Why You Shouldn’t Pressure Wash Your Roof

When your roof becomes streaked with dirt, mold, moss, or algae, the temptation to restore its original appearance with a quick fix like pressure washing may be strong. However, pressure washing a roof—especially one made of asphalt shingles—can do far more harm than good. While it may deliver instant cosmetic results, it poses serious risks to your roof’s structure and longevity. This article explains why pressure washing a roof is bad for asphalt roofs and provides proper maintenance techniques to ensure the longevity and performance of your roof.

The Problem with Pressure Washing a Roof

1. Loss of Protective Granules

Asphalt shingles are coated with tiny granules that help reflect sunlight, protect against weather, and improve fire resistance. Pressure washing a roof can strip these granules away, significantly diminishing the effectiveness of your shingles. Even if the roof looks cleaner, its structural integrity and life expectancy have been compromised.

2. Shingle Damage and Uplift

The high-pressure spray can dislodge or lift shingles, leaving your roof vulnerable to wind damage and water intrusion. Asphalt shingles are not designed to withstand the direct force a pressure washer produces—up to 3,000 PSI (pounds per square inch) or more. Even when applied at a steep angle, the pressure can force water underneath shingles and into the roof deck, causing hidden moisture damage.

3. Water Intrusion and Mold Growth

Roofs are designed to shed water, not to have it forced upward or sideways under shingles. Pressure washing a roof can push water under the roofing materials, which can become trapped and lead to wood rot, mold growth, and long-term structural damage. This is especially risky in humid or wet climates.

4. Voided Warranties

Many roofing material manufacturers explicitly state in their warranties that pressure washing a roof will void the warranty. If you experience premature roof failure or a leak after pressure washing, you may be left to cover the repair or replacement costs out of pocket.

Safe and Effective Alternatives to Pressure Washing

To properly maintain your asphalt roof and ensure its longevity, homeowners should adopt safer, roof-friendly cleaning and maintenance methods. Here are the most effective alternatives:

1. Gentle Roof Cleaning with Soft Wash Systems

A soft wash system is a better alternative to pressure washing a roof. Soft washing uses low-pressure nozzles combined with environmentally safe, biodegradable cleaning solutions that eliminate algae, mold, mildew, and dirt without damaging the shingles.

This method allows the chemicals to do the heavy lifting while preserving the integrity of your roof. Professional roofing or exterior cleaning companies often perform soft washing, which is the industry standard for safe roof cleaning.

2. Routine Roof Inspections

Regular inspections are critical in catching problems before they become major expenses. Have your roof professionally inspected at least once a year, or after any significant storm or weather event. A roof inspection will identify issues like loose or missing shingles, minor leaks, flashing damage, or clogged gutters.

Roofing professionals like those at Pressure Point Roofing can evaluate your roof’s condition and recommend preventative maintenance that extends the life of your roof without risking damage from improper cleaning methods.

3. Trim Overhanging Tree Branches

Shade from overhanging trees creates a damp environment that promotes algae and moss growth. Trimming branches back at least 10 feet from your roof improves air circulation and sunlight exposure, reducing the conditions that allow mold and algae to thrive.

This helps keep your roof dry and reduces the risk of falling limbs and debris damaging your roof during storms or wind events.

4. Remove Moss and Algae Safely

If moss or algae have already taken hold, avoid scraping them off or using a power washer. Instead, apply a moss-killing solution specifically designed for roofs. These can be found at hardware stores or supplied by roofing professionals. The solution typically kills moss over several days, after which it dries up and can be gently removed with a soft brush or left to fall off naturally.

Avoid using homemade solutions with bleach or vinegar unless a professional recommends it, as they may damage roofing materials or nearby landscaping.

5. Install Zinc or Copper Strips

A proactive step to prevent future moss and algae growth is to install zinc or copper strips near the ridge of your roof. When it rains, small amounts of these metals wash down the roof and inhibit organic growth. These strips are an inexpensive addition that can significantly reduce the need for roof cleaning over time.

6. Keep Gutters and Downspouts Clean

Clogged gutters can lead to water overflow and backflow under shingles, especially during storms. Regularly cleaning your gutters ensures proper drainage and prevents water from pooling at the roof’s edge. Consider adding gutter guards to keep leaves and debris from accumulating.

7. Hire a Roofing Professional for Maintenance

Even with DIY upkeep, the best way to maintain your asphalt roof is by establishing a relationship with a trusted roofing company like Pressure Point Roofing. Regular professional maintenance visits can help spot minor problems early, clean your roof safely, and ensure your warranty remains intact.

Roofers can also perform minor repairs, such as replacing a few damaged shingles, resealing flashing, or applying algae-resistant treatments, which can save you from bigger repair costs down the line.

Choose Smart Maintenance, Not Destructive Cleaning

While it might be tempting to restore your roof’s appearance with a quick blast from a pressure washer, pressure washing a roof is a risky and potentially costly mistake for asphalt shingles. It can remove vital protective granules, cause shingle damage, and lead to water intrusion or mold, all of which reduce your roof’s lifespan.

Instead, protect your investment by choosing safer alternatives like soft washing, moss treatments, and professional inspections. Proper maintenance practices—combined with the expertise of roofing professionals—can keep your roof functioning properly and looking good for decades.

If you have concerns about your roof’s condition or want professional help maintaining it, contact the experts at Pressure Point Roofing. We’re here to help you care for your roof properly. Pressure Point Roofing is proud to serve the Southern Oregon community with expert residential and commercial roofing services, maintenance, and roof inspections to help you protect your most valuable asset—your home.