Should I Pressure Wash My Roof?

Pressure washing a dirty surface can be satisfying to watch, but that doesn't mean it's good for your roof.

Gettyimages 1263676961Marina Lohrbach

Pressure washers are a versatile tool in any homeowner’s arsenal. They can be used to prep home exteriors for painting, clean driveways and sidewalks, and even peel potatoes. But if you’re looking up at a dirty roof and wondering if you can just blast the grime away with your handy pressure washer, be warned — that’s probably not a good idea.

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Why You Should Not Pressure Wash Your Roof

Pressure washers produce highly-pressurized jets of water that can be used to blast sediment off surfaces. This cleaning method works really well when the surface being washed can stand up to that level of water pressure.

But while asphalt shingles are made to handle heavy rainfall, raindrops are not quite the same as a concentrated beam of water from a pressure washer. Simply put, unless you have it on a low (and much less effective) setting, cleaning your roof with a pressure washer would likely do much more harm than good.

The water pressure won’t damage just the shingles, either. There’s a good chance the jet of your pressure washer could work through the adhesive bond holding your shingles together, or seep into and damage your roof’s fabric underlayment. Plus, pressure washers tend to blast sediment into the air, so it’s likely any dirt you do scrape off your shingles is bound to fall back down onto another section of your roof.

On top of all that, most pressure washers are simply not made for roof work. You could seriously injure yourself trying to lug your pressure washer up a ladder. And once it’s up there, there’s no guarantee the weight of the machine won’t damage your shingles.

Alternative Ways To Clean a Roof

The main reason to not use your pressure washer to clean your roof isn’t that the water jets will damage your shingles. It’s just that there are better, more effective methods.

If your roof is covered in leaves, moss and dirt, try a leaf blower to sweep the roof clean. Got moldy roof stains? Just use a garden spray nozzle and some nontoxic chemicals to remove those ugly black streaks. That should get your shingles looking as good as they were on the day they were nailed into place.

Most of the time, though, a dingy-looking roof isn’t a sign it needs to be cleaned; it’s a sign it needs to be replaced. Repairing a few shingles is a simple enough process that any DIYer with a head for heights can tackle. Tearing off a roof entirely and then reshingling the whole thing is a much more complicated process best left to the pros.

Cleaning Roofs With Uncommon Shingles

The above advice applies to roofs with asphalt shingles. If you have a less common style of shingle on your roof, it may be safer to use a pressure washer to clean them. Homeguide actually recommends homeowners with clay roof tiles use a pressure washer set at 1200 psi to clean their roof.

If your roof does have specialty shingles, do further research and check with the manufacturer to learn exactly what kind of cleaning methods they recommend.