High-altitude settings require special consideration when it comes to selecting building materials. For a wooden deck, for example, the boards in a high-altitude environment are more quickly broken down by the intensity of UV rays. With the right maintenance regime, it is possible to delay those effects, but it will need to be done carefully and consistently. I have several loyal clients who – after they’ve hired me to build a deck – will continue to hire me year after year to take care of these decks in their mountain vacation homes.

Luckily, over the years I have found that there are some materials better able to handle the challenging weather of high-altitudes – with less maintenance than wood. Having spent a few seasons working for clients up in the mountains and the high desert, I can appreciate the value of reduced maintenance, and I like to think that I’ve also discovered the best decking for a high- altitude. Here’s what I’ve learned through trial, error, and research.

The Effects of a High Altitude on Your Deck

For many of us, the first thing we think about when we hear the words “high-altitude” is the cold, followed closely by snow. But in many ways, the sun is an even more powerful adversary. It’s no great secret that UV rays literally dry out and cook materials over a long enough time span (think of your skin burning in the sun). Here’s why a high altitude can be hard on your decking:

• UV Rays Are More Intense: This is the case because for every 1,000 meters in elevation, exposure to UV rays increases by 10%. If the local area is both mountainous and sunny, this effect is magnified. The effect is also stronger the closer one is to the equator.
• Materials Break Down More Quickly: This increased exposure to UV rays increases the rate at which materials subjected to this radiation are broken down. UV rays will weather materials by weakening and breaking down chemical bonds. One of the materials UV breaks down in wood are its lignins, which are important to maintaining wood’s structure.
• Colors Fade More Quickly: One of the most noticeable effects of the way the sun breaks down chemical bonds is the fading and loss of a material’s color. This means that with extended time in the sun--particularly at high altitudes--wood grays, paint fades, and sealants give out.

The Best Decking for a High Altitude

In my building work, I generally use two main materials for decks: wood and fully capped composite. The strategies of protection for the two of them vary greatly. Protecting a wooden deck is a matter of selecting the best possible stain, paint, or sealer for the situation. Protecting composite decking is an exercise in picking out a brand with the most innately protective elements. Below I’ll walk through my recommendations on maintenance at high altitudes, as well as what I consider to be the best choice for decking.

How to Protect Wood from UV Rays

For many years, the most common decking material in my practice was certainly wood: cedar, redwood, pressure-treated, ipe, or otherwise. These are a couple of the usual methods for keeping a wooden deck healthy, no matter which of these woods you select.

• Opaque Finishes: Finishes that are opaque, such as solid stains and paints, are the most successful at blocking UV rays from reaching the wood. The more tint in a stain or paint, the greater the protection it provides. These opaque finishes vary in how often they’ll need to be reapplied. Their longevity usually depends on whether they are oil-based or water-based stains. Of course, the relative merits of oil-based and water-based stains is a long discussion unto itself, but in general an oil-based product will last longer and work better than a water-based one.
• Transparent Finishes: Some homeowners and builders choose a wood with the idea of showcasing its natural finish. When this is the desire, transparent or mostly transparent stains are used. Since these don’t have any pigment, they allow UV rays to penetrate into the decking board. If sun damage is a concern, this isn’t a particularly good option. However, when clients are adamant about this, I make a compromise by finding an oil-based stain with a small degree of pigment in it. Still, I don’t recommend this path for high altitudes, as the sun will deteriorate the wood more quickly than it should and the wood will require more frequent recoating. 

Protecting Composite Decking from UV Rays

While protecting a wooden deck involves selecting the best possible protective coatings for the job, protecting a composite deck is a matter of picking the best possible version of composite decking, since it doesn’t require paints, stains, or finishes. So, what should you look for in composites for your high-altitude deck? There are a few features you’ll want to seek out.

• Fully Capped Boards: One of the great advancements of composite decking was the addition of a protective capping material which keeps the core board safe from the ravages of sun and moisture, which helps prevent chipping, swelling, and warping. Initially, most decks only had the capping on the top deck surface. However, this did not prove to be enough to protect a deck from the elements. And while the surface is the most important part of the deck to protect in a high altitude situation, you’ll likely be getting lots of fog and snow as well, which can cause issues with moisture on the underside of the board. For this reason, more recent generations of fully capped composite decking is the only way to go – since it will make your decking water resistant as well as UV resistant, from any angle.
• UV Inhibitors: Pigments similar to those found in some of the best stains and paints are simply “baked into the cake” of a good capping material. With the best products, this is done in a way that has significantly reduced color fade.
• A Warranty: On any deck project, you’re likely to be making a significant investment. Therefore, it makes sense to choose one with a good warranty. This is especially important when you live in a location that can be hard on building materials. Some decking manufacturers have 25-year limited warranties that can give you peace of mind about your investment.

I never used to build composite decks, and until recently I certainly wouldn’t have considered them for a high-altitude location. But advancements in the design of high-quality composite means that it’s now an excellent substitute for wood that takes much less work to keep beautiful. A decking board with a resin cap, manufactured with plenty of UV inhibitors, can last for years while looking just as good as it did when it was first installed. While I still use both wood and fully capped composite decking to build decks at high elevation, I tend to prioritize recommending the latter. This is especially true for people with vacation homes – since these boards require so much less maintenance and care. If they choose composite, one of my first recommendations is Fortress Building Products, as their boards use one of the most advanced capping materials on the market, designed to resist even the sun at high altitudes. Fortress decking doesn’t mold, mildew, or absorb moisture, either. After we get the deck installed, and other projects arise, I sometimes recommend taking a look at Fortress®' other products, like railings and fences. All of these building products are high quality and extremely durable, making them great choices for high altitudes.