Taking Care of the Roof You Have

The Roofing Series, Lesson 6 · Taught by Professor Elias Walls · Researched and reviewed by Grant Doutt, Certified Master Inspector®

🎓 The Professor's Quick Answer

You can't make a roof younger. You can keep it from aging faster than it has to.

In Florida, three things take years off a roof before its time: debris and water that sit where they shouldn't, trees that touch the roof, and the cleaning methods people use on those black streaks. That last one does more damage in this state than almost anything else, because a pressure washer strips the protective granules off asphalt shingles in minutes and voids most manufacturer warranties while it's doing it.

Those black streaks are algae, not dirt. Whether the algae itself is taking years off your shingles is not settled, and we're not going to tell you we know. What is settled is how you get rid of it: a chemical cleaner does the work, and nothing mechanical touches the roof. No pressure washer, no brush, no broom.

This lesson is about the handful of things that actually buy you years, the things that cost you years, and what your roof warranty really covers, because most homeowners have never read theirs.

🏫 Welcome Back to the Knowledge Center

Last class we talked about repair versus replace — how to tell where your roof is in its life, what a fair proposal looks like, and why the roof matters more than anything else a buyer looks at.

Today we close the series out with the part you can actually control. You didn't pick the roof's install date. You don't control the sun, and you certainly don't control the storms. But almost every roof we inspect that failed early failed for a reason somebody could have done something about.

So let's talk about getting every year out of the roof you already own.

🖤 Those Black Streaks Down Your Roof

Drive any Central Florida neighborhood and you'll see them: dark streaks running down from the ridge, usually worse on the north side, usually worse under trees.

That's not dirt. It's not mildew and it's not "the shingles going bad." It's an algae called Gloeocapsa magma, and it is eating the limestone filler that's blended into asphalt shingles. It spreads by airborne spores, which is why one streaky roof on a street tends to become five.

It grows heaviest on the north and shaded slopes because those stay damp longer, not because those shingles are failing.

Does it actually hurt the shingle?

Worth getting right, because you will hear this argued both ways, and most of the people arguing it have something to sell you.

What's not in dispute is that the algae feeds on the limestone filler in the shingle. What's in dispute is what that costs you:

• The Asphalt Roofing Manufacturers Association — the shingle makers' own technical body — treats algae as discoloration. Its bulletin on the subject never says algae shortens a roof's life. Every damage warning in it is about how people clean it.

• GAF warranties its algae-resistant shingles against discoloration, not against damage. The only premature-failure language in their bulletin is about power washing.

• The National Roofing Contractors Association's technical staff put it flatly: there is no evidence blue-green algae harms asphalt shingles.

• On the other side, some manufacturers who sell algae-resistant shingles say it loosens granules, costs the roof its reflectivity, and shortens its life. They publish no test data behind it.

• And every roof-cleaning company in Florida will tell you it's destroying your roof.

Where we land: nobody has settled this, and we're not going to pretend otherwise in either direction. Here's the part that keeps us from waving it off, though. The organism has to have sustained moisture to live. So a heavily streaked slope is, by definition, a slope that stays wet — and sustained wet is hard on a shingle regardless of what's growing in it. That's reason enough to take it off, and reason enough to be careful how.

Moss and lichen are a different conversation

These two we will tell you to deal with, because the mechanism is physical and nobody argues about it.

• Moss holds water against the shingle and up under the edges of the tabs. Wet shingle deteriorates. It's slow, and in Florida it's mostly a shaded-roof, north-slope, under-the-oaks problem — but it is real damage, not staining.

• Lichen is the worst of the three. It bonds into the asphalt itself. Pulling it off pulls granules with it, and the scarring it leaves behind can look like blistering to someone reading the roof afterward. Lichen reliably costs you shingle.

So when somebody says microbial growth shortens a roof's life, they're right — about moss and lichen. The black streaks are the one where the industry's own technical bodies won't go that far.

