Pros and Cons of DIY Pressure Washing

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Subject: Pressure washed, frayed wood, now what? HELP

I had my deck cleaned by a 'professional pressure wash company' and they did too much damage to the wood. It is frayed and I'm not sure what to do. I figure I need to act quickly. Do I need to sand it or use a special chemical? I do plan to restain it. Please help.

John Wilson

Subject: Washing from the top down

Always wash from the bottom up to prevent streaking caused by runoff especially if in the sun which will burn the water streaks into the siding.

Ted Welch

Subject: Power Washing Wood - a caveat

The scenario goes like this:
A homeowner gets his wood deck power washed. He either does it himself or gets a pro to do it. Then he seals the deck "to keep it looking good longer."

A year or two later he notices that the deck has a "splotchy" appearance - almost as if the sealant coating had failed.

He asks the guy who power washed it before to look at it. Chances are he'll be told that the "sun damaged the sealant' and it'll have to be cleaned and sealed again."

What's really going on here?

Chances are that whoever did the initial power washing either used too much pressure or didn't hold the spay tip at the correct angle and far enough away from the wood or he moved the tip too slowly across the surface. All of these failures of good technique result in damage to the surface of the deck.

What is happening is that in addition to removing the algae and dirt on the surface of the wood, the water jet is tearing loose wood fibers on the deck's surface. The more wood fibers that are torn loose, the "newer" the cleaned surface looks. Remember, the surface graying of unfinished wood, (teak, cedar and cypress especially) is caused by solar UV radiation, and is a natural weathering process, NOT an indication of dirt that needs to be removed.

Observed under low power magnification, the raised wood fibers on an improperly power washed deck give the deck a rough, "bristly" appearance. When this surface is sealed, or painted, many of the standing wood fibers may be laid flat onto the deck, but others will not. The still erect wood fibers are soon worn down by deck traffic, leaving a stump with an exposed surface which will act like a pore or opening allowing moisture to penetrate through under the surface coating.
It is this moisture and the fungal spores that it carries that will gradually spread out under the deck coating causing it to blister and blacken in spots all over the deck.

As a retired remodeling contractor with 25 years of experience, I am an advocate of gentle deck washing to remove algae (the dangerously slippery green to black stuff) that grows in especially damp areas of your deck,away from lots of sunlight. A good algaecide, once a year, properly diluted and applied and rinsed, will keep any wood deck looking good for a long time. Eschew use of a power washer.

Larry Smith

Subject: Power washing Homes

I second what Dana Chapman said, and would add that if you get moisture behind clapboard siding in a dry climate, it wants to find a way out. One way is to migrate through the wood and lift the paint off. After years of peeling paint and touch-up, I instructed our painter not to use power washing and got a paint job that lasted 15 years.

I have also seen a neighbor power wash a concrete driveway. Looks cleaner for a while, but power washing also loosens and removes small pebbles from the surface of the concrete, leaving it pock-marked.

Roy McMillan

Subject: Pressure Washing

Wow! A lot of good pressure washing tips here and some comments were very helpful as well. Unfortunately mistakes can be made without proper knowledge or with a novice technician. Thanks.


Subject: Warning with Pressure Wash

Had my house professionally pressure washed. The company I used did not protect my cable box. The water knocked out my FIOS which includes internet tv and phone. Had to wait hours for Verizon service and they only showed up that day because I have a medical device which requires the Internet. Else a one week wait!! Verizon tech says he sees cable boxes knocked out by spray washing all the time. Bottom line protect your box or be without cable for a week. Phil

John Catapano

Subject: Eco Pressure Washing

While it's more difficult to remove stains, I find that an oxi cleaner is effective for my deck and siding - and won't do any harm to garden vegetation and shrubs. Avoid bleach-like products and scrub the stains out instead. I do find myself scrubbing a lot harder but in the end, cleaning your siding and deck isn't that difficult. Just requires a lot of work.

Also, as mentioned in the article, don't overdue it with pressure. Usually a garden hose will suffice if you loosen up the stains with a deck brush or mop. Work your way from top down so gravity can help.

Lee Olson

Subject: Pressure Washing Chemicals

It is not the pressure that cleans, it is the chemicals. Most professional get better chemicals had have "secret" ingredients which cause the chemicals to adhere to the vertical and angled surfaces. This allows the chemicals to work and not slide off the surface. A gentle pressure is then used to wash the chemicals and grime off.

I have a pressure washer and have done enough cleaning to know that it is economical to hire a good professional with proper equipment that can do a much better and quicker job than I could ever do.

Typical DIY homeowners get a pressure washer for about $300 and end up etching their deck to get the grime off. I did that one once. The right chemicals and a garden hose will actually do a good job on most decks. I got to know a few pressure washers and did a lot of reading and now know a lot more about the subject when I just assumed that all you needed was high pressure and bleach.

A professional with $20,000 to $60,000 rig and the right chemicals can consistently get better results than a weekend warrior with a $300 rig from a big box store. I do use my pressure washer for small cleaning jobs which it is designed to handle.


Subject: Power Washer PSI recommendations

What would be a recommended PSI for washing down concrete driveways and wood decks/ fencing?

Thanks for any suggestions!


Subject: Power Washer

I Been Thinking of Buying A Presser Washer to Clean My Driveway...( Oil and Grease Stains....) I Don't Know The Right PSI Power Washer To Buy.????


