I have a job opportunity to clean an older home that has horizontal cedar siding. The new owners don’t know much about the history. If it was sealed or stained it was likely a while ago. They will seal it themselves after I clean it. The parts that have been beating in the sun are very soft and fragile, long grains that look like the metal fins on the outside of a radiator. What’s odd is (mostly on the north side) the bottom third or so has a gray/whitish appearance and then goes to darker brown and then to lighter brown at the top. Not really any organic growth anywhere. My inclination is to softwash wash using my 12v pump for applying sodium percarbonate and rinse with xjet, followed by citric acid treatment and final light rinse. For the north side, I feel like I would need to do a 1000 psi 20-40 tip to rinse the grey off, just like a fence with the dead wood fibers. But my concern is the soft areas, where at least 1/8” of the outer decaying wood may fall off or just mat the wood fibers in, making it look weird. Is there a better process to clean this? Anything I should do differently?
Metasilicate 3/4 to 1 cup per gallon. 800 psi 40 degree tip over whole thing. Oxalic 1 cup per gallon and then rinse
Thanks man. 3/4 to 1 cup per gallon of water with 12v pump, not downstreaming correct?
Also, would citric work instead of oxalic?
Looks like a combination of sprinkler wash (very white section down low), raised grain (lignin is gone between the rings, rings are the high points) upper is less effected because it doesn’t get as much sun. Surface Therapy suggestion of metasilicate is a good one. Where it’s very white there is going to be a ton of wood pulp, that’s really not attached to the house anymore. Plan on sanding or using an Osbourne brush to even things out. What they use for stain will impact the final results so don’t take responsibility for that.
Correct
Stain it as well and make some serious money.
Not for me. I don’t like that kind of work, I stick to what I know. Had to stain a deck last year and it sucked lol.
You’re constantly buying new equipment to do various things. So might as well get an airless sprayer. 
It’ll easily be paid for with this one job with money to spare.
Is that because of the dead fibers laying matted against the solid wood behind it after?
The white areas are trashed so even if you used nothing but low to medium pressure it is going to pulp all over. It takes lots of rinsing and when you come back and it’s dry it will look like there is cotton all over the ground.
