As a building material, wood is susceptible to a lot of things that can damage it. That list of things includes the elements (weather), fungus, fire, and insects. It's for that reason that some wood materials need to be treated with chemicals that act as preservatives. Otherwise, damaged wood would eventually lead to structural problems in the future.
Of course, caution is required any time a chemical needs to be used around a building or structure. The reasons for this should be obvious because of the way the human body and even the environment will react to certain toxins. Actually, the use of preservatives for lumber requires a bit of a balancing act. Given the threat of toxin contamination, preservative-treated lumber should only be used when necessary. The question becomes, when is the right time to use preservative-treated lumber?
Why Use Preservatives at All?
There is an expectation that whenever something is made of lumber, that lumber will endure and stay strong over the years. Should that not happen, there could be serious consequences.
Preservatives are used when lumber's exposure to any of the aforementioned issues would weaken the lumber, hence weakening whatever the lumber was used to make. If that happened to be a building or a home or even a piece of furniture, the exposure to problems could range from repairable damage at the low end to the injury/death of bystanders in a worst-case scenario.
Bottom line: Preservatives are used to make sure lumber is able to endure for as long as reasonably possible under adverse conditions.
When To Use Preservative Treated Lumber
Before discussing specific circumstances under which using preservative-treated lumber is the right choice, there must first be a comment made regarding the avoidance of using preservative-treated lumber.
Preservative-treated lumber should only be used when untreated lumber will not suffice. Whenever and wherever possible, using untreated or natural lumber is always preferable for two reasons. why? First, exposing the human body and environment to any more chemicals and toxins than necessary is just not a good idea. Second, treating lumber or purchasing pretreated lumber is more costly than using natural lumber materials.
If using preservative-treated lumber is necessary, it would most likely be under one of the following circumstances.
When the Lumber Will Be in Direct Contact With Soil
When lumber is placed in direct contact with soil, it will get exposed to ground moisture. Exposure to ground moisture could lead to the creation of decay fungi and or exposure to certain insects like damp wood termites.
Note: Some lumber materials have the protection of natural chemicals/preservatives called extractives. Extractives, when present, will act to preserve lumber against moisture and fungi. Some of the durable heartwood that contains these natural chemicals would include black cherry, black locust, black walnut, bur oak, cedars, osage orange, red mulberry, redwood, and white oaks.
If a lumber material doesn't have these natural chemicals/preservatives and will be used in direct contact with soil, preservative-treated lumber would be highly preferred.
When the Lumber Will Exposed to Water and Humidity
In arid regions (deserts), lumber will seldom get enough exposure to moisture to cause concerns about durability or exposure to decay fungi. Conversely, lumber used in areas with high rainfall, high humidity, or near ocean environments will be susceptible to enough moisture to compromise a lumber's durability. In fact, decay fungi are very common in moist regions. The only realistic way lumber will be able to maintain any reasonable level of durability is if it has been properly treated with moisture retardant chemicals/preservatives.
To Prevent Damage From Termites
Nothing will destroy a structure or product made with lumber quicker than an infestation of termites. Where are termites most prominent? Termites tend to thrive in warm and moist climates. They can reproduce at unbelievable rates in such environments. That is why some lumber products being used in warm/moist climates need to be treated with preservatives.
Under Circumstances in Which Lumber Could Be Exposed to Fire
Some environments are often exposed to the possibility of fire. Warm forest areas come to mind. If lumber is going to be used in an area where there is a realistic chance of exposure to fire, the lumber needs to be treated with fire-retardant chemicals/preservatives.
Selecting the Right Preservatives
There are two primary types of preservatives used to treat lumber: oil-type or waterborne.
Oil-type preservatives are made from creosote and creosote solutions. Creosote is mostly comprised of a tar-like oil material that is very potent in the battle against wood-destroying organisms like mold, fungi, and insects. It's also very easy to apply and very durable. However, it's a highly toxic chemical, which restricts its usefulness. In other words, lumber treated with creosote solutions is only suitable for use on lumber that is intended for outdoor construction. It's not suitable for use on lumber intended for indoor use because the toxins are potentially very harmful to humans and pets.
For what it's worth, creosote is highly flammable and combustible until it gets a few months of seasoning. The storage costs of lumber after it has been treated with this type of preservative will add to the price upon sale.
For treated lumber intended for indoor use, waterborne preservatives are far more appropriate. Since waterborne preservatives are first dissolved in either water only or a solution made of water and ammonia, it's a much cleaner preservative. It's also much more receptive to paint or varnishes and it doesn't give off an odor or remit toxins.
The information in this section is relevant to anyone who might prefer to treat their lumber on their own.
If you are a builder or developer choosing to get pretreated lumber, call Silvaris to consult with the lumber specialists for more information about getting the best deals on your bulk lumber orders.
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