Outdoor wood painting and sealing

Whether it is pressure treated, cedar, cypress, mahogany or even high-end exotic hardwood, proper care will keep and protect the outdoor tree and keep it in good shape for years to come. Painting and sealing outdoor wood is one of the best ways to protect it from the various effects of the weather.

Know your coatings

The most common outdoor wood coating is clear oil. These water-repellent preservatives stop mold, and some products contain ultraviolet light absorbers that protect from the sun. Available in both oil and water based, the resin penetrates the wood pores to provide pigment and block the damaging effects of the weather, while allowing the natural wood grain and texture to shine.

The second category is a film-forming sealant that adheres to the surface of the wood, such as paint or shellac. These products give the wood a shiny look, while allowing the natural grains to appear in their actual appearance. Available in oil or water based finish, they form a durable, beautiful, satin finish. Pigments are added to change the color of the wood and add protection against UV radiation. Film-forming sealants should be avoided in areas subject to regular walking, as wear can also occur through the film coating.

Outdoor wood coatings are usually made with water or oil. Most water-based sealants have tiny particles of pigment and resin that adhere very tightly when the finish dries, much like a mottled blanket. With an oil-based finish, the fine particles chemically blend into one large, sheet-like substance, which results in a safer finish and is less likely to create an amber hue. Check the product label to make sure the quality of the coating is looking for references to “non-yellowing” properties.

Water-based finishes are usually characterized by their ease of use. Compared to oil-based sealants, they are easier to clean, smell less and are often cheaper. However, most water-based coatings require more coatings and are still less durable than oil- or “alkyd” -based coatings, which generally provide longer durability of wood preservation.

New wood

Allow the new pressure-treated wood to dry before painting or compacting. Treatment of sawn timber with aqueous preservatives leaves moisture in the wood.

As a result, fresh lumber from the supplier often reaches the customer in a wet manner, and moisture can impede color absorption. For the best paint and stain coatings, allow the treated wood to dry for 2-4 weeks before application. It is difficult to determine exactly how long treated wood will need to dry, and much depends on how much time has elapsed since the wood was treated, exposed to the sun, the surrounding weather, and so on.

Wood with natural preservatives, such as western red cedar, cypress and mahogany, does not need as much drying time because the wood was never treated with pressure and preservative.

Contrary to popular belief, new wood still needs to be cleaned to remove any development unevenness that has occurred during the grain compaction process and can cause stains to float or be released without absorption. Clean the surface with oxygen bleach.


When wood is exposed to sunlight, ultraviolet rays can damage the wood fibers over time, causing the surface to turn gray. The most direct way to restore the look is to sand or wash the surface with pressure. However, sanding can be very difficult and time consuming and pressure washing can remove gray paint but can cause surface blurring or chipping, creating a risk of ‘touching’ areas such as deck surfaces where people can walk barefoot. When using a washer, limit the pressure to no more than 1000 or 1,200 PSI.

Some individual boards can be severely affected by the weather. Replace them completely, clean the existing boards, then stain them all so that they match.

A tree with old oil

It is usually best to remove the old sealant before re-applying, especially if you change products or colors. The old varnish will usually appear through the sealant, leaving pimple stains at the finish. Before applying the clear oil, the “film-forming” stains must be completely removed. However, if you plan to treat with the same color and the same type of oil (and your deck is in proper condition), you may be able to achieve this by doing a thorough cleaning. As always, follow the manufacturer’s best practice recommendations.

If old stains have formed on the deck, you may need to remove them with something stronger than oxygen bleach. Stain removers are more corrosive, but they remove most weather stains in one go. After the deck has dried, small, uneven stains can be removed with a hand sander.


An often overlooked step in outdoor design is the application of wood bleach. These chemicals open the grain of the wood to improve the penetration of the oil and help restore the wood to its proper condition. The product can be simply sprayed on a wooden surface, giving it a few minutes to act as a “magic” liquid and then rinsing with very little work.

After any chemical treatment, use plenty of water to clean and prepare the wood to completely remove traces of the product, and then allow it to dry before applying the oil or sealant.


Always mix the sealant thoroughly to evenly mix the solids and ensure an even color tone throughout the project.

For both horizontal and vertical structures, brushing is the best method for oil / sealant application, as the bristles press the product evenly into the wood grain to increase absorption. Using a sprayer or roller, the stain can be applied faster, but both methods leave a large part of the stain on the surface without proper penetration of the pores. This surface product can wear unevenly, so you still need to lubricate the wood grain to get the most appropriate look and protection.