Subject: Prices for Services are accurate, but crazy

If you are a DIYer of even moderate skills, you can save a lot of money doing these things yourself - with or without a power washer - depending upon the state of your deck. It probably will take you a few hours to thoroughly clean your deck, but if you can spare the time, it is definitely worth it. Look on the internet for several, environmentally safe ways to clean your deck - especially if it is in reasonable shape - or you can choose to use alternative cleaners - just be careful to cover your plants and place plastic sheeting under the deck if you have plants or tree roots under your deck.
Using an average of the prices listed in the article, power washing costs 87.5 cents per square foot. To hire a company to clean a deck that is 400 sq. ft. would cost you at least $350. I cleaned my 400 sq. ft. mostly shaded deck, that had some mildew problems due to the shade, in about 4 hours. My deck was in good shape other than the mildew stains, a few small spots where the solid stain had peeled and overall normal dirt/pollen accumulation. My materials cost was less than $75 including buying new heavy-duty chemical-resistant gloves and boots as well as 6 mil plastic sheeting to put under my deck. I did not power wash my deck - I just did mine by hand.
After a little hand-sanding of and around the bare spots (and removing all stain and wood fibers with a tack-cloth), I stained my two-colored custom deck with 3 gallons of high quality stain (2 relatively thin coats on all surfaces) for under $200, including 2 rolls of green frog tape and 1 roll of yellow frog tape (because of having to tape the around the edges of floor boards where the accent boards abut the other colored boards) as well as stain applicator pads. I did a much more thorough job cleaning and staining than the previous contractor - who charged me $2000 for the same work. So $275 vs. $2000. Pretty significant difference (I ended up paying myself about $150 per hour) - not too bad!

Bill Walrman

Subject: Did Pressure washing

If you pressure wash your deck yourself do yourself a favor and use a detergent made for the job. DON'T use the high pressure tip! I did and had to replace the deck as a result. The higher pressures dug out the wood gain and effectively ruined the deck! According to all that I have read since you can use the lowest nozzle with plenty of detergent and it won't wipe out the grain.


Subject: Power washing decks

Be careful to not use too high a pressure. Too high pressure can splinter the surface of a pressure-treated wood deck.

Richard Joseph Meier (m&m Painting-ETC)

Subject: pressure washing

Good article on pressure washing, Angie and Shannon, you both have the basics covered yet I believe that one of the more important aspects was overlooked. Unless I overlooked something.
Chemicals. The proper chemicals can remove, mitigate, and kill,that nasty mold, mildew,& many other exterior issues which we all face when attempting this task. Chemicals can, if used properly, remove the need for higher PSI machines and also create a safer environment during the process.

Make it Great Day!

RJ Meier

P Robertson

Subject: pressure washing photo

Your photo of a deck, assumedly before and after pressure washing, implies that a deck that looks like the one on the left (like one I have) can be resurrected to look like the one on the right simply by pressure washing. I have a hard time believing that. Please explain, because at present, I don't see any benefit at all from pressure washing the deck that looks like the one on the left. Thanks

Randy Duchesne

Subject: Soft Washing

Soft Washing contractors use the lowest available water pressure and allow their professional grade detergents combined with an increased volume of water to wash away even the toughest dirt and stains. There is no better or safer way to wash your home, roof, deck, fence or screen enclosure.


Subject: Power washing

Soft washing depending on solvents to clean can also damage surfaces such as Hardie Plank and other sidings. Be sure your surface can handle things such as bleach or other solvents before using these methods.

Dan Dykstra

Subject: Pressure Washing

What kind of companies can I hire to pressure wash a home and a wood deck?
I would recommend that you do not hire a company off of craigslist for starters. While there are some companies that will put an add on craigslist most of the time it is part time pressure washers, or people brand new with no training. Make sure the company your looking at has the proper commercial insurance for pressure washing, make sure they have had training, are they certified by any national org. like UAMCC (united association of mobile contract cleaners) Also make sure the person knows that high pressure against house can cause damage, ask if they know the term soft wash and what it means, never allow them to blast away at your deck with high pressure and a stream tip.


Subject: pressure washing

It was suggested that starting @ the top and work your way down. VERY FALSE!
If you are using a chemical cleaner, it will leave stains @ the bottom that won't come out.
The reason is the lower portion is not wet & as the chemical hits the dry area and will streak.
If you've ever wondered why you have streaks on any surface that won't come out regardless of what you do...this is why.


Subject: pressure washing

Agreed. I'm not a pro, but I believe this is also true if you are cleaning aluminum or some other type of siding on a second story above a first story brick wall. I've found that the brick wall should be soaked with water before cleaning up higher. This fills the pores of the brick and mortar with water so the dirt and dead paint pigment running down doesn't get sucked into the porous surfaces. If that happens, you'll only drive the dirt and pigment farther into the brickwork when trying to remove it and it becomes a permanent stain. There are a number of houses in my neighborhood where this appears to have happened, either naturally from rain or from someone cleaning the top first above the lower dry brick.

Mark Kuprych

Subject: Top to bottom prevent damage

The top-to-bottom recommendation is to prevent the high pressure water from shooting up under clapboards, shakes, siding, etc, where the entrapped water can do damage. It is possible to rip siding off or crack it if the pressure stream gets under a compromised piece of siding.

Dana Chapman

Subject: Power washing Homes

When power Washing any walls always start at the bottom and work up otherwise you very well may have stains on the lower portion from any types of cleaners you use running down the wall. Also; many times you might consider just Scrubbing instead of using power washers. Very high water pressure can get behind your siding and cause mold or rot. The reason is that siding is made to keep out rain,snow etc but not several thousand PSI of water.

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