Safe chemicals recommended for cleaning painted clapboaards


Hi All great site, been searching/reading and learning a lot. Cant find answer about cleaning painted clapboards without lightening the color while still killing mold/algae. I know SH is not recommended for porous surfaces. read about quats. NEED ADVICE. worried about fading the paint color. thanks


If there’s any question test an inconspicuous area. Some won’t wash SW paint or certain colors.


yes thank you. but what is considered best practice and/or a safe alternative to SH


Best practice is to do what was mentioned above. If it can’t be cleaned with SH, walk away.


If you are talking organics I am not aware of an effective alternative. Choices come down to take your chances or as IBS said walk away.


You can use high pressure but that’s likely more dangerous than SH.


If your just downstreaming standard housewash mix, painted surfaces are fine.

I always wet painted surfaces first as a precaution.

Do a small test area first to ease the stress.

Just make sure you wait till its completely dry before checking.


Not necessarily. Some paints have organic pigments and will discolor when SH is applied.


Yep. That’s what we are discussing. Do a search for Sherman Williams or hardiboard and you’ll find multiple threads.


I wash Hardboard all the time.

The right ratio mix is fine.

Too strong, which alot of guys do will damage alot of things not just paint.


Have you experienced this?

The only issue I have ever seen is an idiot using a 12v on painted surfaces or way too strong house wash (which is debatable).


Well frankly I think the issue is more paint with organic pigments. And possibly the Hardiboard with factory finish. Otherwise the substrate is unimportant.


Ok thats fine.

Have you experienced this?

Im just asking because I personally haven’t after many years of washing.

I understand the concept behind it, but are “professional” guys and gals experiencing this “pigment” phenomenon?


I haven’t but I am new. I definitely heard vets warn about it. Search for either Sherwin Williams or Hardiboard. What do you consider safe mix hitting surface?


Downstreaming is the safest method.

Xjet or 12v is a different story.


I’ve had to repaint a house because of it. Personally seen it happen a half dozen times.


From downstreaming?


Yes. That is why I avoid certain colors. I washed about 4000 houses for one particular painter, even ran paint crews for them when I was still at the fire department at the fire department. I know they painted at least a dozen or so houses on SW’s dime before they stopped accepting blame.


Quats are a thing, you can find them in products like spray and forget and wash N forget. The thing is though is that the house doesn’t LOOK clean that day. Some people can sell that to customers, others don’t even try the Quat approach.

SH is the GO TO thing, however, I have heard of hydrogen peroxide being a safe alternative. Of course you would have to test on that particular paint, but I’ve seen it work.

After that I’d say the next best alternative is a house wash. Something that has been certified by the EPA’s safer choice or Green seal as “safe” would be my best bet because at least you know it doesn’t have a super high pH, and doesn’t contain weird things…again, always TEST.

Apart from that, go look at your local home depot/lowe’s/hardware store type place. They have a contractor section I’m sure.


Only Once. I’ve turned down a wash because of this. It was a darker shade of brown painted Hardiboard that in the test spot lightened up after it was dry. I told the owner i wasn’t going to wash his home.