Plywood is an essential part of any major construction project. Whether you are building scaffolding, creating a theatre set, or filling out the walls of a backyard shed, plywood will come in handy. As plywood is often used as a load bearer, you may be concerned about how much of a load plywood can bear.
Marine plywood and MDF can sustain several hundred pounds per sheet, whereas cheaper types of plywood can typically bear anywhere between 5 and 50 pounds per sheet.
The amount of weight a sheet of plywood can hold is related to several factors, such as its thickness, flexibility, species, glue, layering, and type.
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Thus, it is crucial to be prescient of which qualities you will need in your plywood before you begin construction. Keep reading to learn more about plywood’s various qualities, how they affect the amount of weight your plywood can hold, and which types of plywood work best for various projects.
What Affects Plywood’s Strength?
Plywood is a deceptive building material. Most types of plywood are relatively thin, but plywood is one of the most robust materials commonly used in construction. This is due to the method in which plywood is made.
Plywood consists of layers of wood grain and wood chips, each placed perpendicular to the next layer and bonded together with glue under high pressure.
This method of alternating each layer’s grain pattern gives plywood a strength advantage over other sheets of wood of comparable size and thickness.
There is also plenty of discrepancy in strength between different types of plywood. Plywood can vary in many ways depending on its type, but the major discrepancies that have to do with its strength can be observed in its thickness, flexibility, species, glue, and layering. Let’s take a look at how each of these qualities can affect a sheet of plywood’s strength.
It stands to reason that the thicker the sheet of plywood is, the stronger it will be. However, this thickness also relies on a good span rating to sustain more weight. A sheet of plywood’s span rating is the amount of maximum load-bearing space on the sheet of plywood.
Here is a chart that details precisely how the thickness and span rating of a sheet of plywood work together in making your plywood as strong as possible:
|Span Rating||Thickness||Maximum Live Load|
|16 oc||19/32 inches||185 pounds|
|24 oc||19/32 inches||270 pounds|
|20 oc||23/32 inches||240 pounds|
|32 oc||7/8 inches||295 pounds|
As is evident in this table, both thickness and span rating must work together to increase the strength of a sheet of plywood. If the thickness increases but the span rating decreases, the maximum live load your sheet of plywood can hold will decrease as it will have less room to sustain the weight.
Another crucial factor in improving your sheet of plywood’s strength is its flexibility.
The flexibility of your plywood, which is also commonly referred to as shear strength, will help prevent your sheet of plywood from cracking or breaking when sustaining heavy loads or being built on uneven frame structures.
This is an important quality that will come in handy for a myriad of different projects.
Although there are many different types of plywood, there are only two recognized species of plywood. These two species, hardwood and softwood, pertain to the wood source used in the making of the plywood, which could refer to hundreds of different types of trees.
Trees like maple and oak trees fall under the hardwood category, whereas trees like cedars and pine trees fall under the softwood category. Hardwood trees are typically the stronger, more durable species of plywood.
However, there are a few exceptions, such as balsa trees, a hardwood that is much softer and weaker than other hardwoods, and some softwoods.
Another way softwood plywood can be superior to the typically brawnier hardwood plywood is its manufacturing. Some manufacturers use exterior glue on softwood plywood that is receptive to the glue.
This glue helps make these types of softwood plywood more durable over time as they can block out moisture that would weaken it.
Last but not least, the number of layers a sheet of plywood has is crucial to determining its strength. In fact, the number of layers in a sheet of plywood is directly related to its strength (source).
For instance, a ¾ inch sheet of plywood with fewer than four layers is known as shop grade plywood, which is the weakest of all grades of plywood.
If the sheet of plywood has between four and seven layers, this is a more versatile type of plywood with moderate strength. If the sheet of plywood has more than seven layers, this grade of plywood is referred to as multi-ply and is the strongest grade of plywood available.
What are the Different Types of Plywood?
Now that we have gone over the qualities that are essential in determining the strength of different types of plywood, let’s take a look at some of the different types of plywood.
Many different types of plywood fall under the hardwood and softwood species categories. Additionally, some types of plywood may fall under either category depending on the specific subtype of wood used.
First, let’s take a look at the various types of hardwood plywood:
- Mahogany Khaya
- Mahogany Sapele
- Oak Red
- Oak White
- Pine Knot
Now, let’s take a look at the various types of softwood plywood:
- Douglas Fir
- Marine Plywood
With all of these different types of plywood laid out, it may be a bit intimidating to choose just one for your construction needs. The following section will detail exactly which types of plywood will be best suited for various projects.
Which Type of Plywood Should You Use?
The general consensus is that softwood plywood is generally used in major construction projects as support. In contrast, hardwood plywood is typically used as decorative wood for home projects like furniture or shelving.
This may seem contradictory to what we know about the strength of hardwood versus softwood, as hardwood is typically stronger than softwood.
However, when treated with exterior glue, softwood can be stronger than hardwood and certain types of softwood. Marine plywood is far stronger than any hardwood.
Thus, if you are looking for the best plywood to use as structural support for scaffolding or a subfloor, marine plywood and MDO are the best options for you.
If you are looking for decorative yet sturdy plywood that can be used in your furniture or shelving projects, then there are plenty of hardwood plywood options available for you.
You may gravitate toward darker woods like mahogany khaya, teak, walnut, or wenge. On the other hand, you may prefer lighter woods such as maple, fir, ash, or pine knotty.
Ultimately, the major takeaway here is that hardwood plywood should be used for decorative projects, and softwood plywood should be used as structural support.
By the end of this article, it should be clear exactly how the various types and qualities of plywood affect the amount of weight your plywood can hold and which types of plywood work best for different projects.
Ultimately, if you consider the importance of every factor, such as thickness, span rating, flexibility, species, glue, and layering, you should be able to pick out the proper plywood for your needs.