Can You Pressure Wash A Roof

Can You Pressure Wash A Roof

Pressure washing your roof can be an effective way to restore your home’s curb appeal and potentially extend the life of your roof. However, using too much pressure or the wrong technique can actually damage your roof and cause leaks. In this blog post, we’ll discuss whether you can pressure wash a roof, the risks involved, and tips for safely cleaning roof shingles with a pressure washer.

What Is Pressure Washing?

Pressure washing utilizes a mechanical sprayer that connects to a standard garden hose and emits a focused, high-pressure stream of water. Pressure washers increase the water pressure coming out of the hose to provide enhanced cleaning power for surfaces like siding, decks, concrete, and roofs. The pressure is typically measured in pounds per square inch (PSI).

Pressure washers come in electric or gas-powered models and range from about 1,300 to 4,000 PSI. Pressure washing works by using the concentrated jets of water to scrub away and lift off dirt, mold, mildew, pollen, and other debris.

Is Pressure Washing Safe For Roofs?

Pressure washing uses high-pressure water to remove dirt, mold, mildew and other debris from surfaces. When done correctly, it is generally safe for most roofing materials including asphalt shingles, metal, tile, and newer composite shingles. However, there are a few considerations:

  • Avoid Old or Brittle Shingles: Old, brittle or cracked asphalt shingles are more prone to damage from the intense water pressure. Inspect your roof carefully beforehand and avoid washing any damaged or worn sections.
  • Use Caution with Composition Shingles: While composite shingles are durable, intense water pressure can still cause damage if aimed directly at the seams or edges. Take care when washing near vulnerable areas.
  • Start at Low Pressure: Begin at a low 1000-1500 PSI and only increase pressure if needed. High pressure levels above 2000-3000 PSI can lead to granule loss and other damage.
  • Use Fan Tips: Fan tips spread out the water pressure over a wider area, reducing risk of damage. They allow you to clean at a safer distance.
  • Avoid Power Washers: Gas-powered pressure washers run at very high PSI. Electric power washers with adjustable PSI are safer options for roof washing.

With proper precautions, most roof types can safely be pressure washed without damage. Always inspect and test a small area first.

Factors That Increase Risk of Roof Damage

  • High pressure above 2,000 PSI
  • Direct spray closer than 8-10 inches from the roof
  • Holding nozzle in one spot for too long
  • Pre-existing damage or aging roof near end of lifespan
  • Brittle or fragile tile or shingle materials

Signs of Roof Damage from Power Washing

  • Visible punctures, cracks, chipped edges on shingles
  • Granule loss exposing asphalt mat below
  • Curled or lifted shingle tabs
  • Leaks through the roof after cleaning

So while you can pressure wash a roof, it’s vital to take precautions and use the proper settings and techniques to avoid causing damage.

Benefits of Pressure Washing a Roof

When done safely at the proper pressure, power washing a roof can provide excellent results, restoring beauty and function. Benefits include:

  • Removes dirt, grime, mold, mildew buildup
  • Improves aesthetics and curb appeal
  • Clears clogged gutters and downspouts
  • May extend lifespan by preventing deterioration
  • Allows for closer inspection of roof condition
  • Can be more eco-friendly than chemicals if cleaning solution is biodegradable

Taking the time to properly pressure wash your roof helps protect your most important asset – your home. Just be sure to take every precaution against causing damage in the process.

Preparing to Pressure Wash a Roof

Proper preparation is key to safely and effectively washing a roof:

  • Inspect the roof and identify any damaged or fragile areas that need to be avoided.
  • Clear the roof of any debris that could clog drains or gutters like leaves and branches.
  • Cover all vents with plastic and painter’s tape to prevent water intrusion.
  • Wet down vegetation around the home so spray and runoff doesn’t damage it.
  • Set up ladders safely and cordon off areas below roofline.
  • Test wash a small inconspicuous area at low pressure and inspect for any issues.
  • Adjust washer settings and pressure as needed based on test area results.

Taking these steps before starting will help prevent water damage and allow you to pressure wash the roof safely.

How to Pressure Wash a Roof

Once you’ve completed prep work, follow these steps for washing:

  • Start at the highest point of the roof and work downward methodically. This prevents streaking from runoff.
  • Maintain a distance of at least 1 foot between roof and nozzle. Fan nozzles should be 2-3 feet away.
  • Keep nozzle perpendicular to the roof, avoiding angling it as this can force water underneath shingles.
  • Apply detergent first if roof is very dirty. Let it soak briefly before power washing.
  • Use horizontal back and forth motions for washing. Vertical motions increase risk of lifting shingles.
  • Overlap washing passes to ensure full coverage washing from peak to eaves.
  • Rinse at low pressure diagonal to washing direction to prevent streaking.
  • Inspect and wash any remaining dirty spots after initial wash. Spot clean vs washing entire roof again.
  • Final rinse the roof thoroughly to remove all soap residue which can damage shingles over time.

