Figuring out how to clean cedar shingles is one of those tasks that sounds intimidating until you actually get started. If you've looked at your siding or roof lately and noticed it's looking a bit more "haunted house" than "coastal charm," you aren't alone. Cedar is a tough, beautiful wood, but it's a living material that reacts to its environment. Over time, moisture, shade, and debris lead to moss, mold, and that dreaded gray-black discoloration. The good news is that you don't need to be a professional contractor to get it looking fresh again; you just need some patience and the right approach.
Before we get into the nitty-gritty, we have to talk about the one thing you should almost never do: grab a high-pressure power washer. I know it's tempting to just blast the grime away, but high pressure is the enemy of cedar. It tears the soft wood fibers, leaves ugly "fuzz" on the surface, and can even blow water right behind the shingles into your wall cavity. We want to clean the wood, not destroy it.
Getting your gear together
You don't need a massive budget for this, but you do need a few specific items to make the job easier. First, you'll need a good garden hose with a decent spray nozzle. Not a jet stream, just a solid, steady spray. Next, grab a soft-bristled brush on a long pole. Think of something you'd use to wash a car—nothing with stiff wire bristles that will gouge the wood.
For the cleaning solution itself, you have a couple of choices. Most pros suggest oxygen bleach (like OxiClean, but often sold in bulk powder form for decks). It's different from the liquid chlorine bleach you use for laundry. Oxygen bleach is much kinder to the environment, it won't kill your bushes, and it doesn't strip the natural color out of the cedar quite as aggressively. If you have a really bad mold problem, you might consider a specialized wood cleaner, but for most of us, oxygen bleach does the trick just fine.
Don't forget safety gear. You're going to be getting wet and probably a bit messy. Wear shoes with good grip, especially if you're working on a ladder, and grab some safety goggles. Even "eco-friendly" cleaners don't feel great when they splash into your eyes.
The importance of the "pre-soak"
One of the biggest mistakes people make when learning how to clean cedar shingles is applying the cleaner to dry wood. Cedar is like a sponge. If you put the cleaning solution directly onto dry shingles, the wood will suck it deep into the grain immediately. This makes it harder to rinse out and can actually cause the wood to dry out too much later on.
Instead, give your shingles a good soak with plain water first. You want them damp but not dripping wet. This "saturates" the wood fibers so that the cleaning solution stays on the surface where the mold and dirt are actually hanging out. It makes the whole process way more effective and saves you from using twice as much product.
Applying the cleaner and the waiting game
Once the shingles are wet, it's time to apply your mixture. If you're using oxygen bleach, follow the instructions on the package to dissolve the powder in warm water. A pump-up garden sprayer is the easiest way to get an even coat onto the shingles. Start from the bottom and work your way up—this prevents the cleaner from running down and leaving "streak marks" on dry wood.
Now, here is the part where most people fail: you have to wait. The cleaner needs about 15 to 20 minutes to break down the organic matter. You'll probably see it start to bubble a little. That's the oxygen doing the heavy lifting. Keep the surface wet during this time. If it's a hot day and the shingles start to dry out, give them a very light mist of water. If the cleaner dries on the wood, it's a pain to get off and won't work as well.
The gentle scrub and rinse
After the cleaner has had time to sit, it's time for a little elbow grease. You don't need to scrub like you're trying to remove paint. Just a light pass with your soft brush will help loosen the moss and lichen that the cleaner has already softened up. You'll see the gunk turning into a brownish slurry—that's a good sign! It means the dirt is letting go.
When you rinse, always spray downward. Think about how rain hits your house. Shingles are designed to shed water that comes from above. If you spray upward, you're forcing water under the shingles, which is a recipe for rot and mold inside your walls. Use a steady stream of water and keep going until the water running off the bottom of the wall is clear.
Dealing with stubborn moss and lichen
Sometimes, a single pass won't get everything. Lichen, those crusty little spots that look like tiny seafoam-green maps, are particularly stubborn. They actually root themselves into the wood. If you encounter these, don't try to scrape them off with a putty knife. You'll just take a chunk of cedar with them.
Instead, hit those spots with a second round of cleaner and let it sit a bit longer. If they still won't budge, it might be better to leave them to dry out and die. Once they are dead, they usually lose their grip and will wash away during the next heavy rainstorm or the next time you give the house a light rinse.
Why you should avoid chlorine bleach if possible
A lot of old-school advice on how to clean cedar shingles involves heavy amounts of liquid chlorine bleach. While it definitely kills mold fast, it has some downsides. For one, it can turn the cedar a weird, ghostly white color that looks unnatural. It also breaks down the "lignin" in the wood, which is basically the glue that holds the wood fibers together. Over time, too much bleach makes cedar shingles brittle and prone to cracking.
Plus, if you have a garden or nice landscaping around your house, chlorine bleach is a nightmare. It'll turn your hostas into brown mush pretty quickly. If you must use it for a severe infestation, make sure you soak your plants in fresh water before, during, and after the process to dilute any runoff.
Aftercare and keeping it clean
Once the shingles are clean and dry, they're going to look a lot lighter. This is the perfect time to evaluate if you want to apply a stain or a sealer. Cedar has natural oils that protect it, but those oils eventually dry out. Applying a clear water repellent or a semi-transparent stain can help the shingles last another decade or two.
Just make sure the wood is completely dry before you put anything on it. We're talking 48 hours of clear, dry weather. If you trap moisture inside the wood with a sealer, you're just inviting rot to start from the inside out.
For general maintenance, try to keep trees trimmed back so they aren't touching the house. Airflow is cedar's best friend. If the shingles can dry out quickly after a rainstorm, moss and mold won't have a chance to get a foothold. A quick rinse with a garden hose once a year to get rid of pollen and dust also goes a long way in preventing the deep cleaning sessions from becoming a yearly requirement.
Cleaning cedar shingles isn't exactly a fun way to spend a Saturday, but seeing that natural wood grain pop back out after years of being hidden under grime is pretty satisfying. Take it slow, stay off the pressure washer, and your cedar will keep your home looking great for a long time.