Natural wood is the most widely used material for building outdoor structures because it’s traditionally affordable, widely available and exceptionally versatile. Pro builders know that not all wood is equal, however, and homeowners planning an outdoor project should learn what to expect from the various grades and species.
Treated Lumber
When lumber prices are up, treated wood still remains one of the most economically priced materials for exterior projects. If you want to use real wood for an outdoor project and expect it to withstand termites and fungal decay, your principal choices are either a naturally durable wood (such as cedar or cypress) or wood pressure-treated with preservative. Even when composite or synthetic materials are specified for decking or handrails, they’re usually supported by a strong framework of treated lumber made of spruce, pine or fir. More than 80 percent of all U.S. decks are built entirely or partially with preserved wood.
The lumber grade of treated wood, typically made of SPF (spruce, pine or fir), is important to consider for your next project. Grades are assigned at the sawmill where the logs are cut, and the lumber is primarily graded on the strength of the board. For the most part, lumber is available in three tiers of quality: Good, Better, and Best.
Even when composite or synthetic materials are specified for decking or handrails, they’re usually supported by a strong framework of pressure-treated lumber made of spruce, pine or fir.
Good–Number 1 and Number 2 grades are commonly sold at local lumberyards. They offer good strength ratings but come with imperfections such as large knots, rounded bark edges, and some bowing or twisting. No. 1 will have fewer imperfections than No. 2. These grades are ideal for a cost-conscious DIY homeowner.
Better–A bit more expensive, the Prime grade of Number 1 and Number 2 lumber features the same strength properties, but are listed as Prime based on appearance (regarding the amount of bark on the edges or the number of knots). This lumber is a bit more expensive, but you get what you pay for.
Best–To guarantee the most beauty for your back yard, ask you lumber supplier for C & Better or Select Structural grade products, which offer the strongest lumber properties and better appearance. The boards should have no bark on the edges and only a few small knots.
KDAT—The best treated lumber grades are also available in kiln-dried options, which eliminate the waiting period typically required before painting or staining for “wet” lumber. KDAT (kiln-dried after treatment) lumber is a high-grade product that offers a number of benefits. Treatment companies such as Great Southern Wood Preserving (the makers of Yellawood) even back their KDAT lumber with a lifetime warranty. The kiln-drying process reduces the lumber’s natural tendency to shrink, cup and warp, and it weighs less than freshly treated lumber. KDAT products are easier to handle, cut and install, have greater strength, more stiffness and increased holding power. Plus, the lumber is ready to be painted, stained or sealed immediately.
Pre-colored lumber? That’s right. Now, you can skip the wood stain by building with treated lumber that has pigment driven deep into the wood grain during the preservation process. Photo © Prowood Lumber.
Pre-colored treated wood, however, is a growing trend because it offers tinting options without the need of paint or staining. For example, Prowood Lumber offers Dura Color lumber made with a color-infused preservative that allows the wood's natural grain characteristics to remain visible. Rather than relying on a topical finish or stain that may quickly fade, the Dura Color pigment is driven deep into the wood fibers so it's guaranteed to stand up to the elements for years.
Western Red Cedar
Native to the northwestern United States and southwestern Canada, Western Red Cedar offers substantial advantages for building, finishing and long-term performance, and the main reason this species of wood isn’t more widely used is due to its availability and higher price.
Cedar has a very low shrinkage factor and resists warping, twisting and checking, which makes it a good choice for narrow boards widths in outdoor applications such as latticework or pergola purlins. Photo courtesy of Western Red Cedar Lumber Association.
The natural qualities of Western Red Cedar make it an excellent choice for outdoor projects like decks, pergolas and outdoor furniture. Cedar is one of the lightest commercial softwoods, so it’s easy to transport and handle. Cedar has an even, consistent grain, low density, and a low shrinkage factor superior to other coniferous woods which makes it less likely to swell, warp, cup and twist than other soft and hardwood species. As a result, it lies flat and straight—a huge help when assembling your project.
