The Deck Handbook (Continued):

Wood Decks

Three-Level Western Red Cedar wood deck makes effective use of a sheltered corner of a house in the Lincoln Near South area. Wood is by far the most popular material for decks. Wood decks can be created in an endless variety of tones and patterns, and modern sealing products ensure they will last for many years with regular, routine maintenance.

Homeowners face a wide range of choices when planning a wooden deck. Some wood products are extremely costly – particularly tropical hardwoods. Others, while inexpensive, do not provide the look or low-maintenance that most homeowners prefer.

When planning your deck, it makes sense to use more expensive wood where it will show, and less expensive materials for concealed structural members. For example, It is typical to use relatively inexpensive pressure-treated pine for structural members and more expensive exotic woods for the decking and railings. Some designs go one step farther and use a less costly wood for the decking, and highlight the railings and fascia with more attractive materials.

Domestic Wood for Decks

Wood used in decks must be rot-resistant. If it is not naturally resistant to decay, it must be treated to make it so. The untreated native American woods most commonly used in decks are Western Red Cedar, Redwood and Cypress. Redwood is expensive, increasingly scarce and not considered a "Green" material. More common in California, it is rapidly being supplanted by imported tropical woods such as Ipe. Cypress is in the same category. The large Cypress swamps native to Florida and Georgia have been largely harvested. Cypress now on the market comes from salvaging and cutting logs buried in swamps were they have been immersed in water for many years — difficult and expensive work which is reflected in the price of quality Cypress wood. This leaves Western Red Cedar (WRC) which is still relatively abundant and available from just about any lumber store. It is naturally decay resistant and with proper maintenance will last as long as 25 years. It is now the preferred natural wood in the Midwest for decks.

Treated Pine

By far he most wood most commonly used for decks is pressure-treated pine. Industry analysts report that more than 70% of all decks in the U.S. are treated pine. So if you are planning a pine deck, you are in good company. Even if another wood is used for the visible portions of a deck, you can bet the house that the structure underlying all of that pretty wood is plain old pine.

The new pressure-treated pine results in more attractive decks that are brown rather than green. The trade off is that pine treated with the new, safer processes is more expensive. Pine is not naturally a decay-resistant wood. Exposed to the elements, pine will decay to uselessness in about two years. To make is more resistant, the surface of a pine board is infused with a chemical solution containing copper. The former standard treatment containing copper and arsenic (Chromium Copper Arsenate or CCA) is no longer used. The trade-off however is that pine boards treated with the new technology — Alkaline Copper Quaternary or (ACQ) or Copper Azole (CBA) — contain so much more copper that they corrode steel nails and screws very quickly. Special coated fasteners must be used to build treated pine decks. The reasonable life expectancy of the exposed boards in a treated pine deck is about 10-15 years with regular maintenance. Structural boards (more sheltered from the elements) will last quite a bit longer.

Joists, beams, posts and stair stringers which are important for structural integrity require pressure treated pine in most localities. Deck flooring boards, railings and other non-structural parts of a deck may be made of other woods, composite materials or vinyl. These elements do not have to be as strong. Most composite and vinyl manufacturers stress that their materials are non-structural. This means that the newel post, deck post or beam that you see that looks like composite or vinyl is probably pressure treated pine wrapped in composite or vinyl for appearance. Railing balusters or spindles can be made of manufactured materials because they are considered non-structural.

One nice feature of the new treated "greenboard" is that it is no longer green. The new boards are usually a more attractive "brownish" color.

The Cedars

Red cedar is stable, decay resistant wood very suitable for decks and porches. Both Eastern and Western Red Cedars naturally resist decay and insect damage, weather well, and can be expected to last up to 20 years with proper care. Of the native woods, the cedars are arguably the most beautiful wood for decks. The rich grain and color of the natural wood make the material a prime choice where appearance is important. Janka Hardness

The Janka hardness test measures the dent resistance of wood by determining the force required to push a 0.444 inch diameter steel ball into a block of clear wood to a depth of 1/2 the ball's diameter. In the U.S., the result is stated as pounds/force (lbf) needed, usually in the form "xxxx janka". For example the hardness of southern yellow longleaf pine is 870 janka, meaning it takes 870 pounds of force to sink the steel ball half way into the wood. The higher the number, the harder the wood. The test was adopted by the American Society for Testing and Measurement in 1927 as ASTM D 143.

