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how treated wood is made

by Prof. Dayna Morar II Published 1 year ago Updated 2 months ago

How Is Pressure Treated Wood Made?

  1. Right Thickness of the wood Before starting this process, we make several bundles of timber. The thickness should not be too much. ...
  2. Making pressure in cylinder with chemicals The bundle of wood is inserted into a long cylinder whose length varies from 80 feet to 220 feet. ...
  3. Open the cylinder and remove the wood

Full Answer

How is pressure treated wood made?

What follows is a discussion of pressure treated wood and its different uses. To make pressure treated wood, lumber is first placed in a pressure chamber comprised of a horizontal steel cylinder (called a “retort”) that resembles a rail car.

What is treated wood and how is it used?

What Is Treated Wood? Treated wood is wood that has been appropriately treated with preservative chemicals with the intent of prolonging its intended usefulness lifecycle compared to untreated wood. Different types of applications and preservatives are used to protect wood fibers from:

What is the difference between treated and untreated wood?

Treated wood is wood that has been appropriately treated with preservative chemicals with the intent of prolonging its intended usefulness lifecycle compared to untreated wood. Different types of applications and preservatives are used to protect wood fibers from:

What chemicals are used to inject into wood?

The process involved forcing a solution of water and chemicals into the wood at very high pressure. The three most common chemicals that are injected into the wood are: copper azole, alkaline copper quaternary or micronized copper azole.


What Is Pressure Treated Wood?

Pressure treated wood is a kind of lumber that is processed by applying a vacuum which serves to inject preservatives as well as fire retardants into the wood. By nature, wood is a material that can degrade and decompose.

How Is Wood Pressure Treated?

Pressure treatment of wood involves several steps. Firstly, the treatment facility orders wood from suppliers. The common types of wood that can be pressure treated include Douglas Fir, Southern Yellow Pine and Western Red Cedar. When the wood arrives at the treatment plant, it is checked for moisture.

The Chemicals Used in Pressure Treatment of Wood

There are a number of chemicals that are used in the treatment of wood. Most of these elements are EPA approved and listed on their website. The most common chemicals belong to a class called isothiazolinones.

Reasons to Pressure Treat Wood

There are many reasons to pressure-treat wood. The highest on the list is to increase its capacity to resist decay due to natural elements. Wood is a beautiful material for construction and is used both on the interior and the exterior of the home.

Benefits of Pressure Treated Wood

Before we dive into the advantages that come with pressure treated wood, it is important to note that not all wood acquires the same capabilities after the process. That being said, the biggest benefit of treating lumber with pressure is to increase its resistance against moisture and fungus.

Disadvantages of Pressure Treated Wood

Pressure treated wood has numerous benefits in terms of durability and life but there are an equal amount of drawbacks to it as well. First and foremost, the chemicals that are used in the treatment, despite being EPA approved, are not suitable for indoor use.

Where Can Pressure Treated Wood Be Used?

The application and use of pressure treated wood is mostly outdoors. The properties that the material obtains including fire, insect and moisture resistance are more relevant on the exterior of homes. Contractors and homeowners frequently use this type of wood for siding, roofing, garden docks and a variety of other purposes.

How is pressure treated lumber made?

To make pressure treated wood, lumber is first placed in a pressure chamber comprised of a horizontal steel cylinder (called a “retort”) that resembles a rail car. Once the lumber is properly secured in the retort, a vacuum removes the air from the cylinder and from the cell structure of the lumber. The retort is then flooded with treatment ...

What is pressure treated wood?

Pressure treated wood is wood that has undergone a special process to make it more durable and less susceptible to decay, insect infestation, mold, and water damage. Some pressure treatments can even make the wood fire retardant. There are different types of pressure treated wood, all of which are useful for a variety ...

What is CCA treated wood used for?

For general residential indoor and outdoor use, wood treated with water-borne preservatives such as CCA treated wood is ideal. It is used in decks, fences, docks, and building structures.

What is CA treated lumber?

Copper Azole (CA) Treated Lumber is pressure-treated with copper-based preservative that provides long-lasting resistance to decay, rot, and termites.

How far should pressure treated wood be from the ground?

For above-ground projects, the wood should be at least six inches from the ground and can only be used when the wood has proper ventilation and drainage.

How much pressure is used to dry lumber?

Using 160 pounds of pressure, the treatment chemicals are driven into the cell structure of the lumber. Once the pressure treatment is complete, the lumber is moved to a drip pad until it cures and dries enough to be shipped to a supplier. The amount of time it takes to dry depends on the climate and exposure to sunlight.

What is creosote preservative used for?

Wood treated with creosote preservatives is used in heavy construction of bridges, guardrails, and docks. Oil-based preservatives are used to treat lumber for use in utility poles, crossarms, and indoor pools.

What is the process of treating wood?

