How To Treat Untreated Wood For Outdoor Use

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When spring rolls around, and we begin thinking about outdoor projects  – gardens, fences, wooden furniture, decks, patios, pergolas – we woodworkers have a variety of projects to choose from.  The new wooden deck I built behind my house, surrounded by a meditation garden, was built with pressure-treated wood, ground contact rated.

I expect to get 20 years from it, although I did use a deck stain and sealant to preserve it that might extend to 25 years.  That’s longer than I expect to be alive, so all is good.

Key Points:

  • There are many safe and eco-friendly treatments for untreated lumber used in outdoor projects.
  • Wood sealants and oil finishes can protect untreated woods from the elements and prevent rot and decay from water (rain, snow, etc.) and UV damage. 
  • While some woods are naturally rot and decay resistant, they still should be treated in some way to extend their lifespan outdoors.

But, pressure-treated wood does have its drawbacks, and many consider there to be more eco-friendly options to choose from for outdoor projects. The advantage of pressure treatment is that you really don’t have to worry as much about sealing it as you would with untreated woods.

So the question then becomes whether there are exterior woods that work well without treatment and don’t carry with them environmental concerns.

Is Pressure-Treated Wood Environmentally Safe?

Pressure Treated Wood

Pressure-treated wood is wood that has been treated with chemicals to make it more resistant to rot, decay, and insects. The chemicals used to treat pressure-treated wood can be harmful to the environment if they are not properly disposed of.

The most common chemicals used to treat pressure-treated wood are chromate copper arsenate (CCA), alkaline copper quat (ACQ), and copper azole (CA). CCA was the most common type of pressure-treated wood until it was banned in the United States in 2003 due to concerns about its health and environmental risks.

ACQ and CA are the two most common types of pressure-treated wood used today.

The chemicals used to treat pressure-treated wood can leach into the soil and water, and they can also be released into the air when the wood is burned. These chemicals can harm plants, animals, and people. They can also contaminate drinking water and cause other environmental problems.

If you are considering using pressure-treated wood, it is important to weigh the risks and benefits. Pressure-treated wood can provide a long-lasting and durable material for outdoor projects, but it is important to use it safely and dispose of it properly.

Here are some tips for using pressure-treated wood safely:

  • Choose the right type of pressure-treated wood. CCA-treated wood is no longer available in the United States, so you should choose ACQ or CA-treated wood.
  • Use the wood in a well-ventilated area. When you are cutting, drilling, or sanding pressure-treated wood, it is important to use a mask to protect yourself from the dust.
  • Dispose of the wood properly. If you are no longer using pressure-treated wood, it is important to dispose of it properly. You can take it to a hazardous waste disposal facility, or you can burn it in a well-ventilated area.

What Causes Wood To Rot Or Decay?

So maybe that is enough to dissuade you from considering pressure-treated woods for outdoor use, and we need to look for other types of wood for our deck or outdoor furniture.  There is that sticky issue of rot and decay to deal with, though.

There are many factors that can cause wood to rot or decay, including:

  • Moisture: Wood needs to be kept dry in order to prevent rot and decay. If wood is exposed to moisture for an extended period of time, it will eventually start to rot.
  • Fungi: Fungi are the most common cause of wood rot and decay. There are many different types of fungi that can attack wood, and they can cause a variety of different types of rot.
  • Insects: Insects can also cause wood to rot and decay. Insects such as termites and carpenter ants can bore into wood and weaken it, making it more susceptible to rot.
  • Temperature: Extreme temperatures can also cause wood to rot and decay. Wood that is exposed to very hot or very cold temperatures can become brittle and weak, making it more susceptible to rot.
  • Sunlight: Sunlight can also cause wood to rot and decay. The ultraviolet rays in sunlight can break down the cellulose in wood, making it more susceptible to rot, so we need UV protection to be considered when selecting outdoor woods.

There are a number of things that can be done to prevent wood from rotting or decaying, including:

  • Keeping wood dry: This is the most important thing that can be done to prevent wood from rotting or decaying. Wood should be kept dry by using a water-repellent finish, such as paint or varnish.
  • Treating wood with a preservative: There are a number of different wood preservatives available that can help to protect wood from rot and decay. Wood preservatives can be applied to wood in a variety of different ways, including by brushing, spraying, or dipping.
  • Installing drainage: If wood is located in an area that is prone to moisture, such as near a pool or spa, it is important to install drainage to help keep the wood dry.
  • Inspecting wood regularly: It is important to inspect wood regularly for signs of rot or decay. If any rot or decay is found, it should be repaired immediately to prevent the problem from getting worse.

How Long Will An Untreated Wood Last in Outdoor Use?

The lifespan of untreated wood outdoors can vary depending on a number of factors, including the type of wood, the climate, and the exposure to the elements. In general, untreated wood can last anywhere from a few months to a few years outdoors.

