At some point in your life you may have already worked with this green-tinted material, but how much do you really know about it? Here are quite a few things that you need to know about working with pressure-treated stock.
We have been using pressure-treated wood for well over 70 years, but few of us have actually took the time to learn more about this popular building material. Let’s start off by looking at the typical wood that is used to manufacturer pressure-treated wood. Generally, it is a soft wood like southern yellow pine that has been treated with chemicals to resist termites and decay. The boards are then rolled into large pressurized tanks where chemicals are introduced into the fibers of the wood. Once finished, the end product is perfectly designed for all of your outdoor building needs including decks, playgrounds, fences, sheds, and other assorted outdoor building projects
It is important to remember that not all treated wood is manufactured in the same way. The amount of rot resistance is related to how many chemicals are placed directly into the wood. If the lumber have been stamped with the words for “Above Ground Use” it must only be used in areas where it will not touch the ground in such areas like fence boards and deck railings. If the lumber has been designated for “Ground Contact” it has the ability to be placed directly on the ground.
You want to make sure that you are using the right type of lumber for your project and this can be found by looking at the stamp for its chemical retention level. This number is used to represent the minimum amount of preservatives found within the wood. It is typically written in pounds of preservative per cubic foot of wood. If you are looking for more rot-resistant wood it is best to look for higher numbers. Boring I know, but good to know.
Many people with outdoor projects get confused by the retention levels of pressure treated wood. In fact, conditions change at such a fast pace that many professionals have a hard time keeping up.
Much of the confusion began once the industry ceased using chromated copper arsenate in the use of residential wood. This preservative was used since the mid-1940’s and had an exemplary track record in decay resistance. This chemical was stopped due to concerns about health issues in 2003 in residential areas. However, it can still be found in telephone poles, boardwalks, commercial buildings, and docks.
In the past CCA retention levels were .25 for above ground use and .40 for anything used for ground contact. However, retention levels now are dependent upon the preservative that is used. As an example, a typical wood treatment that is used is micronized copper azole, which has a retention level of .06 for ground use and .15 for anything requiring ground contact. Many people are left wondering if these lower retention levels lead to an inferior product. In fact, it could not be further from the truth. These new treatments actually provide the same or in some cases better resistance against decay and insects.
With today’s pressure-treated lumber it is treated with inorganic chemicals rather than harmful arsenate of yesterday. Other chemicals that are often used are Alkaline Copper Quaternary, Copper Azole, Sodium Borate, and Micronized Copper Quaternary. These new chemicals are less toxic than those of the past, but they do contain higher levels of copper, meaning they are more corrosive than the older CCA-treated lumber.
Most of the manufacturers of pressure-treated lumber recommend using stainless steel bolts, screws, anchors, and nails with the lumber and other materials. Due to the fact that these new wood treatments are corrosive to aluminum, it is a better option to use copper of vinyl flashing or wrap the wood in a protective rubberized membrane.
Below are several more tips to consider while using pressure-treated lumber.
– Always wear gloves when using pressure-treated wood and be sure to thouroughly wash your hands before eating or drinking.
– Wear safety goggles and an adequote dust mask while sanding, drilling, and cutting.
– Cut wood outdoors as opposed to an enclosed area. – Under no circumstances should treated wood ever be burnt for recreational use.
– Always allow treated wood to dry before painting or staining. You can test the dryness of wood by dropping a small amount on the surface of the wood. If the water beads on the surface, it means that the wood is too wet and needs additional drying time. If water soaks into the wood it is dry enough to be stained or painted.
– If you are not going to stain or paint the wood, a clear wood preservative should be used on an annual basis to maintain the wood’s water resistence.
– Before you drive a nail or screw into the wood, it is best to drill a pilot hole to help prevent the wood from splitting. This is especially true when you are fastening near the end of the board.
– Over a certain period of time, pressure-treated lumber will shrink as it begins to dry out. When you are placing fence boards or decking always take this shrinkage into account.
-Once the lumber has remained outside for a period of six to twelve months, it will begin to develop cracks on the surface of the board. The “checks” are simply part of the drying process and should be expected.