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Building Principles: The Times, They are a Changing . . .
For more than half a century, outdoor construction’s primary defense against rot and insect damage has been that greenish blue lumber — also known as pressure treated, salt treated, or, under the trade name, “Wolmanized.” Throughout the country, tens of thousands of projects have been built with this type of lumber. Decks, swing sets, and even whole buildings continue to serve properties where long lasting, sturdy construction was a must.
The secret to the longevity of the product is the process by which a chemical solution is forced under pressure into the fibers of the rough-cut lumber. The wood is then kiln dried and later milled to final dimensions. The final product is water and rot resistant, as well as toxic to wood destroying insects. The infused chemical is known as chromated copper arsenic, or CCA. As the copper oxidizes, the wood takes on a blue-green hue, making it easy to identify.
In the past decade, there has been increasing debate over the material’s toxicity to people. Industry trade groups and repeated, long-term government tests indicate that the product is safe when properly used. The treatment process physically and chemically binds the CCA to the inside of the wood fibers. Only when the fibers themselves are damaged or destroyed do the chemical salts separate from the wood.
Special precautions need to be taken when cutting pressure treated lumber. In particular, the saw dust needs to be contained, controlled, collected, and disposed of properly. Pressure treated lumber should not be sanded. Precautions should be taken to prevent inhalation of the dust — including workers wearing dust masks during cutting, saws set up behind wind breaks or tarps, and power tools installed with dust bags that are emptied into garbage cans frequently. Scrap lumber and collected sawdust should never be burned. Since burning destroys the wood fibers, leaving concentrated copper and arsenic behind, the scrap lumber and sawdust should be delivered to the municipal landfill in the regular garbage cycle. All of these safety measures have been well documented in literature widely available from lumber yards, home centers, and the Internet.
However, like so many other products on the market that have a potentially dangerous aspect, some people ignored the warnings and became seriously ill from arsenic poisoning. Consumer groups then commissioned their own tests and asserted that the product was a wholesale hazard to the public.
Where does the truth lie? Given the statistically low incidence of sickness, the long standing use of the material and the huge volume of test data from multiple sources, we are inclined to come down on the side of the industry groups which contend that the product is safe when properly handled.
However, citing the growing number of recent class action lawsuits filed against manufacturers of products ranging from tobacco to guns and hot coffee, the pressure-treated lumber industry announced last year that it would no longer endorse production of CCA products for uses other than utility poles and roadway projects (like bridges and guide rails).
Effective January 1, 2004, there will be no more pressure treated lumber available at the home stores or lumber yards. This begs the question, “OK, now what do we do?” We’ll look at the alternatives — by product and then by application. First, however, it’s very important to note that each of these products may have properties that are different from materials you’re used to using. Read and follow the supplier’s recommendations to the letter. If you’re thinking about using the product in a way that is not specifically named, contact the company’s sales and technical help department to make sure that it will provide a warranty for the application.
Wood-Guard® (www. wood-guard.com) manufactures a lumber that is plastic-coated on the outside for weatherability and is also treated internally with borax to resist insect attack. The company literature claims that its coating will resist yellowing and chipping, and the product carries a twenty-year warranty. Its structural properties are similar to CCA lumber, so it can be used just as your carpenter or builder has been accustomed to building. The insecticide — borax — is generally non-toxic, but like with any dust or particulate, use a filter mask to prevent inhaling. It is suitable for rail/riding area fences and porch railings. Its surface is quite smooth, so we would expect it to be very slippery when wet. As best as we can tell, it only comes in white, but more colors may be forthcoming.
