Even though plywood is more expensive, and OSB stronger, my recommendation for a shed roof is 5/8” or 3/4″ construction-grade exterior rated (CDX) T&G plywood.
When planning to build a shed you have to make decisions. What to sheath the floor, walls and roof with are important considerations. Do you buy plywood for the shed? OSB? Pressure treated? What thickness? Then there are the prices!
So what type of plywood to use for a shed? Use pressure treated 3/4 inch construction grade exterior plywood for the floor. It’s solid, won’t sag, and protects the substructure and is easy to sweep. On the shed walls use exterior rated 1/2 inch plywood for a waterproof finished look, and 3/4 inch CDX plywood on the roof for strength.
In this article I’ll explain my recommendations, the differences between plywood and OSB, and why plywood is a better option for exterior shed walls.
What is the Best Material for Shed Floor?
The best material for the shed floor is pressure treated 3/4 inch construction grade exterior plywood. Being pressure treated means wet tools or snow from the snow-blower or your boots, won’t damage the floor. It also will protect the floor structure from moisture too.
I stay away from tongue and groove as it leaves a gap that collects dirt. Just make sure the seam is on a joist or supported by a cross piece. The exterior grade has football shaped plugs to create a smooth finish, which is easier to sweep and paint.
OSB can be used for the floor of the shed, but even the smooth side has a roughness that collects dirt. It is stronger than plywood of the same thickness and is available in sheets up to 8 feet by 24 feet – great for larger uses. However, sliding items across it can cause chips to flake or tear off.
Oriented strand board is more water-resistant than waterproof; even though it is supposed to be waterproof. It will swell and shrink if exposed to moisture, and takes longer to dry out than plywood. It dries better on a vertical than a horizontal surface.
Can you use 1”x 6” PT lumber for the floor of the shed? Dimension lumber doesn’t have the measurements by which it is sold. It starts out that size, and then goes through a planning mill, which makes it smooth with rounded edges, but also thinner. 1” X 6” PT lumber is 3/4″ X 5-1/4″.
1” X 6” lumber may be great for fencing or use on decks with extra support, but not for a shed floor. It isn’t as strong as plywood and will shrink creating gaps in the floor.
3/4-inch-thick T&G plywood is another option and is better than pressure treated lumber. However, it is susceptible to water damage and the crack where the tongue and groove interlock collects dirt and tends to catch edges when sliding objects across the floor.
Pressure treated plywood is the best option for a shed as it provides a smooth, almost seamless floor. The surface withstands objects being slid across it; it is easy to paint and to sweep clean. Additionally, the pressure treated product is resistant to water damage and will protect the floor from moisture.
What Kind of Plywood Should You Use for a Shed Floor?
Softwood plywood is the most common. It is made from 3 or more layers of pine, spruce, or fir veneer (thin sheets) glued together. The grain in each layer is perpendicular to the previous layer. This makes it stronger than an equivalent thickness of the wood. The sheets are cut into 4’ X 8’ panels. Hardwood or cabinet grade plywood is made the same way as softwood plywood, but the two exterior faces are hardwood.
is the most common. It is made from 3 or more layers of pine, spruce, or fir veneer (thin sheets) glued together. The grain in each layer is perpendicular to the previous layer. This makes it stronger than an equivalent thickness of the wood. The sheets are cut into 4’ X 8’ panels. Hardwood or cabinet grade plywood is made the same way as softwood plywood, but the two exterior faces are hardwood. Marine plywood is specifically designed for boats. There are no gaps in its construction and water boiled proof glue is used to keep it together. It’s 3 times more expensive than softwood plywood.
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is specifically designed for boats. There are no gaps in its construction and water boiled proof glue is used to keep it together. It’s 3 times more expensive than softwood plywood. Particle Board is made of sawdust and glue. Is very brittle and doesn’t survive moisture. MDF is made of wood fiber and glue. It is slightly stronger than particle board but as susceptible to moisture.
is made of sawdust and glue. Is very brittle and doesn’t survive moisture. MDF is made of wood fiber and glue. It is slightly stronger than particle board but as susceptible to moisture. OSB is made of wood chips or strands glued together. About 50 layers make it stronger than the 5 to 7 layers in softwood plywood. It’s used for subfloors, roof decks, and wall sheathing where it can be protected from moisture by other layers.
is made of wood chips or strands glued together. About 50 layers make it stronger than the 5 to 7 layers in softwood plywood. It’s used for subfloors, roof decks, and wall sheathing where it can be protected from moisture by other layers. Baltic or Russian birch and ApplePly are made from multiple layers of thinner veneer. Often used for furniture or design work, it is much stronger than regular plywood. However, it is much more expensive.
