Using Untreated Wood Outside – How Long Does It Last?

Wooden lumber

There is no limit to the amount of different projects that you can use wood for. Woodworkers love to busy themselves with many different kinds of woodworking projects, like fences, decks, and benches, and usually experiment with different woods and materials. One question that comes up a lot from amateur and intermediate woodworkers alike is with regards to using untreated wood outside. More specifically, many wonder how long untreated wood will last outside.

Whether you are working on a project professionally or recreationally, there is no doubt that you wish for your woodworking project to be a success. If you are looking to build a deck, bench, or some other outdoor wooden piece using untreated wood, you will need to plan properly in order to assess the relevant risks.

While generally speaking, untreated wood can be used outside, certain assessments must be made, and steps should be taken to make your untreated wood last longer outside. In this article, we will discuss the risks involved when using untreated wood outside, along with some tips to make your untreated wood last longer. If you are wondering what the best way to use untreated wood outside is, you have certainly come to the right place!

Risks of Using Untreated Wood Outside  

There is no straightforward answer to the question about how long untreated wood will last outdoors. There are so many potential factors, such as type of wood, age of wood, climate and weather, whether it is sealed or painted, and what type of project it is.

When starting a project with untreated wood outdoors, there are multiple risks that need to be assessed before diving in. The outdoor elements can be very harsh on untreated wood, and in this section, we will outline the various risks you will need to look out for.

1. Moisture

As you may know, prolonged exposure to moisture is generally not great for the health of most types of wood. This is especially true of untreated woods as they absorb moisture very easily. If your untreated wood starts to collect moisture, this will most likely cause it to rot and decay.

Moreover, wet conditions make for an ideal fungal breeding ground in the wood, which will certainly damage your wood in irreversible ways. If this doesn’t happen, you can be sure that over time, prolonged exposure to moisture will cause swelling and cracks in your wood.

If you are looking to use untreated wood outside for your next woodworking project, this is something you must keep in mind. The effect of moisture on wood changes dramatically depending on the amount of humidity and rainfall that is experienced where you live.

2. Sunshine

Sunlight is another potential hazard to wood, especially if it is untreated and outdoors. If your wood is exposed to UV-rays from the sun for a long period of time, this will surely deplete the natural oils from your wood, causing it to dry out and begin rotting,

One simple way to protect against the damage to untreated wood caused by UV-rays is to keep your wooden project in a shaded area and minimize exposure to direct sunlight as much as possible. This will ensure that your untreated wood will last longer outside.

3. Temperature Control

It is important for the overall health and longevity of your wood to keep it in a place where the temperature is controlled. Usually, the outdoors is not a place where you can control the temperature, and so using untreated wood outside might mean assessing the general temperature fluctuations in the weather in your area.

In warmer temperatures, you are more likely to experience fungus growth on your untreated wood. This is because fungus tends to thrive in temperatures above 32 degrees Celsius, or 90 degrees Fahrenheit. This is especially true if there is plenty of oxygen and moisture in your environment, as there is in a backyard.

Therefore, if you live in a place that experiences high humidity and average temperatures above 90 degrees Fahrenheit, you may want to reconsider whether or not using untreated wood outside is a good idea.  

How Long Does Untreated Wood Last Outside?

As mentioned in the last section, there is no clear-cut answer to the question of how long untreated wood lasts outside. This is because there are far too many factors to consider, and every type of wood behaves differently depending on the natural environment it is used in.

Keep in mind that untreated wood will eventually become unhealthy and damaged outside. The question here is not whether it will last or not, but for how long. When thinking about how long untreated wood lasts outside, it is important to take the following points into consideration.

  • Is the wood in a shaded or sunny area?
  • What is the geographical location you live in?
  • What are the average and extreme weather conditions that your location experiences? This includes temperature, humidity, sunshine, rainfall, and others.
  • What is the type of wood you are using?
  • Have any sealants or paints been applied to the wood you are using?
  • How much ground contact does the wood in question have for this project?

All the above factors will figure into the longevity of your untreated wood outside. If you are using good quality wood that has been sealed, this may last longer than others but may become damaged due to high levels of sunshine and humidity in your area.

Due to any one of these factors, the health and integrity of your wood could become jeopardized in just a few short years. Even though the wood may remain usable for quite some time afterward, especially after some milling, the project you used them for will certainly not last very long.

Along with these factors, it is also worthwhile to consider what type of project you are using your untreated wood for. A project like a garden bed may be able to take some damage and still remain in use, while a backyard bench or a wooden deck may not. Depending on the project you are working on with untreated wood, the amount of damage that can be sustained before the wood gives up will differ.

