Preparing And Staining Old Cedar Siding

cnw20

My cedar board and batten house is 20+ years old and has never been stained. I am told that I new to clean it first with bleach - can I use houshold bleach and dilute it or do I need another product? Also will a power washer harm the old cedar and should I just use the hose to wash off the bleach?

Mike Finley

There are 2 camps in regard to using house-hold bleach on wood. One says go for it, the other says you are crazy. I'm sure if enough posts are made here you will get some of both.

Cedar usually involves 2 cleanings. One to deal with removal of any mildew and another to deal with removal of black staining caused by the large amounts of water soluable tanin in the wood.

I would clean it once with a oxygen-type bleach (this is not household bleach) Products in this category are usually based on disodium peroxydicarbonate, commonly known as sodium percarbonate. The sodium carbonate acts as a built-in detergent, removing dirt and other deposits. Thus, sodium percarbonate-based cleaners are effective in removing dirt, mildew and weathered grey residues. Once treated the wood returns to its natural original appearance.

Rinse with pressure washer.

I would follow this up with a Oxalic acid-based product. Neither chlorine bleaches nor oxygen bleaches are effective against tannin stains or iron stains. Oxalic acid, on the other hand, solubilizes tannins and iron stains and renders them colorless.

Rinse with pressure washer.

Grumpy

Rinse the acid off rather promptly as a matter of fact. You don't want that sitting there too long.

Quality Painter

yes max is 30 min with the oxalic acid but you do not want it to dry out, and you can skip the oxygen type bleach, if you have a good power washer, it just strips off the graying and dirt from raw old wood, i use a 3500 psi and it works really sweet, then the oxalic acid will restore the wood to a new wood look. be very carefull to use evenly spaced strokes with the pw wand and not to get to close since you can cut right into wood with that much presure. never use house hold bleach on raw wood, but you can use a TSP, water and clorox mixture to etch old sealer before a primer app. then paint, works really nice. best of luck , dave