If you are planning on building something out of wood, one of the choices that you have at your disposal is Douglas fir. With that being said, how strong is this wood?
Today, we are here to answer a number of vital questions, including whether or not Douglas fir is a hardwood or a softwood, and whether or not it is strong. We are going to take a much closer look at this material and examine it based on a number of important factors to determine how strong it actually is.
Is Douglas Fir a Hardwood or Softwood?
Douglas fir is a gymnosperm and a coniferous tree, which means that it produces seeds inside of cones, as opposed to being a flowering tree. What this means is that it is also a type of softwood.
Although it is called a softwood, in the grand scheme of things, it’s not actually that soft at all. In terms of softwood, Douglas fir is actually quite durable and ranks quite highly, especially when compared to the other common types of softwood found in North America. However, compared to hardwood, it is relatively weak.
Douglas Fir Strength: All You Need to Know
Today, we are going to take a closer look at Douglas fir to see exactly how strong it is. Generally speaking, it is relatively strong for softwood, and it is typically weaker than most types of hardwood.
To determine exactly how strong this wood is, we are going to evaluate it based on five main factors.
These include the compressive strength, the modulus of rupture, the modulus of elasticity, the hardness, and the density or weight. We will then also compare Douglas fir to a number of other types of trees, both softwood and hardwood, to provide you with a good point of reference.
Compressive Strength
Douglas fir features a compressive strength of 6,950 lbs per square inch (47.9 MPa). That is harder than eastern hemlock, which comes in at 5,410 lbs, sugar pine, which comes in at 4,460 lbs, and black spruce, which comes in at 5,410 lbs.
Generally speaking, you can expect Douglas fir to be stronger in terms of compressive strength than most types of softwood. However, whether we are talking about maple, cedar, mahogany, ebony, or anything in between, Douglas Fir has a lower compressive strength than all of these.
The compressive strength of lumber may also be known as the crushing strength. The compressive strength is in reference to how much weight a certain piece of wood can take parallel to the grain.
As a visual reference, picture a stick standing up vertically. Now, imagine piling bricks on top of that stick. How many bricks can the stick take before it snaps in half and crumbles?
Bending Strength
Douglas fir features a bending strength of 12,500 lbs per square inch (86.2 MPa). That is higher than eastern hemlock, which comes in at 8,900 lbs, sugar pine, which comes in at 8,200 lbs, and black spruce, which comes in at 10,100 lbs.
Just like with compressive strength, Douglas fir tends to have more bending strength than most other types of softwood, although it has less bending strength than virtually all types of hardwood.
The bending strength of wood may also be referred to as the modulus of rupture. This measurement is in reference to how much weight a piece of wood can handle perpendicular to its grain.
Keep in mind that compressive strength is about how much weight a piece of wood can handle parallel to the grain while bending strength is measured perpendicular to the grain.
As a visual reference, picture a horizontal piece of wood that is attached to a wall on one end so that it is hanging freely on the other. How much weight could you hang off of that piece of wood before it snaps and crashes downwards?
Stiffness
Douglas fir features a modulus of elasticity of 1,765,000 lbs per square inch. That’s higher than hemlock, pine, and spruce, which respectively come in at 1,200,000, 1,190,000, and 1,523,000 lbs per square inch. As you can see, it is stiffer than virtually all other types of softwood. However, it’s not nearly as stiff as most types of hardwood.
The stiffness of wood is also referred to as the modulus of elasticity. This is in reference to how much weight a piece of wood can hold in the middle before it begins to bend or sag. As a visual reference, picture standing on a board. How heavy would you have to be to make that board bend in the middle?
Hardness
Douglas fir features a Janka hardness rating of 620 lbf. As a point of reference, eastern hemlock comes in at 500 lbf, sugar pine at 380 lbf, and black spruce at 520 lbf.
As you can see, Douglas fir is harder than most types of softwood, although much softer than virtually all types of hardwood, whether we are talking about mahogany, maple, cedar, or anything in between.
For those of you who don’t know what the hardness of wood is, this refers to how physically solid or hard the surface is. This will determine how resilient it is towards physical damage such as denting and scratching. Hardness is generally measured on the Janka hardness scale.
Density
Douglas fir features a density of 32 lbs per cubic foot (510 kilograms per cubic meter).
Eastern hemlock comes in at 28 pounds per cubic foot, sugar pine at 25 pounds per cubic foot, and black spruce at 28 pounds per cubic foot. As you can see, Douglas fir is therefore heavier than most types of softwood, yet, again, lighter than most types of hardwood.
The density of wood refers to how heavy it is based on a certain size. This is generally measured in pounds per cubic foot or kilograms per cubic meter. This is important to know because it has to do with durability, as well as how easy that piece of wood will be to work with.
Is Douglas Fir Strong?
In the grand scheme of things, Douglas fir is actually quite strong as far as different types of softwood are concerned. As you can see from our analysis today, Douglas fir is generally stronger than most other types of softwood, and this is true on all fronts.
However, at the same time, Douglas fir is also much weaker than virtually all types of hardwood. Therefore, if you need a really strong softwood, this wood is a fantastic option to consider, and it does come close to some lower-end hardwoods, especially if you need something for a decent price.
What it really all comes down to is that if you want an affordable type of wood, softwood is always a good option to consider, and yes, Douglas fir is fairly affordable.
For its price, it stacks up really well against other materials. This can also be said when compared to many types of hardwood. Although it is a soft one, you could almost call it a low-end hardwood.
Summary
If you are looking for a very high-quality softwood, then Douglas fir is a fantastic option to consider. Just remember that if you are looking for something super durable and structurally sound, you probably want to go for hardwood.