Yes, high pressure power washing can damage roof shingles, and it is one of the most common ways a cleaning job goes wrong. The black streaks on an Orlando roof look like something that needs blasting off. They are not. They are a living film, and the safe way to remove it is gentle pressure plus the right cleaning solution. Here is what goes wrong with a pressure wand and what a better method looks like.
What are the black streaks on my Orlando roof?
Most dark streaks on Central Florida roofs are algae, usually a type called black algae or cyanobacteria. Heat, humidity and a long wet season from roughly June to September give it ideal conditions. It spreads from the shaded, damp parts of the roof first, which is why streaks often start on the north-facing slope or under tree cover.
Because the growth is organic, it is not stuck on like paint. It sits on the surface of the shingle and its roots hold on to the granules. That matters, because a strong jet of water that pulls the algae off can pull granules off with it.
- Streaks usually run down the slope, following the water.
- Moss and lichen are less common here than algae, but they do show up on shaded roofs.
- Dirt and pollen can mix in and make the staining look darker.
How can high pressure damage asphalt shingles?
An asphalt shingle is a fiberglass mat coated in asphalt, with a layer of mineral granules on top. Those granules protect the asphalt from sun and rain. Once they are gone, the shingle ages faster, and in Florida sun that can happen quickly.
A pressure wand held close to the roof can do several things at once:
- Strip granules. You may see bare dark patches and a pile of grit in the gutters afterwards.
- Lift or crack shingles. Water hitting the edge of a tab at an upward angle can break the seal strip that holds it down.
- Force water under the shingle. Roofs are built to shed water running downhill, not water driven uphill under high force. It can reach the underlayment and the decking.
- Cause slips and falls. A wet, algae-covered roof is slippery and a person pushing against a pressure wand can lose balance.
The damage is often not obvious on the day. A roof can look clean and then show leaks or early wear a season or two later.
What about concrete and clay tile roofs?
Many Orlando homes have concrete or clay tile roofs instead of shingles. Tile is tougher, but it is not immune. High pressure can crack tiles, wash away the surface coating on some concrete tiles and drive water under the tile into the underlayment. Tiles can also break under the weight of a person walking on them, which is a separate reason many cleaners prefer to work from a ladder or the ground.
Metal roofs have their own risks, such as scratched paint finishes and water forced into seams. In every case, the right question is not how much pressure is needed, but how little is needed once the cleaning solution has done the work.
What is soft washing and why is it safer?
Soft washing uses low pressure, about what comes out of a garden hose or a little more, together with a cleaning solution that kills algae at the source. The solution is applied, left to work for a short time, then rinsed off gently. The rinse removes the dead growth without any need to blast the surface.
Because the chemistry does the cleaning, the shingle surface is left alone. That is the main reason roofing manufacturers and industry groups generally advise against high pressure on shingles. Many also publish guidance on cleaning, so it is worth checking the manufacturer's advice for your roof, especially if it is still under warranty.
Soft washing needs care of its own. The solution can harm plants, metal fittings and finishes if it is not controlled, so a good crew wets down and protects landscaping and rinses runoff before and after. Our roof cleaning page explains how this works in more detail.
What should I ask a roof cleaner before booking?
A few questions will tell you a lot about how a company works. You do not need to be an expert to ask them.
- Do you use low pressure or high pressure on roofs? The answer should be low.
- What do you use to kill the algae, and how do you protect my plants and gutters?
- Will you work from the ground, a ladder or on the roof itself, and why?
- Do you carry liability insurance, and can I see proof? Ask to see it rather than assuming.
- Is the quote in writing, and does it say what is included?
If a company says it will blast the roof clean quickly, or cannot explain its method, that is worth treating as a warning sign. Cheap and fast is the usual pattern behind damaged shingles.
When should you clean a roof, and when should you call a roofer?
Algae stains are mostly cosmetic at first, but left for years they can hold moisture against the roof and shorten its life. Many owners also clean because of HOA letters. Some Orlando communities have rules about the look of roofs and exteriors, so check your deed restrictions or ask your HOA what is expected.
Cleaning is not a repair. If you can see cracked, curling or missing shingles, bare patches, sagging or stains on the ceiling inside, call a roofer first. A cleaner cannot fix those, and a roof in poor shape may not be safe to wash at all. After a hurricane or a strong storm, have a roofer look at the roof before you book any cleaning.
A roof that is healthy but stained is a good candidate for soft washing. Because cleaning solution works over time, results can keep improving over the first week or two as the dead growth rinses away with the rain.
What is the right next step?
Pick the method before you pick the price. A soft wash costs different amounts depending on roof size, pitch, height and how heavy the growth is, and a written quote should explain those points. A pressure-only quote should make you pause.
If you have streaks on an Orlando roof and want it cleaned without risk to the shingles, start with our roof soft washing and algae removal page. If the rest of the house is stained too, see house washing, and our pressure washing Orlando home page lists everything we clean.