If you are planning to build anything made out of wood, then plywood is always a material of choice. It is an extremely versatile building material with many applications. With that said, there are many different types of plywood out there. Two of the most common ones include MDO and marine plywood.
Right now, we will do a side-by-side comparison of the two to figure out which one, if any, is better suited for your use case.
What Is MDO?
MDO stands for medium density overlay. Medium density overlay plywood is a very special type of weather-resistant plywood.
However, those three letters (MDO) actually refer to the fibers in between each layer of plywood. If we look at normal plywood, those layers are very thin, and they are just glued together, with the grains being at an angle to each other. However, MDO has very thin layers of fiber resin that bond each layer together.
Moreover, the exterior surface is generally finished with a layer of resin. This means that MDO plywood is much stronger, more durable, and more weather resistant than normal plywood.
It was first designed for sign makers who needed to make billboards that would withstand the weather. This is one of the more weather-resistant types of plywood out there. Keep in mind however that it is not 100% waterproof. In fact, medium density overlay is often considered to be a somewhat inferior version of marine plywood.
What Is Marine Plywood?
On the other hand, we have marine-grade plywood, which is also a very special type of plywood that is manufactured with high standards in mind. One of the defining features of marine plywood is that each layer is made out of solid hardwood, and each layer is selected based on quality.
Only the highest quality of wood is used for this type of plywood. There are absolutely no gaps in between any of the layers. Moreover, each layer is glued together using a very special type of weather-resistant adhesive.
The bonding process also involves very strict heat requirements and pressure requirements. Just like medium density overlay plywood, marine plywood is also not 100% waterproof, although pretty close.
MDO vs. Marine Plywood: What Are the Differences?
Before we get into looking at the differences between medium density overlay and marine plywood, we just want to hammer home the fact that neither of these is 100% waterproof. Yes, both are extremely water and weather-resistant, but neither is 100% in this regard. You can do some things to improve this property, though.
Either way, let’s now look at the main differences between these two types of plywood.
1. Overall Weight
One big difference between these two types of plywood is that they are not at all the same weight.
Medium density overlay is slightly lighter in weight than marine plywood is. This means that if you need to keep your construction lightweight, medium density overlay is the plywood type of choice between these two. Due to it being a bit lighter, it is also easier to work with.
2. Cost
If we compare both MDO plywood and marine plywood to normal plywood, they’re both much more expensive. The fact is that both of these types of plywood have more stringent manufacturing processes and also use higher quality adhesives and wood.
That said, medium density overlay plywood is by far the cheaper of the two when compared to marine plywood. It’s relatively cost-effective nature makes MDO plywood the choice for outdoor use. Marine grade plywood can be up to twice as expensive as medium density overlay.
3. Flexibility
One of the biggest advantages that marine grade plywood has is that it is fairly flexible. Remember that marine plywood was originally designed to build boats. Boats do of course have rounded parts to them. Marine grade plywood can be bent a little bit, which makes it ideal for construction jobs that require a bit of shaping and molding.
Due to the addition of fiber resin in between each layer of MDO plywood, it is much less flexible than marine grade plywood. If you need your plywood to bend and flex, then medium density overlay is not the best choice.
4. Finish
Another primary difference between these two types of plywood has to do with the finish that they have. Marine grade plywood generally comes with a veneer finish. However, normal marine plywood can at times be difficult to paint. It’s definitely not the easiest to work with in this sense.
On the other hand, MDO plywood has a layer of resin on the outside which gives it a very smooth finish. It is therefore very easy to both sand and paint. Keep in mind that it was designed for people who make signs and billboards, so it definitely has to be easy to paint.
5. Durability and Strength
Both medium density overlay and marine plywood are very strong, both much stronger than normal plywood. However, a big difference here is that marine plywood is made only with the very best of wood. Only the highest quality of wood is used for marine plywood, unlike MDO plywood, and this means that marine plywood is the stronger of the two.
6. Moisture Resistance
In terms of moisture resistance, both medium density overlay and marine plywood are extremely resistant. After all, billboards spend all of their time outdoors and marine plywood is designed to be used for boat building, and of course, boats are in the water. Both are ideal for water-resistant purposes, although marine plywood is slightly more water-resistant.
When to Use MDO?
This type of plywood is best used for exterior paneling, fascia, and outdoor signs. This type of plywood is also ideal for concrete forms. Many people also use it for bathrooms and kitchens, due to its water resistance, strength, and great appearance. Much commercial furniture is also made out of this material.
If you need something fairly durable, lightweight, cost-effective, and weather-resistant, then MDO is a great option.
When to Use Marine Plywood?
If you are doing anything that involves water, such as building a boat, a dock, or a pier, then marine plywood is the way to go. Keep in mind that marine plywood is very expensive, but in all reality, it is the best type of plywood. Therefore, if you are going for top strength, water resistance, and overall quality, marine plywood is the option to go with.
Alternatives to MDO and Marine Plywood
There are more cost-effective alternatives to both of these types of plywood.
You’ve got interior and exterior grade plywood, medium-density fiberboard (MDF), particle board, cement board, birch plywood, oriented strand board (OSB), laminated veneer lumber (LVL), laminated strand lumber (LSL), cross laminated timber (CLT), and composite board.
There are too many alternatives to cover, however, all of the types of engineered wood mentioned here do excel at specific purposes.
Summary
Now that you know what the differences between marine plywood and MDO are, you can make an informed decision between the two.