Can exterior cleaning remove storm debris stains?

What a storm leaves on the outside of a house sorts into three piles, and the documents speak to only two of them.

• A mark: a stain left where wet leaves, wood or tree debris sat on a surface.
• A deposit: something the wind carried and left on top of a surface, such as dirt, plant matter or spray.
• Possible damage: anything cracked, lifted, missing or broken, which is not a cleaning question at all.

Telling the first two apart is harder than it sounds. ARMA writes that algae discoloration “may be mistaken for fungus growth, soot, dirt, moss, or tree droppings,” so a dark patch after a storm is not necessarily from the storm.

Spray is a real deposit, though no source read measures what it leaves on a building; what the published guidance does say about salt, frame by frame and plant by plant, is under what salt air does to a home exterior.

The storm calendar itself is the National Hurricane Center's: the hurricane season runs June 1 to November 30, with a climatological peak on September 10 and most activity between mid-August and mid-October.

The one published treatment that fits storm debris marks directly is a line in ICPI's Tech Spec 5, and it is written for concrete pavers only.

ICPI's stain table lists leaf, wood rot or tobacco stains and, for them, says to “apply household bleach and scrub with a stiff bristled brush.” That is a treatment, not a promise. The table names what to use and stops there, and it is a concrete paver line: it is not an instruction for a roof, for travertine or for glass.

ICPI carries a separate warning about the rest of the yard. Acidic cleaning products “may harm vegetation and grass,” it writes, and “These cleaners should not run onto vegetation.” Where strong acidic stain removers might drain onto plants, ICPI says to saturate the vegetation with water first. ARMA's roof bulletin carries the parallel line for its own bleach solution: “Take proper precautions to protect landscaping and surrounding areas from the chlorine bleach solution.” Glass near a roof has a line of its own. The National Glass Association's examples of what may harm laminated glass include “Bleach (or other solutions containing sodium hypochlorite)”, and PGT describes its own hurricane windows and doors as laminated, so keeping a bleach roof solution off impact windows is a technical requirement of the work.

The rest of what a paver cleaning takes off, and how the trade approaches it, is set out under what a paver cleaning removes.

On a roof, ARMA draws a line between what debris does and what algae does.

ARMA writes that algae discolorations “should not be confused with moss or tree droppings, which typically produce only localized discoloration.” A mark where a branch or a mat of leaves came to rest is localized by nature. Long streaks down a slope are a different pattern, and the organism behind those is explained under the black streaks on a Naples roof.

On results, ARMA is modest about its own method. Of bleach-solution cleaning of algae discoloration it writes: “The effectiveness of such cleaning is only temporary, and the discoloration may recur.” No roofing document read says a debris mark will come off completely, and a page that claimed it would be claiming more than the documents do. Whether old tile stains can be removed completely is its own question, with its own answer.

The third pile has its own instructions, and they come from Florida's Department of Financial Services rather than from any cleaning document.

Those steps, the photographs or video for the company adjuster and the records of any repairs, are quoted in full on the roof answer linked below. None of them is cleaning advice, and none says what an insurer will decide.

A cleaning does not find, judge or repair damage. Questions about a roof's condition after a storm belong with a licensed roofing contractor, and questions about a window with its maker or installer. The order for a roof, the roofing contractor and the documentation before any wash, is set out under whether a roof can be cleaned after a hurricane, and the general boundary is under what an exterior cleaner is not.