Exterior Hardwood Decking and Siding
"How long will the finish last on my decking and siding project?"
Our clients often want to know how long a particular finish will last on their hardwood project. Although we can offer an educated guess, the most accurate estimate will depend on a multitude of factors that vary significantly from site to site and even from board to board.
This page will explore the various finishing options and how they can affect the longevity of your unique decking or siding project.
UV INHIBITING SEALER OR COATING
Whether or not you want your hardwood decking or siding to maintain its original “like new” wood appearance or you prefer that your decking weather out to a silvery gray patina, it is best to apply a UV inhibiting sealer or coating to the surface of the hardwood.
This UV protection helps to minimize surface checking and allows the exterior woods to acclimate more slowly. This first “sunscreen” helps to protect your decking or siding and allows your wood to better adjust to their new home.
If you want to allow your hardwood siding or decking to weather to the gray, simply allow the coating to wear off naturally over time. If you want to maintain more of a “new wood’ type of look for your decking or siding, additional coatings of your chosen finish may be applied over time as the coatings show signs of age, fade or wear off. Depending on the coating you select, always follow the coatings manufacturer’s instructions for best results.
LESSONS WE HAVE LEARNED ABOUT DECKING AND SIDING FINISHES
Here’s what we’ve learned firsthand over the past few decades about finishing exterior hardwood decking and siding:
High density hardwoods like Ipe, Cumaru, Garapa, Machiche and others have tight, nearly non-porous, cellular structures that allow these woods to be very durable and last for decades. This same property makes it very difficult for coatings, sealers or stains to penetrate into the surface of the decking or siding wood.
Most traditional exterior sealers and stains do not work well (or for very long) with high density hardwoods.
We have tested scores of different coatings over the past twenty or so years and are still looking for the “magic coating” that will look beautiful and also last a long time. Although we have not found the magic coating yet, we will continue our search as new products and technologies become available.
What we have found is several coatings that work fairly well, and each of them have some benefits and limitations.
WHAT WILL AFFECT THE FINISH OF DECKING AND SIDING
Key Factors Affecting the Longevity of a Finish On Exterior Hardwoods
What type of coating? (different coatings perform differently on different woods)
What type of hardwood? (Each hardwood species has different characteristics and will perform differently with various coatings)
What type of installation? Horizontal, like a deck or railing? Or vertical like fencing, siding or posts? (Horizontal surfaces take a significant beating from the elements including UV rays, rain, snow and traffic)
What type of environment? Marine? Desert? Forest? Arctic? Inland? (The weather and natural climate variances of different regions effect the durability and performance of different sealers)
If a residential deck: How much traffic and what kind of traffic activity will the deck receive? Kids? Adults? Pets? Furniture moving (chairs in and out, etc.) Dancing? Partying?
If a public walkway, boardwalk or dock: How much traffic and what kind of traffic will the deck receive? Skateboards? Bicycles? Vehicle traffic? For this type of application it is a good idea to apply at least an initial coat of UV inhibitor and then, if desired, allow the deck or deck to weather to a low maintenance silvery gray patina.
Is the site shaded or partially shaded? (typically, the more UV ray exposure, the harsher the beating of the sealer)
Are there other buildings or barriers that shield the sunlight at different times of the day?
How much sunlight does a deck or siding receive and at what time of day and year?
In general the more sunlight that decking or siding is exposed to, the faster the coating will fade. Here we are not just talking about the difference between Maine and Arizona, or winter UV rays versus summer UV rays, but also the orientation of the exposure.
The harshest solar orientation for a deck is a southerly exposure because the sun is directly overhead and the UV rays are mercilessly beating directly down on its exposed surface all day long. The western orientation is typically the second harshest exposure for a deck.
With vertical applications like exterior siding, we have found the western exposure to be the harshest on the siding or coating because the sun is perpendicular to it and shows little forgiveness. The southern exposure is usually the second harshest exposure in the summer, because the sun is nearly overhead and only offers a glancing blow to the siding. Winter sunlight on that same southern wall could very well be harsher on the siding and the coating because of the angle of the UV rays and the duration of the exposure.
TEST RESULTS AND FINDINGS OF HARDWOOD FINISHES
While we are continuously testing a variety of finish manufacturers’ products, we are always on the lookout for newer and better solutions. Here are the best coatings we have found so far - along with their strengths, weaknesses and a few pointers.
Penofin® Penetrating Oil Finish for Hardwood instantly delivers a beautiful and shiny appearance when it is first applied on exterior hardwood decks or siding. The Brazilian rosewood oil which Penofin uses in their formulation is uniquely effective because of its remarkably small particle size. Unlike other finishes, Penofin successfully penetrates the surface of the high density hardwoods and provides some protection for the wood decking or siding. Penofin oil finish will enrich the look of the hardwoods and darken their appearance somewhat which helps blend the various graining and color variations that are inherent in high density tropical hardwoods. We have found that Penofin also provides some UV protection and helps the woods to acclimate more slowly and gently.
The downside of the Penofin oil finish is twofold: the initial coat will fade out or flash off over a short period time and, when used on decks, dirt may stick somewhat to the oily finish initially.
Apply the Penofin as directed by the manufacturer - do not over-apply this finish or it will likely get gummy. We have seen and heard from many clients that in most decking applications, Penofin typically lasts between one to two years. Some clients re-coat their deck every year, some wait longer (1-1/2 to 2 years) and others will simply allow their deck to age naturally after a period of time. The choice of appearance is truly your decision.
When you decide that it’s time for the decking or siding to be re-coated with Penofin, always clean it first and follow the instructions for a new coat. When re-coating, bear in mind that the UV rays and exposure to the elements is likely to have changed the color of the wood from its original color over time. Test a small area first to see if that’s what you like best.
Seal-Once™ Eco-Friendly Exotic Wood Sealer is another product that we have tested with some encouraging results (semi-transparent tinted products). Compared to numerous other sealers, we have found that Seal-Once’s tinted products have stayed truer to their original colors for the longest periods of time in extremely harsh test conditions. Seal-Once has a matte finish and a range of commonly used tint colors are available.
We have many architectural clients whose clients want a low maintenance finish that will immediately make their new wood look like it has gracefully aged for years. For this type of application we have had very good success with their Cape Cod Gray semi-transparent tinted product. The beauty of applying a gray tinted finish is that all the boards start out with a fairly uniformly grayed appearance. While there is certainly a lot of color and grain variation from board to board, this “pre-graying” process allows designers and property owners to ‘get where they are going faster’. It has been our experience that as these tints slowly fade from UV exposure the underlying boards slowly turn their natural gray color for a relatively seamless transition to a natural patina. (An intermediate re-coat may be required along the way, depending on the orientation, amount of UV exposure and other factors.)
We have also tested Seal-Once with Bronze Cedar semi-transparent tint on Ipe, Garapa, Cumaru and Machiche hardwood siding and found it to provide the best protection and hold its color longer than any other products we have tested. When this product wears out or fades out it is a very simple matter of applying an additional coat according to the manufacturer’s instructions. We have found that a maintenance coat, after the siding has acclimated and been exposed to the sun and weather, is more absorbent and lasts longer than the initial 'sacrificial' coats.
Ongoing Testing to Find the Best Hardwood Coatings
In an effort to provide our customers with the most effectual, attractive and long-lasting finish solutions for their decking and siding projects, we continuously test a host of different exterior coatings and sealers. We also work closely with several coatings manufacturers to test their products at our facilities. We will update our customers with our findings regularly.