A pressure washer makes quick—and satisfying—work of blasting away gunk. For cleaning walkways and stripping old paint from a deck, nothing compares to the unbridled power of these machines.

In fact, it’s easy to get carried away (or even inflict a serious injury—but more on that later).

More on pressure washers

“You might be inclined to pressure-wash just about everything around the house, but that’s not always a great idea,” says Dave Trezza, the test engineer who oversees pressure washer testing for Consumer Reports. “The supercharged stream of water can damage paint and nick or etch wood and even certain types of stone.” 

Below is CR’s guide to knowing when it makes sense to clean with a pressure washer and when a garden hose and a scrub brush will suffice.

How CR Tests Pressure Washers

We measure how much pressure each model can produce, in pounds per square inch, giving a higher score to those with a higher psi. Then we fire up each pressure washer and use it to strip paint from painted plastic panels, timing how long it takes. Models with a higher pressure output tend to perform better on this test. 

We also measure noise, and you should know that almost all pressure washers are loud enough to require hearing protection. Finally, we size up ease of use by evaluating basics like the process of adding fuel and noting features that improve the experience. (A model whose engine automatically shuts off when oil is running low will score higher.)

Regardless of performance, it’s CR’s policy to recommend only models that do not include a 0-degree nozzle, which we believe poses an unnecessary safety risk to users and bystanders. 

Read on to find out whether it makes sense to pressure-wash your deck, siding, roof, car, or driveway.

Deck

Should You Pressure-Wash It?
Yes.
Decks made from South American hardwoods such as Ipe, Camaru, and Tigerwood will hold up to the power just fine. Decks made of pressure-treated wood are generally okay, too, assuming you don’t hold the nozzle too close. Pressure-treated wood is typically southern yellow pine, which is pretty soft, so start with a low-pressure nozzle on an inconspicuous spot to make sure the spray is not etching or marking the wood. You’ll want to check your owner’s manual to see which nozzle and setting the manufacturer recommends for cleaning decking, and how far away from the surface you need to keep the nozzle. In any case, work along the length of the board, going with the grain of the wood.

For this job we recommend the Greenworks GPW1951, $189, which offers effective cleaning at an excellent price. 

Not all decks need to be cleaned with a pressure washer. Newer composite decks from brands such as TimberTech and Trex often resist deep staining in the first place and can be cleaned with a light scrubbing. If a light scrub and rinse with a garden hose isn’t enough to get your composite deck clean, check the terms of the warranty before using a pressure washer to make sure you don’t void it. 


Before you shop for a new pressure washer, check our 
buying guide and ratings of gas and electric pressure washers.

Roof

Should You Pressure-Wash It?
No.
Tempting as it might be to blast away unsightly moss and algae, using a pressure washer to clean your roof is dangerous, not to mention potentially damaging. For starters, we never recommend using a pressure washer while you’re perched on a ladder because blowback could throw you off balance. The powerful stream of water can also loosen roof shingles and, with asphalt shingles, strip them of the embedded granules that help extend the life of your roof.

Instead, spray down the roof with a cleaner that kills mold and moss or apply a 50-50 mixture of bleach and water in a pump sprayer and let the moss die on its own. Make sure to build up pressure in your pump sprayer from the safety of solid ground before climbing a ladder to spray your roof.

A longer-term strategy, if there’s an excessive amount of shade, is to trim overhanging branches or cut down trees to allow sunlight to hit the roof. That’s the key to preventing moss from growing in the first place.  

Car

Should You Pressure-Wash It?
No.
 Plenty of people use a pressure washer to clean their car, of course, but it can do more harm than good. Using a pressure washer can damage or nick the paint, which could lead to rust. And a car wash usually gets the job done just fine—so do a garden hose and soapy sponge. Use a little elbow grease and a specialized cleaner on problem spots such as wheels.

Concrete Walkway and Driveway

Should You Pressure-Wash It?
Yes.
Concrete can readily withstand a powerful cleaning without much concern over etching. Generally, a finer nozzle will prove to be more effective at spot-cleaning grease stains. For moldy or mildew-covered cement, use lower pressure and coat the surface in suds first. The Cub Cadet CC3224, $500, among the most powerful models in our ratings, would serve you well for this task, but it includes a 0-degree tip, which we advise discarding if you buy this unit (see “Pressure Washer Safety,” below).

Siding

Should You Pressure-Wash It?
Sometimes.
Vinyl siding is pliable and can typically withstand pressure washing without much concern. The same goes for fiber cement siding. Aluminum siding, however, can dent, so it’s best to start on the lowest pressure setting with a broad nozzle, and use more concentrated blasts only for problem spots—the Troy-Bilt 020568, $300, is an effective model that’s particularly easy to handle and maneuver, which is nice when you’re working your way around an entire house. 

Wood clapboard siding can be effectively washed, too, but if your house was built before 1978, have the exterior paint tested first by an EPA-licensed lead-remediation specialist. If you knock old lead paint loose, it will settle in your soil and never break down because lead is a heavy metal.

When using a pressure washer to clean any siding, you need to prevent water from becoming trapped between the siding and your home’s sheathing, because the moisture promotes mold. Repair or replace loose, damaged, or missing siding, and take special care not to spray water directly into any gaps around doors, windows, or under the lap joints on siding runs. 

Don’t pressure-wash shingle siding—the pressure can knock the shingles loose.  


Pressure Washer Safety

Pressure washers come with nozzles ranging from 0 degrees to about 40 degrees. The higher the number, the wider the spray pattern and the less concentrated (and potentially dangerous) the stream of water. Consumer Reports recommends against using a 0-degree nozzle at all because it poses an unnecessary safety risk. Water concentrated to such a fine point can pierce many surfaces, including protective boots.

If your pressure washer came with a red 0-degree nozzle, toss this nozzle out. The next size, a 15-degree nozzle, will do just fine for detail work, such as removing moss from the grooves between pavers. And always wear hearing protection, protective footwear, and gloves while you work.


Pressure Washing Tips