How to Keep Untreated Wood from Rotting

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Naturally, we always want to protect any kind of investment we’ve made, whether small or big; and why not?  It’s our hard-earned money after all. The same goes for lumber or wood. We want to make sure that it lasts as long as possible. But lumber or wood is also a material that’s prone to rotting, especially when left untreated. It more often than not needs to be taken care of in order to maximize its life.

There are several ways to keep lumber from rotting. One of the toughest options is getting wood pressure treated, however unfortunately the most durable options for outdoor use are toxic and while there are now safer options available for indoors, those same options won’t survive outdoors; though even while keeping them inside one still needs to be careful and avoid direct contact from them. So, since pressure-treated wood’s safety is something quite complicated, how to get lumber to be long-lasting without having it pressure treated?

Options to Protect Untreated Wood from Rotting

So let us start with the basics and explore the main options you have in order to prevent lumber from decaying.

Keep it Dry

Bare lumber without any protective layer needs to be stored in a dry space, preferably inside or under a roof. Any dampness could quickly break down the lumber and start the rotting process. Also, that space should have good air circulation in order to dry out any moisture that may be present in the wood. Close and damp environments will only invite trouble.

Keep it Shaded

If you do need to keep lumber outdoors, try to keep it in the shade as much as possible. This way the lumber will be more protected from the sun’s harsh rays, which can dry it out and make it vulnerable to decay. Sunlight can strip the wood of its natural oils and cause fading and degradation. Wood’s natural chemicals, such as lignin, get used up, which isn’t a preferable situation. 

Controlled Temperature

If you can, store lumber in a space that has controlled temperature and humidity levels. This will protect the lumber from warping and cracking, which can speed up the decaying process. Too much moisture or too little moisture will both deteriorate lumber over time.

Choose The Right Type of Wood

Different types of lumber are more durable than others. Hardwoods, such as teak, cedar, redwood, cypress, white oak, and fir are some of the toughest, most weather-resistant species and are naturally more resistant to rot than others. Always do your research before you buy lumber, so you can choose the most durable type for your specific needs (we’ll help with that later in the article).

Chemical Protections

There are some chemical options to help prevent lumber from rotting. Wood sealers, paints, stains, and other finishes can create a barrier against moisture, helping lumber stay healthier and protected while exposed to the elements. However, these chemicals can sometimes be toxic and may not be suitable for indoor use. If you need lumber for indoor use, be sure to carefully choose non-toxic chemical protectors.

The Borate Option

Nisus 30201 PenShield 128oz Borate Wood Preservative, Clear

Borate is a non-toxic chemical that can help preserve lumber and prevent rot. Borate inhibits the growth of fungi and bacteria, which helps lumber stay strong and durable. It’s often used in pressure-treating lumber, but it can also be applied to untreated lumber as a sealant or spray yourself. While borate is generally safe, it’s important to do your research before using this chemical on lumber, so you can ensure that it’s the right option for your needs.

How to Treat Untreated Wood Against Rot

Now, time to learn how to treat lumber in order to prevent it from rotting. As mentioned above briefly, applying some sort of protection to lumber is always a good idea, be it a sealant, paint, stain or other finish. These products will create a barrier between the lumber and moisture, helping to keep it healthy and long-lasting. Followings are some of the best ways to protect lumber against rot:

Outdoor Wood Sealers

Hope's Pure Tung Oil, Waterproof Natural Wood Finish and Sealer, 16 Fl Oz

One of the simplest ways to protect most woods from rotting is by applying a wood sealer. These products are typically non-toxic and can be easily applied to lumber with a brush or sprayer. Wood sealers are used to protect wood against moisture, allowing it to remain dry and protected from UV rays and mold growth.

Exterior Paint

KILZ 10211 Exterior Siding, Fence, and Barn Paint, White, 1-gallon, 1 Gallon (Pack of 1), 128 Fl Oz

Another option is to paint or stain lumber. These products can also help create a barrier against moisture, though they can be a bit more labor-intensive to apply. Always choose an exterior-grade paint or stain, preferably one that is specially formulated for lumber. This will ensure that the product is durable and long-lasting. Additionally, painting your lumber also gives you the opportunity to add some color and style to your outdoor space!

Clear Coats – Spar Urethane

Minwax Helmsman Water Based Spar Urethane, Quart, Gloss

If you wish to keep the natural look of lumber, you can apply a clear coat. Clear coats are typically made from spar urethane, a type of polyurethane that is often used on lumber. These products have high UV resistance; protecting lumber against deterioration from sunlight. Additionally, they are resistant to moisture and prevent lumber from cracking and warping.

Wood Oils

FurnitureClinic Boiled Linseed Oil for Wood | Natural Formula Wood Furniture Polish | Restore Finish on Indoor & Outdoor Wood, 8.5 oz/250ml

Wood oils are a natural option for protecting lumber. These products typically contain chemical-free ingredients, such as linseed oil or tung oil, which help to keep lumber healthy and prevent rot. Wood oils are also easy to apply, typically requiring just a few coats for maximum protection, though keep in mind that this option will require regular maintenance. However, if that’s not an issue for you, it is recommended to use linseed oil, teak oil, or danish oil for this project. They are great at protecting lumber and can also help to bring out the natural beauty of the wood.