Before we decide which plywood is the best for a shed floor, let’s take a look at what options there are. The term plywood originally meant layers of wood veneer glued together. Today, it refers to all types of engineered panels made from wood products.
Softwood plywood is as strong as pressure treated plywood of the same dimensions. However, pressure treated plywood is resistant to water damage. It will also protect the floor structure from moisture damage and rot.
Although there are many types of plywood to choose from, by factoring in use, it is easy to make a decision. If the shed is for light tools then 1/2 inch pressure treated plywood is acceptable. If the shed is for heavier storage, then pressure treated 3/4 inch exterior-grade CDX plywood is the best.
What Plywood Can I Use for Shed Walls?
When building a shed , remember that the sheathing helps to strengthen and square up the walls. It provides a base for siding to be nailed to. It should be the appropriate thickness and also rated for walls.
The material I would use for the exterior walls of my shed is 1/2 inch CDX rated plywood. It is more resistant to moisture and rot. I can paint or stain it, or cover it with siding.
What you sheath the walls with depends on if you’re going to put siding on them, or leave it bare and paint or stain it. The thickness of the sheathing also is determined by the finish. If painting or staining, it can be 3/8” thick. If covering with siding, it should be strapped or ½” or thicker to ensure nails don’t stick through.
OSB can be used for exterior shed walls but needs to be covered or sealed soon after installation. It takes longer to get wet but also takes longer to dry than plywood. Moisture can also cause it to degrade more quickly. Be aware that stain and paint don’t always adhere to board, and cut edges tend to flake more easily.
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If you decide to use plywood, it too should be covered, stained or painted. It may get wet more quickly than the oriented strand board, but it will dry more quickly and cut edges don’t flake. Paint and stain roll onto the smoother plywood surface more easily too.
When selecting plywood for exterior walls, make sure you get exterior grade plywood. The glue used is waterproof, so it is better suited to withstand the elements. It is resistant to moisture and rot. X stamped plywood is suitable for exterior use and doesn’t have to be painted or stained.
What Kind of Plywood Should I Use for a Shed Roof?
There are some factors to consider when looking at your shed roof; slope, snow load, wind, and what you’re going to finish it with. The spacing of your rafters or trusses is also a factor – 12”, 16”, or 24”. Steel, asphalt shingles, cedar shakes, need to be fastened to whatever material you use. And finally, the size of the roof; the bigger it is, the more your budget factors in.
Even though plywood is more expensive, and OSB stronger, my recommendation for a shed roof is 5/8” or 3/4″ construction-grade exterior rated (CDX) T&G plywood.
The higher the slope, the more quickly the snow and rain will be shed, but also the greater the wind force. The lower the slope, the more weight for snow load, but less wind force. Having had my foot go through a couple of roofs, I always use ¾” thick material.
To ensure the nails and screws have enough material to grip, I recommend a 5/8” for a slope over 5/12, and 3/4-inch-thickness for anything less. It provides a solid base for walking on, doesn’t sag, and nails and screws have a good grip. I’ve heard the arguments for ½” material, and yes, you can use it, but I’ve seen too many roofs sag over time.
Hammering nails into plywood seems much easier than into OSB. Driving screws into either is about the same. If using oriented strand board, it’s recommended the smooth side is down.
To make sure the edges are supported between rafters, I use with T&G. I’ve used H-Clips, but they leave a gap in the roof deck that insects and moisture seem to find. If you’re building for yourself, skip the H-Clips.
Exterior grade plywood and OSB are the two main choices for roofing. While strand board is stronger in shear force, plywood of the same thickness is lighter – easier to lift on your own. Exterior grade plywood is more water resistant than strand board – based on my observations, exposed edges or leaks cause more damage to OSB than to plywood.
Related Searches: Shed Roof Plywood Thickness
Plywood thicknesses for roofs start at 3/8” in areas with light load requirements on rafters at 16” centers. Thicknesses of 1/2 to 5/8 inch are common with rafters spaced at 24” centers. For heavy load rated areas, 3/4-inch-thick plywood is recommended, regardless of rafter spacing.
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Photo: Taryn Elliott
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