WOOD - Materials for Civil and Construction Engineers - page 422

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10.12.4 Construction Precautions

There are a few issues that should be recognized during the design and con-
struction with pressure-treated materials. Care should be taken to avoid
inhaling saw dust during cutting of the wood. Hands should be washed
after handling pressure treated wood and before consuming food or bever-
ages. Clothes should be washed separately from other items. Waste material
must be disposed of properly; it should not be burned.
Pressure-treated wood promotes corrosion of hangers and other fasteners.
Generally, galvanization was adequate. However, there is some evidence that
the new preservatives are even more corrosive. The higher metal corrosion
rates associated with ACQ-treated wood have raised concerns with the
federal Consumer Product Safety Commission (CPSC) and a Bay Area district
attorney who recently issued a consumer alert (e-builder, 2005).

“CPSC is recommending consumers use stainless steel brackets and fasteners in
conjunction with ACQ-treated lumber,” said commission spokesman Scott Wolf-
son. The CPSC is considering whether it needs to study the corrosion issue fur-
ther, based on information from the connector industry and Contra Costa County.
That county's district attorney, Bob Kochly, warned in a recent consumer alert
that wood treated with ACQ and copper azole “may result in serious and prema-
ture corrosion … especially in wet or moist conditions unless stainless steel con-
nectors are used.”

10.13 Engineered Wood Products

Engineered wood includes a wide variety of products manufactured by
bonding together wood strands, veneers, lumber, or other forms of wood
fibers to produce large and integral units. These products are “engineered”
to produce specific and consistent mechanical behavior and thus have
consistent design properties. There is a wide variety of engineered wood
products produced for many applications. Only the products used in struc-
tural applications are considered here.
An engineered product consists of wood stock material glued together
with an appropriate resin or adhesive. These are predominantly wood ma-
terials, so they are liable to the same concerns as natural wood products
with respect to the effects of fire, moisture, and decay. The wood stock may
consist of veneers, strands, or dried lumber as shown in Table 10.6.
Veneer-based materials consist of wood plies that are glued together. A
ply is a thin sheet of wood. To produce plies, logs are saturated by storage in
ponds, water vats, steam vats, or water sprays. Prior to processing, the logs
are moved into a boiling water bath. Next, they are debarked and sectioned
into the desired width. The segments are rotated in a giant lathe and peeled
into continuous sheets of veneer, or sliced, as shown in Figure 10.14. These
segments of veneer are trimmed and combined into continuous rolls. Each
roll of veneer is seasoned, dried to the desired moisture content. The plies,