Preservative-Treated Wood and Alternative Products in the Forest Service
Alternatives to Treated Wood
Alternatives to treated wood are being used more
frequently. Examples of alternatives to treated wood are native decay-resistant
woods, exotic decay-resistant woods, composite woods (plastic woods), vinyl,
and rubber (figure 4). Only the heartwood of decay-resistant
species is durable. The decay resistance of the heartwood of native species
is listed and described in the Wood Handbook and
AASHTO standard specification, M 168.
Figure 4—Alternatives to treated wood include rubber wood
and solid- and hollow-core plastic-wood composite decking.
Table 2 lists the advantages and disadvantages of different alternatives to
treated wood.
Table 2-Advantages and disadvantages of five alternatives to treated wood.
| Material |
Description |
Advantages |
Disadvantages |
| Native decay-resistant woods |
Redwood, cedar, juniper, bald cypress, pacific yew, chestnut, black locust,
osage orange, black walnut. |
Resistant to decay and insects. Attractive. Dimensionally stable. Provides
a use for invasive species, such as locust and juniper. |
Expensive.
Surfaces may be soft (susceptible to denting and scratching). Susceptible
to moisture. Life expectancy is not as long as that of treated wood. |
| Exotic decay-resistant woods |
Includes mahogany and a variety of ironwoods (Ipe), also known as Pau
Lope. |
Durable. Resistant to decay and insects. Attractive. Virtually knot free.
Resistant to water. |
Expensive. Difficult to work with (requires predrilling for fasteners).
Environmental concerns (except for lumber certified by the Forest Stewardship
Council). |
| Composites (plastic woods) |
Solid material made of wood, fibers and recycled grocery bags, recycled
milk jugs, or virgin plastic. |
Doesn't split or chip.
Variety of colors to choose from. Less need for sealing or staining. Requires
little maintenance. Free of knots. |
Expensive. Unnatural appearance. Generally not rated for structural use.
(Usually, wood is used for structural supports and subframes.) Susceptible
to mildew, mold, and stains. Color fades in sunlight. (Some products
are reinforced with fiberglass and meet ASTM standards.) |
| Virgin vinyl |
Hollow building material, a molecularly bonded blend of 100-percent virgin,
hi-polymer resin. (Some are made with UV inhibitors to prevent damage from
sunlight and impact modifiers for greater strength.) |
Doesn't warp, split,
chip, or rot. Variety of colors to choose from. Never needs sealing or
staining. |
Expensive. Unnatural appearance. Not rated for structural use. (Wood
is required for structural supports and subframes.) |
| High-density polyethylene HDPE) |
Thermoplastic. |
Weather resistant. Can be cut or drilled cleanly. No grain to split or
chip. No need to predrill lumber. Suitable for agricultural uses. Good
at low temperatures. Impact resistant. Excellent chemical resistance. |
Susceptible to stress cracking. Not as stiff as polypropylene. High mold
shrinkage. Poor UV resistance. Not rated for structural use. (Wood is required
for structural supports and subframes.) |
| Rubber lumber |
Composed of 50-percent plastic and 50-percent old tires. |
Durable. Impervious to water. Resistant to insects. Resistant to UV rays.
Variety of colors. Uses recycled materials. |
Unnatural appearance.
Color isn't guaranteed to last. Not rated for structural use. (Wood is
required for structural supports and subframes.) |
—Courtesy
of the U.S. Environmental Protection Agency with the addition of
information on the naturally decay-resistant hardwoods. |
