News Coverage
Deck Lumber, Hardware Present Risks
Published April 30, 2004
When Hurricane Isabel lashed the region in September, it toppled a towering oak in Alyse Graham's Northwest Washington back yard, destroying her deck and privacy fence. It also opened her eyes to the dangers of a pesticide impregnated in the wood of millions of decks nationwide, theirs included.
The Grahams' damaged deck and fence were constructed of pressure-treated lumber saturated with chromium copper arsenate (CCA), which has an arsenic base that makes outdoor structures practically impervious to decay but also potentially hazardous to health, especially for young children. Until recently, such wood was the nation's top-selling material for decks, fences, playground equipment and other outdoor uses.
Homeowners who choose to keep their CCA-treated decks can reduce health threats with proper maintenance.
Those who build new decks still aren't clear of worries. The new generation of pressure-treated lumber raises its own safety issues, particularly about possible incompatibilities between wood and deck hardware.
David Deegan, a spokesman for the Environmental Protection Agency, said federal authorities long ago declared arsenic a carcinogen but still maintain that the risk through exposure to deck surfaces requires more study. Public advocacy groups disagree, saying the research is conclusive and the risk considerable.
Graham, who has two children, has studied the research of advocacy groups that have battled against CCA-treated wood, including the District-based Environmental Working Group. They say most pressure-treated decks are loaded with arsenic; the chemical can rub off on contact; and the lumber remains dangerous for 10 to 15 years.
U.S. manufacturers on Dec. 31 voluntarily stopped selling CCA-treated wood for residential applications. However, the Wood Preservative Science Council, which represents the industry, continues to defend the product. "CCA-treated wood is safe for people, plants and animals when used as recommended," the group says on its Web page. It has frequently said that children are more likely to receive larger doses of arsenic from their daily food and drinking water than they are from contact with treated wood. Graham concluded that she doesn't want her children exposed to the danger, so she plans a new deck. "Both of my children are or were at that developmental stage where they're always on their hands and knees, holding onto steps, grabbing rails, and constantly putting their hands into their mouths," she said.
For those who plan to keep their CCA-treated decks, activists and regulators agree on a couple of recommendations:
* Test for arsenic. "Up to 20 percent of decks don't put out much arsenic, while some are really bad," said Richard Maas, director of the Environmental Quality Institute at the University of North Carolina at Asheville. "If you know how much arsenic is coming off your surfaces, you'll likely be more careful about washing your hands." (Test kits are available from organizations including the Environmental Working Group; Web site: www.ewg.org .)
* Seal arsenic. If presence of arsenic is a concern, it's possible to put a barrier between people and the chemical. "Most pressure-treated lumber gives off substantial amounts of arsenic when you touch it, making it a significant cancer risk," Maas said. "The question is how to seal it so it's not dangerous."
Maas said that while removing pressure-treated lumber may be "the best solution," he acknowledged that many people cannot afford this. EPA recommends that parents wash their children's hands frequently and that homeowners consider sealing their decks.
About five months ago, Maas's research staff launched a study of commercial and experimental sealants, hoping to separate the gold medalists from the 98-pound weaklings by December.
Declaring that more pigment means better protection, Maas said: "The conventional oil-based water seals -- the clear stuff -- really don't work well at all. After about four months, they aren't doing anything. The semi-transparent deck stains work better than the clear [sealants], and the solid stains work better still."
Maas said pigmented deck stains should provide 18 to 24 months of protection, less in high-traffic areas. The Environmental Working Group suggests reapplying sealants every year or so.
The arsenic is going to start coming through before you would actually redo it from a visual aesthetic," Maas said.
While Maas praises specially formulated deck paints as the current gold standard, the maintenance ritual he outlines isn't hassle-free. Becaue of exposure, even top-drawer deck paints -- Maas cautioned against using common house paints -- begin cracking within five years.
Contrary to the usual procedure for prepping a painted surface, he said, "The last thing you want to do is any kind of sanding."
Sanding CCA-treated lumber kicks up arsenic dust particles that can be inhaled. Maas suggested instead a maintenance regimen in which homeowners blast off peeling paint with a high-pressure washer and then reapply new paint. He also cautioned against pressure washing unsealed CCA-treated decks, as the water spray may spread diluted arsenic over a wide area.
Maas reserved a final caveat for "deck washes." "Our research shows that the more powerful [cleaners] oxidize the chromium-3 that's already in CCA-treated lumber, turning it into the highly carcinogenic chromium-6," he said.
