Power wash question

I have a composite deck that has plaster stains and I’m stumped as to how to clean it. I tried the turbo nozzle and a 2% SH mix.
No luck, once the deck dried the stain was still there.

I’m stumped and I’m too intimidated as a noob to go post that in PWR as my first post.

@ProWindowCleaning I’m green to PW as well, but maybe you just needed more dwell time? I looked up products and the one specially made for composit decks wash was just sh and wetting agents. Maybe a combination of Elemonator and GG4? Im interested to see what someone else has to say. I am curious though how sh could affect was appears to be mineral deposits?

I get not wanting to post on pwr. They can be brutal! But just like here lots of knowledge.

Also, now that I’m pressure washing I don’t know why in the world I didn’t start sooner!

Here you go, @ProWindowCleaning:joy:


You’re gonna get me killed via internet bullies over there! Haha

Thank you!


It ain’t so bad over there, once you get to know everyone :smirk:


First bit of advice, never use a turbo nozzle on wood or composite. You may have damaged the deck.

As far as getting the plaster off, I would ask in the F9 Professionals group on Facebook.

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Plaster is usually water soluble. Maybe warm or hot water will help let it sit for a while.

Ya like Chris Says no turbo nozzle , or pressure. on composite … Not good !

Are they sure it’s plaster an not paint ? Or maybe they tied to get it up with miners spirits or something an it stained.

Just guessing !

Brand new home, these were here after the plaster guys came in and finished some work.

If I can’t get it off the realtor is replacing the deck for her client, I’m going back today.

I’ve got an assortment of things to try, test spots of course.

I had no idea the turbo nozzle was such a huge mistake, won’t be using that on a composite deck again.

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How did you make out ?

The homeowner was on site and informed me that “the painters spilled paint on the deck and if I can’t get it out he’s going to have them replace the deck”

Well, I wasn’t prepared for paint removal as I was told it was plaster… sooooo the painters get to pay for my time trying to remove the “plaster” and then they get to pay for a new composite deck.

Yup !! I knew it was paint , an it looks like they tried to get it up an realized they were ruining the deck. Had to be oil base paint.

Because if it were latex they could of just rinsed it with water an it would of came off.

Costly mistake !

Oil based paint should strip off with Sodium Hydroxide fairly easily.

Not sure what effect it might have on the composite deck, though.

Do you know if it’s 1st or 2nd gen Trex, @ProWindowCleaning?

It’s brand new, I’m not sure if that means much.

However, I put enough time into that job and it’s going to end being covered by the painters insurance (insurance? sure)

I have dumped enough of my time and energy on that project and sent the invoice for my time. As years go on I know when to tap out, walk away, and send a bill.

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Totally get where you’re coming from. Gotta know when to call it a day.

But for the sake of posterity, I’ve taken some time to answer your question:

That would be 2nd gen, then. The older style of composite decks (15+ years ago) was semi-porous and the maker of Trex got their pants sued off for selling it as a maintenance free, stain resistant decking material, when it was in fact quite the opposite. It can be a real nightmare to try and work with.

The new stuff is a fully encapsulated PVC product. Much nicer to clean and maintain.

The Sodium Hydroxide probably wouldn’t hurt it at all, and at this point, if the painters wanted to give it a shot with some hydroxide based paint stripper, they have nothing really to lose.

But that’s none of my business… :frog: :coffee: