Cleaning unfinished redwood siding

Hello there.
I recently purchased a home in Northern California with redwood plank siding from 1972. Never stained I believe.
My questions are more about the cleaning process and what product to use? I don’t want to use bleach. And of course want something more biologically efficient than soap and water.
I expect to use Oxalic Acid as the second step.

Any advice on the process is appreciated!


Hi, welcome. You might be best served to call a local contractor and discuss with him.

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I appreciate that, but don’t like to waste anyones time that I will not be hiring.

Well, we’re all contractors here, so…

Very sorry. I have seen a great amount of good ideas from informative people willing to help on this platform. It’s a forum afterall. Almost everyone seems willing to lend an idea.
Maybe you should go be grumpy somewhere else?

Without some pics, hard to help. Saying you’ve got dirty wood not much help. Just out of curiousity, why do you not want to use bleach? It may be the best solution, but until we see what you have it’s all guessing.


Hey Racer, thanks. I should have!

2 photos attached. one in the warm sun and one in the shade.

Granted the sun lit one looks pretty good, but it can be twice as good!

I didn’t want to use bleach because I had understood that using a different chem to darken the tannens then oxalic acid was a better method.


Sun shot here

Completely my bad. I misunderstood you when you said you didn’t want to waste anyone’s time that you wouldn’t be hiring.


Wow, that looks pretty good for 25 years old. Some good quality wood too, not a lot of knot holes. Hard to find like that anymore. Beautiful wood.

Oxalic acid is sold as a wood cleaner, brightener at most big box stores, ie Home depot, etc. Or you can buy in bulk, a lot cheaper, and mix 1cup (8oz of the powder) to a gal of water. Spray on and you can scrub with brush or use pressure washer at no more than about 500psi on it. Redwood is very soft. Don’t let it dry, do in sections. Let it sit for about 5-10 min and then rinse at appropriate psi. If it’s all pretty much like pics, then that should do it.
Stain wise, makes a nice redwood stain that’s a penetrating oil that you don’t have to back brush and has a couple more that have a reddish tint to them. The mahagony is nice. Good luck. Be sure to post some after pics.

Post a few more pics of house, would like to see. I love Redwood homes. Extremely rare around here.

Hey Racer, thanks again!

Do you think that I do not need to have a ‘cleaning’ phase?
Yes, I will prewet, keep it wet and go in sections. Thanks
I only have a high pressure washer. My thought was to use it from 6’ I have worked with redwood before and know how soft it is. I don’t want to etch any away or fur it up for sure.
Its 50 years old! As far as I can tell, never stained or cleaned. Just good air in West Sonoma County! :wink:
I don’t plan to seal or stain. We are ok with what it does naturally. If this is easy enough, we may do it every 5 (or whatever) years.

Thanks again

That looks pretty clean, I would use sodium percarbonate if it was me….mild cleaner.

Out of curiosity, what ratio to water? And how many pounds to cover 226 linear feet @ about 8’ high average OR 1800 sq/ft?
Trying to anticipate how many pounds of cleaner and Oxalic to buy.


The easiest way to handle this by far would be to trade me that Bronco for clean siding. I’ll even rinse off the porch!

That’s not a bronco I think it’s a land cruiser


8 ounces per gallon of water for downstreaming or 2 ounces per gallon for pump sprayer direct application.

I was going to suggest the percarb if you just want to clean it as @Kentuckywash suggested. They’ll both work. But since you don’t have any mildew or mold I’d just go with the oxalic. It’s a cleaner also. Either will work, but especialy if you’re not going to stain it, the ox will bring the color out a little more, ie why they call it a brightener. Here’s example below. Just Google, lots of choices

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Even better!

What year is the TR-6? Have had 6 of them in my lifetime. Fun little cars.