  • Softwoods, such as pine and fir, are less durable than hardwoods, such as oak and maple. Softwoods are more likely to rot and decay when exposed to the elements.
  • Wood that is exposed to moisture and sunlight will deteriorate more quickly than wood that is protected from the elements.
  • Wood that is in contact with the ground will deteriorate more quickly than wood that is not in contact with the ground.

To extend the lifespan of untreated wood outdoors, it is important to protect it from the elements. This can be done by painting or staining the wood with a water-repellent finish. It is also important to inspect the wood regularly for signs of rot or decay and to repair any damage as soon as possible.

Here are some tips for extending the lifespan of untreated wood outdoors:

  • Choose the right type of wood. Hardwoods are more durable than softwoods and will last longer outdoors.
  • Protect the wood from the elements. Paint or stain the wood with a water-repellent finish.
  • Keep the wood dry. If the wood is in contact with the ground, raise it off the ground on blocks or bricks.
  • Inspect the wood regularly. Look for signs of rot or decay and repair any damage as soon as possible.

What Are The Best Untreated Woods For Outdoor Use?

Cypress Wood

Here are 5 of the best untreated woods for outdoor use:

  • Cedar is a naturally rot-resistant wood that is also insect-resistant. It is a good choice for outdoor furniture, decks, and other structures.
  • Redwood is another naturally rot-resistant wood that is also known for its durability. It is a good choice for outdoor furniture, decks, and other structures that will be exposed to the elements.
  • Cypress is a good choice for outdoor use because it is naturally resistant to rot and decay. It is also a good choice for use in wet areas, such as near pools or spas.
  • Ipe is a tropical hardwood that is known for its strength and durability. It is a good choice for outdoor furniture, decks, and other structures that will need to withstand a lot of wear and tear.
  • Mahogany is a tropical hardwood that is known for its beauty and durability. It is a good choice for outdoor furniture, decks, and other structures that will need to look good for years to come.

It is important to note that even these naturally rot-resistant woods will eventually need to be refinished or replaced if they are exposed to the elements for an extended period of time.

Are Hardwoods Better Than Softwoods For Outdoor Use?

Teak Wood

Hardwoods are generally better for outdoor use than softwoods. Hardwoods are denser and have a higher natural resistance to rot and decay than softwoods. They are also more durable and can withstand more wear and tear.

Here are some of the most popular hardwoods for outdoor use:

  • Oak: Oak is a strong and durable hardwood that is naturally resistant to rot and decay. It is a good choice for decks, fences, and other outdoor structures.
  • Maple: Maple is a beautiful and durable hardwood that is naturally resistant to rot and decay. It is a good choice for furniture, decks, and other outdoor projects.
  • Teak: Teak is a tropical hardwood that is naturally resistant to rot, decay, and insects. It is a good choice for decks, furniture, and other outdoor projects that will be exposed to the elements.

Generally speaking, softwoods are not a good choice for outdoor use.  They are more susceptible to the elements and will not last long without treatment.

Even with treatment, they are not going to last as long as one of these hardwoods.  Cedar is an exception, though, to this general application in that it is naturally resistant to rot and decay.  As mentioned earlier, it is a good choice for decks, fences, and other outdoor structures that will be exposed to the elements.

How Should You Treat Untreated Wood For Outdoor Use?

You’ve decided on wooden furniture for your outdoor project and are considering which exterior wood will work best for it.  You’ve eliminated pressure treatment and simply want an outdoor wood that will give you more than just a couple of years. 

As we noted earlier, even naturally rot-resistant woods will eventually need to be refinished or replaced if they are exposed to the elements for an extended period of time.  Since that’s the case, let’s just treat them from the start.  But, how?

There are a few different ways to treat untreated wood for outdoor use. The best method for you will depend on the type of wood you are using, the climate you live in, and your budget.

Wood Sealer

A wood sealer is a clear liquid that helps to protect wood from the elements. It does this by creating a barrier that prevents water and moisture from penetrating the wood. Wood sealers are available in a variety of different finishes, so you can choose one that will match the look of your outdoor project.

Varnish

Varnish is a clear, hard finish that provides a more durable protection for wood than a wood sealer. Varnish is also available in a variety of different finishes, so you can choose one that will match the look of your outdoor project.

Finishing Oil

Finishing oil is a natural product that is made from vegetable oils, such as linseed oil or tung oil. Finishing oils provide a water-resistant finish that helps to protect wood from the elements. They also give wood a natural, warm look.

Pressure-Treated Wood

Pressure-treated wood is wood that has been treated with chemicals to make it more resistant to rot, decay, and insects. Pressure-treated wood is a good option for outdoor projects that will be exposed to the elements.

Yes, we know we sort of ruled this out at the beginning, but there are some good qualities in pressure-treated for an outdoor wood project, and more environmentally-aware companies are using safer chemicals in their pressure treatment process.

