Oxygen bleach uses hydrogen peroxide as a base and won’t harm wood when using it as a cleaner. On the other hand, chlorine bleach breaks down wood at the cellular level and causes irreversible harm. Although you may not see immediate damage to wood after exposing it to chlorine bleach, its strength and integrity are now compromised.

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. 

Yes, pressure-treated wood can occasionally turn green due to certain preservatives, such as copper-based chemicals, used during the treatment process. These chemicals react with the wood, creating a greenish tint. The good news? It's temporary, and the color will fade over time. Staining or painting can also help hide any unwanted hues.

The number of coats you need to apply when whitewashing a surface depends on how opaque you want the final product to be. If you're going for a transparent, barely there look, a single coat or two may suffice. For fuller coverage, you'll want to use multiple coats. Another option is to use a less diluted paint to get a thicker coverage.