Selecting the Right Wood for Your Outdoor Pergola

Pergolas are a wonderful accent structure to add to a garden, patio or uncovered deck. They are extremely versatile and the perfect way to set apart a seating or entertainment area from the rest of the yard. Additionally, pergolas tend to be fairly simple to construct, as the average design is rectangular, roofless and consists mostly of beams and pillars.

Wood is primarily used for pergola construction since it tends to be readily available, easy to work with and durable when exposed to outdoor conditions. But before you rush to the lumber yard to grab your materials, you should consider which type of wood is best for your project and your needs.

You can build a pergola with essentially any wood you'd like, but these four primary types are the best options for a professional-quality structure.

Pressure-Treated Wood

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When budget is a big factor in material selection, pressure-treated (PT) wood is often the go-to choice. It’s easy to work with, very versatile in what you can do with it and it’s available at virtually every home improvement store or lumber yard. Through the treatment process it undergoes, the wood becomes more resistant to rot, decay, and insects, making it a durable choice for exterior applications like a pergola. However, the chemicals used in PT can be very toxic which is less than ideal for something people or pets may come into contact with.

While pressure-treated wood is indeed cost effective, most homeowners may not find the look of it to be attractive. PT wood often has a green tint or blue streaking, which is why it’s not typically considered a great option for appearance projects. When building a pergola with this type of wood, most choose stain it to the color of their choosing for the best looking outcome. While having the ability to choose the color of stain is nice, it also means a more expensive project with additional maintenance costs down the road when it comes time to re-stain and seal the wood.

At the root of it, pressure treated wood is an entirely viable option for pergolas, however it may not be as economical as it may appear when taking maintenance costs into account. Plus the chemicals that are pressurized into the wood could be harmful to families and pets.

Western Red Cedar and Redwood

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Western Red Cedar and Redwood are the two most commonly used woods for pergolas, aside from pressure-treated wood.

Western Red Cedar (WRC) and Redwood are both naturally stunning woods and often lumped together. However, there are a few key differences between the two. First off, despite having "red" in both names, Redwood has the darker red-brown hue while WRC is more on the yellow side. Secondly, Redwood can be found with a larger grade variety and its grain tends to be more on the subtle side compared to the more rustic and pronounced grain of clear WRC.

Both species are naturally rot- and insect-resistant, so you don’t have to worry about harmful chemicals. Plus they’re both rather durable woods, Redwood being only slightly stronger than WRC. However, depending on where you are located, you may find these to be rather expensive options with limited availability, which can be very frustrating.

If you’re wanting a more rustic and natural looking pergola, Western Red Cedar and Redwood are both good options. Just be sure to check local pricing and availability before you commit to this type of wood for your pergola.

Tropical Hardwood

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For diehard wood lovers, tropical hardwood is a hard choice to beat for a real wood pergola. Tropical hardwoods are widely known for being ideal for exterior projects (i.e. decking, cladding, etc.), making them a wonderful option for pergolas. The most common tropical hardwood species include teak, ipe, mahogany and rosewood.

In addition to their beauty, tropical hardwoods are sought after for their density and resilience to the elements. Janka ratings relate directly to the density or hardness of a wood. The harder the wood, the stronger and more resilient it will be.

To put tropical hardwoods into perspective, consider that pressure-treated Southern Yellow Pine has a Janka rating of 690 and Redwood comes in at 450. Ipe (also labeled as Brazilian Walnut) has a Janka rating of over 3,500. All tropical hardwoods have a 1,500 or higher Janka, while many are into the 2,000 numbers and higher.

Why aren't all pergolas made out of tropical hardwoods, then? Well, the three main issues are availability, cost and eco-friendliness or lack thereof. Tropical hardwoods can be difficult to source and even after you find a source you might be shocked to find just how expensive some species can be. A pergola made of a tropical hardwood will be 3x or more expensive than a high-grade Redwood pergola and the price difference is even more drastic compared to a PT pergola. Even in circumstances where price isn’t an issue, tropical hardwoods are looked upon unfavorably for their disservice to the environment. Many tropical hardwoods are not harvested using responsible foresting practices, which has lead to the devastating destruction of some of the earth’s most precious forests. These trees take a hundred years, at least, to grow and mature so without responsible management and regrowth plans, the growth of tropical hardwood as a building product could eventually mean the loss of these forests entirely.

So while tropical hardwoods offer incredible durability, the cost, availability and detriment to the environment tend to downgrade their popularity when it comes to pergolas and other outdoor construction projects.

Modified Wood

(The Apollo by Landscape Architect Bureau [LAB] LLC, photo by Sean O'Rourke Photography)

Modified wood might just be the perfect option for an exceptionally strong pergola that offers the real wood character without bringing harm the environment.

Modified wood takes sustainable, fast growing species and enhances the wood cell structure with a non-toxic bio based liquid. After this process is complete the wood cell walls are much thicker, making the wood perform like the most durable tropical hardwoods. Additionally, modified wood has a beautiful finish that highlights the natural grain and will eventually weather to a silver-gray patina (same as the species mentioned above).

A huge advantage of modified wood is how durable it is for a wood product. In fact, it's on par with composite and other non-wood materials. Kebony Clear (Radiata Pine) modified wood has a Janka rating of 1,618, making it a very dense lumber that performs as you'd expect a tropical hardwood to.

Best of all, Kebony modified wood requires no surface treatments and only the most basic of cleaning for care. This material is highly water-resistant, so much so that it's often used for docks and piers. This makes it perfect for a no-fuss, long lasting pergola in wet, coastal, and high-humidity regions.

Plus, Kebony modified wood offers an incredible 30 year warranty on their products, which is a stand out feature compared to the rest that you’d be hard pressed to find a warranty for at all.

The wood you choose for your pergola will determine how long your structure will last, how much maintenance it will require, and ultimately, how much enjoyment you'll get from it. Balance durability with what visually appeals to you and for the best result, choose modified wood for your pergola.

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