How to Lighten Cedar Siding
This Old House host Kevin O'Connor turns to painting contractor, Rich O'Neil for advice on cedar siding finish turning dark
The clear finish applied to the siding of our cedar home about 20 years ago has turned dark, and we'd like the wood to be a lighter color. My husband tried wood bleach, but to no avail. Any ideas on how to proceed?
—Patricia Sayre, via e-mail
According to Rich O'Neil, a painting contractor who has appeared on Ask This Old House, you can't lighten wood until the finish is gone. And the best way to do that is with a product made for stripping deck finishes. You'll need a pump-type garden sprayer, a hose, and a long-handled brush with fairly soft bristles. "Stiff bristles can rough up a soft wood like cedar," O'Neil says.
Before you begin, protect the plants close to the house by wetting them down and covering them with tarps. Also, tape plastic over every other part of the house that you don't want to strip, including windows, doors, and trim. Finally, protect yourself: your eyes with goggles, your hands with rubber gloves, your face with a dust mask, your arms with a long-sleeve shirt.
Now fill the sprayer with stripper and start spraying on the shaded side of the house, out of the sun, and work from the bottom up. The stripper needs to sit on the old finish about 15 minutes to soften it up but will stop working if it dries out. Just reapply more stripper if it does start to look dry. When 15 minutes has passed, scrub the wood with the brush to loosen the old finish, then rinse it off with water, working from the bottom up. Repeat the treatment in any spots where finish remains. When you're done, remove the tarps and soak your plants with more water.
After a few days, when the siding is dry, go back and spray the wood with a wood brightener, scrubbing and rinsing as before. The most effective brighteners use oxalic acid to dissolve the decayed, sun-damaged fibers and expose the fresh wood color underneath. "Even with all this work, the cedar probably won't be the same color it was when it was new," O'Neil says, "but it should be much lighter than it was before you stripped it."
To preserve that color, he says you'll need to coat it with a clear, oil-based translucent finish like Sikkens' Cetol Log & Siding. It's loaded with mildewcides and with finely ground pigments that fend off the sun's rays but still let you see the wood. You'll want to put the finish on as soon as the wood is dry, he warns, before the sun has a chance to decay the wood fibers.
With this kind of finish, O'Neil says, you'll need to regularly apply additional coats as the previous one succumbs to the sun and the elements. That might be as often as every two to three years on the sunny south- and west-facing sides of the house, and every four to five years on the shadier north and east sides. O'Neil admits that this kind of maintenance isn't for everyone. "But if you don't keep after it, the cedar will inevitably turn dark again."
— This Old House host Kevin O'Connor