Pressure Treated Lumber: Definition, Advantages and Disadvantages of Pressure Treated Lumber

Pressure treated lumber is used in many applications such as for fencing or as building materials. But people often wonder what exactly is pressure treated lumber and what can it be used for? Pressure treated lumber is best used outside away from any vegetation that will be consumed by humans or animals.


What is Pressure Treated Lumber?

Pressure treated lumber is lumber that has undergone a process that forces chemical preservatives into the wood. The wood is placed inside a closed cylinder. Then vacuum pressure is applied to force the preservatives into the wood. These preservatives help protect the wood from any termites or other such insects. It also prevents fungal decay.

pressure treated lumber definition
pressure treated lumber

There are several different types of pressure treatments available. Waterborne, Creosote and Oilborne are the three categories for pressure-treating wood. Waterborne treated lumber is generally used in building structures that are residential, commercial and industrial. Creosote treated lumber is mostly used for treating guardrail posts, railroad ties and timbers used in marine structures. Oilborne treated lumber is used when treating utility poles and cross arms.


Advantages of Pressure Treated Lumber

The advantages of pressure treated lumber are listed below:

  • Protection from the Elements – Wood must be chemically protected, or pressure treated to withstand the ever-changing elements. Lumber that has been pressure treated can last for 20 years or more. Most manufacturers of pressure treated lumber will attach a limited lifetime warranty to it because the lumber is treated to last for many years.
  • Building Code Compliant – Most building codes throughout the United States now require that the lumber being used in new construction to be pressure treated. Using pressure treated lumber meets those building codes and keeps the project on schedule.
  • Protects Against Fungal Decay – Pressure treated lumber has protective chemicals that saturate the wood. This protective treatment keeps any fungal decay from occurring and makes the lumber longer lasting.


Disadvantages of Pressure Treated Lumber

Pressure treated lumbers has also some disadvantages. These drawbacks are as followings:

  • Special Fasteners – Since there is a large amount of copper in pressure treated lumber, standard fasteners become corroded. They will corrode up to five times faster when used on pressure treated wood. Galvanized or stainless steel fasteners with metal components work best and minimize the corrosion effect.
  • Warping and Shrinkage – The wood has to become saturated with the chemical solution and the wood will take several months to completely dry and cure. There will be some shrinkage and warping of the lumber as it dries. Pressure treated lumber has to rest for three weeks to six months before it can be stained or painted for the stain or paint to take hold.
  • Sawdust is Bad for Health – It is recommended that you use a heavy duty dust mask and eye protection when cutting pressure treated wood. When cutting pressure treated wood it is best to lay a disposable tarp and cut only in one area. Once the project is finished, roll up the tarp and properly dispose of it. The chemicals within the pressure treated wood are released when it is cut and can cause health issues.
  • Cannot Be Burned – Only professionals can burn pressure treated wood. There have been government studies that show toxicity in the smoke and ash. The ash must be properly disposed of due to the high toxicity within it and the smoke must be contained as to not affect the air.
  • Cannot Use for Food Prep – Pressure treated wood cannot be used to make cutting boards or any food preparation surfaces. Picnic tables and other surfaces such as counters are fine as long as no food is prepared on them. Pressure treated lumber cannot be used for garden beds or raised gardens.
  • Outdoor Use Only – For the most part, all pressure treated lumber must be used outdoors only. There are a few exceptions to this rule. Local building inspectors will be able to tell you what the exceptions are. Sill plates are generally pressure treated wood instead of Douglas fir.

While pressure treated lumber is great for keeping rot, termites and fungus away, therefore making the lumber long-lasting, there are several disadvantages that need to be considered when deciding on treated lumber verses untreated lumber.

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