The toxic top: The environmental and structural risks of treated lumber supports on rooftops.
The market has been shifting away from treated wood blocks for rooftop support of pipes, HVAC equipment, and ductwork, etc., largely because they are subject to biodegradation—in other words, rot. When the sleepers deteriorate, they cause pipe sag and unbalanced HVAC equipment which shortens operational life. But there are other issues—critical ones—for moving toward other types of support.
Toxic Chemicals
Another problem with wood sleepers is that most are filled with pressure-treated biocides. These chemicals are water-borne and over time will leach out of the wood into ponding water. At one time, CCA—chromium/copper/arsenic—were common chemicals in treated wood. although arsenic has been phased out and sleepers rely more on higher copper content. While older installations may contain arsenic, the more current arsenic-free lumber still presents hazards. Even though treated lumber has fixative agents, over time toxic biocides can still leach out. Water carrying such leached agents eventually flows to the ground, presenting toxic risks.
Structural
Risks
Additionally, there are dangerous structural issues. High copper-treated lumber is very corrosive to metal fasteners including nails and screws. Numerous deck collapses—some resulting in fatalities—have been reported because of corrosion. Hot-dipped galvanized fasteners, or even better, stainless steel, are the right choice but oftentimes the composition of the fastener can’t be determined simply by sight. Staining around fasteners is an early indicator of corrosion.
The KnuckleHead Solution
All of these risks can be eliminated by converting to KnuckleHeads. High-strength, glass-reinforced nylon is waterproof and presents no toxic risk. It is compatible with any type of mechanical fastener and remains stable throughout the life of the installation. In fact, KnuckleHeads should outlast the roof, and likely the life of the building where they are installed.