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Pressure Washing a Roof – What to Know

May 21, 2021
pressure washing roof

More and more advertisements are popping up that offer power washing services for roofing. At first thought, it makes sense. You can power wash your driveway, siding, car, etc., so what could be wrong with pressure washing a roof? First, we have to look at how power washing works. Pressure washers produce highly pressurized jets of water that can be used to blast sediment off surfaces. This cleaning method works well when the surface being washed can stand up to that level of water pressure.

PRESSURE WASHING A ROOF – WHAT TO KNOW

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. Unless you have it on a low setting, cleaning your roof with a pressure washer will likely do more harm than good. The extreme pressure can remove the protective coat of granules on asphalt shingles. As a result, this would make the shingles more prone to hail damage and extreme weather.

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. Additionally, pressure washing tends to blast sediment into the air, so it’s likely any dirt you spray off your shingles will settle onto another section of your roof.

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.

A BETTER, SAFER WAY TO CLEAN YOUR ROOF

The biggest 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. However, 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 replacing the whole thing is a much more complicated process best left to the professionals.

BUT WHAT ABOUT NON-ASPHALT ROOFS?

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. For example, homeowners with clay roof tiles can use a pressure washer set at 1200 psi to clean their roof. Wood shakes, rubber/plastic synthetics, and metal roofs can all be safely power washed. However, this is as long as you are careful with the pressure and distance that you spray.

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.

Additional Reading: Spring Roof Maintenance Checklist

TRUST THE EXPERTS AT MCKINNIS

If your roof looks dirty or has stains and you’re not sure if you need a cleaning or a replacement, give us a call today at 402-426-2644, visit our website at www.mckinnisinc.com or fill out our contact form. Our roofing and exterior experts are highly trained and always ready to help!