Hardness usually varies with the direction of the grain. If testing is done on the surface of a plank, with the force exerted perpendicular to the grain, the test is said to be of “side hardness.” This is the standard. End grain tests are unusual, but if done, the fact that it is an end hardness test must be stated in the results. End grain is uaually more dent-resistant than side grain. Moisture content also affects the wood hardness. Wet wood is softer than dry wood. Test are usually conducted with a moisture content of 12%, typical of air-dried wood.

Janka hardness is a good indication of how well a wood species will resist denting and wear over time. For flooing and decking, dent resistance is particularly important.

Janka Hardness of Selected Wood Species
Species	Hardness
Balsa	100
Western Red Cedar	350
Douglas Fir	660
So. Yellow Pine (loblolly & short leaf)	690
So. Yellow Pine (longleaf)	870
Tamarack	886
Eastern Red Cedar	900
Paper Birch	910
True Teak (Tectona grandis)	1000
Black Walnut	1010
Red Oak (Northern)	1290
Ash	1320
White (Burr) Oak	1360
Cypress	1375
Hard (Rock) Maple	1450
Hickory/Pecan (All Varieties)	1820
Jarrah (Australian)	1910
Mesquite	2345
Bamboo (Woven Strand)	2850
Jarrah (Atlantic)	3190
Cumaru	3540
Ipe	3680
Lignumvitae	4500

Dimensionally stable, the wood lays flat and is less prone to warp and twist than treated pine. It stains evenly and holds stain well. Its natural oils are non-toxic to humans and pets, but dicourage insect attack and slow decay due to exposure.

The cedar most commonly used in decks is Western Red Cedar ("WRC") (Thuja Plicata), also known as Giant Arborvitae, Western Arborvitae, Giant Red Cedar, Pacific Red Cedar, Shinglewood, and Canoe Cedar. A member of the Cypress family, WRC is a commercial wood, harvested on the slopes of the Continental Divide in huge quantities and available at almost any home center or lumber yard. In most of the country, this is the only cedar readily available.

In Nebraska, however, we have more choices because of our locally harvested rot-resistant deck woods. The most common is Eastern Red Cedar ("ERC") (Juniperus virginiana), which is, interestingly enough, a juniper, and also a member of the Cypress family. Obviously the Cypress has a large family. It has all of the same insect and decay-resistant properties of WRC and looks and even smells like WRC. Eastern Red Cedar grows throughout the Eastern United States and most of the Midwest. In fact, it enjoys the widest geographic distribution of any American connifer. As a consequence it has so many known common names that we will not even bother to list them here. Nearly every region of the country has its own pet name for the Eastern Red Cedar.

You are probably most familiar with this Nebraska native as Aromatic Cedar used in closet linings - its primary commercial use. A lot of Nebraska's cedar is shipped back East to be turned into closet panels and aromatic chipboard, then shipped back to Nebraska to be sold in Home Depot, Lowes and Menards as closet lining. With grain that is a little more striking than that of WRC, the Eastern variety is also more aromatic — giving off that characteristic cedar smell that repels insect pests of all kinds. A deck made of any Red Cear is a natural bug repellent, but ERC smells better longer thn WRC.

ERC is also a harder, tougher wood. Western Red Cedar is a very soft wood (350 Janka) that works very easily, but also dents and mars easily. Eastern Red Cedar is much harder (900 Janka) and denser, and consequently much more resistant to the accidents of normal use.

Purple-red when first harvested, the Cedars after a very short exposure (one day or less in Summer) to sunlight fade to a pale brown. Over time the wood becomes an attractive silver gray. Fading may be halted at any time by merely sealing the deck with a UV-protecting sealer. This allows you to pick your deck color and preserve it when that color is reached in the natural fading process.

Cypress

Cypress decking and railing. Cypress is probably the most rot-resistant native wood for decks, but it is not being managed well and is fast disappearing. North American Cypress (Taxodium distichum), can be found in wet, swampy areas along the East Coast from Delaware south to Florida and west along the Gulf Coast and up the Mississippi River Valley. It grows best in the swampy areas of Florida and the lower Mississippi river where it can reach heights of up to 145 feet. Common names for cypress include: Bald Cypress, Swamp Cypress, Southern Cypress, Red Cypress, Yellow Cypress, White Cypress, Tidewater Cypress, Gulf Cypress, Black Cypress, and Cow Cypress.

