Douglas fir was very commonly used in decking projects and outdoor construction in the past. People still use it for making patios and similar projects. Having resistance to warpage, rot, decay, and insects, Douglas fir seems like an obvious choice for outdoor use. However, it is a softwood and that means it is not as dense as other hardwood options. Not to mention it is not completely waterproof either and needs a good oil finish to help prevent moisture damage. So in this article, we are going to talk about what kind of oil finish is best for Douglas fir wood.
Tung and teak oil are the best suitable oil finishes for Douglas fir wood. Pure tung oil is one of those products that works in most situations. It is a drying oil that hardens as it dries and cures. Not to mention it really brings out the beautiful colour of Douglas fir. Teak oil on the other hand is great for use in outdoor teak furniture. It also works well for Douglas fir wood and helps make it resistant to water. You might even find some teak oil products that have UV inhibitors to protect the wood against sun degradation.
Douglas fir is wood that can survive all odds if given enough care. It has been used on boats for seats, as decking on homes as old as 100 years that are still in great condition, and for patios as well. It is a softwood that has a Janka hardness rating of 660, which is pretty decent. However, it means that it can be easily scratched and dented since the rating is still under 1000. Though it more than makes up for its lower Janka rating with other qualities like repelling insects and preventing rot and decay. It also does not warp even if it soaks in tons of water it does not warp or shrink. Though it is susceptible to water damage and sun degradation, that is where a good finish comes in.
Best Oils for Douglas Fir Wood
1. Tung Oil
Natural tung oil is very versatile and so it is found in most oil-based finishes. Whether it is teak oil or Danish oil, they contain some quantity of tung oil in them. After all, it is a favourite amongst woodworkers because of its outstanding quality as a finish. Douglas fir is a pretty durable piece of lumber that is slightly on the expensive side. However, it is very commonly used in construction due to its qualities. Having said that, it is still a softwood that can benefit vastly from the use of a drying oil like tung oil.
Applying a natural oil finish that penetrates into the wood will harden from inside giving Douglas fir durability from inside out. Not to mention you can always apply a coat of your favourite clear coat finish with UV inhibitors like Spar Urethane to prevent sun degradation while the oil prevents the wood from drying out from the inside. Tung oil will also help in preventing decay and rot that might set in from water damage in Douglas fir.
The best tung oil in the market at the moment is Hope’s Natural 100% Pure Tung oil that you can buy online or at your local hardware store if available. It not only penetrates the wood for protection but also accentuates the look of the Douglas fir without altering its natural tones.
2. Teak Oil
Teak oil is sold under many names and most brands have different components added to their product. Though the most common are linseed oil, mineral oil, petroleum distillate, and drying agents. It is most commonly used on outdoor furniture, specifically one made from teak wood. This is because teak wood is pretty water resistant and does not usually require finishing. However, every now and then a coat of teak oil helps prevent it from fading in colour and protects it from further moisture.
Teak oil can be used for outdoor furniture and construction, which makes it ideal for Douglas fir wood. Some brands even include UV inhibitors or filters in their blend of teak oil. This makes it even better as an oil finish for an outdoor setting. Not to mention the linseed oil and mineral oil helps highlight the beautiful colour of the Douglas fir.
Liberon Teak Oil with UV Filter is an excellent product that not only helps wood with added water protection but the UV inhibitors prevent sun degradation which can cause the wood to dry out, crack, and even wash out the natural colours of wood.
Best Treatment for Douglas Fir
Most people have the common misconception that since Douglas fir resists rot and decay, it is immune to moisture. While it holds a good amount of water and dries out without warping or shrinking, if exposed to water for a prolonged period of time it will decay and rot as wood does. So to prevent that from happening most people will apply a finish to it that repels water. However, a normal finish will only help repel water from it, but not prevent it from drying out in the sun.
What Douglas fir needs is an oil finish that will replenish it from inside out and also prevent it from drying which can cause cracking. However, an oil finish alone will not do as UV degradation is also an issue with outdoor furniture and construction. After a few coats of the oil finish of your choice, you will want to apply a few coats of something like Spar Urethane from Minwax. This has UV inhibitors that can help Douglas fir avoid sun degradation. It also creates a barrier that prevents moisture from touching the wood at all.
Tips for Oiling Douglas Fir Wood
- Good preparation will ensure a successful application of the oil finish of your choice. To prepare your Douglas fir wood, you need to sand it. You start off from 80-grits and thoroughly sand the whole surface. After which you move on to higher grits all the way up to 180. A sanded surface allows finishes to adhere to the surface better and also smoothens it.
- Wipe off any excess oil that has not been absorbed by the Douglas fir. When you apply the first coat of oil, your lumber will become saturated. After which any leftover oil will sit on top of the wood without getting absorbed. This will end up just increasing the time the oil needs for drying. In most cases, the oil never fully dries and leaves the surface of the wood sticky.
- When you are leaving the wood to dry between coats, wipe off any excess oil that the Douglas fir has expelled. When the wood becomes saturated any more coats of oil you apply will end up being expelled by it in the form of droplets. You need to wipe these droplets off as they will prevent a smooth oil finish and also make the surface sticky as it never truly dries.
- You can also sand in between the coats of oil to make the surface of your Douglas fir wood more glossy. The higher the grits of sandpaper you use the more glossy the finish will be.
- Apply the final grits of sandpaper by hand in the direction of the grain as you will get much smoother results from that.
Benefits of Oiling Fir Wood
Douglas fir is mostly used in decking projects and patios of houses. This leaves it exposed to the sun and elements most of the time. Even if the sun is not as strong where you live and it does not rain a lot, wood will become weathered out as time passes by. Even strong winds can brush with lumber and make it dull than how it used to be. To make sure that your decking and outdoor construction stay fresh looking, you need to apply an oil finish to it every now and then. An oil finish not only prevents wood from drying out but also dries to a hard finish helping wood to avoid damage from the elements.
Douglas fir wood is also not hardwood, it has a Janka rating of 660 which is good enough for it to be considered for flooring and decking. However, it still isn’t as strong and can dent easily, so when you oil the lumber of the Douglas fir tree, you help give it more strength to endure abuse. Not to mention no finish will give you the beautiful look as an oil finish does. Douglas fir is a beautiful wood, and an oil finish will help highlight its beautiful colour and grain pattern.
FAQs – Frequently Asked Questions
Best clear finish for Douglas fir wood?
Spar Urethane by Minwax is one of the best clear finishes for Douglas fir wood. If it is not available where you live, any urethane finish with UV inhibitors will also do.
What is the best natural finish for Douglas fir?
Tung oil is the best natural finish available for Douglas fir wood. It not only strengthens the lumber but also gives it a beautiful look and accentuates its grain pattern.
Does tung oil darken Douglas fir wood?
No, pure tung oil does not darken the colour of wood, it has a light amber tint but that is it. Tung oil will only highlight the true colours of the Douglas fir.
Douglas fir wood is incredible lumber to work with, but it slightly lacks hardness. However, what it lacks in density, more than makes up for it with its qualities. To ensure that you can utilize this beautiful wood in your outdoor construction, applying an oil finish every now and then will help out. Using any of the oils mentioned above in our article, you can make sure that your Douglas fir wood projects live long.