Western Red Cedar is also pitch and resin-free so it’s ideal for accepting and holding a wide range of finishes including dark stains, bleaches, solid colors and semi-transparent finishes.
Furthermore, Western Red Cedar fibers contain natural compounds called “thujaplicins” that act as preservatives to protect against rot and insect infestation. As a result, the wood will last without the need for chemical treatments. Learn more about cedar at www.realcedar.com.
Cypress
Cypress contains a naturally occurring preservative oil, similar to cedar. Cypress trees generate cypressene, which makes cypress heartwood resistant to insects, decay, chemical corrosion and other damaging elements. For this reason, the wood has long been a favorite choice for long-wearing outdoor applications such as siding, decking, fence posts, docks and even railroad ties.
These cabinets are built of cypress to withstand the rigors of the outdoor environment. Photo courtesy of What Wood
Cypress works well with both hand and power tools. The wood planes easily and resists warping. Although cypress is resinous, it glues well, sands easily, and can be painted or stained, offering a variety of finishing options. Its original honey-like hues can be maintained by applying a clear sealer. Left untouched, it will weather naturally to a gray.
Most cypress trees are natives of the South and grow in the Atlantic and Gulf Coastal Plains from Delaware to Texas, as well as in the Mississippi Valley from the Louisiana Delta to southern Indiana. Learn more about cypress at www.cypressinfo.org
It should be no surprise that wood which grows in wet environments can naturally withstand wet environments, as seen with this outdoor shower made from cypress. Courtesy of Bart Michaels Photography
Exotic Hardwoods
For the high-end tastes of demanding homeowners, exotic hardwoods have taken hold in the outdoor building market. Be prepared to pay a premium price for the material, but rainforest hardwoods such as Ipe and Pau-Lope offer an unmatched level of beauty and unique character as well as hardness and durability that far exceeds conventional lumber.
Known for its tight, uniform grain and warm red tones, Ipe is an exotic hardwood that sells for a premium because its beauty is coupled with low-maintenance performance that can last nearly a hundred years.
These exotic hardwoods offer significant advantages to justify the high price. Ipe, for example, grows in the Brazilian rainforest, so the trees contain natural oils and very dense tree fibers that protect it from insect infestation and the growth of mold and fungi (which lead to rot). Ipe also exhibits remarkable heat dispersion, which makes it popular for decks because the surface won’t burn bare feet. The wood will be cool to the touch all summer long, and it’s also naturally fire resistant—a superb material in wildfire-sensitive areas.
Ipe is known for a smooth, uniform texture and a very fine grain with a slight wave, noted for its warm, red tones. It’s the natural aesthetics combined with superior performance that make exotic hardwoods such premium materials. A very dense exotic species like Ipe requires very little maintenance, and with proper care the wood can last close to 100 years.
SIDE NOTE
Kits Can Save Time & Labor
Interested in improving your backyard but short on free time for home improvements? Or, are you a DIY’er who has yet to acquire all the woodworking tools needed to build a pergola, garden bench or picnic table? You might consider purchasing a pre-fab kit.
With a pre-fab kit, all the cutting (including any tricky notching) will be done for you, and all the materials and hardware from the smallest screw to the largest board will be shipped to your house. Because all the prep work is done, assembling a pergola, arbor or outdoor furniture is usually a quick job, often completed in a weekend or less.
A prefab kit eliminates errors because it’s been designed by engineers who create detailed blueprints and instructions to provide exactly the results you expect.
Sometimes prefab kits can be more expensive than building your own design. However, for detailed projects such as a pergola, by the time you source the materials, carefully compare material costs, and drive to pick them up (or pay for delivery), you’ll likely have spent more time and money than you expected.
A pre-fab kit is still someone else’s design, of course, so you’ll be limited in choices that might not precisely fit your particular parameters or suit your tastes. With a custom build, you’ll have the liberty to decide which type of wood, hardware and architectural details to use.
Your best move is to research your options and compare costs to see what designs are available as kits and which approach to assembling the project best fits your lifestyle and available work time.