Advantages of Using Untreated Wood

You may be thinking by now that since there are so many possible ways for untreated wood used outdoors to become damaged, then why not just stick to using treated wood. While this is definitely an appropriate question to ask, there are numerous advantages to using untreated wood.

Untreated wood can be thought of as wood in its natural form. In fact, unless you are willing and able to chop down your own tree, untreated wood may be the closest thing you will get to wood in its natural form. Many people simply appreciate the organic aesthetic and natural smell that untreated wood gives off and use it in their woodworking projects for this reason.

1. Toxicity Levels

Untreated wood doesn’t just smell good because it is natural, but it smells good when compared to treated wood because it doesn’t contain any of the chemicals that are used to preserve treated wood. Up until the early 2000s, manufacturers used toxic, arsenic-containing compounds with which to treat wood. This made treated wood very unsafe to use without proper protection.

Today, several preservative formulas are used to treat wood that are far less toxic than the arsenic-containing compounds used in the past. However, untreated wood is still far safer to use than treated wood, as when working with treated wood, one must use a dust mask, eye protection, and gloves.

Moreover, for this reason, treated wood should never be used for a project that people will be in close contact with, like a playground. The advantage of untreated wood is that it can be used for any type of project without worrying about the health of the woodworker or those using the project once it is completed.

2. Gardening Projects

Treated wood also contains chemicals that repel insects. Since untreated wood does not have any such chemicals, it can be used in gardening-related projects, like in the construction of a garden bed, without worrying about any damage to your soil.

3. Affordability

Another advantage that comes from all of this is affordability. Ever since cheap methods of treating wood using arsenic-containing compounds were taken off the market, newer treatment methods started using copper, which is more expensive. This has driven the price of treated wood up in the last two decades considerably, and by comparison, untreated wood has remained a much more affordable option.

4. Fewer Health Concerns

The main advantage when it comes to using untreated wood is that you can use it with greater peace of mind. When using untreated wood, you do not have to cover up your skin and eyes out of fear of endangering yourself. While you are advised to use a dust mask to avoid breathing in sawdust, whether you are working with treated or untreated wood, there is no doubt that there are much fewer health concerns when working with untreated wood.

Advantages of Using Treated Wood

Despite the many health-related hazards that are essential to consider, treated wood does come with its advantages. The primary one being the very thing that treated wood was designed for, which is to withstand the natural elements for longer periods of time.

1. Protection From the Elements

Exposure to moisture, sunshine, and high temperatures can break down the fibers of the wood over time if untreated. The treatment process of wood is also known as pressure-treating and involves using pressure to force preservatives into the wood. These preservatives protect the wood from collecting moisture and consequently keep the wood from rotting or becoming subject to fungal decay.

2. Insect Resistant  

Treated wood also has the added advantage of being resistant to many different types of insects. Termites and Carpenter Ants are perhaps one of the biggest causes of damage to wood, as they tend to bore holes into the wood fibers and breed there.

Pressure-treating makes use of chemicals that are toxic to most insects, which gives your wood protection from these pesky little wood-boring creatures.

3. Fire Retardant

During the pressure-treating process, fire retardant agents are also often added to the wood. While this does not make your wood fire-proof, it does mean that it will take longer to catch on fire and will burn much slower.

Wood workshop

What Is the Longest-Lasting Wood for Outside?

When using untreated wood outside, it is important to be aware of the fact that, with time, your wood will certainly become damaged. This is simply due to prolonged exposure to the natural elements. This, however, does not mean that you cannot use untreated woods outside, as proactive thinking can go a long way to make your wood last longer.

Part of this proactive mindset is choosing the right kind of untreated wood based on the project you intend to make and the environment in which you reside. Several species of wood have naturally occurring chemicals that help them resist the natural elements and insects.

Therefore there is no clear-cut winner for the longest-lasting untreated wood for outdoors. Each different species of wood has its own benefits, and lasts for a different amount of time depending on the natural environment and the manner in which you use it. The following are some of the longest-lasting untreated wood species for outdoors.

1. Cedar

Cedar is well-known for its aromatic smell and natural beauty. It has a natural ability to fend itself against insects and natural decay via moisture. It is widely available, and due to its straight grain and dimensional stability, is often used for purposes where brittle wood is ideal. This includes fencing, decking, and trim.

2. Redwood

Redwood is certainly a favorite among outdoor projects due to its unique reddish color. More importantly, Redwood is known for its integrity and its ability to protect itself against the elements through naturally occurring chemicals.

The problem with Redwood lies with availability, as regulations to protect the larger and older Redwood trees have decreased Redwood lumber production.