Loctite Epoxy Five Minute Instant Mix 0.47-Fluid Ounce Syringe (1365868)

Epoxy resin is another option for protecting lumber, a time-consuming option, but an option nonetheless. This product creates a strong and thick durable barrier against moisture, all thanks to its high resistance to liquids. Epoxy resin is typically used to repair lumber that has been damaged, but it can also be applied as a sealant on untreated lumber. The one thing you need to actually think about is that epoxy isn’t UV resistant, thus it is likely to need reapplication often. In order to create a nice tough sealed barrier, you’ll first have to apply wood oil to your lumber, then apply epoxy resin on top; finally, finish by putting some UV protection on top of the epoxy to help protect it from sunlight.

How to Prevent Untreated Wood From Rotting

prevent untreated wood from rotting

Untreated lumber has a tendency to rot over time, especially if it is exposed to moisture or sunlight. While there are several different methods you can use to prevent lumber from rotting, the importance of regular checkups cannot be ignored. There are many signs and symptoms to look out for, so let’s go over them in this section so that you may know what to keep an eye out for.

Look out for these Trouble Spots

  1. Cracks and holes in the caulking around windows, doors, dryer vents, doorposts, and other areas
  2. Stains on the ceiling, as well as stains around the fireplace, can be an indication of possible leakage issues
  3. Gutters and downspouts that hang and leak
  4. Shrubbery and tree branches are overgrown to the point that they’re less than 2 feet away from the siding or roofing, resulting in rubbing against the wood during high winds
  5. Peeling paint and cracked painted surfaces
  6. Leaves and other debris clogging the crawl space vents
  7. Litter, leaves, and twigs have gotten stuck between decking boards

Best Types of Wood for Outdoor Use

best type of wood for outdoor use

As mentioned before in this article, though wood is not a very durable material for outdoor use, there are some types of lumber that are more resistant to moisture, UV damage, and other factors that can lead to rotting. Some of the best and most popular types of lumber for outdoor use include Pine, Cedar, Redwood, and teak. So let’s take a closer look at each one in order for you to be able to make a more informed decision.


Pine lumber is softwood that is often used for construction purposes. It is a popular choice for many homeowners due to its low cost and somewhat resistance to rot. Pine lumber is also known for its attractive and warm wood grain, making it a great choice for outdoor furniture or decks. However, keep in mind that it may require more maintenance than the rest of the options given here. You’ll have to periodically check the lumber and make sure it is properly sealed, stained, or painted to prevent water damage and rotting. Also, pinewood doesn’t do well in dry climates and may start to warp and crack, so if you live in a dry area, it is best to avoid this type of lumber.


Cedar lumber is another great choice for outdoor use, as it has a natural resistance to rot and decay. This type of lumber is highly durable and can last for many years with only minimal maintenance. Cedar lumber is great for building structures such as decks and fences, as it is sturdy and long-lasting. In addition, cedar wood has a beautiful wood grain that will add charm and value to your home. It’s a bit pricey when compared to pine wood, but it is well worth the investment. You only need to treat cedar wood with linseed oil or a water sealer for optimal protection against the elements.


If you’re looking for lumber that is strong, beautiful, and highly resistant to rot and decay, then redwood lumber is a great choice. This lumber has been used for centuries to build homes and other structures, as it is durable enough to withstand the harsh elements. Unlike other wood types, redwood lumber does not need to be treated or sealed at all, as it is naturally resistant to moisture, decay, insect, and even fire. It also comes in multiple grades, depending on the type and quality of lumber. However, be aware that redwood lumber is currently very expensive due to its popularity, so it may not be the best option for those on a budget.


Finally, teak lumber is another great choice for outdoor use, as it is naturally highly resistant to rot, insects and water. Teak lumber is also very attractive looking, strong, and durable, making it ideal for building structures such as decks, furniture, and even boats. This lumber is extremely durable and will last for several years with little to no maintenance. It doesn’t shrink or warp like most other lumber types, making it an excellent choice for outdoor use. The only disadvantage of teak wood is its high cost and scarcity, owing to its exceptional qualities and difficulty to cultivate. However, if you can afford it, teak lumber is definitely worth the investment. After years of use, you’ll only need to apply some teak oil to it in order to revive it back to its original luster.


As you can see, there are many different ways to keep lumber healthy and protected against rot. By choosing the right type of lumber and giving it the proper care, you can ensure that your lumber will last for many years to come.  

Whether you choose to use lumber for construction, furniture, or outdoor structures, be sure to do your research and select the best option for your needs. With a little bit of effort, you can keep your lumber looking great and prevent it from rotting. Thanks for reading!

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