For all wood-framed buildings, the use of engineered wood is common. Whether you are investing in a construction project or striving for a visually appealing structure, it will be a different work based on the type of engineered wood.
You might be looking for lumber that is engineered to give you maximum strength or maybe you are struggling to choose the perfect one according to your budget.
Different structural engineered wood will indeed behave differently to different factors. For example, if you are looking for a stunning appearance, your preference will be the type of wood having that capability.
Here, we will compare two famous engineered kinds of wood i.e. PSL vs lvl. Let's go!
What is PSL?
Parallel strand lumber is a type of structural composite lumber. The main purpose of engineering this wood is to hold up heavy loads. They are capable of supporting open floor spaces with long-distance lengths. PSL beams are veneers placed in the form of parallel strands bonded together.
Veneers are thin slices of wood. They have 300 lengths to width proportion. Thinner than 3mm, they can be obtained by slicing a trunk or any piece of wood. By neatly cutting these veneers into parallel strands bonded with strong adhesive, you get nice parallel strand lumber.
These veneers strands have an average length of at least 1.8 m or 6ft. PSL beam can be prepared by using any kind of wood. However, some woods strands provide more strength. These special woods are douglas fir, southern pine, yellow poplar, western hemlock.
You'll see the PSL beam containing dark glued lines. It is very powerful for construction material. As this engineered structural composite lumbers have more evenly distribution of knots, grains, or splits after being manufactured.
Let us talk about how PSL
is formed by discussing it in detail.
How Parallel Strand Lumber is Made?
PSL was introduced in the 1960s. MacMillan Bloedel invented and commercialized PSL under the brand name parallam. This company is now present under the name of Weyerhaeuser. It is the only commercially manufacturer of PSL products.
As PSL is designed under high pressure, they tend to have a very richer texture and powerful structure. Made at a moisture content of percent, chances of shrinking and warping are very low. Wood strands in this type of SCL are very long. Phenol-formaldehyde is the adhesive used to bond these long strands together in the form of large billet.
This wood gets manufactured in two rectangular cross-segment:
- First one is 12 by 12 inch
- Another one is 12 by 18 inch
These larger segments then get cut down to small sections or sizes. They are available in different thickness measures that are 68mm, 89mm, and 133mm (2-11/16 in, 3-1/2in, 5-14in).
Typical depths of these strands are 240, 360, 300, 410, 460mm. The maximum depth can be 457mm (18 inches). The length of engineered beams is limited to the only 20m for their transportation.
As this specific structural composite lumber plays a great role in commercial construction. You might want to know it's benefits and uses in detail!
Support heavy loads due to its highly bending strength of almost 2900, It is commonly used as heavy and light beams and columns. They create any construction structure beautifully strong and stiff. This makes it possible to use them for longer spans.
As they knot re almost evenly dispersed in wood grains, each log in a building structure will have maximum strength support.
Available in Long Lengths
You are already aware of this structure's power and strength, so you know that they provide a great firm to longs spans construction. This is because they are available in longer lengths.
They are formed in a very long section. However, for transportation and handling reasons, manufactures have to cut them down to a specific length.
If you ever have seen a stunning deep long spanned building and wondered about its beam type. It can be a parallel strand lumber beam. These types of lumber display a very beautiful rich texture. That's why you can choose a parallam beam for intense and warm looks.
Being available in different designs, depths, lengths, and dimensions, it is impossible not to praise them for such versatile appearances.
One big reason of why to choose these beams among other SCL beams is that they are stainable. They can be finished with a very appealing and elegant shade.
In more exposed areas, they provide a great strength to environmental factors. It is because a parallam number can be easily managed by treating and curing them with preservatives.
During the conversion process of PSL into a commercial product, it can get defected due to various reasons. A fresh finished parallel structured lumber can easily get any chip mark on it.
You should know that though they display a very warm look, a wood stain cannot fully cover the natural grain and shadow of this wood.
In some conditions, your favorite beam can get mold. If a PSL carries more than 25% moisture they are prone to fungal infection. On a dry weight basis, lumber usually contains moisture above 25 percent.
What is LVL?
You have already read about one type of structural composite lumber i.e., parallel strand lumber (PSL).
