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This
article appeared in the Lincoln Journal Star Newspaper
Unprotected
wood used outdoors for decks or landcaping can be damaged by
termites and decay. To increase the longevity of wood, homeowners
have several options, including several types of pressure-treated
wood, naturally resistant wood and composite materials made
of wood and plastic.
Pressure-treated
lumber. Pressure-treated lumber is highly resistant to decay
and insects. Through a series of pressure and vacuum cycles,
wood preservative is forced deep into wood pores, forming a
chemical barrier against termites and decay.
Many
people are familiar with green Chromated Copper Arsenate (CCA)
treated wood. It has been widely available since the 1970s;
literally millions of decks have been built of CCA-treated wood.
It is very resistant to termites and decay, but because arsenic
is a known carcinogen, this wood will not be available for residential
use after January 2004.
The
decision to phase CCA-treated wood for residential structures
has people asking what to do with existing structures made of
this material. The EPA does not suggest tearing down structures
made of CCA-treated wood. According to the EPA, people should
take common sense precautions, especially when it comes to children.
Kids should wash hands after playing on structures and keep
food from direct contact with CCA-treated wood.
Some
non-arsenic substitutes for CCA-treated wood include:
Alkaline
Copper Quaternary (ACQ). This treated wood has been used
successfully for more than 10 years and has the same green look
as CCA treated wood, but does not contain arsenic or chromium.
It has been found to have performance characteristics similar
to wood treated with CCA. Preserve®, Preserve Plus®,
NatureWood® are brand names for ACQ pressure-treated wood.
Copper
Boron Azole (CBA). CBA is a copper-based preservative with
an organic fungicide. The treated wood is a dark honey brown
color and turns a silver-gray after it weathers. Wood products
treated with Copper Azole have been used successfully since
1992. Wolmanized Natural Select™ is a brand name for CBA-treated
wood.
How
long will treated wood last? It depends on the use and location.
For best results, it is important to use a treatment level appropriate
to the end use. Retention is the amount of wood preservative
placed in the wood. When selecting treated wood, refer to the
following chart.
Minimum
recommended retention for various applications
| Application |
Retention
(lbs/cu. ft.) |
Uses |
| Above
ground decking |
0.15
+ water repellent |
Decking, hand rails, spindles, trellises, gazebos, fence
boards |
| Above
ground - general use |
0.25 |
Framing
lumber, trim and fascia, flooring, sill plates |
| Ground
contact |
0.40 |
Deck support posts, fence posts, landscaping |
| Critical
structural members |
0.60 |
Permanent
wood foundations, building poles |
Naturally
Resistant Woods. Naturally resistant woods include redwood,
cypress and cedar, but these woods are not long-lasting as treated
lumber. For maximum termite and rot resistance, it is important
to use the heartwood where resistant compounds are concentrated.
Construction common grade wood contains sapwood and will only
last a few years with ground contact.
Plastic
and Composite Materials. There are two types of lumber products
made from recycled plastic. One is 100% plastic. The other type
is a composite material made from recycled plastic and waste
wood fiber, like sawdust. Plastic and wood composite lumber
needs no maintenance or sealing and does not rot, chip or warp.
It is also impervious to insects Composite products have guarantees
ranging from 10 to 50 years.
Because
more than 90% of all termite infestations get started from wood-soil
contact, using treated lumber is an important way to prevent
termite damage to porches, decks and other wood in contact with
the soil.
 More
Termite Control Resources
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