Think Pressure Washing Your Roof Is Safe? Think Again

Your roof takes a beating from weather, sun, and debris from nearby trees. After years of abuse it can start to look dirty, with algae growth, mold and dark streaks. You might be tempted to pressure wash it to return it back to pristine condition. Resist the urge. There are few ways you can destroy your roof more quickly than by pressure washing it. 

Related: Why You Should Never Pressure Wash Your Windows

What Pressure Washing Does to A Roof

While roofs are designed to shed water, they aren’t designed to withstand high pressure water. When you pressure wash a roof, you can do significant damage in just a few seconds. Pressure washing your roof can damage it in a variety of ways:

Reduce the shingle lifespan

Asphalt shingles have granules that protect your roof from wet weather. Over time those granules break loose, wear off and eventually need to be replaced. This is a slow process, which is why the average asphalt shingle roof lasts around 20 years. When you pressure wash your roof, you accelerate that process by blasting those granules off the shingle surface. 

Force Water Under the Shingles

Your roof is designed to send rain down from the apex of the roof to the gutters. Your roof isn’t designed to defend against water that’s forced from the other direction. Pressure washing lifts your shingles up and forces water under them. And once water has infiltrated your roof, it can reach the roof decking and create leaks into the living space below. Water trapped under your shingles can cause mold and mildew growth or even rot the roof decking. 

Void Your Warranty

Most roof manufacturers put a warranty on their roofs. Since power washing can do so much damage to shingles, there’s often a stipulation that voids that warranty if power washed. That means you're responsible for repairs or replacement should something happen to your roof down the line. 

Related: Pressure Washing vs. Soft Washing: Which is Safer for Your Home?

Pressure Washing Your Roof Is Dangerous

Working on top of a roof is inherently dangerous. Doing so in wet conditions while using a pressure washer that can create kickback that throws you off balance is extremely dangerous. Not only should you not pressure wash your roof because it can damage your shingles but also because it can lead to serious injury. 

How You Can Safely Clean Your Roof

Soft washing

This is the industry standard for cleaning roofs and one that most professional roof cleaning companies use. Unlike pressure washing, soft washing uses low pressure water and a special cleaning solution to kill algae, moss, mold, and dirt without damaging your shingles. Unlike pressure washing which uses the force of water to remove dirt and grime, soft washing uses the power of detergents. Since soft washing follows roof manufacturers guidelines for roof cleaning, it doesn’t void your warranty (though you should still double check before soft washing). 

Use A Professional Service

You can attempt to wash your roof on your own, but washing your roof is risky given that you’re working from height on a wet surface. There’s also a greater chance of you damaging your roof when washing it when it is for an experienced professional. Roof washing is not a DIY job. Leave this one up to the pros.