Can Roof Shingles Be Pressure Washed?

Is it safe for your shingles to be power washed? If your wondering this then you are in the right place.

Roof shingles can be pressure washed, but it should not be the first solution to cleaning your roof. Pressure washing can be damaging to the protective coating of the shingles, so use your hose first. If that is too light, move to the pressure washer from the lowest setting and working up.

If there are algae growing then using a pressure washer is preferred to use against scraping the algae off, which can cause damage to the shingles grit and protective coat. For mold, you can use a cleaning chemical with the pressure washer that will help get rid of mold.

It would also be beneficial to call your nearby roofing expert to ask if the problem is manageable, ask what chemical works to get rid of the mold, or to see if the problem is too big and if they can fix it for you.

Types of Pressure Washers

There are pressure washers for cleaning cement, patios, outdoor furniture, vehicles, fences, driveways, and more. They are sold in various styles, come in gas or electric options, and have different PSI (Pounds per Square Inch). The two main types of pressure washers you see are ones with a spray gun attachment and ones with the surface cleaner attachment.

The spray gun attachment is going to be a handheld device that you attach to the hose of the pressure washer machine. With it, you can aim high and low and change the pressure of the water to define how precise you want the cleaning to be.

For more of a quick rinse, you would lower the PSI and sweep the area in bigger horizontal or grid motion. For a deeper clean, you would up the PSI and sweep in a grid motion.

In the video by Home Depot above, they go into further detail about different nozzles to use, how to turn them on and off, and they show you examples of how they use them.

A pressure washer with the surface cleaning tool is used differently. This is not handheld, it is big and it stays on the floor to more precisely clean the ground. It is most often used for driveways, patios, cement ground, and other hard surfaces that get dirty over time.

In this video, you can see how they prep the driveway for the cleaning, then the technique they use for the pressure cleaner. They recommend using it in a horseshoe/circle-like pattern, but another technique is to use the grid pattern.

The grid pattern ensures a deeper clean because you go over the same spot twice. You can decide what is best based on the shape of the area you are trying to clean and how deep of a clean you are looking for.

As you can tell, the surface cleaning pressure washer can only be used on the ground. Whereas the spray gun washer can be used on the ground and walls, and it can be used on more types of surfaces compared to the surface washer.

How to Get Rid of Mold

To get rid of mold on your roof you should first verify there is mold on your roof and not a different substance. Next, you should try and determine what type of mold it is. If you believe it is black mold, you should call your local roofers and inquire if you can fix the job yourself or if the job is too big and they need to come out to fix it. If it is a job you can fix, then you should ask about any chemicals or cleaning solutions you should use when cleaning it.

Steps for cleaning:

  1. Place a ladder on the roof where it is easy to get on and off it, and where you won’t make any damages to the roof.
  2. Attach spray gun to the hose of your pressure washer.
  3. Fill the pressure washer with a recommended cleaning solution/chemical that will get rid of mold.
  4. Spray down the roof. Start with a light PSI to make sure you do not damage the shingles, then increase it as needed. You should also start out by spraying down a small section to test if the pressure washer is taking off the grit and protective coat of the shingles. Test out each new PSI you try to be sure that you are not damaging your roof.
  5. Start spraying at the opposite end of where the ladder is so that when you are done you can exit safely without walking on the wet roof.

Recommended tips for safety and efficiency:

  • Wear soft sole non-slip shoes. The soft sole will prevent you from damaging your shingles from your shoes, and the non-slip will prevent you from slipping when walking on a wet roof.
  • Wear protective eye gear to protect your eyes from the water splashing up any dirt and rocks that can harm the eye.
  • When starting to spray down your roof, stay on dry parts of the roof for as long as possible to prevent you from slipping.
  • Spray a small section of the roof on each PSI you try to make sure the amount of pressure you are using will not damage your roof and it will not spray off the protective coating or the grit that is on the shingles.
  • Make sure to step carefully. Try to reach the roof from the same position, only moving back toward the ladder as you cover the roof. Taking unnecessary steps puts you at a higher risk of falling.
  • Spray off the walls and plants below the roof so that the chemicals do not harm them. Be sure to spray them down before and after.

How to Get Rid of Moss

Unlike mold, moss is easier to clean and should be able to come off with just water, no solutions or chemicals needed. The steps should look about the same as the steps listed above for getting rid of mold.

Steps for cleaning:

  1. Set up the ladder in a safe position for you that will not damage the roof.
  2. Prepare your pressure cleaner with the spray gun attachment.
  3. Test out the lowest PSI setting, work your way up to the PSI level you want, check the level again to make sure it will not harm the shingles on your roof.
  4. Get on the roof and work from the far end back toward the ladder.

The video above shows these steps in action so that you can understand better how to clean off moss from your roof.

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