Old Trex job

Customer needs his Gen 1 Trex cleaned, fair amount of black mildew spots. Did a lot of reading and the general consensus is 2% SH and a lower pressure rinse.


The actual composite manufacturers say not to use SH for various reasons, one being that the bleach can’t kill mold in the boards, just temporarily on the surface.

Anything else I could be using?

Tell the customer it can come out lighter in color when your done. Also they look terrible when wet. Clean it and let it dry before you decide to go over it twice. You’ll see black and browns when it’s wet. They disappear when it dries. I hate first Gen. Plus most first gen decks have been blasted with pressure over the years bu the homeowner and now suck up algae and mold.

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I don’t do gen 1 decking. Never really looks that great after, just turned one down last week. Not worth their money, each their own on that one though.

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@dcbrock I’m not saying this is the right way but I just did one last weekend and I started off very light on the SH got almost no results, kept adding more Sh to my mix until it was a 50 50 mix maybe a bit more…hot seemed the way to go on this deck…it had already been brutalized by past pressure washings…
Hot mix and light pressure is what i used worked like a champ…heres some before, halfway and after pics



Wow that’s crazy!

Mine is nowhere near that bad, still a light grey but has speckles of black.

I’ll just try a small section first before charging him. Doing some nasty, gross concrete for him as well so no biggie if I can’t help the deck.

Now when you say light pressure, we talking 800 or so?

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@dcbrock I was using the pressure nozzle thats on my J rod its a 2515 i think…I’m running a Hydro max CW6040HG…so 6gpm 4000psi.
I was holding it like 24 inches off the deck…kind of found a sweet spot, no damage and it cleaned up nicely

The speckles of black could be part of the composite. They might not go away if so.

I frequently brush really bad spots on decks. Works great and doesn’t make lines too much pressure can.

1st gen around here are in bad shape. Staining from grill oils and pressure washing marks. Most have no spacing between boards causing drainage problems, more mold and algae. You basically have to nuke
it with sh, color change for sure after. Have waiver for warranty issues because of cleaning if it’s the original owner of the deck, that decking fades, flakes apart all sorts of issues. Any cleaning will be scrutinized prior to claim. So…set expectations and have some form of warranty waiver. I don’t do them, better for homeowner to replace the stuff in my opinion. But if they want to just clean it, tell them your process and go for it. From my understanding you can stain the older generation composite decking, so that’s an option for the homeowner.

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I second this. Cleaned a red gen 1 composite deck, thought I did a terrible job since you could still kinda see the black mold spots all over when wet but once it dried it turned out as great as it’s going to get.

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I believe it’s two part process on older trex. If use sh, you would need to neutralize with oxalic after, calm down those wood tannins. High % of sh can damage the wood within the composite. If it’s not encapsulated I have no interest in them. But they can be cleaned.

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Yup, that’s similar to the one I bid, just grey. What was your process?

Can’t argue with that, came out great :ok_hand:

I didn’t treat it any different then the normal wood decks I clean. Light house wash mix, dwell, rinse. I think I used ox after to balance the wood particles PH back. The deck looks brighter because of those small wood bits on the composite. I got nervous because this decking loved to shed and throw red pigments on the side of the house and under, no matter how light the pressure was. But it was just fine once the composite dried I think in some areas where it had lichen I used a pump up with my post concrete strength mix and I hit those with a fine mist to kill them off.

I’ve had a grey deck turn to a yellowish tan color. I hit it with a strong mix with my 12v because I didn’t wait for it to dry to reassess. Customers didn’t care because it was so bad before I cleaned it. I brush it now with a deck brush before I go to heavy with the SH or try more pressure. It’s safer and only takes a second for spot treatment. Plus the homeowner thinks your busting your hump. Lol. I’ve never used ox since there is only fine wood fibers in the deck and I don’t want it to lighten it anymore than I have too.

Honestly I feel like the customer doesn’t mind and likes the lighter look. The “clean” look. Vs what they had before they will love it either way.

But the reasons I use ox after isn’t for brightening it’s more to balance the ph of the wood fibers back to normal since SH breaks down wood fibers and I don’t want to shorten the life of the deck any more than it already is


I second the hot mix. Seems to be the only thing that works (in a timely manner) for me also.

Did the Trex job today, it had a ton of lichens and old algae. 3%, dwell and 800 psi rinse. Took awhile but came out really nice.

Pics ?

Totally forgot to take one. I was so busy packing up it slipped my mind.

You can see the rails in this one at least.:laughing: