Underlayment

The Florida tile installation manual defines underlayment in one line, and each part of it matters.

The FRSA-TRI Florida High Wind Concrete and Clay Tile Installation Manual (7th Edition, 12/31/23) says the terms in its glossary “are used in the context of concrete and clay tile roofing,” and its entry for underlayment reads: “One or more water-shedding layers of roofing applied to a sloped roof prior to the installation of roof tiles.” One or more means a single layer or several. Water-shedding names the job, carrying water off. Prior to the installation of roof tiles puts it on the roof first, beneath every tile laid after it.

TRI Alliance's guidance for anyone who must walk on the roof fills in what lies below. The part of a tile to step on, “the bottom three inches of the installed tile,” it says, “is supported by the lapped tile beneath it, and weight is transferred through to the deck below.” Read with the manual's entry, that puts the tile on top, the underlayment beneath it and the deck under both, with the underlayment covered by tile on a finished roof.

The same glossary supplies the words for the roof's edges, among them the eave, “The horizontal lower edge of a sloped roof,” and the drip edge, set “to allow water run-off to drip clear of the underlying construction.”

One warning carries the underlayment into tile owners' guidance, and TRI Alliance and Eagle Roofing Products print it in nearly the same words.

“Broken tiles may cause problems by allowing water and UV rays to penetrate through to the underlayment and damage it,” TRI's Roof Maintenance Guide says, and Eagle's owner information repeats the sentence for tiles broken by foot traffic. TRI's instruction that follows is to have broken roof tiles replaced as soon as possible, and it “strongly recommends that you contact a professional roofing contractor to repair or replace broken tiles.”

A roof cleaning works on the other side of the tile. TRI places roof growth on “the accumulation of dust and other organic materials that settle on tile,” the tile's outer face; the underlayment lies beneath, and reaching it means lifting or replacing tile. TRI adds that a “professional roofing contractor will notice and report potential maintenance issues that a cleaning company would overlook,” so a cleaning is no check on the layers under the tile. Who handles a broken tile is settled in the answer on broken roof tiles and whose job they are.

Whether a given roof has a broken tile, whether water has reached the underlayment and what condition that layer is in are findings for a roofing contractor's inspection, not a cleaner's. Eagle's owner information, for the case where “inspection is desired or repair work is required,” points first to “the original roofing contractor” and, if that contractor is unavailable, to “another qualified licensed roofing contractor.” The roofing-contractor routing recurs in the answers on a roof cleaned after a hurricane, a roof cleaned before an inspection and pressure washing a tile roof, while whether roof cleaning can cause a roof leak gets its own answer, with the sourced ways water gets in.