Cypress trees are one of two American decidious conifers, meaning conifers (softwoods) that shed foliage in the fall, a characteristic normally found only in hardwoods. The other is Tamarack (see below). Although a softwood, it has traditionally been grouped with hardwoods. It is, in fact, graded as a hardwood by the National Hardwood Lumber Association.

Cypress is naturally rot and insect resistant - very rot resistant. Logs submerged for decades in swamp water are routinely raised and harvested for sound wood. The wood needs no chemical treatment or sealing to survive up to 100 years in a deck — far longer than the typical treated pine supporting structure will last. It is also very dent and wear resistant at 1375 Janka — harder than oak, and nearly as hard as rock maple.

Much of its rot resistance can be attributed to the fact that Cypresswood is especially water tight. It takes a long time to remove moisture from Cypress, but once dry it resists reabsorption with the same tenacity. The wood also contains cypressene, a natural resin that repels insects and prevents fungus and mildew, but is harmless to humans nnd pets.

Stable and not very prone to twisting or warping, cypress will weather to a nice splinterless gray appearance, holding its nails, screws and shape very nicely for dozens of years.

We discourage the use of Cypress because it is not by any conceivable measure a "green" material. We are quickly running out of it. The large, old trees that contain abundant cypressine are especially rare — and the massive destruction caused by hurricane Katrina did not help the situation at all. Nor does the fact that young trees are routinely cut down and ground up for mulch. Fortunatly even fallen cypress trees submerged for many years can be raised and harvested for sound wood, a process that has extended the supply. But the current rate of harvest is absolutely not sustainable, and native Cypress is fast disappearing. Australian Cypress (Callitris glauca) is being imported to supplement the native supply.

Tamarack

Tamarack is becoming a more important deck wood in places where Western Red Cedar is getting expensive. It is used mostly in the Norteast where it is abundant. Known by various names including American Larch, Eastern Larch, Takmahak and Hackamatack; Tamarack (Larix laricina) is a hard (886 janka), extremely durable North American softwood native to Northern marshland forests - primarily along the Northeast coast and north to the Hudson Bay. There is also a disjunct Alaskan population. Its cousin, the Western Larch (Larix occidentalis), found only in the Northwest U.S. and Southwest Canada is also sometimes called Tamarack, causing a nice bit of confusion once in a while. To add to the fun, one subspecies (Murrayana) of Lodgepole Pine (Pinus contorta) is also commonly called the Tamarack Pine.

The Tamaracks are coniferous, but also deciduous — losing their needle-like leaves every Fall and regrowing them in the Spring. The only other conefer that does this is the Cypress (see above). Eastern Tamarack thrives in wetlands where it helps drain and dry out the soil so that trees like oak and pine that prefer firmer, dryer habitats can get a foothold. Eventually these more aggressive newcomers drive out the Tamarack. The name "tamarack" supposedly comes from an Algonquin word, "akemantak", meaning "wood used for snowshoes." More commonly its historical use has been in water-edge structures such as wharfs and docks, and as ships' timbers.

Eastern Tamarack is very much the Cypress of the north. Its natural resistance to decay, rot, insect damage and salt makes it a excellent wood for long-life exterior decking. Similar in appearance to Western Red Cedar, it does not age quite as well, tending to look a little shabby after a few years. In the Midwest it is virtually unknown. But on the East Coast, it is becoming a significant player as a replacement for Western Red Cedar. Expect its role to grow in the next few years as Cedar becomes scarcer and more expensive.

Other Native Nebraska Wood for Decks

Other native woods that are suitable for decking are Catalpa  and Honey Locust. There are, however, definitely premium woods. Very hard and difficult to harvest, they are quite a bit more expensive than Cedar — but also very beautiful and perfect for the premium Nebraska deck. (For more information on native Nebraska wood species, check out Guide to Nebraska Hardwoods for Cabinetmakers and Woodworkers.)

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Last revised: 12.08.07