The EPA recommends that whatever CCA-treated wood is removed from a deck -- including sawdust and scraps -- be disposed of properly. Throw it in the trash. Don't use it for compost or mulch, and don't burn it. Toxic chemicals could be released into the smoke and ashes.
Since U.S. manufacturers stopped production of CCA-treated wood, they have turned to a new chemical compound, alkaline copper quaternary (ACQ), to pressure-treat lumber for deck, fence and playground applications. Another new and similar ingredient is copper boron azole, which is also known as CBA and CA-B.
David Wilks, sales manager for Long Fence in Montgomery County, said: "We see ACQ lumber as a lateral move in terms of maintenance and longevity, but with a 15 to 20 percent price increase. With older decks, we're taking off CCA surfaces and putting down ACQ or composite products."
Noting one potential downside, Joan Griswold, executive vice president of sales and marketing for California-based Penofin, a high-end deck maintenance product line said: "Our first reports say [ACQ] is more prone to mildew."
Mildew is one thing. Deck collapse is another. According to experts, the increasing use of ACQ-treated wood raises a far more serious - and potentially hazardous -- issue.
Steven Slaght, supervisor of residential inspections for the Fairfax County government, said: "The new chemical formulation of ACQ lumber causes a serious corrosion of standard fasteners and connectors. We don't know how long this takes, but they will rust and corrode through," leading to possible failure and collapse.
Homeowners who inherit a neighbor's leftover joist hangers or deck fasteners -- or purchase a retailer's old inventory -- should double-check that these components are ACQ-compatible.
Brian Foley, chief structural engineer for the Fairfax County Government Office of Building Code Services, said ACQ and CBA lumber require hangers and fasteners with far more protective galvanization than their CCA counterparts. He said the county specifies that deck hardware be galvanized with 1.85 ounces per square foot of zinc (G-185 coating), or be stainless steel of Type 304 or better.
But ACQ's incompatibility goes beyond CCA-generation joist hangers, lag screws, carriage bolts, nails and deck screws.
"You can't use aluminum flashing any longer. Aluminum deteriorates even more rapidly when in contact with ACQ lumber than do the old fasteners," Slaght said.
Foley recommends copper flashing. A recent check with a local home-improvement retailer found employees either unaware or dismissive of the incompatibility between aluminum and ACQ-treated wood.
Foley and Slaght say deck builders are still buying noncompliant materials.
Foley said: "We recently saw a manufacturer in Pennsylvania claim that its galvanized steel flashing is ACQ compatible, but it's of a very inferior level of galvanization, so we won't allow it."
Slaght said: "I just talked to someone who bought old fasteners and new lumber. Now he's going to have to change out what he already installed.
"If people are using the wrong hangers to support ACQ [or CBA] joists, they'll have to change those. If they've already driven nails and bolts in, they can leave the old ones in, but they'll have to double up with new ones, making the old ones dead weight."
For people buying a house with a deck, Slaght outlined the early signs of incompatible fasteners: "The smallest connectors -- the small staples or nails that hold the pickets on the rails -- will start to loosen up or start to fail. This is a clear indication that the problem is going to get worse."
He added that deck collapse might occur with little or no warning. Would-be home buyers should ensure their home inspector is savvy about the issue.
And while expensive stainless steel hardware pieces are another alternative, Slaght said, "I almost never see them outside of marine environments."
To complicate things more, the EPA has given retailers until mid-May to sell the CCA-treated lumber already in their supply pipelines, creating what Foley calls a confusing transition period. Building inspectors advise people with questions to contact the city or county office that issues deck building permits.
Pressure-treated wood isn't the only option for decks and other outdoor construction. There is also an array of environmentally friendly, high-performing composite (part wood, part plastic) and synthetic (all plastic) decking alternatives available. Among the dozens of composite manufacturers is Trex Co., a Winchester firm whose part-sawdust, part-recycled-plastic-grocery-bags lumber boasts low maintenance and zero arsenic. Priced at roughly twice the cost of ACQ lumber, Trex and its newer cousins stain and fade less readily than their forerunners.
Long Fence's David Wilks said synthetic surfaces -- think vinyl - perform generally well, but suffer from uneven expansion and contraction, producing a ragged look at a deck's edge.
Gary Bowman of TW Perry, a Chevy Chase-based firm that sells building materials to contractors, noted that his company is seeing increased interest in such "non-composite alternatives" as the Brazilian hardwood Ipe, plantation-grown mahogany and cedar. Those woods don't require pressure-treating to make them last.
Noting that composites and synthetics may not completely resemble wood, he said, "They also don't have the cracking, checking, warping, and upkeep of wood."