The treating process utilize s pressure that forces the preservatives into the wood fiber. While there are a variety of preservatives used today, the manufacturing process is virtually the same for all.

What is preserved wood?

Preserved wood manufacturers start the process by purchasing kiln-dried lumber from sawmills or specifically selected round poles from forest companies . To meet national standards for use in applications where the wood will be in contact with the ground, Western species such as Douglas fir and Hem-Fir must be incised on all four sides prior to treating. Incising consists of making small incisions in the wood to allow proper penetration and retention of the preservative. See the publication PreserveTech - Incising for more information.

What is treated wood?

Treated wood is wood that has been appropriately treated with preservative chemicals with the intent of prolonging its intended usefulness lifecycle compared to untreated wood.

What is pressure treated wood?

Pressure Treatment (PT) is the general term to describe the process for infusing/impregnating the wood fibers with preservative chemicals and removing any excesses, leaving behind only enough chemical in the wood fibers (retention) to protect the wood.

Why is treated wood better than untreated wood?

Advantages of Treated Wood. Because treated wood is intended to extend the usefulness and life of wood, fewer trees are required to perform the same function that is required when untreated wood is used. Wood that has been appropriately treated can significantly reduce the number of trees that would otherwise need to be harvested.

How long does treated wood last?

If untreated wood only lasts 5 years and treated wood lasts 25 years or more, it would take at least 5 times as many trees over the same period of time, as well as the incremental labor, to continually harvest, ...

How long does it take for untreated wood to rot?

Unprotected wood can begin to rot within 1-2 years depending on the environment. The structural integrity of untreated wood can be greatly reduced within weeks due to termites and certain marine organisms. Without chemical treatments, wood can be quickly consumed when exposed to flames.

Does paint protect wood from insects?

Although regularly coating a surface with a paint or sealer may help protect wood from the elements, it won’t necessarily prevent it from rotting or being attacked by insects.

Is wood preservative regulated by the EPA?

marine organisms. flames. All chemical preservatives are registered pesticides and, as such, they are regulated by the US EPA. The American Wood Protection Association (AWPA) writes various standards that determine use levels for wood preservative formulations as well as their suitability for the intended end-use.

What is treated wood?

Wood used for construction, telephone poles, railroad ties, and garden beds may be treated with pesticides to prevent rotting. Wood treatments are not meant to be water resistant. These products are used to extend the life of wood by limiting damage from insects and mold. Treating wood also reduces the waste of forest resources by delaying the need for replacement due to decay.

What are the different types of treated wood?

The two main groups of treated wood are water-based and oil-based. Water-based preservatives are applied to wood with a water solution. Oil-based products are applied to wood in an oil-based solution. Surfaces of oil-based treated wood may not be paintable and odors may be stronger. 1 Manufacturing methods for treating wood include pressure treatment, dipping, or soaking. Some paint-on products are also available. 2 Each type of wood preservative has a different mixture of ingredients. Only a few wood preservatives are discussed in this fact sheet.

What precautions can I take when using treated wood?

Risks related to treated wood depend on the use site and type of treated wood. Using the correct type of treated wood for your project may help keep the risks low. Whether wood is used in a garden bed or another structure, keep these tips in mind:

Can treated wood be used in garden beds?

Certain types of treated wood may be used in backyard projects. Compounds like chromated copper arsenate (CCA), creosote, and pentachlorophenol are not registered to treat wood for consumers, including use in garden beds. 14,15,18 The risks of using recycled wood treated with CCA, creosote, and pentachlorophenol have not been evaluated by the EPA. However, it is expected that the amount of leaching from used wood is less than from freshly treated wood. 8,14,15

Can plants take up ingredients from treated wood?

If compounds leach from treated wood, they may be available for uptake by garden plants. However, it is difficult to predict the amount of plant uptake. Materials used in treated wood that leach into soil may be bound to soil. They also may change into different forms that plants cannot take in through their roots. Information about plant uptake is limited.

How do I dispose of treated wood?

Treated wood that has not been fully weathered (new boards or poles) may be considered hazardous waste. If treated wood is not considered to be hazardous waste, it may be disposed of at a landfill or through municipal trash collection. Contact a hazardous waste program in your state for specific regulations about treated wood.

Can certified organic farms use treated wood?

Only specific pesticides defined by the U.S. Department of Agriculture (USDA) may be used to produce organic foods. Lumber that contacts food, animals, or soil may only be treated with substances on the National List of Allowed and Prohibited Substances. Certain ingredients, such as arsenic, are not allowed for use in organic systems. Different rules may apply if treated wood will not contact soil, animals, or food. Consider contacting a certifying agent for details on how to comply.

What chemicals are used to treat wood?

The three most common chemicals that are injected into the wood are: copper azole, alkaline copper quaternary or micronized copper azole. As the water from the treatment dries out, the chemicals stay behind and help preserve the wood and significantly increase the life of the wood.

