This is a very common misconception and a question we hear a lot. Pressure washing your roof can cause a lot of damage to the shingles…and even lead to water getting under the roof immediately. Best case it will just shorten the lifetime of your roof. Worst case, it can cause damage to your home. And all it does is make the roof look a little nicer for a brief period of time.
The time involved can be much more than you expect…or if you hire someone it probably isnt as cheap as you would think. Pressure washing a patio or driveway can be pretty routine. But when you go on a roof, there is a lot more involve – longer hoses, taking adequate safety measures and of course the challenges that come with working on a sloped surface off the ground. If you hire a professional they too have to deal with these difficulties and they also have to pay Workers Compensation Insurance (“LNI” in WA) rates that can be almost $10 an hour.
My dad had his old cedar shake roof cleaned and treated and the cost was almost $5,000! I advised him against but they were moving and didn’t want to replace the entire roof. 18 months later, even with the aesthetic upgrade of a fresh cleaned roof, his real estate agent told him he had to replace the entire roof before putting the home on the market. Not the best use of those funds!
The biggest reason we caution against pressure washing your roof is that it doesn’t do anything long term to improve the look or performance of your roof. We recommend getting a good cordless blower to blow the needles and leaves off every couple months. If you get any moss or algae build up, sprinkle a little baking soda on the roof and that will do the trick… you just have to be patient!