bluepearl2

Hi folks. I'm looking for some advice. My house was built in 1965 using tounge and groove redwood siding. The wood has never been finished. It is a very large single story home and most of siding is somewhat protected by a 2-3 ft overhang. The wood seems to be in very good shape dimensionally and I see no (or very little) indication of serious wood damage. The issues are: 1.) The upper 3/4 of the boards (mostly protected from direct sun and rain) are very black. I think it is a cocktail of dirt, mildew, decay and perhaps some bleed. 2.) The lower 1/4 of the boards of greyed and have obvious mildew buildup. There is some obvious splashing going on and I am looking into ways of eliminating this via gutters or other means. I have tried an amateur clean up using bleach as well as sod. perc. via scrubbing and low pressure. Basically the wood went from black to reddish black. I also sanded (60 grit) a few boards and this was very effective and revealed a honey, red, and brown color. I am quite reluctant to use high pressure as the wood is quite soft. As I said the house is very large. I am thinking however of focusing on the sides of the house that are most visible. I know that I can clean the wood if not be scrubbing then by sanding without high pressure or caustics but it would obviously be very time consuming. Assuming I do this is there any advantage to putting a finish on it given the durability of the wood is very high and it has already lasted 40+ years? If so would kind? thanks!

Folks thanks for the input so far. As I understand the acid cleaners and in particular ox. acid which is the one I have don't kill mildew. The sod. perc. I'm using is removing the mildew and the years of accumulated dirt and decay. Surprisingly to me there doesn't appear to be that much bleed. I ox. acid definitely lightens up the wood and it is a good tool in this battle. But ultimately there is probably a 1/16 inch if dirt, grime, and mildew that needs to come off first. I will definitely look into that sanding tool you suggested. At this point, this project is a labor of love. I'm babying it but I tell you what the thing is a beast but man what beauty lies beneath. thanks.

I wanted to put in a small update to my original post. I have gotten better results with the sod. perc. cleaning procedure by increasing the concentration and leaving it stew longer. I have noticed however that the cleaning does not seem to bring out the reddish brown color that the sanding does. There is also a small amount of fur on some boards left that could easily be lightly sanded off. I'll also add a bit about the siding. The boards are about 30 inches wide by 4 inches tall. They are tounge and groove. Between the boards there are vertical douglas fir batons which cover the face nails on the ends. For the most part, high quality fasteners (most likely aluminum) were used although there are some boards where someone fixed the siding and probably used the wrong kind of nails as the discoloration is apparant. Sanding and ox. acid seems to provide a temporary fix to this but I know it is not a long term solution. thanks!