Wash Stained Wood Siding & Painted Trim

Hey all, I had an estimate today where the customer has painted wood trim, and stained siding. He wants to have ot washed to prep for painting the trim, but he is not re-doing the siding yet.

Im worried the house wash mix may have negative effects on the siding. I know it would be fine for the painted trim and eaves.

Anyone have experience using SH on stained wood siding? I have and am still searching on older threadsPART95152894005395995IMG952018061395143123

I’m going to make a video of the five or six test bottles I always have when I show up to a new house. When in doubt a test bottle of your mix will answer 99% of your questions when it comes to stuff like this.


Agreed! Customers will appreciate it! Ask them if you can do a test in an inconspicuous spot and show then the results. I’ve done that and had customers write reviews that we really cared for their home.


Thank you for the tip guys, and @squidskc I would be happy to see what I should have on hand for less common jobs like this.

That should just be your regular mix. In the SH test bottle it’s a 2% mix. Twice as strong as I normally use to see if any problems arise.

Test bottles:
SH mix
Purple Power or Zep Citrus Degreaser
Weak oxalic mix.


Thanks for sharing. I’ll make sure to grab what i don’t already have.

Do you have them pre-mixed and ready to use for testing, or mix up the test bottles as you go?

The SH gets mixed up weekly or bi weekly when I fill the tanks.

Everything else is stable for a long time. There’s only about a cup of each in those bottles. And they’re handheld pump sprayer bottles since they’re air tight.


Like this. Except I’m fairly certain they’re cheaper at Menards.


Great info, I appreciate the knowledge as always. Going to implement this starting tomorrow!

Has anyone had problems in the past when using a basic house wash mix on stained wood? If so, what did it do?

Just prewet the wood and hit with your normal HW mix unless stain is really bad. Down at bottom where it’s green you’ll probably need to use a little pressure, like 300-400 psi to get all the green off. Maybe not though.


So this job with stained wood siding is far away, i will do the spray bottle test before applying but are the odds greater that i’ll have to cancel or that i’ll be able to wash? If it’s too risky i’d rather cancel now than drive back and forth but Racer you say if i pre-wet then apply normal housewash mix it should be ok? Very moldy stained wood siding. I normally walk away from stained wood but this is a regular gutter cleaning customer.


Basically from previous threads i thought they couldn’t be softwashed but now i read this thread and i’m not sure what to think. Worth a try?

If they’re a regular gutter cleaning customer, why not tell them you’d be happy to test (and wash) it the next time you’re out…that didn’t get that dirty since you were there last, and they didn’t all of a sudden care that it’s mildewed, lol

I think i’ll do that. Do you wash any stained wood siding at all? How to avoid issues besides spot test and pre-wet?

nope, that would be the way to go…I’d probably dilute the mix a little more and do multiple applications if needed, but the test would let you know.

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I think you’re going to have to hit a couple of times with strongest ds you can get. What’s up in the first pic, that area at bottom of downspout that looks like fresh paint? That looks good there.
I’d prewet and try a section. I’d tell him there’s a chance that it may look sort of molted looking in places. But see how you’re test goes. Do a decent sized area ds your mix.

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