Which brings us to the part that actually ages roofs in this state, and it isn't any of the above. It's what homeowners do about it.

Every year we inspect roofs that were in fine shape and are now five years from replacement, for one reason: somebody cleaned the streaks off with a pressure washer.

🚫 Why Pressure Washing Ruins a Roof

An asphalt shingle is a mat soaked in asphalt with a layer of ceramic-coated granules pressed into the surface. Those granules are the shingle's sunscreen. They are the only thing standing between Florida's UV and the asphalt underneath, and once they're gone, the asphalt dries, hardens, and cracks.

A pressure washer blasts them off. Not all at once in an obvious way — it comes off as a gritty black runoff you'll find in the gutters and all over the driveway. Those are years of roof life lying on your concrete.

We say it this way in the field: a pressure washer ages a roof ten years in ten minutes.

It gets worse. High pressure also:

• Drives water up under the shingles, backwards against the way the roof is designed to shed, and into the underlayment and deck

• Breaks the self-seal strips that bond each course to the one below, which is exactly what holds shingles down in high wind — the thing we spent all of Lesson 3 talking about

• Cracks and dislodges tile, on a tile roof, and tile that's been walked and blasted is tile that leaks

• Voids the manufacturer's warranty. Nearly every shingle manufacturer specifically excludes damage from pressure washing. You can lose the warranty and the roof in the same afternoon.

If a contractor shows up with a wand and a ladder and talks about "blasting that right off," send him home.

The right way: let the chemical do the work

The Asphalt Roofing Manufacturers Association's instruction on this is blunt, and notice that it rules out more than the pressure washer: do not use a power washer or any type of brush or broom to clean algae from the roof surface. No pressure. No scrubbing. Nothing mechanical at all.

What's left is chemistry, and that is the actual answer. A cleaner kills the growth and then time and weather take it off the roof:

1. Use a product made for this. The one most homeowners will find at the box stores is 30 SECONDS, which makes a roof-specific version — use the one labeled for roofs and follow its label. Professionals mix their own, generally a sodium hypochlorite solution in the neighborhood of 50/50 with water.

2. Wet down the landscaping first. Plants, shrubs, and grass get soaked before you start and rinsed again after.

3. Spray it on. Hose-end sprayer or a low-pressure pump sprayer. The sprayer is a delivery method, not a cleaning tool.

4. Let it dwell. This is where the work actually happens. Follow the label's time.

5. Rinse gently, downhill, at ordinary hose pressure.

6. Do not scrub. Heavy growth gets a second application, not a brush. The moment anyone puts bristles on an asphalt shingle, granules come off.

The roof does not come clean while you're standing there watching, the way a pressure washer makes it appear to. The streaks keep fading over the following days and weeks as the dead growth weathers off. That's normal, and it's the trade you want.

One caution: this is still roof work — on a roof, with chemicals, in Florida. There's no shame in hiring it out. If you do, ask the contractor two questions: what pressure do you use on shingles, and is anybody getting up there with a brush? If the first answer is a number in the thousands or the second answer is yes, keep calling.

🧪 Keeping the Streaks From Coming Back

Cleaning treats the symptom. There are two ways to slow the regrowth.

Zinc or copper strips at the ridge. Metal strips installed just under the ridge cap release trace amounts of metal ions every time it rains, and those wash down the slope and suppress algae growth. They work — with a real limitation. The effect gets weaker the farther the water travels, so on a long slope you'll often see a clean band near the top and streaking resuming lower down. On tall or steep roofs, additional strips partway down the slope help.

Algae-resistant shingles. Most major manufacturers now sell shingles with copper-containing granules mixed into the surface. These carry a separate algae warranty, often 10 to 25 years depending on the line. They aren't a guarantee of a spotless roof forever, but they meaningfully delay the streaking. When you re-roof, ask for AR shingles. The upcharge is small and in this climate it's worth it every time.