Now, it will be so easy for you to understand another type of SCL known as laminated veneer lumber (LVL).
This type is also used as beams. However, it is used lumber for edgy materials. It is highly identical to glued laminated timber (Glulam). The main difference between these two is allowable stress. Glulam is also a type of structural engineered wood. Laminated veneer lumber has typically higher stress.
It is made up of overlaid veneers bonded together under special conditions. For bonding these veneers, different methods are used.
That is why they have different designs and formulations. LVL was developed in the 1970s and was popular for construction material. Today, you can see them as beams, purlins, and columns including other structural constructions.
This wood can also be engineered to almost any length same as parallel stranded lumber. However, it is restricted to a specific length for transportation purposes as well. Do you know that it is has a history of various manufacturing processes to become this successful as a beam? Let us dive into that!
History Of Laminated Veneer Lumber
In the early 20th century, famously used wood was plywood. In the 1970s the very first from of LVL was invented in the form of an oriented strand board. However, a proper form was first manufactured in the 1980s.
But still, it wasn't given the name of laminated veneer lumber. In 1991, the manufacturing of these veneers bonded together was labeled as LVL.
At the commercial level, you can give credit to Arthur Troutner and Herold Thomas for the invention of this lumber.
They announced a product " truss joists" under s big company. Today this company is known as TJ international USA. They used parallel veneers without forming them in cross-lamination. It was only designed to form the top and base of the I-shaped beam.
This company continued experimenting with it. They were soon able to form an LVL supporting unique floor beam having great support and strength. After that, it became very famous and was ready to introduce at a higher scale.
However, these beams required a high supply of strong flanged timber. And it was impossible to get timber at that rate with maximum strength.
Troutner's then used a parallel overlaid collection of 2.54 mm thick veneers of Douglas Fir. It possessed the same uniform strength to use as a flanged material. This was the first successful product launched in the market under the name "MIcro Lam".
Troutner proved its structural strength by making a house in Hagerman with it.
Manufacturing of LVL
In North America, this is a widely manufactured product by companies that produce I-joists. I-joist is a structurally engineered structure that has more strength for its weight and size as compared to other wood joists.
LVL is very famous among residential builders and designers because of I-joists, floor applications, and roof support.
Under specific heat and pressure, thin piles of wood are laminated together to form LVL. Before lamination, each slice of wood is dried and then grains of the strand get oriented in the same direction. That is why LVL is stronger and has a uniform dispersion of knots.
The maximum width of the LVL is 2.5 meters. The length limit is 25 because of transportation concerns. The thickness of LVL beams is different due to its various formulations. It can vary between 27 - 75 mm.
A veneer can be prepared by laminating veneers in cross-sectional bonding or glued in a longitudinal direction by parallel laminating.
You can better understand the structure of laminated Veneer lumber by considering the following specifications
- LVL typically has a bending strength of 2800psi. However, the bending stress of LVL composed of entirely high-grade veneers is 4250psi.
- Very common elasticity module is 2,000,000psi.
- It has a perpendicular compression of 500 psi.
- The horizontal shear strength of this structural lumber beam is 285psi.
We are sure that you have now complete details of what LVL is and its historical background. For the sake of why to choose LVL, take a look at the advantages of LVL.
It produces a very natural appearance. So, if you love nature colors, consider this one. This is just not about the natural look of wood but it also has very few environmental defects like knots, the slope of grains, and wanes.
It gives a very uniform surface with a finished product. This is the reason they are widely used for building materials like or the structure of the family house or other big buildings.
It is a very strong material and can support different designs. They require fewer wood fibers as compared to a man in other woods. It doesn't
warp, twist, damage due to material dimension stability.
The veneers use in LVL are so strongly bonded with a powerful resin, that any bending of final lumber is not possible. They are also available for long spans and in different widths.
Due to phenyl-formaldehyde resins are static against strands, this lumber has very good resistance against fire and doesn't burn easily. That's why they are widely used in constructing fire-rate buildings. This capability of LVL is similar to sawn timber or glued laminated timber.
They have the limitation of densification during production. Densification of material is strength-enhancing while subjecting it to higher pressure. So,its strength remains less than many other engineered lumbers.
