Wood Fact Sheet
There are three primary categories of lumber used for fence construction.
- Oil-based, chemically pressure-treated southern yellow pine
- Water-based, chemically pressure-treated southern yellow pine
- Natural (no chemical treatments) cedar, redwood, spruce, cypress, hemlock, douglas fir
The two most commonly used types of lumber in the Midwest are southern yellow pine and cedar. The overwhelming majority of southern yellow pine used in the fence industry is treated using the water-based process. The use of the oil-based treatment process is minor by comparison. Eastern red cedar and Japanese cedar are the most commonly used natural wood with the other choices being mostly regional.
What is pressure-treated wood? It is a process in which preservatives are forced deep into the cellular structure of the wood in a closed, pressurized cylinder. With the exception of naturally durable lumber like redwood and cedar, this process enables the wood to maintain a chemical barrier against termites, decay and fungi for longer periods of time.
Oil-Based Treatment- (Pentachlorophenol (Penta), Copper naphthenate, and Creosote)
- Pentachlorophenol is a manufactured chemical that can be dissolved in different oils. The use of Pentachlorophenol has been restricted to certified applications and is no longer available to the general public. It is not recommended for areas where it comes into frequent contact with human hands.
- Copper naphthenate is a mixture of naphthenic acids and copper salts dissolved in oil. The most commonly used oils in the treatment process are diesel fuel oils and mineral spirits. Even though human health concerns do not require copper naphthenate to be listed as an RUP (restricted use pesticide), precautions such as the use of dust masks and gloves should be used when working with wood treated with copper naphthenate.
- Creosote is made from coal tar, which is a by-product of the carbonization of the coal during steel production. Creosote-treated wood has a dark brown-black color with an oily surface and strong odor.
Water-Based Treatment - (ACQ, AZCA, MCQ, CC, CBA, CDDC)
- ACQ (Alkaline copper quat) contains copper and a quaternary ammonium compound. ACQ is a common water-based preservative used in the fence industry. Because water-based preservatives leave a dry, stainable surface, they are commonly used to treat wood for residential applications such as decks and fences.
Natural (No chemical treatments) - Red cedar
- Western red cedar’s naturally occurring oils make it resistant to decay. WRC scores high in dimensional stability and resistance to cupping.
- Eastern red cedar’s naturally occurring oils make it resistant to decay and termites. ERC scores high in dimensional stability and resistance to cupping. ERC is the only cedar listed by ASTM as termite resistant.
- Japanese cedar’s naturally occurring oils make it resistant to decay. Japanese cedar is durable and known to be straight-grained.
Advantages | Disadvantages | |
---|---|---|
COPPER NAPHTHENATE Southern Yellow Pine oil-based treatment |
inexpensive, longevity | warpage, cupping, shrinkage, odor |
ACQ Southern Yellow Pine water-based treatment |
inexpensive, longevity | warpage, cupping, shrinkage |
CEDAR | longevity, environmentally safe, natural resistance to decay, little warpage or shrinkage, great smell | different qualities (larger knots), costs more |
Although there is no perfect lumber when exposed to nature’s elements, staining will help keep the natural look.