Trex® (www.trex.com) manufactures a product that combines plastic resins with sawdust. The primary application of this product is decking. The manufacturer contends that this combination of materials provides the best of both products — the plastic component does not rot, and the wooden component protects the plastic from UV degradation and adds strength. It is molded in several colors and never needs to be painted, but can be. It is slightly textured to aid in wet traction. There are some issues with which the owner must contend. Although the wood particles add some strength, this product is not as strong as similarly sized, wooden components. This means that the supporting structures (joists) need to be closer together to make up for the stiffness not provided by the decking itself. In addition, since this is not considered a structural material, the parts which actually provide the support (joists, beams, stairs, posts, etc.) all must be constructed of other materials such as steel or lumber. The Trex® construction details indicate that these components should be “lumber,” and in years past, this was implied to be treated lumber. It is unclear what substitute materials are being considered by the manufacturer.
Naturally Resistant Woods
Cedar, teak, and cypress, among others, have natural resistance to rot and insect invasion. Depending on your geographic region, these may be a financially reasonable alternative. However, for the large majority of the country, these woods are considered fairly exotic and may well be extremely pricey. To make a reasonable comparison of a project of any size, a detailed comparative cost estimate and depreciation analysis will likely be required to determine whether one of these materials is cost effective.
There are still fairly effective post-construction-applied products that will help preserve projects and lengthen their overall life spans. Water sealants such as Thompson’s Water Seal® and any number of other protectant stains will help prolong the life of exposed wood. Good quality paint, when properly applied to well-prepared surfaces, will go a long way toward keeping things in good repair. Bear in mind that none of these solutions will have any affect on wood-damaging insects — for that you’ll need to engage a licensed exterminator. Several of my facility managers tell me that the inspection and primary repairs associated with preparing to paint is what really extends the life of exposed surfaces.
Plastics (in general)
There has been almost explosive growth in the use of plastics for outdoor structures. Companies such as Jet Float (www.boat-float.com) and Shore Master make UV stable plastic floating docks that can be used in place of their traditional wooden counterparts. These have the benefit of using the water itself as support for the structure, and therefore can concentrate their structural strengths for very specific applications. This makes for an efficient design. One potential shortcoming is that these systems are, by their nature, not interchangeable, and an investment in a particular manufacturer is likely to be the beginning of a long-term relationship. Historically, the home-built dock could be modified or repaired with materials available at the lumber yard or home center at a moment’s notice.
Fiber-reinforced Concrete Siding
For exterior coverings of houses, cabins, or other habitable structures, many organizations have used treated plywood. At least one manufacturer, James Hardie (www.jameshardie.com) has created a fiber-reinforced, cement product that nails to the exterior of the structure like traditional lap siding. Although it requires periodic painting like most other sidings, it is not sensitive to temperatures (like vinyl), it does not burn (like wood), and is impervious to insects (as you would expect from concrete). It is heavier than similar lengths of eight-inch or nine-inch lap siding and is best cut with special shears, but can be cut with a circular saw or chop saw with special blades. Cutting with spinning blades instead of the shears creates a lot of dust.
Changes in Construction Practice
There are also things that can be done to reduce the final project’s exposure to damaging elements such as water and runoff. By thoroughly planning the project before construction begins and directing roof and ground runoff away from structural components, the wood is passively protected. Ensure that there is adequate ventilation and air circulation around all sides of the project by not building too close to the ground. Provide at least eighteen inches of separation between the ground and wood fiber with concrete, metal, or other non-tasty (to insects) materials.
Advice for Camps
Over the next few years, new replacement products will find their way to market as well as improvements to the ones listed here. In the meantime, there are already issues arising as CCA treated lumber stocks begin to draw down at the retail and wholesale outlets. Our advice to outdoor professionals is:
- plan to complete CCA projects this fall;
- protect the CCA stocks of materials you have on hand;
- care for the CCA structures you currently have; and
- dispose of waste and discarded CCA materials to licensed landfills.
Rick Stryker is a professional engineer with Camp Facilities Consulting providing study, design, permitting, and construction consultation services to the camp and conference center community. Camp personnel may contact him at 570-296-2765 or by e-mail at email@example.com.
Originally published in the 2003 July/August issue of Camping Magazine.