Pressure Treated Lumber
Because of it's strength, low cost and resistance to decay, pressure treated lumber is the most widely used material in deck construction. In addition, all decks are framed with pressure treated lumber unless specifically enginered otherwise. A clear Cedar or Redwood deck will almost always have a pressure treated substructure.
After the milling process, the lumber (usually southern yellow pine) is then treated to prevent insect and rot decay. The chemical preservative is pressurized deep into the wood fibers. The amount of pressure that's applied into a piece of lumber will be indicated by tags on each board. The most common pressure treatment would be 40 pounds per square inch (p.s.i.) which is commonly found in deck construction.
A new process has been introduced in 2005 that makes pressure treated lumber a safe product to use. The CCA (chromate copper arsenate) that may have been a concern for some has been removed from the preserving process.
When working with wood, use protective clothing, dust mask and eye protection.
Premium boards, #1 grade with relativity few knots and blemishes used primarily for deck boards and railings
#2 grade has knots and other abnormalities that make it better suited for deck framing. A mixture of both grades is often the case in most deck construction projects.
Pressure treated lumber will shrink and some of the grain may rise or open up. These so-called splits and splinters are a natural occurrence with pressure treated lumber and may happen within a few days after being exposed to the sun. Wood such as cedar and Ipe are less likely to develop the attributes that are associated with pressure treated lumber. However, all wood decks should be periodically cleaned and sealed to protect the wood from degrading.
Generally the preferred method is to install boards close to each other. Depending on the moisture content of the lumber, boards will generally shrink 1/4 - 1/2 inch in length and width. Butting the borads together will assure you that after the boards shrink the space that remains will not be too large. This will help eliminate the possibility of women's high heals or other small objects from falling between the boards.
When securing boards we recommend pre-drilling and screwing. This will take extra time but the results are well worth it. Drilling the boards will help avoid splitting lumber and using screws rather than nails will alleviate problems such as nail heads popping up above the wood and eliminate the indentations left behind in the wood from hammers and pneumatic nail guns.
Resent studies have found no advantage in which side of the board is installed up. At one time it was suggested that the bark side of the board face up to help minimize the wood from cupping. This is no longer supported and standard construction practice is to put the best looking side up.
Pressure Treated Lumber is economical and plentiful. When properly cleaned and sealed, pressure treated lumber will continue to look good years after construction.
It is by far the least costly building material available in deck construction and comes in a variety of dimensions.
|Pressure Treated Lumber, #1 and #2 Grade