What is pressure-treated Lumber?

When building your dream home you need everything to be perfect. From the roof all the way until the deck. During your decision on picking out the wood for your deck, you would want it to be ideal. You would rather it to be rot and insect resistant. Some decks need major overhauls after less than 10 years. Others stay strong and good looking for decades. What’s the secret? Well, its obvious pressure-treated lumber, a lasting deck that is put together with strong, durable fasteners.

Why Pressure-Treated Lumber?

stack of pressure treated boards

The main reason why most deck builders choose pressure-treated lumber for the deck framing is that it is chemically infused to last longer outdoors and be able to undergo unpleasant weather conditions. The lumber wood is treated with Ecolife (EL2), a unique formula that contains a built-in wood stabilizer which reduces cracking, repels water, and keeps the wood in incredible conditions for an extended amount of time. These preservatives will provide literally decades of protection from decay fungi and insects such as termites. At Vandeck Builders, we use treated lumber to build the support systems for decks because it holds up well and is often masked by the deck flooring. Additionally, treated wood is better than untreated because unprocessed lumber tends to rot faster than pressure-treated lumber. As well as Its source is a renewable and quickly replenished resource grown on managed timberlands, it requires less energy to produce than alternative building materials, making it better for the environment.


History of Structural Lumber


Of course, humans have used wood for thousands of years to build numerous structures. But, it has been only since the late 1930s, when doctor Karl Wolman invented a procedure for infusing wood with a chemical preservative, and that is when treated lumber became a building material option. This process is called pressure treatment, and it requires that wood be loaded in a cylindrical holding tank while all of the air is being removed through a process called depressurization. Then, the preservative chemical is pumped into the tank under high pressure, making it go deep into the wood.


Species & Retention Levels For Pressure-Treated Wood


The species of treated wood is a regionally available softwood.  The most common are:

Southern Yellow Pine - Southern pine is the most common deck framing material in the eastern United States. It is strong and stiff. SYP logs yield a high proportion of sapwood, which works well to absorb preservatives.


  • Red and Ponderosa Pine - Less strong than SYP, found in northern U.S. and Canada. 

  • Douglas Fir – It is very strong and is less prone to warping and splitting than SYP.

  • Hem-Fir – It is weaker and more prone to warping and splitting than Douglas fir, but more receptive to preservation. It encompasses a group of western species.

Different applications impose different hazards on wood and require different amounts of preservative for protection. These amounts are called “retention levels,” referring to the amount of preservative retained in the wood after treatment.


Most common use category description:

  • UC1 - Interior Dry

  • UC3A Exterior Above Ground, Coated with Rapid Water Runoff

  • UC4A Ground Contact, General Use

  • UC5A Marine Use, Northern Waters (Salt or Brackish Water)

  • UCFA Interior Above Ground Fire Protection

  • UCFB Exterior Above Ground Fire Protection



Why Does Lumber "Checks" or "Splits"?

A check is a term used to describe a crack that runs through a board, usually running lengthwise. There are two ways by which checks and splits can form in wood elements: during seasoning, or drying. During the seasoning, tension develops in wood as a result of differential shrinkage which can often to lead checking, splitting, and even warping. Moreover, separation of the wood fibers also results in checking and splitting. Due to the innate characteristics of wood, it shrinks and swells differently. Additionally, checks and splits occur when the wood has dried in place. Lumber dries too quickly because of the low relative humidity in the air. You might be asking, “ How long does it take for Lumber to dry?” Well, it’s not exactly a fast process, and it depends on the humidity of the environment in which the lumber is located, but usually, lumber air dries 1” per year. You can ready more on Wood Checks by following this link. https://www.vandeckbuilders.com/post/wood-checks-why-does-lumber-split-and-cracks

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