Can a roof be too old to clean?

Start with a roof on the day it goes on and follow its surface forward, the way the tile association and a shingle maker describe it. Neither account puts a year on any stage.

For tile, the Tile Roofing Industry Alliance begins with durability: “The combination of elements that destroy most other roof coverings will not seriously affect the protective properties of a tile roof.” Then it adds that “over time the surface of any product will show signs of aging, including roof tiles.” The first visible stage depends on how the color was made. Slurry-coated tile, TRI says, “can oxidize and turn chalky before gradually wearing down to the concrete base,” while integral-colored tile “may show some surface lightening, but will retain its base color indefinitely.” That oxidation and the chalking that follows are changes to the colored face, and TRI says the erosion after them “will never affect the physical properties of the tile.” Why a tile roof ends up looking powdery is answered in why a roof looks chalky.

For asphalt shingle, CertainTeed explains that granules are crushed rock particles pressed into the surface of the asphalt, and that they “block ultraviolet (UV) light from reaching the asphalt in the shingle.” It adds that “UV rays, if allowed to reach unprotected asphalt, will age the asphalt prematurely,” and that the asphalt is the shingle's waterproofing agent and what holds the granules in place. The granules stand between sunlight and UV degradation of the asphalt, so each granule lost leaves more of the asphalt without that shield.

Both accounts describe an order of change rather than a timetable. How far along that order a particular roof has come depends on that roof, and reading it is a roofing contractor's work.

Where the documents warn about harm to a roof during cleaning or foot traffic, the cause they give in each case is something done to the surface.

For shingle, ARMA's bulletin says: “Avoid scrubbing the surface, as this friction may loosen and remove granules.” It says high-pressure washing systems “are likely to damage asphalt roofing” and should not be used on it for any purpose. On a shingle whose asphalt already depends on the granules it has left, granule loss is the named risk. How a shingle roof is cleaned without adding to that loss is the subject of shingle granules and roof cleaning.

For concrete tile, Eagle Roofing Products' Owner Information says “Walking on or putting pressure on tiles can potentially cause damage,” and recommends staying off the roof. TRI Alliance says tiles damaged by foot traffic should be replaced, and that broken tiles “may cause problems by allowing water and UV rays to penetrate through to the underlayment and damage it.”

None of those warnings is written for old roofs in particular, and none of them starts at a stated age. What they share is a surface under stress: friction, pressure, weight. An older surface may have less margin for any of the three, which is why the question of age turns into a question of condition, and condition is not something a document can settle from a distance.

The one roof age with legal weight in Florida sits in the insurance code, and it answers a different question from this one.

Florida Statutes 627.7011(5) uses fifteen years for issuing and renewing homeowner's policies, and it counts a roof's age from the last date the whole roof surface was built or replaced. What that count leaves unmoved is set out in whether cleaning a roof before an inspection changes the result, and the inspection right it gives an owner in the right to an inspection before an insurer requires a new roof. The statute is quoted with the other rules that bear on the job among the Florida rules that touch a roof cleaning.

Nothing in that subsection mentions cleaning. Treating fifteen years as a cutoff for washing a roof takes an insurance number out of the statute it was written for.

An old roof raises a condition question before it raises a cleaning one, and the sources send condition to one trade.

TRI Alliance strongly recommends contacting a professional roofing contractor to repair or replace broken tiles. Eagle Roofing Products' Owner Information starts with the original roofing contractor for inspection or repair and, failing that, another qualified licensed roofing contractor. Whether a particular older roof can take foot traffic, and whether any wash is sensible on it, is that contractor's judgment rather than a cleaner's.

The same question from the other end of a roof's life is answered in how soon a new roof can be cleaned. A cleaning is also not a way to buy an old roof more years, and the reasons are set out in whether roof cleaning helps a roof last longer.

Metal strips are no workaround for an existing roof either. ARMA says adding zinc or copper strips to an existing asphalt shingle roof is not recommended, because it means exposed nails that can cause leaks over time or a broken sealant bond that may lead to wind damage, a point taken up in whether copper strips keep roofs clean.