If you’re building something outdoors, you need something strong and weather-resistant to withstand well. On the other hand, plywood suits many projects well and is used widely for its versatility and strength. However, not every plywood can be used for all types of projects.
You might be wondering if you can use plywood for an outside project or not.
Can plywood be used outside?
Plywood can be used outside but it needs to be of the right type. Regular plywood is not suitable for outdoor projects. But different types of exterior grade plywood resist well against moisture and rot to be used outside. It can be a good idea to seal plywood before outdoor use.
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Bear with us and find out if the following plywoods are suitable for outdoor projects.
Luan plywood:
Luan plywood has both interior and exterior grades. The exterior luan usually comes with phenolic glue. But luan plywoods are most suitable for interior use as they are quite lightweight and strong.
Marine plywood:
Marine plywood can be used outside. These are specially made to withstand water longer. But, marine-grade plywoods are quite expensive compared to other exterior plywood.
RTD plywood:
RTD plywoods can be used outside. They are quite durable and do well to hold up when exposed to constant moisture. They can be used for roofing and other applications.
Birch plywood:
Birch plywoods are not suitable enough to use outdoors. They don’t come with water-resistant properties to protect against moisture and rot.
OSB plywood:
OSB can be used outside. It works well when semi-exposed to nature. OSB can be used in humid conditions. Constant exposure to water can ruin them.
Regular plywood:
You can’t use regular plywood outside as they are not designed for outdoor purposes. Regular plywood can’t stand moisture for too long and can start to disintegrate.
Interior plywood:
You should not use interior plywood for outdoor projects. Interior plywoods are designed for indoor use where appearance plays the most important role. They are not fit to hold up against weather changes.
Exterior plywood:
You can use exterior plywood for outdoor use. These plywoods are designed for outside use so they are made with layers glued together with strong adhesives to stand against moisture and rot.
MDO plywood:
MDO stands for medium density overlay. It is a special type of plywood that can be used both indoors and outdoors. It is durable and resistant to swelling and warping as it protects against moisture.
Sande plywood:
Sande plywood can be used for outdoor projects and applications. It is made for marine purposes and marine-grade plywoods do well in outdoor conditions. It is made of high-quality wood.
Hardwood plywood:
You should not use hardwood plywood for outside projects. Hardwood plywoods are used for various indoor projects. Using them outside untreated may cause them to disintegrate at one point.
Can plywood be used outside if painted?
You can use painted plywood outside but regular plywood won’t last that long. Paint can’t protect regular plywood from moisture for a very long time but it can delay the process of disintegrating and give it some extra years.
In this case, all the sides and edges need to be painted with high-grade exterior paint.
When it comes to exterior plywood, you can use it outside both painted and unpainted. Exterior plywood is sturdy enough to withstand humidity and moisture on its own for a long time.
If you want to paint plywoods for an outdoor project, try to apply three heavy coats to seal them completely.
How long will regular plywood last outside?
Regular plywoods are not meant for outdoor use where weather change is inevitable. They are designed focusing mainly on appearance as they are used for interior finishing and cabinetry.
They are not resistant to moisture or temperature and if you use regular plywood outside, it won’t last very long.
On the other hand, outdoor plywoods are often not pretty to look at as they come with knots and spots. But these are durable and the layers are attached with strong waterproof adhesives to withstand moisture.
If you use regular plywoods on outside projects, they will soon start to warp when exposed to water for a long time.
What plywood is good for outdoors?
You can use the following plywoods for outdoor use –
Marine plywood:
Marine plywood is a great option for outdoor use. It is quite similar to CDX except for the fact that the sheets don’t include knots. Without the knots, marine plywood has little to no risk of water pocket formations.
It is more durable and has the best quality exterior plywood. It has a more refined appearance so it can be used both indoors and outdoors. It is easy to install and requires little maintenance.
CDX:
It is the most common type of plywood that works best for outdoor projects. The X in the name stands for outdoor or exterior use. The C and D mean that it is of construction grade.
CDX comes with three levels of thickness. It is less expensive compared to other exterior plywood. Another common option is ACX where A stands for premium grade used for cabinetry.
Pressure-treated plywood:
Pressure-treated plywood is a combination of regular plywood and chemicals and is built under pressure. The chemical infusion gives the plywood a greenish tinge. It has an oily surface.
Pressure-treated plywood is resistant to mold and mildew so it makes a great option for outdoor use to protect against drastic weather change. It doesn’t need any extra protection and its life expectancy is 30 years or more.
Overlaid plywood:
Overlaid plywood is similar to ACX or CDX. It has a cleaner finish which makes it a good option for better-looking projects. It looks more attractive compared to ACX or CDX and it also stands well against weathering.
Oriented strand board:
This is an engineered plywood substitute. Many builders love it as it is less expensive compared to any exterior grade plywood. It performs well in areas that are semi-exposed to nature. It is mainly used for roof decking and sheathing.
T1-11:
It is another exterior-grade plywood, mostly used for siding. This plywood comes with a rough-sawn look. You can paint or stain the plywood after installation to fit any color scheme.
Can you make plywood waterproof for outdoor use?
You can make plywood waterproof for outdoor use. Waterproofing regular plywood can help keep the qualities intact for longer. But you’re not supposed to use regular plywood outside as they can’t stand the weather change and delaminate easily.
Even though exterior grade plywoods can last long by themselves, waterproofing can make them last longer.
You can use epoxy sealant, polyurethane varnish, spray-on latex, drying oil, or waterproof paint to seal plywoods. You need to sand the plywood before applying the chosen sealant.
Also, opt for multiple thin coats instead of a few heavy ones, and don’t forget to dry each coat well in between.
Does plywood have to be behind the cement board outside?
Cement boards are more stable than plywood and perform well when exposed to water and humidity. Plywood does not have to be behind cement board when used outside for all types of projects. Usually, for ceramic floors, cement boards are installed over the plywood subfloor.
You shouldn’t put tiles directly over plywood. A plywood top layer should be covered by a cement board before the installation of tiles for better adhesion and security.
How do you prepare plywood for outdoor use?
The following steps will help you to prepare plywood for outdoor use.
Choose and prepare the right working space:
You need to choose the right working space for your job. Make sure to clear the area so you can work freely. It is better to choose a well-ventilated space.
If your steps include sanding and sealing the plywood, you should prepare safety goggles and gloves. Also, you can cover the floor and any other important spaces to protect them from sealant and sanding dust.
Use wood filler to cover up uneven spots:
In this step, you can choose to fill up any uneven spots or grooves with wood filler. You need to be extra careful around the sides. As you fill the spots, wait for the filler to harden and dry fully.
Sand down the plywood:
If you plan to apply a sealant over the plywood, you need to sand it down first. Before that, you should wipe down the entire surface. You can first use a medium-grit sandpaper and then fine-grit sandpaper to make the surface smooth.
Wipe the surface with a dry cloth or soft-bristled brush.
Apply the sealant and dry completely:
In this step, you can choose your sealant and apply it according to the user guide of the sealant. Make sure to apply multiple coats for better protection. Dry between the coats and after the full application, wait for at least a day before installing the plywood.
Final Thoughts
Plywood can be used outside, but only the right type of plywood can withstand weather changes. Regular plywoods are not suitable for outdoor use and can disintegrate fast. You can choose different exterior-grade plywood for outdoor use. Sealing plywood is a great way of protecting from moisture.