Exterior stains, both oil- and water-based, provide protection to outside wood like house siding, decks and fences. They each have benefits and drawbacks, however. A homeowner should give some thought about which kind would work best for the particular application circumstances and conditions before deciding whether to paint with an oil- or water-based stain.
If the surface has been painted or stained in the past with an oil-based stain, a water-based stain will adhere better. For woods such as cedar, cypress or redwood that naturally resist deterioration, a water-based stain is recommended.
Oil-based or alkyd stains offer better penetration ability than water-based and are very durable. They are generally recommended for high-traffic areas that receive a lot of use. They are also recommended for areas that are regularly exposed to extreme conditions.
Water-based stain, also referred to as acrylic or latex, retains colour better. This is a factor when a colour that isn't a natural wood tone is desired--for example, blue or green.
Specially formulated oil-based deck stains provide extra protection designed specifically for decks. Oil-based stains generally do not resist mildew. Some oil-based stains are mildew-resistant; these will say so on the label.
Water-based stains resist mildew.
Oil-based stains take longer to dry, which makes it easier to get more even coverage. An oil-based gel stain does not penetrate deep into the wood and allows for better control during application. Gel stains will not raise the wood grain and also do not drip as much during application as regular oil-based stain. They require two or more coats for good colour depth and consistency.
Water-based stain is nonflammable and does not give off the unpleasant odour and fumes commonly found with oil-based stains. It dries faster than oil-based stain and cleanup is done with soap and water. Water-based stain is better for the environment in general.
Oil-based stains contain volatile organic compounds (VOCs). VOCs are harmful and considered an air pollutant. All oil-based stain, rags and brushes must be disposed of properly.