Can moss grow on a Florida roof?

ARMA describes moss by what it needs to survive, and nothing in that description rules out Florida.

ARMA writes that “moss is a non-vascular plant that obtains water through its leaves, unlike most plants that gather water through its root system. Moss must therefore have a moist environment to survive.” The same bulletin adds that “in North America, moss tends to grow on north facing roof planes that receive less direct sunlight and stay damp longer than south facing planes,” and that “overhanging tree branches provide additional shade and drop debris on the roof that further holds in moisture and acts as a food source for moss.”

ARMA's sentence covers North America and names no climate where moss cannot grow. What branches over a roof add is the subject of roofs getting dirty under the trees.

ARMA draws a sharp line between moss and algae on asphalt shingle.

ARMA states that “unlike algae, moss can be detrimental to asphalt shingle performance. Moss can cause the leading edges of the shingles to lift or curl, which increases the risk of shingle blow-off during wind events.” In severe cases, the same page says, “moss build-up can cause lateral water movement resulting in moisture damage to the roof deck or may even cause leaks.” ARMA's Algae Discoloration of Roofs bulletin refers questions about the effects of moss on asphalt shingles, and its removal, to the shingle manufacturer.

That bulletin also tells algae apart from moss and tree droppings, which “typically produce only localized discoloration,” unlike the black streaks algae can leave. Telling moss from lichen or wet algae on a given roof is the green fuzz on a roof question. Lifted or curled shingle edges, like granule loss on a shingle, are for a licensed roofing contractor to assess, not a cleaner.

On concrete and clay tile, barrel tile included, TRI Alliance places moss on what settles on the tile, not on the tile itself.

TRI Alliance's guide says mildew, algae and moss “do not grow directly on tile” but on the dust and organic material that settles on it. Moss reaches that film through the air: ARMA says “moss spores may also be carried by wind or animals and can easily spread throughout neighborhoods.”

ARMA's steps for discouraging moss and algae are trimming branches back so more sunlight reaches the roof, clearing debris with a leaf blower or similar non-abrasive method, and keeping gutters clean. For moss on asphalt shingle, ARMA's procedure notes that after a bleach treatment “moss will loosen over time and may be removed with a leaf blower,” and that “in severe cases, it may take more than one bleach treatment to kill all of the moss.” That is ARMA's shingle procedure, not a statement about a tile roof or about any company's work. Because moss must stay moist to survive, it is also part of the answer to why a roof is turning green.