If you are planning to build anything out of wood, plywood is always one of the best options to consider. That said, there are plenty of different types of plywood out there for you to know about.
Two of the most popular and commonly used types of plywood are exterior grade and marine-grade plywood. Today, we are here to figure out what makes them different, and which you should use for particular applications.
Exterior-Grade vs. Marine-Grade Plywood: What Are the Differences?
Before we get to talking about which type of plywood is best for certain situations, let’s first figure out what makes exterior-grade plywood and marine-grade plywood different from each other.
Species of Wood Used
One of the biggest differences here has to do with the type of wood that is used to manufacture these types of plywood.
With marine-grade plywood, because it needs to be extremely dense and waterproof, only the very highest quality and densest of hardwood is used.
However, exterior-grade plywood does not need to be quite as dense, and therefore lower grades of hardwood, or even softwood on occasion, may be used.
Thickness
Another difference between these two types of plywood has to do with how thick they usually are. Marine-grade plywood may come with plies that are anywhere between 0.5 millimeters and 3.8 millimeters thick. It can actually be very thick, which helps make it durable and waterproof.
On the other hand, exterior-grade plywood may come in much thinner boards. This sometimes does make it easier to manipulate, and it can also make it more cost-effective. Do keep in mind that generally speaking, marine-grade plywood will be more expensive than exterior-grade plywood.
Adhesives Used
One of the largest differences between these two types of plywood has to do with the type of adhesive that is used. With marine-grade plywood, extremely high-quality, weatherproof, and boil-proof adhesive is used.
This is to ensure that it is indeed able to withstand high levels of moisture. With exterior-grade plywood, high-grade adhesive is also used, although it’s not boil-proof, and it’s not totally weatherproof such as the adhesive used in marine plywood.
Strict Quality Standards
Marine plywood also features some extremely strict quality standards that it needs to meet in order to qualify as marine-grade. There are actually three separate factors to account for here.
For this wood to qualify, there must be absolutely no core gaps, the veneers used must be extremely high quality, and the glue needs to be waterproof.
There are no such strict quality standards for exterior-grade plywood. It can therefore be much lower in quality than marine-grade plywood.
Level of Water Resistance
One of the biggest benefits of marine-grade plywood is that it is nearly 100% waterproof, or even 100% waterproof, if treated right. This is of course why it is used for building piers, docks, boats, and more. Marine-grade plywood, as the name implies, is designed to be around water.
Now, exterior-grade plywood is fairly water-resistant, extremely so actually, but it’s not totally waterproof, especially not to the same level as marine plywood. You cannot submerge exterior-grade plywood underwater as you can with marine-grade plywood.
Aesthetic Qualities
Due to the very high-quality wood and manufacturing standards that marine-grade plywood needs to adhere to, it generally ends up looking very nice. This is a high-quality type of plywood that has great aesthetic value.
If you want something to look very nice, marine-grade plywood definitely makes for a great option. On the other hand, exterior plywood, while not bad, certainly doesn’t look as nice as marine plywood.
In both cases, you can take some extra steps to make the plywood look good.
Pest Resistance
Because it is much denser, has absolutely no core gaps, and is totally waterproof, marine-grade plywood is also more resistant to pests than exterior-grade plywood.
Overall Strength
The other main difference to keep in mind here is that marine-grade plywood is generally much stronger than exterior plywood.
Exterior plywood is still strong, and structural in nature, but not like extremely high-quality marine-grade plywood. Marine plywood can absorb more bumps per square inch than exterior plywood.
When to Use Exterior-Grade Plywood?
Exterior-grade plywood is best used for general construction purposes, especially when the outdoors is concerned. Do keep in mind that exterior plywood doesn’t look all that nice, so it’s not something that you would finish your house with.
However, if you aren’t particularly concerned about aesthetic qualities, using exterior-grade plywood to build a shed or something similar is certainly feasible.
Exterior plywood is also something that you would use as house sheathing for walls before you add the final layer, such as the exterior wall or stucco. Exterior grade plywood may also be used for outdoor shelving, small outdoor structures, outdoor furniture, and other related projects.
When to Use Marine-Grade Plywood?
Simply put, if there is water involved, you definitely want to use marine grade plywood. This is the case if you are building a boat, a pier, a dock, or anything similar.
On that note, if you live in an extremely moist climate, such as right beside an ocean, then you also might want to consider using marine plywood.
If you have a shed sitting right next to the ocean, it’s going to constantly be damp, so having plywood that is waterproof is going to be beneficial. If something is always near water or even submerged in it, then marine plywood is going to be what you need.
Alternatives to Exterior and Marine-Grade Plywood
There are some good alternatives to both exterior and marine-grade plywood:
- If you are building furniture and cabinets, and you want them to look nice, sanded plywood is a good option.
- If you are making interior cabinets, cabinet doors, or other small pieces of furniture that don’t need to bear much weight, MDF is always an option to consider.
- If you are building furniture, and you want it to look very nice, and also have a natural aesthetic, softwood plywood makes for a good choice.
- If you are building something that requires a strong load-bearing frame, hardwood plywood is also a good bet.
Summary
You should now know all of the relevant differences between marine and exterior plywood to make an informed choice between the two. Both are some of the best options to consider if you need to use plywood outside.