No matter which method you choose, it is important to follow the instructions on the product label carefully. This will ensure that you apply the treatment correctly and that it will provide the best possible protection for your wood.

Here are some additional tips for treating untreated wood for outdoor use:

  • Choose the right wood. Some woods are more naturally resistant to the elements than others. If you live in a wet climate, choose a wood that is naturally rot-resistant, such as cedar or redwood.
  • Prepare the wood. Before you apply any treatment, the wood should be clean and dry. If the wood is dirty, you can clean it with a mild soap and water solution. If the wood is wet, you should let it dry completely before you apply the treatment.
  • Apply the treatment evenly. Make sure to apply the treatment evenly to all sides of the wood. If you are using a clear finish, you may want to apply two coats for better protection.
  • Reapply the treatment as needed. The frequency with which you need to reapply the treatment will depend on the type of treatment you use and the climate you live in. In general, you should reapply the treatment every few years.

What Are Some Good Good Wood Sealants For Outdoor Use?

 Sealing your outdoor wood is crucial to a long life.  We already know the elements your wood needs protection from – rain, snow, sun, and UV protection – and a sealant must be able to offer that protection and not just provide some color.

Here are some good outdoor wood sealers:

  • Thompson’s Water Seal is a clear, water-based wood sealer that provides excellent water resistance and UV protection. It is easy to apply and dries quickly.
  • SEAL-ONCE is a penetrating wood sealer that helps to protect wood from water, dirt, and fading. It is available in a variety of finishes, including clear, semi-transparent, and opaque.
  • Rain Guard is a water-based wood sealer that provides excellent water resistance and UV protection. It is also resistant to mildew and fungus.
  • Defy is a clear, water-based wood sealer that provides excellent water resistance and UV protection. It is also low-odor and non-toxic.
  • Olympic Maximum is a clear, water-based wood sealer that provides excellent water resistance and UV protection. It is also mildew-resistant and easy to apply.
Thompson’s WaterSeal Multi-Surface Waterproofer Stain, Clear, 1 Gallon
  • WATERPROOFING STAIN – Bring out the beauty of your outdoors with Thompson’s WaterSeal Clear…
  • CLEAR STAIN – This outdoor wood stain and sealer provides a clear finish. It will hide the grain,…
  • FADE RESISTANT FINISH – The advanced polymers in this outdoor wood and deck stain deliver…
Seal-Once Nano+Poly Penetrating Wood Sealer with Polyurethane – Premium…
  • WATER-BASED POLYURETHANE WOOD FINISH: Our sealant provides top-notch protection against wear and…
  • WOOD SEALANT: Unlike many sealers that only form a topcoat, our protector penetrates below the…
  • FLOOR SEALER APPLICATOR: Our premium gloss is ultra-low VOC and great for enhancing the extended…

Each of these wood sealants will offer good protection against the elements and help your wooden deck or wooden furniture weather them (pun intended).  When choosing a wood sealant, it is important to consider the type of wood you are sealing, the climate you live in, and your budget.

Are Wood Oils A Good Treatment For Outdoor Use?

We don’t mean to ignore wood oils as another wood treatment for outdoor projects.  An oil finish can also be a good choice.  They help to protect wood from the elements, such as water, sun, and insects. Wood oils also help to enhance the natural beauty of wood.

There are many different types of wood oils available, so it is important to choose one that is right for the type of wood you are using and the climate you live in. Some of the most popular wood oils for outdoor use include:

  • Teak oil: Teak oil is a good choice, even though it has nothing to do with the teak tree.  It is a blend of linseed oil, tung oil (which does come from the tung tree), mineral spirits, and varnish.   It is a good choice for outdoor use because it is water-resistant and UV-protective.
  • Linseed oil: Linseed oil is a natural oil that is made from flaxseed. It is a good choice for outdoor use because it is a drying oil, which means that it hardens over time and provides a durable finish.
  • Tung oil: Tung oil is a natural oil that is made from the nuts of the tung tree. It is a good choice for outdoor use because it is very water-resistant and provides a durable finish.

When applying wood oil, it is important to follow the instructions on the product label carefully. Wood oil should be applied in a thin coat and allowed to dry completely before applying a second coat. Wood oil should be reapplied every few years, depending on the type of wood and the climate.

A Video With Further Information

Maybe you thought we’d forgotten about exterior paint and stain as a suitable treatment for outdoor wood, but if you did, you’d be wrong.  We found a video that discusses these options and demos what they would look like on your outdoor wooden furniture.  

Spring is the time of year for outdoor projects for both gardeners and woodworkers.  You don’t have to use pressure-treated, and some woods don’t necessarily need treatment (cedar, for instance), although we do recommend treating all woods for outdoor projects regardless.

We’re going out now to sit on our pine Adirondack chairs treated with an outdoor wood sealer and enjoy the sunny day.

Last update on 2024-02-27 / Affiliate links / Images from Amazon Product Advertising API

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