The best paint for an older deck depends on the material and whether or not your deck already has a coat of paint. Generally, if your deck already has paint on it, you should choose the same type of paint when repainting the deck. For example, if an old deck has oil-based paint on it, stick with oil; if your deck has water-based paint, choose water-based paint. 

Staining or sealing a cedar deck or fence is highly recommended to extend its lifespan and protect it from the elements. While cedar is naturally resistant to mold and mildew, it is not impervious to damage from moisture, sun exposure, splintering, fading, and rot over time. Applying a protective finish creates a shield that preserves the wood's strength and appearance, potentially extending its life by five to 10 years.

When choosing a finish, it's helpful to understand the difference between a sealer and a stain. A sealer sits on top of the wood, whereas a combination stain and sealer soaks into the top layer. Because it penetrates the wood, a stain generally offers better protection against UV damage and rot and lasts significantly longer. For the best results that also preserve the wood's natural color, consider using a near-translucent stain.

To maintain protection, plan on reapplying the stain or sealer every two to three years, either as a DIY project or by hiring a professional.

Whitewashing isn’t permanent, but it can last for a long, long time. When you apply it correctly or have a seasoned pro whitewash your brick, whitewashing can last for 20 to 30 years or longer. Whitewash is very durable and typically requires little maintenance, making it a great project for most DIYers.

Applying a sealer or topcoat after staining wood is highly recommended, though not always strictly required. A sealer protects the wood from moisture, UV rays, and weather-related issues, which is especially important for outdoor surfaces like decks and fences. It also enhances the stain's durability, prevents fading over time, and gives the wood a cleaner, more professional-looking finish. For some indoor applications, a sealer may not be necessary, depending on the type of stain used and the level of protection needed. It's always best to check the stain manufacturer's recommendations and consider the wood's intended use and exposure when deciding whether to apply a sealer.