3. Cypress

Cypress is another popular wood that can be anywhere between yellow to reddish-brown in color. This type of wood is not naturally insect resistant, and while cypress is moderately resistant to decay, it does not come close to the natural preservative properties of Cedar and Redwood.

For this reason, Cypress is best used outdoors in hot and dry climates. Further, this species of wood is very stable and does not split easily, making it useful for a wide variety of applications.

4. Teak

Before steel became widely produced, teak was the go-to wood species for boat-building in many cultures across the world. This is due to the fact that it does not crack under pressure easily and does not turn black when used in conjunction with metal like other species do.

Furthermore, teak has a naturally high oil content, making it resistant to moisture, rot, and decay. It is hence known for its incredible durability and longevity when confronted with natural elements. Teak wood is also naturally resistant to termites and many other types of insects.

However, due to many decades of overharvesting, teak is only available today in limited quantities. Due to this rarity, it is also much more expensive than all the other wood species and hence is not as widely used as they are.

How to Tell the Difference Between Treated and Untreated Wood

For those who do not have much experience working with different types of lumber, it can be a little difficult to be able to tell the difference between treated and untreated wood. The first thing you can do is to ask your wood supplier.

However, if you want or need to be able to tell the difference on your own, there are a few ways you can do this. For one thing, many treated kinds of wood have a seal or marking on them that verifies that they are treated. If not, pressure-treating tends to leave a slight greenish tint to the wood. If your wood has a subtle green tint to it, this probably means that it has been pressure-treated.

The final thing you can do to tell the difference between treated and untreated wood is to smell it. Untreated wood will have a very natural scent to it and will smell like the outdoors. Conversely, untreated wood will have a more chemical and manufactured odor to it.

How Do You Seal Untreated Wood?

If you are using untreated wood outside, one thing you can do to help it last longer is to seal it. Sealing is a common way to bring some life back into the wood while maintaining its natural beauty and increasing its longevity.

Before deciding on whether or not you want to seal untreated wood, you should carefully check whether or not your wood is experiencing some decay or rot. If it is, you may not be able to save it by much through sealing. However, if everything checks out, you can be sure that sealing will do wonders to benefit your wood’s health.

Step 1

The first step to sealing is to clean the wood and make sure it is completely dry. The last thing you want is for dirt, grime, dust, or moisture to get trapped inside the sealed wood. By using air dry, you can ensure that you eliminate all moisture from your wood. Air drying will take between 48 and 72 hours to fully dry your wood.

Step 2

For the sealant itself, there are many different products you can choose from, and woodworkers generally don’t agree on which one is the best. The most common types of sealant are lacquer, shellac, polyurethane, and varnish, and each provides its own unique benefits depending on the species of wood you are using.

Step 3

Using a regular paintbrush, you can add a single coat of sealant on the surface of your wood, after which you should leave it to dry again. Once completely dry, add a second layer and leave it to dry for the last time. Make sure to only add a thin layer each time and to wear gloves.

Once the wood has dried for the final time, you will see how sealant adds aesthetic beauty to your untreated wood. Alongside this, your untreated wood will be sure to stand up to the natural elements for longer once sealed.

Tips to Increase Longevity of Untreated Wood

If you are dead-set on using untreated wood outside for your woodworking project, that’s all well and good. However, you will need to make sure you take proactive measures to keep your wood healthy and protected so as to increase its longevity.

1. Keep Your Wood Dry

Keeping your wood dry during the most humid months of the year can have a huge positive impact on your wood’s health. This can be achieved by using a large outdoor fan or by cleaning your wood with a dry cloth regularly.

In this way, you will protect your wood from excess moisture, which, if allowed to accumulate inside the wood, can lead to microorganisms and fungus eating away at your precious project.

2. Water-Proofing Wood

Another step you can take to increase the longevity of untreated wood is to water-proof it. There are three simple methods by which you can water-proof your wood and hence protect it from moisture, rot, swelling, and decay. Applying a coat of linseed or Tung oil is one popular way of water-proofing your wood and creates a beautiful finish as an added bonus.

Most types of lacquer, varnish, and polyurethane are also water-proofing agents as well as being protective sealants. Finally, a stain-sealant combination is a great way to water-proof wood as well, and such products can easily be found at any hardware store.

Summing Up

When taking on an outdoor woodworking project, the choice to use untreated wood over treated wood is entirely yours to make. When using untreated wood outside, it is essential to understand that it will not last as long as treated wood due to prolonged exposure to the natural elements.

However, by evaluating the task at hand, committing to regular care, and carefully considering factors such as species of wood and environmental conditions, you can make sure to get the most out of your untreated wood before it eventually gives up.

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