Learning how to clean cedar shakes is one of those home maintenance tasks that looks a lot more intimidating than it actually is. If you've got a cedar roof or siding, you already know how much character it adds to a house. That natural, rustic look is hard to beat, but let's be honest: cedar is a bit of a diva. It doesn't just sit there and look pretty forever without some help. Over time, your beautiful wood can start looking gray, dingy, or—worst of all—fuzzy with green moss and mildew.
The good news is that you don't necessarily need to hire an expensive professional crew to get it looking new again. If you've got a free weekend and a little bit of patience, you can do a great job yourself. The trick is knowing which chemicals to use and, more importantly, which ones to avoid so you don't end up damaging the wood fibers.
Why Cedar Needs a Special Touch
Cedar is unique because it's packed with natural oils and tannins that help it resist rot and insects. That's why it lasts so long. However, those same qualities make it a bit sensitive to harsh cleaning methods. If you go at it with a high-pressure power washer or drench it in straight laundry bleach, you're going to strip away the "good stuff" along with the dirt.
When you see cedar that looks "fuzzy" or has white fibers sticking up, that's usually a sign that someone was a bit too aggressive with the cleaning. You want to remove the mold, mildew, and pollutants without shredding the wood surface.
Getting Your Gear Together
Before you start, you'll need a few basics. You probably have half of this in your garage already.
- Oxygen Bleach: This is the gold standard for cedar. Unlike chlorine bleach (the stuff in the laundry room), oxygen bleach (sodium percarbonate) is much gentler on the wood and won't kill your bushes and flowers.
- A Pump Sprayer: A standard garden sprayer works perfectly.
- Soft-Bristle Brush: Think of something you'd use to wash a car. You want it to move the dirt but not gouge the wood.
- Garden Hose: You don't need a massive pressure washer for most of this.
- Safety Gear: Gloves, eye protection, and shoes with good grip. If you're heading up on a roof, please use a harness. Wet cedar is incredibly slippery.
Step 1: The Prep Work
Don't just start spraying. First, take a walk around the house. Look for any shakes that are cracked, curled, or literally falling off. There's no point in cleaning a shake that needs to be replaced. If you find any major damage, swap those out before you get the wood wet.
Next, give your plants a good soak. Even though oxygen bleach is much safer than the alternative, it's still a chemical. Drenching your landscaping with plain water beforehand helps the leaves shed any runoff. You can also cover your favorite prize-winning roses with a tarp if you're extra worried.
Step 2: Mixing the Solution
When you're figuring out how to clean cedar shakes effectively, the mixture is everything. Follow the directions on your oxygen bleach container—usually, it's a certain amount of powder dissolved in warm water. Warm water is key here because it helps the powder dissolve fully so it doesn't clog your sprayer.
Give it a good stir and let it sit for a few minutes until it's clear. You'll notice it starts to fizz a bit; that's the oxygen doing its thing. That fizzing action is what actually lifts the mold and dirt out of the wood grain.
Step 3: Application and Dwell Time
Start from the bottom and work your way up if you're doing siding, or start from the peak and work down if you're on a roof. Spray the solution onto the cedar until it's dripping wet.
The most important part of this whole process is the "dwell time." You need to let the cleaner sit on the wood for about 15 to 20 minutes. Don't let it dry out! If it's a hot day, you might need to mist it with a little more solution or a tiny bit of water to keep it active. You'll see the gray or green gunk start to turn a brownish color—that means it's working.
Step 4: The Gentle Scrub
Once the solution has had time to eat away at the grime, it's time for some manual labor. Take your soft-bristle brush and gently scrub the shakes in the direction of the grain (usually up and down). You don't need to put your whole weight into it. If the cleaner did its job, the dirt should roll right off.
If you have a particularly stubborn patch of moss, you might need a second application of the cleaner. Whatever you do, resist the urge to use a metal brush or a scraper. You'll leave marks in the wood that will be visible from the street.
Step 5: The Big Rinse
Now, grab your garden hose. Rinse the cedar thoroughly from the top down. You want to make sure every bit of the cleaning solution and the loosened debris is washed away. If you're working on a roof, pay extra attention to the gutters. All that moss and gunk you just scrubbed off is now sitting in your gutters, and if you don't flush it out, you're just trading one problem for another.
To Pressure Wash or Not?
This is the big debate when it comes to how to clean cedar shakes. If you ask a pro, they'll probably tell you to stay away from pressure washers unless you really know what you're doing.
If you absolutely must use one, keep the pressure very low—usually under 1,000 PSI—and use a wide fan tip. Never get the nozzle closer than 12 inches to the wood. High pressure can "fur" the wood, which basically means it rips the fibers apart. Once that happens, the wood becomes more porous, holds more water, and actually rots faster. Most of the time, a regular hose with a good nozzle is plenty.
Post-Cleaning Maintenance
Once the shakes are clean, they're going to look much lighter—almost like new wood. But don't celebrate just yet. Clean wood is thirsty wood. Once the cedar has had a chance to dry out completely (usually takes 48 to 72 hours of dry weather), it's the perfect time to apply a protector.
You can choose a clear sealer if you like the natural look, or a semi-transparent stain if you want to add some color back in. This step is vital because it locks out moisture and provides UV protection. Without it, the sun will turn your freshly cleaned shakes gray again within a few months.
Common Mistakes to Avoid
- Using Chlorine Bleach: It's tempting because it works fast, but it eats the lignin that holds wood fibers together. It also leaves the wood looking unnaturally white and "dead."
- Working in Direct Sun: If it's 90 degrees out and the sun is beating down on the wood, your cleaning solution will dry in seconds. Aim for a cloudy day or work on the shaded side of the house.
- Ignoring the Gutters: We mentioned this, but it bears repeating. Clogged gutters trap moisture against the bottom edge of your cedar shakes, which is the fastest way to cause rot.
Finishing Up
Cleaning your cedar shakes isn't exactly a fun way to spend a Saturday, but the payoff is huge. Not only does it make your house look incredible, but it also adds years to the life of your roof or siding. Cedar is an investment, and like any investment, it needs a little "TLC" to keep its value.
Just remember: be gentle, use the right chemicals, and give the wood time to dry before you seal it. If you follow those steps, you'll have the best-looking house on the block without having to spend a fortune on a professional crew. Plus, there's a certain satisfaction in stepping back with a cold drink and seeing that golden wood grain shining again.