Exterior wood finish is a must if you want to protect a wood surface from weathering. Unfortunately, these finishes come in such a variety that it can be hard to determine the best option for a given project. From different types of stains to the protection they offer, here is a quick guide on how to choose the right exterior wood finish for your next woodworking project.
Exterior Wood Finish Factors
There are several factors to consider when choosing the best exterior wood finish for your project. For starters, you need to consider what kind of protection the surface requires. If the wood is exposed to sunlight, for instance, then you’ll need a finish that has good UV protection. You also need to think about the appearance of the stain and whether you want it to highlight the natural beauty of the wood. Other considerations include how long the finish lasts before it needs maintenance, ease of application, and overall cost. With that in mind, exterior wood finishes generally fall into two classes: penetrating stains and film finishes.
Penetrating stains work by soaking deep into the surface of the wood. Their biggest strength resides in the ability to repel water. These finishes do not peel, are easy to apply, and offer the most natural appearance. The biggest downside to penetrating finishes is they offer almost no protection against UV rays. They also do not do well against general wear and dirt, which means a faster turnaround for maintenance.
If you are staining a deck, selecting a water repellent finish is a must. These types of finishes repel water, help bring out the natural beauty of the wood, and are easy to apply. Most water repellent stains feature a solvent, drying oil (or varnish resin), and paraffin wax. Some varieties add a preservative that helps prevent the buildup of mildew and fungus. You can also add a top coat of paint to certain kinds of water repellent finishes, though this varies by brand.
Pigments are the biggest difference between water repellent preservatives and semi-transparent stains. These pigments are usually ground up rocks and clay and help protect the surface of the wood from harmful sun rays. They also come in a variety of colors, which makes them ideal for several different projects. The only downside to semi-transparent stains is cost, especially if you pick out a high-quality finish.
Oil stains also fall into the category of penetrating finishes. The most popular types of oil finishes are tung oil and teak oil. Not only do these stains enhance the natural beauty of the wood, but they are also easy to apply. The downside is that oil stains require more prep work to apply and should be refreshed at least once a year.
Unlike penetrating stains, film finishes work by forming a thin layer of protection on top of the surface of the wood. Film finishes include polyurethane, color stains, varnish, and paint. Although film finishes are a lot more labor intensive to apply, they do have a lot of strengths, including:
- Protection against UV rays, wear, and dirt
- Wide selection of colors and sheen
- Long lasting protection against the elements
- Added depth and beauty to the wood
Exterior Varnish And Polyurethane
Exterior varnish and polyurethane finishes offer a good balance of protection against the elements and preserving the natural look of the wood. The biggest weakness of these stains, however, is that they require a lot of work to apply. If these finishes are not applied properly they can peel or crack over time. Once that happens, you have to strip away all of the finish and reapply, which is a fairly laborious process.
Color stains are similar to semi-transparent finishes when it comes to protection. The biggest difference is that color stains have higher pigment levels, making them ideal for outdoor furniture, siding, and deck rails. They also allow more of the natural wood to shine through than solid paint and have longer lifespans than their oil-based counterparts.