How to Pressure Wash Your Roof: Roof Pressure Washing Basics

Updated: How I Clean 5 min read

Jamey

Many business and home owners strive to maintain their property’s curb appeal and protect their investment with periodic cleanings for moss removal, lichen removal, mildew removal and to eradicate other undesirable debris. Anyone considering attempting to pressure wash roof installations themselves should use caution.

Not only can using the wrong cleaning method or too much pressure damage certain types of roofing, but the task itself can be physically risky. Here, we’ll discuss the question of can you pressure wash a roof and offer tips concerning how to pressure wash a roof safely and effectively.

Here’s Why You Should Never Pressure Wash Certain Dirty Roof Types

professional pressure cleaning roof
Professional roof washing.

Roof pressure wash services can certainly clean up the area, but not all roof materials are best suited for pressure washing. While certain soft washing processes are possible, it’s often best to employ a professional roof cleaning company to do the work to prevent damage such as:

  • Compromising bonding, adhesives or the underlayment of the roofing materials.
  • Roof leaks around skylights, flashing or other roofing areas with joisted or worn seals.
  • Breaks or cracks in clay, shake, slate, cement and metal roofs.
  • Stripping away the granules on asphalt shingles.
  • Accidentally dispersing fungus, moss and other organisms from one part of the roof to the rest of the area.

Because cleaning methods, tools and nozzles to handle the task vary from job to job, hiring a professional for roof pressure washing or roofing company is the safest route.

Can You Pressure Wash Asphalt Shingle Roofs?

While it is possible to pressure wash asphalt roofing, a special process called a soft wash that uses low-pressure rather than high pressure is highly recommended. If the water pressure is set to an excessive PSI level or the wrong nozzle is used, the roof can be compromised, begin leaking, or remove asphalt granules. Using the right temperature, nozzle style and a low-pressure setting is vital to solid results.

Are Other Roof Materials Safe for Power Washing?

Roof composition is the first thing to determine when deciding how to approach achieving a clean roof. Other roofing materials less common than shingles can still be damaged during pressure cleanings, and in some cases the owner’s warranty could be voided. It’s always wise to check the manufacturer’s recommendations before breaking out the pressure washer for a DIY roof cleaning. Here are some general guidelines that a roof cleaning service typically follows.

pressure cleaning roof with power washer
  • Clay Roof Tiles: This material is durable, and one should use a pressure washer set at 1200 psi to clean clay roof tiles.
  • Concrete Tile: These roofs are typically flat and commonly used for industrial or apartment complexes. They can handle a wide array of pressure cleaning settings.
  • Slate Roofs: Slate is another resilient material, but they can be damaged by forceful contact, making them a good candidate for soft wash techniques.
  • Metal Roofs: Typically made of tin alloy, metal roofs are capable of enduring several pressure washing setting levels.
  • Wood Shake: Similar to asphalt shingles, wood shake must be carefully washed with a low-pressure setting.

When Should You Hire Experienced Roof Cleaners?

One of the best indicators that professional roof cleaners are the best option is for owners who have little or no experience with pressure washing. By hiring someone with the right equipment, effective biodegradable cleaning products and know-how, the chances of avoiding the need for unexpected roof repair or costly roof replacement are increased. With the right pressure, nozzles and a good cleaning solution, almost any roof can become free of buildup with a power washer.

When is DIY Roof Power Washing a Good Option?

If your roof is made of one of the more durable materials mentioned earlier, a DIY power washing effort might work out just fine. The standard PSI rating of a pressure washer is 2,600, so it can put out a lot of water at high speeds. Some professional grade models have even more power and generally shouldn’t be used for DIY roof cleaning.

pressure washing roof and gutters
Roof and Gutters Power Cleaning Using Pressure Washer.

There are also various types of nozzles. Some shoot out strong, straight jets of water, and some others have a fan attachment that is gentler on contact surfaces. When the roof is made of metal or concrete, it can often withstand straight shooting nozzles. However, low pressure methods and fan nozzles are best for roofing materials such as asphalt, cedar shake, and certain types of tiles.

How to Safely Pressure Wash Roof Installations

Roof power washing can be accomplished without causing damage, but this takes special care and often uses a low-pressure wash technique roofers call a soft wash. Using a special nozzle tip, even more brittle materials such as asphalt can be free of debris and buildup. Here are the steps and tips for soft washing roofing.

  1. Generously wet plants and landscaping with a garden hose, taking time to cover sensitive flowers with a tarp for protection.
  2. Wet the roof on a low pressure setting.
  3. Apply a bleach or chlorine based gel or a preferred type of biodegradable cleaning products to remove dirt and grime while warding off fungus, algae, moss and mildew.
  4. Allow them to sit for the recommended cleaning time.
  5. Gently rinse from the top down with the pressure washer until the residue is removed.

It is often possible to remove some debris with a soft brush, broom or a leaf blower with a ladder when the buildup isn’t too significant.

Top 5 Ways Pressure Washing Can Extend the Life of Your Roof

Keep the same roof for generations to come with proper care, and save money on unplanned roof repairs or roof replacement. While excessive pressure washing can reduce the lifespan of some roofing types like asphalt, they generally boost curb appeal along with extending the life of your roof system. Here are five reasons why periodic roof power washing is beneficial for longevity.

  1. Algae, moss, mold, lichen and other types of fungus are not only unsightly, but they can invade and erode and rot the base of shingles that shield them from leaks and also loosen the structure’s foundation.
  2. Growths can also become breeding grounds for moss, which can work its way into wood structures, decking and beneath the eaves of certain roofs. Regular pressure washing services can help curb these invasions and save owners concerns about premature roof deterioration.
  3. A clean roof holds less heat that can contribute to roof underlayment erosion.
  4. A dirty roof that not properly cared for can ultimately lose out on warranty claims.
  5. Debris on flat roofs can clog drain openings that lead to ponding on the surface, which can erode detrimental components of the roof membrane.

How to Choose the Best Power Washers and Cleaning Products for Roofs

The best pressure washers we found range drastically in pricing, which is generally relative to how much power it has, whether it is electric or gas, and any key features they may have. For most residential applications, you might consider a mid-range model that has around 2000-3000 PSI, so it can be used for other applications around the house, such as sidewalks, decks and siding.

Choosing a quiet power washer that can do both low and high pressure settings is optimal. Don’t forget about considering those that work with various types of nozzles, are easily portable, and have a hose long enough to get the job done. Foam cannons are another option for soft washing projects, and some people can do a single story structure from a ladder without having to get on the roof. These cannons are somewhat safer and many DIY’er’s find them actually fun to use.

There are many options for chemicals that can successfully clean roofs, but the most common chemicals still in use are bleach mixed with water or sodium hypochlorite when power washing. If there are lichens, algae, mold, other biological growths or staining present, special surfactants can be used to remove them and slow their reappearance. There are also several earth-friendly biodegradable roof cleaning options available today.

Professional Pressure Washing Can Save You Time and Money

Ultimately, calling in an experienced roof cleaning service provider means less work and out of pocket expense for you. No costly equipment to buy, plus there’s no physical risk to you with pros on your side. Many see improvements in energy cost, that their roof lasts longer, and that their property values go up with a clean and sanitary roof.

Jamey

Jamey has been testing and reviewing top pressure washers for 7 years. He worked as a commercial pressure washer at a rendering plant for 3 years and all up has been using commercial and residential pressure washers for 15+ years. He is also a mechanical engineer and while working in the mining industry designed several turn-key light industrial vehicle wash pads.