Under a deck

I may have to get this algae off under a customer’s deck, wanted to ask you all about the best method. I do have a small 12v.

I don’t wash anything that is going to get me wet and icky


Yeah hopefully she just wants the walls and patio. I’m doing the deck and house as well.

Tell her you don’t do undersides. I don’t do decks anymore but made an exception for a past customer. He wanted the underside done, soaked and horrible day. Never again.

Treefiddy in and out in ~90 mins.

Get some rain gear with hood, ppe, and treat it like a roof, couple hot treatments and spot where needed.


I’m not even going to bring it up lol. Just curious in case she points it out.

Nuke it with a pump up sprayer and set and expectation tell her you don’t want to be under a shower of chemicals. I bet you the homeowner will take that option over staring at the green all day. I would never clean the underside of a deck and expect the same finish as the top, that’s overkill.

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I just did one about this size. I usually don’t use a lance on my gun but have an older cheapo gun with a 3 foot lance on it. I just used my high soap tip, walked backwards cleaning one side so I stayed dry, soaped and rinsed another side of the house to let majority of the water drip off and came back, walked backwards doing th opposite side and it turned out great. Didn’t get very wet at all and the algae on the underside comes off fairly easy due to never really drying out from being baked in the sun. All in all it took 15 minutes not including the wait between doing one side of the joists.


@Mbeall777 method is exactly what I do if I do it. I learned to set expectations. Some of green won’t come out of those beams. Make sure they know that. I also charge extra for that. We have a lot of decks like that in my area. I try not to clean them and my guy hates cleaning them too. Pump sprayer is good but the spray going up always creates a mist that will go in your eyes.

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@dcbrock That’ll clean up real nice. I wouldn’t pass on it. Just charge accordingly. I did one about that size two weeks ago. Use a normal deck wash on it. My 4gpm pulls strong so I used that; no 12v. Work backwards spraying the chemical so it’s not raining down on you. It does take going in both directions because you have to hit both sides of the supports.

Set low expectations. The customer will be thrilled at how great it comes out. My customer said I must’ve used “liquid gold” on it, it turned out so well.


I don’t think some people on here get how those shore houses are built until they see them. I know when you say a 2 story, it is more like a 3 story with those stilts (thats what I call them, the poles sunk into the ground). I often wonder if you have a lift, some of those houses are extremely tall. Two decks on the fronts and sometimes side decks and decks on the roof. I’m heading down your way for a couple of days next month. I was suprised to see that the shore house availability is very limited. I’d love to see you tackle one sometime with that shore breeze, must be challenging.

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“Shore breeze” at 25 mph sucks. Lol

Cant that be done with a 79" lance without getting covered ? Curious.

It helps to get a little more distance but I usually just use my 4’ and work backwards. 79" would keep you even further away from the water so definitely helps. Sometimes it can almost be too long though when you get to the edges.