How Long Does Untreated Wood Last Outside? Here’s The Truth!

While there are several benefits to using treated timber, it is not suitable for all applications. While it may be due to personal preference or one of many other factors, untreated wood can also be used outdoors with some success. 

The longevity of untreated timber used outdoors depends on many factors, including the type of wood, the region’s climate, and the degree of sun exposure to which the wood is subjected. Untreated timber will last between a few months and two years if no other measures are taken.

Some types of timber will last for years left outside without any treatment or coating to protect them. Other timbers will rot within a few months if left exposed to the elements. There are several measures you can put in place to ensure the longevity of your untreated timber, but always bear in mind the local climate and type of wood.

How Long Does Untreated Wood Last Outside? 

Without any protective coating such as paint or sealant, it is unlikely that untreated wood left outdoors will last any longer than two years.

How Long Does Untreated Wood Last Outside? Here's The Truth!

There is no hard and fast rule for how long untreated wood will last outdoors. The longevity of untreated wood outdoors depends on the type of wood and how much exposure it has to climatic elements such as sun, rain, heat, and humidity.

Other than the abovementioned factors, several major influences also significantly affect the life expectancy of untreated wood outdoors. How the grain has been cut will have a significant effect. 

The water content of the wood itself also has a significant impact on its longevity. Similarly, the presence and prevalence of bacteria and fungus will affect the life span of the wood used for your outdoor projects. 

Exposure to insects and rodents will significantly impact the longevity of your timber. The same can be said for how much contact the wood has with the ground underneath it, as damp earth can cause the wood to deteriorate more quickly. 

General contact with water will naturally play a significant role in the lifespan of the wood used outdoors. To ensure the timber’s longevity, limit its potential contact with water.

Certain types of timber are better able to sustain long periods left untreated. These timber types include cedar, redwood, cypress, and white oak.

Certain types of timber are simply unable to survive very long in the great outdoors without treatment. These include Alder, Hemlock, and Pine.

Main Causes Of Issues With Untreated Wood Outdoors

One of the leading causes of damage to outdoor timber is the sun. The ultraviolet rays from the sun quickly deplete the natural oils in the wood, ultimately causing it to become dry, disfigured, and discolored. 

Humidity, rain, and snow, essentially any moisture, will cause havoc with untreated timber. This is because wood is porous in nature and absorbs water when exposed to it. This causes expansion of the wood and then shrinkage when it dries out.

Moisture also leads to the growth of mold and fungi on timber that will cause further damage in the long term. Drastic temperature changes in the environment will also cause the expansion and shrinkage of wood by altering its moisture content. This will ultimately cause significant damage.

Sealing Untreated Wood

The best way to improve the life expectancy of your untreated timber is to seal it using a specially-formulated wood sealant. 

Bear in mind that your timber type is also affected by this, as some types of wood react differently to different sealant types. Some sealants are not as effective as others in protecting the timber. 

It’s important to remember that using a sealant does not render your wood invincible. Even properly sealed timber is prone to damage as the sealant wears off. This is why the sealant should be re-applied every one or two years. 

Harsh outdoor environmental conditions tend to break down the sealants. By resealing the wood, you reinforce the protection afforded by the sealant. This is particularly applicable to the UV protection afforded by the sealants.

The first step in protecting your untreated wood is to check for any rot or mold. If there is none, you can proceed to the next stage – drying the wood.

You will first need to wash the wood using a wet towel before soaking up as much of the water as possible using a dry towel. Next, let the wood dry out naturally in the fresh air, ensuring that it is adequately protected from inclement weather and that there is sufficient air circulation.

Do not use artificial means of drying the wood, such as air conditioners, fans, or heaters. A natural, slow drying process is optimal for timber. This will generally happen over three days.

Once the wood is appropriately dry, apply a single coat of wood sealant over its surface. This can be achieved using a paintbrush. Before applying the second coat of sealant, ensure that the first coat is completely dry. 

Once the second coat of sealant is sufficiently dry, your timber should be adequately protected for it to be used outdoors.

How To Use Untreated Wood Outdoors

To protect your untreated timber outdoors, there are several interventions you can attempt. Firstly, you should always ensure that the timber is kept dry as much as possible. 

Ensuring that the timber is not exposed to the sun to a large degree will also help protect it from long-term damage. Simply keeping the wood in shaded areas with no direct exposure to the sun will make a significant difference.

To avoid unnecessary exposure to the elements, bring your outdoor furniture indoors whenever it’s not in use. This will go a long way in ensuring its longevity.

When selecting outdoor furniture, always ensure that the tree species can resist inclement weather conditions as best as possible.


There is no definite period for which a piece of untreated timber will last outdoors. The lifespan of any wood is dependent on several factors that have a significant impact on its longevity. The type of timber plays a substantial role in its life span and exposure to the elements such as the sun, wind, and moisture. 


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