Roof cleaningin Coral Springs.

The streaks are a cyanobacteria called Gloeocapsa magma. It arrives on the wind, lands on the roof, and feeds on the limestone filler in concrete tile and asphalt shingle. It grows a dark protective coating against the sun, which is the black you see, and it holds moisture against the roof so it never fully dries. Behind it come lichen and moss, which root into the tile and shingle and do real damage when they are pulled off.

It is not dirt and it is not soot. It is alive, it spreads, and it is why a roof that was black on the north slope last year is black on two slopes this year. Killing it is the only thing that works, and killing it is what a soft wash does.

Concrete tile, barrel or flat, is the Coral Springs standard. It is porous, so the growth goes deep, and it needs a full-strength roof mix and enough dwell to get down into the pores. Tile can be walked in the right places, along the laps and near the ridges, and cracked wherever it is walked wrong. Michael walks tile where the roof supports it and works from a ladder or the eave where it does not.

Shingle is the one you never pressure wash under any circumstances. The colored granules on the surface are the shingle's UV protection, and pressure strips them into the gutter. A soft wash on shingle is applied gently, allowed to work, and rinsed lightly or left for the rain. Metal roofs, rarer here, clean fastest and show the result immediately.

Florida carriers look at roofs from the air and from the street, and a black-streaked tile roof reads as old and neglected no matter what year it was installed. A clean roof is not a repair and it does not change the roof's age, but at renewal or during a four-point inspection it is the difference between a photo that raises questions and one that does not.

If your carrier or your HOA has sent a letter about the roof, send Michael the letter with the photos. A soft wash is almost always the fix they are asking for, and it is a fraction of what the letter implies.

A roof wash runs off exactly where the rain does: into the gutters, down the spouts and onto whatever is planted under the drip line. Everything under the eave is wet down with plain water first, so the solution cannot sit on it, and rinsed again after. Gutters and downspouts are flushed at the end so nothing pools in them.

Pools are fine. The volume of solution that reaches a pool is small next to the water in it, and the deck is rinsed. Koi ponds and vegetable beds directly under a drip line are different and get covered or diverted, so mention them when you ask for the quote.