts them without reading any one roof.

Efflorescence is the exception that fixes itself: on concrete tile, TRI Alliance and Eagle both leave it to the rain. Which marks stay and which go is laid out mark by mark in whether roof stains are permanent.

The roofing documents do describe a way to renew a tile roof's surface, and it is not a wash.

TRI Alliance says a concrete tile roof, unlike most other roofs, 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 hiring a professional with the right background for any work on a concrete tile roof. TRI also pairs periodic cleaning and resealing with the surface finish of cement or clay tile, and the two steps travel together in that sentence.

Florida law speaks to that second step. Florida Statutes 489.105(3)(e) places coating inside the roofing contractor's scope “except when coating is not represented to protect, repair, waterproof, stop leaks, or extend the life of the roof.” A recoat or a clear coat is a roofing contractor's conversation, and the difference between roof cleaning and roof restoration takes it from there. Where a soft wash stops draws the same line from the method's side.