And the cheapest prevention of all: cut back the trees. Shade and trapped moisture are what let algae establish. Sunlight and airflow are what keep it from coming back.

🧰 The Maintenance That Actually Buys You Years

Short list. Boring list. It's the one that works.

Keep the roof and valleys clear of debris. Leaves and pine needles hold moisture against the covering and dam up valleys, pushing water sideways underneath. Clear them a couple times a year, more if you're under oaks or pines. In almost every case this can be done from the ground with a blower on the lower slopes or by a contractor — not by you walking around up there.

Keep the gutters flowing. A clogged gutter backs water up under the drip edge and into the fascia and sheathing. That rot starts at the edge of the roof and works inward, and it's one of the most common repairs we see written on older Florida homes.

Trim back every branch touching the roof. Branches abrade shingles every time the wind blows, drop debris constantly, and give squirrels and rats a bridge to your soffit and attic. The rule of thumb is roughly six to ten feet of clearance from the roof surface. Trees are also the number one source of catastrophic roof damage in a storm — a limb through the deck is a different kind of day than a few missing shingles.

Replace pipe boots before they fail. We covered this in Lesson 4 and it's worth repeating here, because it's the single most common leak we find in this state. Those rubber collars dry out and crack in ten to fifteen years of Florida sun. The part is cheap. The ceiling it ruins is not.

Look at the roof after every significant storm, from the ground or by a professional. Shingle tabs lifted, tiles shifted, flashing bent, debris left behind — the things that turn into leaks are visible long before the ceiling stains.

Keep the attic ventilated. Soffit vents blocked by insulation, ridge vents covered over, bath fans dumping into the attic — all of it bakes and steams the underside of the deck. Ventilation is a roof-life issue, not just a comfort issue.

Don't let anyone put new holes in your roof casually. Satellite brackets, holiday light screws, solar mounts, antenna masts. Every one is a penetration, and every penetration needs proper flashing, not a bead of sealant.

Keep your records. Permit, contract, invoice, warranty registration, and photos. When you sell this house, or when you have a claim, that folder is worth real money. We said in Lesson 1 that insurers go by the permit, not the appearance — this is where that permit lives.

📜 About Your Warranty — Which Probably Isn't What You Think

Almost everybody says "my roof has a 30-year warranty." Almost nobody has read it. There are actually two separate warranties on a new roof, and they cover different things.

The manufacturer's warranty covers defects in the shingle itself. Important details:

• It is usually prorated. Full replacement value typically applies only in the first several years, after which the payout declines each year. A failure in year 22 of a "30-year" shingle may be worth very little.

• It covers material, not labor, unless you bought an upgraded or system warranty.

• It often requires registration within a set window after installation — commonly a few months. An unregistered warranty can be a reduced warranty.

• It is usually transferable once, within a limited window after a sale, and sometimes with a fee. If you're selling, transferring the warranty is a real selling point. If you're buying, ask whether it can be transferred and do it on time.

The contractor's workmanship warranty covers the installation — flashing, fastening, the things that actually cause most roof problems. This is typically much shorter (one to ten years, varying widely) and it is only as good as the contractor still being in business. In a market with as much storm-chasing activity as Florida's, that matters.

What voids a roof warranty

This is the part worth taping inside a cabinet door:

• Pressure washing, and scrubbing with a brush or broom

• Installing a second layer of shingles over the old roof

• Mounting anything through the roof without proper flashing — solar, satellite, lights

• Inadequate attic ventilation, which most manufacturers specifically require

• Repairs by someone other than an approved contractor, on some system warranties

• Failing to register the warranty in the required window

• Normal weathering and storm damage — which was never covered to begin with; that's what your insurance is for

The common thread: a warranty covers the shingle being defective. It does not cover the roof getting old, and it does not cover what gets done to it afterward.

🏘️ Before You Hire Anyone: Check With the HOA

If you live in a deed-restricted community — and a great many Central Florida homes do — get written approval before you sign a roofing contract.

