If you’ve ever had to use a pressure washer to clean off your stained concrete sidewalks and driveway, then you know how useful they can be. Nothing beats a high pressure blast of water to do some real deep cleaning. But if you’ve used your pressure washer to clean up your wood deck, asphalt shingles, soffit, vinyl siding or stucco walls, then you might be doing more harm than good. There’s an old saying that I just invented: “if ‘said product’ was designed to resist water, then why would you clean ‘said product’ with high pressure blasts of the stuff”? Catchy, isn’t it? In this article we’ll cover where, when and how to use a pressure washer and provide some some less destructive but still effective alternatives.
Wood decks can be a big no-no for pressure washers. The stronger the pressure washer (and the more focused and intense the spray tip is), the worse the damage is. It might seem like the easy road to cleaning green mold and mildew, but in fact, it’s really going to make it worse. Molds and mildews on wood decks need to be removed — that much is true — but when you use a high pressure jet of water to dislodge the debris, you also zap the wood deck fibers with the water too.
Wood fibers are themselves designed to move water from the roots, up the tree to the leaves to evaporate (the phloem and xylem, that’s HomeFixated’s Bio Lesson 101). So what happens when you inject high volumes of water in between microscopic wood fibers? Your deck boards can rot away if you use a pressure washer! Moisture enters the wood decks’ interior surfaces and furthers the decay process. Fungus can easily be introduced into the woods interior and in years (versus decades) your wood deck could begin to experience signs of damage. We don’t want a fungus among us.
Once when I was a kid, an old man (not a lot unlike Herbert from “The Family Guy”) asked me to clean off his roof with a pressure washer. I felt bad for the guy — he had a walker — and he told me “if you don’t do it, I guess I’ll have to climb up there myself and do it”. Whether that was a ploy to get a young boy up on his roof in wet clothes or not — thankfully, I’ll never know; but I’ll never forget what happened that day; I was ripping off shingle granules like nobody’s business with that pressure washer!
Now that I’m older, I know better than to do that to asphalt shingles. Roofing granules are designed to protect the asphalt base from water and sunlight damage. Fiberglass and organic shingles are both made from asphalt which when exposed to sunlight, causes it to harden, become brittle and eventually break apart. Just like the asphalt road by my house the city seems to overlook when repairs are made. A pressure washer can wreak havoc on asphalt shingles.
Once again, siding is either a painted wood product, stained, or simulated painted wood product that can be damaged by a pressure washer. Wood siding should not be pressure washed, as you well know from my previous rant about not pressure washing your dirty wood deck. But what about vinyl or cementitious fiberboard (Hardie Board) siding?
These products will easily take a blast of water from your pressure washer without taking much damage (although any paint on the Hardie Board might peel off) but yield my warning and take heed (or I’ll keep talking like a pirate me matey, arrgh): Don’t blast it from anything less than a 120 degree angle! Keep the nozzle jet wide, angled down towards the ground (as opposed to the facing up and shooting underneath of the siding) and moving in a continuous motion to prevent water damage.
It’s concrete right? Wrong. Concrete has aggregates in it like limestone or granite to help break up the Portland cement’s continuity. The aggregates bond well with the Portland cement and also help to act as a barrier to water intrusion. Stucco is basically sand and Portland cement, with no aggregates. Contrary to popular belief, it’s not impervious to water. Once any protective layer of paint is washed away by a pressure washer, water can enter behind the thin layer of stucco, causing it to separate from its substrate. This will eventually allow microorganisms to enter behind the space and set up shop, where they will help continue to separate the bond between the stucco and its substrate.
So What Can I clean all this Stuff With if I Can’t use my Pressure Washer?
That’s a good question with an even better response. Here’s a list of cleaning supplies for the building materials mentioned above:
- Wood Deck – Use a stiff bristled brush, a bucket of warm water and oxygenated bleach (Billy Mays here for OxyClean. RIP sweet prince) Rinse off with a garden hose. Repeat on stubborn stains.
- Asphalt Shingles – Clean off the roof debris and then fill a pump sprayer with oxygenated bleach so you can spray it on the roof. Use a push broom to gently sweep away the mess and hose it off with a garden hose.
- Siding – Use a bucket of water, oxygenated bleach and a Extendable Hose Brush to reach stubborn stains up high instead of using a dangerous, slippery ladder.
- Stucco – A pump sprayer, oxygenated bleach and Extendable Hose Brush are all the tools you’ll need to keep stucco clean and neat without the need for a pressure washer.
If you are ready to do some cautious and responsible pressure washing, our sponsor Tyler Tool has just about every pressure washer you can imagine. From the tiny, inexpensive, but capable Karcher K2.20 1,500 PSI Electric Pressure Washer to the beefy and powerful Briggs and Stratton 20505 3,400 PSI 2.8 GPM Gas Pressure Washer which will set you back over $600, Tyler Tool has enough pressure washers to take down a building. Just use them to clean, but not to destroy, ok?