Cedar Shake Siding Estimate - 2 story with lots of algae!

I have 2 potential customers wanting an estimate on cedar shake homes. They are neighbors. I’m familiar with cedar shake, but there is a lot of algae on this stuff all the way up to the 2nd story peak on one side. I am really not in the mood to scrub the entire side of the house down or to risk high pressure on these. What’s the best way to get this stuff off? If it’s not feasible to do so that’s fine, I’ll walk away. If it would be a really high price-tag, that’s fine, I’ll give them a high estimate if that’s what’s necessary to make it worth it for me. Worst thing they can say is no!


Google “3 stepping wood” or “3 stepping cedar”. They say it has been an industry standard for years. It’s basically a mix of sodium percarbonate, sodium hydroxide, and water. You then neutralize with oxalic. I have never had the chance to try it. I’m just passing along some of my research. Since it’s a neighbor maybe you can do a test spot first.

Some say not to use SH on cedar and some say it’s fine. It does lighten the wood up some tho. As long as you let them know it’ll lighten the wood some you should be fine. It’ll look much better than it does now.

The least aggressive way is just using sodium percarbonate. I doubt that will do much good with the heavy algae though. The small amount of sodium hydroxide added as part of the “3 stepping” should take care of it.


Here is a project I completed last year. There was no existing finish on this house, so I used Sodium Percarbonate. If there was an existing oil-based finish, I would have used a Sodium Hydroxide to lift old finish. You can use Sodium Hydroxide as a cleaner as well, but your dilutions wouldn’t be nearly as strong as if you were using as a stripper.

I applied cleaner with a 12 volt, 20 min dwell, 40 degree rinse from 8-10". You need to get up close with mild pressure on wood to help lift dead wood fibers off. Neutralize with oxalic acid. After it dried, I stained. You will need a lift or some method of getting up close to the wood. Hard to do something like this off a ladder, and from my experience, you can’t really do it right without a proper rinse.

Very nice work. There is no existing finish. What was your mix ratio for the sodium percarb?

Is F18 MAX good enough for this?

If you order F10 from pressure tek, that is the stuff I used. I just followed the instructions on the container, which was probably 8 oz per gallon. F18 is the hydroxide. I’ve never used it specifically for cleaning, but rather for stripping. With stripping its 8 oz gallon as well. It mentions it can be used as a cleaner at milder dilutions. I’m sure SH would be just fine as well at about a 2-3% mix, just make sure you are neutralizing with Oxalic after. I mix the oxalic at 8-10 oz per gallon and use an x jet with no proportioner. It works. You can see the wood brighten almost instantly. Just rinse it off well. With the Oxalic, you don’t need to rinse like you do after your cleaner. Apply cleaner, 40 degree up close rinse to remove dead fibers, Oxalic with x jet, and high volume rinse like you would anything else during a normal house wash.

Personally, I would consider SH at the above %, simply because there’s no mixing if you run a proportioner. It will kill the organics and clean faster than percarbonate. Maybe others will chime in with their own experiences. I’m just throwing out what worked well for me.