Removing Water Stains From Cedar
Leaks happen, and the results can be unsightly. Here's what you can do
An old roof leak left stains on the unfinished western red cedar inside my house, both the rough-sawn beams and the V-groove ceiling. I’ve had the leak fixed. Now is there a way to get rid of the stains?
—Corey Lee, Rutland, VT
Kevin O’Connor replies: I’ve seen those kinds of stains on tongue-and-groove ceilings, and I assumed that removing them would be a lost cause. But according to Paul Mackie, technical field representative with the , it’s possible to make those stains go away, and it doesn’t involve hiding them under a coat of paint. Here’s what he had to say.
“The stains you see are extractives, the natural preservatives that are responsible for the cedar’s rich color and resistance to decay and insect attack. These extractives are water-soluble, so when the wood gets wet, some of them dissolve, bleed to the surface, and leave a dark stain after the water dries, kind of like the ring around a bathtub. Not to worry; that roof leak hasn’t drained your wood of its desirable properties. There’s still plenty of good stuff left.
“If the bleeding had occurred recently, you might have been able to wipe it off with a damp sponge or cloth. Your cedar probably requires more aggressive action.
“Let’s start with the easier surface to fix: the smooth-faced V-groove ceiling boards. All you need to do is sand them lightly with a fine-grit paper. Test a range of fine grits to see which one gives you the best match with the texture of the surrounding boards. Sanding lightens the color of the wood somewhat, so sand each stained board entirely to avoid random light spots on your ceiling.
“Your rough-sawn beams will be a little more of a challenge. Sanding isn’t an option with them, because that would change their texture. Instead, you’ll need to wash off the stains. Start with a mild citric acid–based cleaner—I’ve even used dissolved packets of unsweetened Kool-Aid lemonade mix—which will be easy to rinse off with a wet sponge. Spray the cleaner on the stain, let it sit for several minutes, then rinse.
“If the stain is still evident after the wood dries, try a cleaner that contains oxalic acid. It’s very effective on extractive stains, but because it’s much stronger than citric acid, it has to be used with care—even when it’s diluted. Be sure to protect your eyes and skin and the surrounding area from drips. Once you’ve scrubbed the surface and allowed the cleaner to work for a few minutes, it’s important to thoroughly rinse it off using a spray bottle, a sponge, and perhaps a wet/dry vac to suck up the drips.
“Whichever cleaner you use, test it first in an out-of-the-way area, then let it dry. That will give you a chance to evaluate its effectiveness before you commit to the job.”