How Cedar Siding and Shake Should Be Cleaned

Cedar is soft wood, and it soaks up water. It does not hold up to the force that harder siding can take. Here is what cedar siding and shake need, what high pressure does to them, and how to care for cedar on a Charleston home.

Why cedar is different from fiber cement

Fiber cement is a hard, man-made board with a factory coat on top. Cedar is wood. It has open grain. It takes in water and lets it out as the weather changes. It is soft enough to dent with a fingernail. That is why cedar needs a different kind of cleaning.

Cedar soaks up water, so it stays damp longer than sealed siding. In Charleston, the shady sides of a cedar home can stay wet for most of the day. Damp wood is just what algae, mildew, and moss need to grow.

What high pressure does to cedar

A pressure washer can damage cedar fast. Some of the damage can never be fixed:

• It lifts the grain and makes it fuzzy.
• It cuts lines and grooves into soft wood.
• It strips stain, sealer, and paint in patches.
• It pushes water deep into the boards.
• It can loosen, split, or blow out pieces of shake.
• The fuzzy surface it leaves gets dirty faster.

Fuzzy grain is the damage people regret most. Once the wood fibers are lifted, the wall stops shedding water and dirt. It gets dirty again sooner, and the next cleaning is harder. Water forced into the boards is a quiet problem. It does not dry fast here. Trapped water can lead to rot and growth inside the wall, long after the wash looks done.

Why cedar turns gray and mossy near the water

Two different things happen on most older cedar homes. It helps to tell them apart.

The first is normal aging. Sun and rain wear down the surface of the wood and its finish. The bare wood turns a silver gray. Many island homeowners like that look and choose to keep it.

The second is growth. Shady walls, north walls, and walls under live oaks stay damp. Near the marsh and beach, salt air leaves a film that holds water on the wood. That is where the green film, the black streaks, and the moss in the shake gaps come from. Growth is not the same as aging. It keeps spreading, and it keeps holding water against your siding.

The gentle way to clean cedar

1. Look at the wall first We check the type of cedar, its shape, the finish, and how much growth is there. All of that shapes the plan before anything gets wet.
2. Apply the right cleaning solution The solution kills the growth at the root, so the cleaner does the work instead of force. Cedar gets a milder mix than harder surfaces.
3. Rinse at low pressure The rinse feels more like heavy rain than a jet. We work with the grain and the way the shake lies, so nothing lifts.
4. Protect what is nearby We wet plants before and rinse them after. We cover lights and guide the runoff. We send you photos when the job is done.

We never use high pressure on siding. Cedar is where that rule matters most.

Is your cedar stained or sealed? Tell us first

Staining and sealing are not the same as cleaning. Do not assume they are included. If your cedar has stain, sealer, or paint, let us know before we start. Then we can adjust how we clean. Finishes are not all alike. An eight year old stain that is already thin behaves very differently from one put on last spring.

Knowing what is on the wood helps us plan the cleaning. It also lets us tell you how the wood will look once it dries. If the wood needs a new finish, we will tell you plainly. A wash cannot do that job.

Shake vs board siding, in plain terms

Cedar board siding is a flatter surface. Water runs off it, dirt sits on top, and it rinses clean with ease.

Cedar shake is made of many small pieces that overlap. That makes edges, gaps, and shady pockets. Water stays in those spots, and moss starts to grow there. You see it most on the bottom rows and under the eaves. Shake also has more small pieces that can come loose, so force is the wrong tool. Shake takes more time and more rinsing than board. It also tends to show growth first.

How often to clean cedar on a coastal home

Most cedar homes near the water do well with a cleaning once a year. Not every side of the house ages at the same speed, though. The sunny front of a home on Kiawah or Sullivan's Island can look clean while the shady side is already green. Cleaning on a steady schedule keeps growth from taking hold. That means each cleaning can be gentler. If you would rather not track the timing, a maintenance plan lets us handle the schedule for you.

Cedar siding cleaning FAQ

Can cedar siding be pressure washed?

It should not be. Cedar is soft and soaks up water. A strong jet of water lifts and fuzzes the grain, cuts the surface, and pushes water into the wood. That damage lasts. On shake, it can also loosen or split pieces.

Why has my cedar turned gray?

Sun and weather wear down the surface of the wood and its finish. The bare wood turns silver gray over time. On shady and coastal walls, you may also see mold, mildew, algae, and moss. Those look green or black, not silver. Cleaning removes the growth. The gray tone is part of how cedar ages.

Will cleaning bring my cedar back to its first color?

Cleaning lifts growth, salt film, and dirt, and cedar usually looks much better after. It does not undo years of aging inside the wood. Bringing back the first color takes a new finish, not a cleaning.

My cedar is stained or sealed. Does that change anything?

Yes. Tell us before we start so we can adjust. Finishes differ in type, age, and condition. Knowing what is on the wood helps us plan the cleaning and tell you how it will look once it dries.

How is cedar shake different from cedar board siding?

Shake is many small pieces that overlap. It has more edges, gaps, and shady pockets, so growth takes hold faster and rinsing takes more care. Board siding is flatter. Both get the same low pressure soft wash. Shake just takes more time to do right.

How often should cedar be cleaned on the islands?

Most island homes do well with a cleaning once a year. Shady sides or walls under trees often need it sooner than the sunny sides. Salt air, damp weather, and shade all bring growth back faster.

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