How to Prepare Cedar Siding for Stain

How to Prepare Cedar Siding for Stain

A good stain job starts with bleaching and power washing the siding

By Stevie Donald

Woman Using Power Washer
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Cedar siding needs to be free of mildew, dirt and discoloration before staining. It also needs to be completely dry, especially if you're using an oil-based stain. Scrubbing and power washing cedar siding is best done on a warm, sunny day because you will get wet. You may also need to do minor siding repair and caulk windows and doors prior to staining. New cedar siding needs little preparation unless it is smooth. If you don't want to tackle this work yourself, use this guide as a handy way to make sure your staining contractor does a thorough job.

  • What You Need to Know
  • While staining cedar isn't difficult, you'll need some special supplies, including bleach, siding cleaner, a power washer or a sand blaster and protective clothing and eyewear.

Step 1:

Assess the siding and take notes of any loose or protruding nails and cracked or rotted boards. Make any necessary carpentry repairs prior to cleaning the siding.

Step 2:

Check for mildew. It can be difficult to differentiate mildew from grime on dark cedar, but if you live in a rainy or humid climate, it's probably mildew. To be sure, fill a spray bottle with a mixture of half bleach and half water, and spray it on the dark spots. Mildew will almost immediately turn from black to light brown, but dirt won't change color much, if at all.

Step 3:

Remove mildew by scrubbing it with either a mixture of bleach and water, or a commercial siding cleaner that contains mildewcide. Wear protective clothing and don't let bleach remain on your skin because it can cause chemical burns. Rinse the siding and any plants below the area thoroughly.

Step 4:

Power wash the siding, using a mild detergent designed for use with power washers. To lighten and even out the color of naturally weathered siding, apply a detergent containing wood lighteners and stain removers with the power washer. There are several different formulas: Follow label directions.

Step 5:

Allow the siding to dry for at least 48 hours before staining, as applying stain to a damp surface can cause shiny spots or a blotchy color.

Step 6:

Caulk around windows, doors and vents with clear, paintable silicone caulking. This can be done before or after staining, although the caulking will be a little less visible if done before the stain is applied.

Step 7:

Sand new, smooth, closed-grained cedar siding lightly, using a power sander and 50- or 60-grit sandpaper to open the grain before staining. New rough or re-sawn cedar siding needs no preparation as long as it's clean and dry.

Step 8:

Follow the manufacturer's or the store's instructions for pressure-treated cedar. Even if the cedar has to weather for 6 to 12 months prior to staining, it should be treated immediately after installation with a clear wood preservative to prevent graying and overdrying of the wood fibers.

  • Tips & Warnings
  • Semitransparent oil stains tend to hold up the best. Solid acrylic or oil-based stains will hide the grain of the wood, but will also cover up heavily weathered cedar siding that cannot be cleaned and brightened.
  • Never mix bleach with ammonia, or any cleaning product containing ammonia. This creates dangerous chlorine gas.
  • The cedar must be completely dry before applying the stain.

About the Author

Stevie Donald is a regular contributor to DexKnows. She has been a painting contractor since 1979.

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