Can You Use Non Pressure Treated Wood Outside?

September 18, 2022

Have you ever wondered what will happen to non-pressure treated wood if you leave them to the harsh elements of the outdoors? I guess you will say that they would not last for several years without exhibiting cracks and checking on their surface. Yet, the answer to this question is not as easy as it seems to be. First, it requires a clear understanding of the difference between pressure-treated and non-pressure-treated lumber. 

Moreover, it necessitates an understanding of the different elements that may compromise the integrity of wood outdoors. Plus, you need to be cognizant of the essential factors to consider when using pressure treated and non-pressure-treated wood. So, allow me, in this post, to distinguish between non-pressure and pressure-treated wood.

The Difference Between Non-pressure and Pressure Treated Wood

Wood manufacturers create pressure-treated wood by soaking the wood into a mixture of chemicals. This mixture includes metallics as well as other toxic elements. Afterward, the wood is subjected to enormous pressure in a pressure chamber to make the chemicals seep into the very wood fiber. This process preserves and protects the lumber against many factors like insect attack, fungal decay, and lumber resistance to moisture intrusion. 

For this reason, pressure-treated lumber will perform better than non-pressure-treated ones. Nevertheless, its use comes with many downsides like discoloration and toxic chemicals whose particles may scatter or spread out when you cut the wood. 

Non-pressure treated lumber, on the other hand, is an excellent alternative to pressure-treated ones, and you can use it for some applications like decorative trim or posts. The non-pressure treated one is topically treated instead of forcing chemicals onto the wood. You can use this wood in areas that don’t have contact with the ground. The topical preservative may prevent problems related to the effects of moisture and insect activities.

Outdoor Elements that Weaken (Non-pressure) Treated Wood

Some factors and elements may threaten the integrity of non-pressure treated lumber. So, if you intend to utilize non-pressure treated lumber outdoor for your deck and other applications, it will be best to be cognizant of the following factors that may compromise the integrity of your non-pressure treated wood:

Water and Moisture

Water, of course, is the most potent threat to your non-pressure treated lumbers. The moment your lumber gets wet or soaked in water, you will quickly see the onset of the growth of molds afterward. 

So, it will be best to ensure that water will not seep into the very fiber of your wood. You can make the wood impervious to water by using a wood sealer. This wood sealer can waterproof the wood and prevent the infiltration of water onto its very fiber.


Sunlight is not only a single-colored ray, as some naïve young lads would think. It consists of various light wave frequencies. One light frequency is the UV rays that can be damaging to pressure and non-pressure treated lumber. 

The UV rays can scorch the wood by draining the oil and moisture out of the wood. This draining of oil and moisture leads to the loss of color and fading. To prevent such a problem, you can use a UV light blocker commonly found in some stains.

Important Factors to Consider When Using Untreated Wood Outdoors

If you consider using non-pressure treated wood, several factors should make you pause and consider, to optimize the use of this type of wood for your outdoor applications:

Risks Concomitant with the Use of Non-pressure Treated Wood

Some risks come with the use of non-pressure treated wood, and if you intend to use this type of wood outdoors, you can never escape these risks if you don’t do something to untreated wood. As mentioned above, harsh outdoor elements like sunlight and water will be unforgiving to untreated wood. 

They will eventually cause the decay of the wood. For example, if you use untreated wood for your fence, you will soon notice that the legs of the fence will exhibit decaying if they are constantly soaked in water or always in contact with the soil. 

On the other hand, if you use it for decking, the rainwater and direct sunlight will cause damages on its surface, cracking its surface and even warping it. So, it is not advisable to use untreated wood for these applications.

Wood Type

There are wood types that are capable of remaining outdoors without succumbing quickly to the harsh outdoor elements. So, when selecting wood for outdoor applications, it will be best to look for wood types that are naturally capable of resisting the adverse effects of harsh elements of nature. 

If you need wood for the deck, look for wood that is great for decking. You can go, for example, for teak, mahogany, or oak. You can use softwood likewise, for they are less costly, but make sure you give them some kinds of treatment.

Non-pressure Treated Wood Lifespan Outside

If you use non-pressure treated lumber outdoor, you can expect it to last from five to ten years. Yet, several factors may also determine its integrity outdoors. These factors include exposure to sunlight, moisture, weather condition, insect attack, fungi growth, and usage. Experts would not recommended the use of untreated wood on your decks, for the harsh elements will indeed weaken and eat up on your wood. 

As a caveat, non-pressure treated wood is best used in areas with no direct contact with water. You can use them for trim with awesome results. Its topical treatment can help prevent issues related to the effects of moisture and insect activities, but it can’t prevent the weakening effect of floodwater.

Protecting Your Non-pressure Treated Lumber From Moisture and Water

There are several ways you can make non-pressure treated wood impervious to the effects of harsh outdoor elements. Thus, to protect non-pressure treated wood from water, you can follow the following three proven ways. 

  • You can utilize tung oil or linseed oil to provide the wood with a protective shield. Rub the oil on the wood’s surface to create a good finish. 
  • You can also use polyurethane, varnish, and lacquer as protective shields.
  • You can likewise utilize semi-transparent stains to turn non-pressure treated ones into waterproof ones.

Sealing Non-pressure Treated Lumber

To prolong the useful lifecycle of non-pressure treated wood outside, you can seal it. But before sealing it, you need to make sure that the wood you are going to use is in perfect condition. It should not have any crack or rotten parts. You should also allow the wood to dry thoroughly. Once these conditions are met, you can then start cleaning and sealing the wood.

If the wood is not entirely dry, allow it to dry for two days to three days. Once it has dried, you can now start sealing its top surface using a top sealing coat. Use the right tool, like a soft brush, when applying the sealer. 

Let the primary coat dry on the surface. Then, you can add another coating over the first one and let it cure. You can also apply a third coat if you want to ensure a perfect seal. But you can do away with two coats to ensure that your wooden structures are protected.


Using non-pressure treated lumber outside is not advisable, especially if the wood would touch the wet ground. However, you can still use it, depending on your projects and applications. If you intend to use it for a project that you want to last for several decades, I will advise you to use pressure-treated wood. 

It will be good to note that the maximum longevity of non-pressure treated wood is up to ten years. But you can still prolong its useful life cycle by engaging in regular maintenance of the wood.

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