Difference Between PSL vs LVL
Now after discussing them one by one, you will get the differences in both engineered lumbers from our comparison between LVL and PSL
The purpose of both engineered lumbers is to decrease the strength of reducing factors in wood. They are both designed in such a way that you can highly predict their strength, bending stress, and uniformity.
Natural defects like knots and splits have been dispersed evenly or removed from both lumbers through manufacturing. Therefore, they are very unique consistent lumbers. They possess the same strengths and can be differentiated by a slight distinction of bending stress.
PSL has greater bending stress than LVL that is 2900psi. However, if we see other qualities for determining strength, we can see they have quite similar strengths. They both possess the same elasticity modules of 2,000,000 psi. Elasticity modules are responsible for the stiffness of any material.
They both offer higher reliability as compared to many other engineered kinds of wood like Glulam. PSL is a little more durable than LVL because of densification under high pressure and different applied techniques. However, in LVL densification to increase its strength is very limited.
Due to this, more bonding pressure also ensures a strong adhesiveness for bonding veneer strands in PSL. As both have a highly designed structure to make them powerful material, they both possess very even very good dimensional stability.
There are fewer chances of shrinking, bending, and warping. Every veneer is so tightly bound together in them that it is very hard for the final form of beams to twist.
If you want to stain your final building structure, then it is obvious to choose LVL over PSL. PSL has an advantage over many other engineered lumbers. It is because of its flexibility for wood finishing. This wood can be beautifully finished with different wood finishes and colors.
However, LVL can also be stained with different paints and stains but these stains are limited. It is usually available in industrial finishes having normal timber stains applied to them. To increase its appearance, manufacturers sand its every surface. This also gives it a strong grip between veneers.
Polyurethane stains and acrylic timber paint are most suitable to coat laminated veneer lumber. It is recommended to sand the surface of any kind of engineered lumber before painting. If you are worrying to have a specific desired shade of wood, always test the paint on a smaller portion before applying.
Available Lengths and Widths
PSL and LVL are manufacturing no longer length. There is no limit for longer spans. But due to transportation issues, manufacturers supply them to a limited length. Another factor that can affect the lengths of this lumber is press size.
These can create very long strands of beams. Before planning to choose one, you should consider other factors of beams like available width and uniformity. The maximum width of LVL is 80mm.
However, compared to sawn timber or glulam, it has relatively less thickness. Moreover, this length of LVL is enough to support heavy structures.
On the contrary, PSL is available in comparable sizes of glulam or sawn timber. As they are formed under high pressure, they tend to have greater stronger and denser material.
Both have wide uses and benefits for developing a building material. If you are thinking about columns, beams or other frameworks to support a structure, two have major roles.
They are famous because of their strength and dimensional stability. LVL can be used for both bearing walls and also for non-bearing walls. They are used in the form of planks, rails, door frames other than just beams.
Due to the I-shapes beam, LVL is majorly used in roof trusses of bigger halls. You know that PSL is also widely used as beams and columns to support bigger and long-span constructions. You should select PSL over LVL when a more appealing paintable construction is required.
PSL is more expensive than LVL. Prices for both lumbersare not predictable and differ. It is because they come in various lengths and designs. If you are looking for a short span project, they buy LVL as they are much cheaper and perfect for short spans.
For floor farming applications, if you buy LVL (1-3/4” x 7-1/4”) in 10 feet span, it will cost you approximately $2.40 per ft. Similarly, for 10 feet span of PSL will cost you around $9.20 for the size of 3-1/2” x 9-1/2”.
So, these prices will differ for longer spans. If you are looking for a 30ft span, LVL (1-3/4” x 7-1/4”) will approximately cost you $7.25/ft. PSL (3-1/4” 14”) on the other hand will cost you $14 per ft.
Both parallel stranded beams and laminated veneer beams provide greater strength to the construction. They are available in various designs and can be modified accordingly. You should not doubt using them as beams, columns, and uniform structures.
We have discussed differences in detail for PSL vs lvl. If you are looking for a better appearance, then no doubt PSL is a better option for you.
However, if you are looking for budget-friendly structured composite lumber, you should go with LVL. Moreover, LVL is just not less costly but it also has the same strength and adhesiveness for shorter spans.
Whatever you choose, we hope that with the help of our information you will get your desired results!