How to get water out of pressure treated wood?

Get a spray bottle and spray a small amount of water onto a piece of pressure treat wood. If you don’t have a spray bottle, you can also just get some water on your finger tips and flick it onto the board. If the wood soaks the water up – it’s dry enough to stain or paint.

Why is it called checking wood?

In the lumber industry, when wood dries too quickly and cracks form, the result is called “checking.” Checking is very common with pressure treated wood due to how wet it is when purchased due to water and chemicals being pressed into the wood.

Why is pressure treated wood wet?

Pressure treated wood is often very wet when you buy it from the store. This is due to the chemicals that have been applied to the lumber to increase it’s durability. Before you can apply any stains or paint to the wood, it’s important that you ensure it has dried sufficiently.

How to avoid checking pressure treated lumber?

The only way to avoid checking is to dry your lumber slowly and evenly. The best way to avoid checking is to store your pressure treated wood in a garage or somewhere away from the outdoor elements and give it several months to dry out on it’s own. When stacking the wood indoors, it’s very important to space the wood and not lay it directly upon other boards to ensure the wood dries evenly. A piece of scrap wood can easily serve as a wood spacer.

What is the phone number to call for pressure treated wood?

If you are concerned about exposure to any of the chemicals, please call the National Poison Hotline at 1-800-222-1222.

Why is wood susceptible to moisture?

Wood, no matter the type, is most susceptible to damage when the ends are expose to moisture. The ends are where wood absorbs the most amount of water and liquids. This is easy to see when staining a piece of wood. As you apply stain to the ends, it gets soaked into the wood much quicker than on the sides.

What is treated wood?

In a process or treatment, the properties of wood, timber, wood structures, or engineered wood are enhanced by preservative chemicals, such wood is called treated wood. There are many types of these treatments. Each treatment has several processes that are dependent on each other. Treated wood is more durable than other common wood.

How Is Pressure Treated Wood Made?

Before starting this process, we make several bundles of timber. The thickness should not be too much. Due to the high thickness of the wood, the chemicals do not reach inside the wood properly. Therefore it is very important to have the right thickness of the wood.

What chemicals are used to treat wood?

One of the famous chemicals uses for pressure-treated wood is Chromated copper arsenate ( CCA) . In this treatment, copper is the primary fungicide, is a pesticide, and also provides ultraviolet (UV) light resistance.

Why is treated wood more durable than other woods?

This process is known as timber treatment, lumber treatment, or pressure treatment. Because this wood is preserved by chemicals to prevent rot and insects. After this process takes place, the life of the wood increases manifold.

How long does it take for wood to dry?

Even after the drop of chemical drops, there is a lot of moisture in the wood. It takes about 48 hours (4 days) to dry such wood during the summer season. While it takes one to two weeks to dry completely in the winter.

How many types of pressure treated wood are there?

There are mainly two types of Pressure Treated Wood.

How to get chemical drops out of wood?

Open the cylinder and remove the wood. Chemical drops keep falling from the wood. The wood is taken out of the cylinder after completing the pressure treatment process. Chemical drops keep falling from the wood. And do not move the wood from its place until the chemical drops stop falling. Even after the drop of chemical drops, there is a lot ...

How to tell if a wood is treated or non-treated?

Non-treated wood will have a pleasant, fresh, and natural smell. Treated woods will have traces of oil or chemical smell.

How to Tell if Wood is Treated Or Not?

After getting some background info on the different types of treated wood, you should finally be able to tell if the lumber you have is treated or if its untreated. That being said, just try to take notice of the following things:

What is CCA wood?

You might be familiar with Chromated Copper Arsenate or CCA Wood. This is wood that has featured with a chromatid copper arsenate preservative, and originally started being used by the mid 1930’s. One huge giveaway of this wood is it’s greenish tint that it usually has.

What does the stamp on wood with arsenic mean?

Wood treated with arsenic has a stamp that reads “L P22” indicating it was treated using arsenic. Arsenic is one of the safe varieties for wood treatment. Wood with a stamp that reads “L P2” should never be used for home furniture or playset for kids. It’s not that toxic, however, it’s better to be safe.

What is the safest wood to use for flooring?

If you want to know the safest treated wood, look for wood that has a stamp that reads “FDN” meaning foundation. This wood is generally used as the base underneath home floorings. Another safe treated wood is one treated with borate. Look for a stamp that reads “Bor”, “Hi Bor”, and or “Tim Bor”.

What does a stamped seal on wood do?

Look for Stamps: Many times if wood is treated for construction, then they might have stamped it with a seal to notify you of what it was treated with. Generally this will be on one end of the lumber, but it might not be on every piece.

What is softwood wood?

All softwoods are pressure-treated wood. Most of them come from coniferous trees like Douglas fir, yellow pine, white pine, and spruce.

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