Following a methodical washing process with proper technique will provide the best cleaning results.

Tips for Effectively Cleaning Different Roof Types

  • Asphalt Shingle Roofs: Use a green tip nozzle and pressure up to 1500 PSI. Wash parallel to the shingle orientation.
  • Wood Shingle/Shake Roofs: Use low 500-1000 PSI and wide fan tip to avoid damaging the wood. Never power wash vertically.
  • Tile Roofs: Use white tip nozzle and 1200-2000 PSI max. Higher pressure only if needed. Be extremely cautious around grout lines.
  • Metal Roofs: White or yellow tip at 500-1500 PSI depending on buildup. Flush water away from panel seams and joints.
  • Low-Slope Roofs: Use white or wide green tip at <1500 PSI. Avoid water pooling and seams. Angle nozzle slightly on TPO and EPDM roofs.

Adjusting pressure, nozzle type and technique based on material will yield the best results cleaning different roof surfaces.

When to Avoid Pressure Washing Roofs

There are some scenarios when pressure washing is not recommended:

  • On older or damaged roofs at risk of shingle blistering, tearing or granule loss. Stick to low pressure soft washing instead.
  • When temperatures exceed 80°F as heat can damage shingles. Wash in early morning when roofs are cool.
  • After a new roof installation. Wait at least a year before pressure washing to avoid disturbing adhesive.
  • On roofs with poor drainage or signs of leaking. The intense runoff can lead to interior water damage.
  • On roofs covered in smooth hand-cut cedar shingles which are very prone to damage.

Avoid washing roofs in disrepair or under weather conditions that could contribute to damage or leaking. An experienced roofer can advise if your roof is unsuitable.

Alternative Low Pressure Roof Cleaning Methods

If you decide pressure washing carries too much risk for your roof, alternatives include:

  • Soft washing – Mix a cleaning solution with water in a pump sprayer and apply manually via a garden sprayer nozzle. Let soak then rinse with a regular garden hose.
  • Low pressure rinse – Use a pressure washer adjusted to under 500 PSI with a wide fan nozzle. Keep it moving constantly to avoid focused spray.
  • Leaf blower – Use a gas-powered leaf blower on dry debris like leaves and pine needles (avoid wet mold or mildew).
  • Manual cleaning – Use a long soft-bristle brush and roof cleaning solution applied by hand. Scrub gently and rinse.

These provide a more gentle clean without using harsh pressure. But they take more time and elbow grease.

When to Pressure Wash a Roof

Aim to clean roofs in dry weather when no rain is forecasted for 24-48 hours. This allows time for the roof to fully dry after pressure washing. Spring and fall are ideal times to clean a roof when algae and moss growth are more common. Avoid intense summer heat that can dry out shingles.

Plan to pressure wash a roof about once every 2-3 years on average to prevent major buildup. Signs it’s time include visible dark streaks, green moss or black algae growth, and debris accumulation. Keep an eye out for leaks after heavy rain or snowmelt and clean as needed to prevent further damage.

Maintaining a Roof After Pressure Washing

To maximize the benefits of pressure washing after cleaning, be sure to:

  • Inspect the roof and make any needed repairs immediately.
  • Clear any debris from gutters and drainage areas.
  • Add sealant or re-coat vulnerable flashing, seams or joints.
  • Prune back overhanging tree branches.
  • Schedule semi-annual roof maintenance and washing.
  • Immediately address any areas of new roof damage or leakage.
  • Remove piled up debris like leaves regularly.

Taking steps to protect and maintain your roof after washing will extend the benefits and provide a cleaner surface long-term.

Hire a Professional Roof Cleaner

For best results and to avoid damage, consider hiring a professional roof cleaning service. They have the expertise and equipment to safely clean and protect your roof. Expect to pay $200-500 for a typical single family home, depending on size and region.


Pressure washing can be an effective cleaning method for most roofing types when proper precautions are taken. Low pressure, the right nozzle and technique are key to safely washing asphalt, tile, metal and other roofs. Avoid pressure washing brittle or damaged roofs. Hiring a professional pressure washer is recommended if DIY washing is a concern. With the right process, pressure washing can extend the life of a dirty roof. Just take care to do so safely without damaging shingles or joints.

Don’t Stop Here

More To Explore
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How To Pressure Wash a Rug: Washing, Drying, and Maintaining

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1. Preparation
2. Choose the Right Pressure Washer
3. Detergent Selection
4. Test Spot
5. Even Application
6. Rinse Thoroughly
7. Allow to Dry

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