Associations routinely restrict roof color, shingle style and profile, tile type, and sometimes the specific manufacturer. We have watched homeowners install a perfectly good roof and then be told to take it off and do it again in an approved color. That is an expensive lesson in paperwork.

The sequence that works: pick the product, submit for architectural approval, get it in writing, then sign the contract. Not the other way around. And keep the approval letter in the same folder as the permit.

❓ Questions From the Back Row

"Is it worth cleaning the roof if I'm not selling?"

We'd lean toward yes, and treat it chemically. Nobody has settled whether the algae itself damages shingles, but it only lives where the roof stays wet, and that's not a condition you want running for years. Moss and lichen are a clearer call — moss holds water against the shingle, lichen grips into the asphalt, and both cost you roof.

"My neighbor's roof was pressure washed and it looks great. Why not?"

It looks great today. The damage shows up later as accelerated granule loss and premature aging, and it's not reversible. Look at his gutters and driveway for the black grit — that's the roof.

"Can I clean it myself?"

The chemistry is simple enough, and a hose-end product like 30 SECONDS is made for exactly this. Being on a Florida roof with a bucket of bleach is the part we'd rather you didn't do. If you're going to try it anyway, work from a ladder at the edge where you can reach, soak the plants first, never run a pressure washer, and keep every brush in the garage.

"Does a roof cleaning help with insurance?"

No. Insurers go by age and condition, documented on the permit and the inspection — not by looks. We covered this in Lesson 1 and it's worth saying again, because it's the exact gap the "add years to your roof" sales pitches live in. A clean 18-year-old roof is an 18-year-old roof on the application.

"How often should the roof be professionally looked at?"

Once a year is reasonable in Florida, and after any significant storm. It's a small cost against the most expensive component on the house.

"I have a tile roof. Does any of this apply?"

Most of it. Debris, trees, gutters, and penetrations are the same. Cleaning tile is different — the tile itself is tougher than shingle, but walking a tile roof breaks tile, and a cracked tile is a leak path. On tile, the person you want on the roof is somebody who knows how to walk one, which is a specific skill.

"The roof is near the end of its life. Should I still maintain it?"

Yes, especially the leak-prone spots. Maintenance on an old roof isn't about adding years to the calendar — it's about not spending money on ceilings, insulation, and flooring while you're saving for the replacement.

🚌 Field Trip — Class Dismissed

One last assignment, and it's an easy one.

Walk the perimeter of your house. Look up at the roof from each corner. You're looking for four things: branches touching it, debris sitting in the valleys, gutters that are full, and rubber collars on the plumbing vents that look cracked or shrunken.

That's it. If all four are clear, your roof is being taken care of better than most we see.

And that closes out our Roofing Series. Six lessons: how the clock on a Florida roof is counted, how to read what a roof is telling you from the ground, what actually holds it down in a storm, where roofs really leak, when to repair and when to replace, and now how to get every year out of the one you have.

The roof over your head is the most expensive thing standing between your family and a Florida sky. Now you know how it works.

Class dismissed.

Sources: Asphalt Roofing Manufacturers Association technical bulletin on algae discoloration of roofs; GAF technical bulletin R-102 on algae staining; National Roofing Contractors Association technical commentary in Professional Roofing; InterNACHI roof inspection material on moss and lichen; standard manufacturer warranty terms for asphalt shingle roofing; and Four Corners Inspection Services field experience in Central Florida. Any specific roof, warranty, or association requirement should be evaluated on its own terms.

Buying a home in Clermont, Lake County, or anywhere in Central Florida? Call (352) 272-1322 or visit fourcornershomeinspections.com.

Taught by Professor Elias Walls · Researched and reviewed by Grant Doutt, Certified Master Inspector® · Last reviewed: October 2026. Professor Elias Walls is the teaching persona of the Four Corners Knowledge Center. Every lesson is researched, written, and fact-checked by the licensed, certified inspectors of Four Corners Inspection Services.