Selecting the right material for a project can be difficult, such is the case of plywood and OSB. They can be used interchangeably, but there are some key differences that make one a better choice than the other for certain purposes. If you’re wondering what the differences are and which is better for your plan, plywood vs OSB, we’re here to help!
OSB and plywood can be used interchangeably for many construction applications. OSB has better shear strength, more consistent density, and is less permeable to moisture. Plywood looks like solid wood, has a smoother finish, holds nails better, can be used for cabinetry, and has better impact strength. Thickness to thickness, though, OSB is 30% to 50% less expensive.
In this guide, we’ll identify what plywood and OSB are and look at some of their pros and cons. We’ll also compare the two products based on key points and include a helpful comparison table. Plus, we’ll discuss which is best for outdoor use or building a shed, and better overall. Our aim is to provide you with the information to make the best decision for your project.
- Plywood vs OSB: Key Points
- What is Plywood?
- What is OSB?
- What Is the Difference Between Plywood and OSB?
- Pros and Cons of Plywood
- Pros and Cons of OSB
- Is OSB Better Than Plywood for a Shed?
- OSB or Plywood for Outdoor Use
- Which Is Better OSB or Plywood?
Plywood vs OSB: Key Points
Plywood and OSB can be used interchangeably for many building purposes. They both have strengths and weaknesses, though, that may sway the selection, one way or the other. To assist with your decision, the Table below offers a quick comparison between the two materials.
|Shear Strength||4.14 MPa to 7.11 MPa or 600 psi to 1031.2 psi.||7.18 MPa to 10.34MPa or 1041.4 psi to 1499.7 psi.|
|Durability||Highly durable even when wet.||Highly durable, less so when wet.|
|Water and Heat Resistance||More permeable to moisture but dries more quickly, but dimensionally less stable. Becomes weaker and can char at 200°F.||Less susceptible to moisture and more dimensionally stable. Untreated cuts or edges will swell and cause flaking. Becomes weaker and can char at 200°F.|
|Lifespan||Exterior lifespan of up to 60 years and interior lifespan as long as the building if properly installed, maintained, and protected.||Interior lifespan as long as the building and exterior lifespan of up to 30 years if properly installed, maintained, and protected.|
|Cost||Depends on grade, thickness, and finish, usually 30% to 50% more expensive than equivalent OSB.||Depends on type, thickness, and quality, but is usually 30% to 50% less expensive per 4’x8’ sheet.|
|Typical Usage||Subfloors, roof and wall sheathing, shelving, cabinetry, interior paneling and wall finishes, painted floors, crafts, toys, and much more due to its solid wood look veneer. Much depends on the type, grade, thickness, and quality.||Subfloors, roof and wall sheathing, and shelving depending on the type, grade, thickness, and quality.|
What is Plywood?
Plywood is a manufactured engineered panel made of layers or ‘plys’ of hard or softwood. The plys are made using special machines that unroll the layers of wood from special peeler logs so they form a continuous sheet. The thickness of the ply depends on the wood species and end-use of the finished product.
The peeled sheet is cut into desired lengths and widths and dried before a special adhesive is applied. The plys are then laid to the desired thickness with the grain of each layer perpendicular to those above or below.
The 3 to 21 or more layer panels are then heated and pressed so the adhesive bonds the layers together. The plywood is then trimmed to size and sanded and may be processed further or sent to market.
The species of wood used, its thickness, the cross-orientation, the number of plys, and their orientation, along with the type of adhesive used, determine its strength and use. Plywood commonly comes in 4’x8’ panels and is available in different finishes and thicknesses between 1/4″ and 1-1/2”. The exterior layers are also often of higher quality or different wood species than the core layers too.
What is OSB?
OSB or oriented strand board is a manufactured engineered panel. It is made up of 1/32” thick 1” wide by 2.5” to 6” long leaf-like strands or flakes of soft or hardwood oriented in different directions. The strands are sliced off debarked logs or waste wood, so usually from trees not suitable for lumber or plywood use. The slices are stored until needed in large vats.
When required, the slices go through a dryer to remove moisture and pass over screens that separate large strands for the outer layer and small strands for the inner layer. The separated strands then pass to blending machines. In the blenders, the dry flakes are mixed with wax resin adhesives which they absorb and are coated in.
The strands are then oriented to form a large mat-like mass up to 50 layers thick. The outer layers are oriented in one direction and the inner mass of layers is in the opposing direction.
The thick mat of strands is then heated to 425°F and pressed at around 600 psi. The thickness of the inner layer or mass determines the finished thickness. The heat cures the adhesive, binding the pressed strands together to form OSB.
The sheets are then cut to size, sanded, and finished, ready for shipping. OSB is available in thicknesses of 1/4″ to 1-1/8”, widths of 4, 5, and 8 feet, and lengths of 8 and 9 feet. Special orders of 24 feet or longer are available upon request.
What Is the Difference Between Plywood and OSB?
Understanding how OSB and plywood are made helps to explain the differences between the two wood panels. Both panels can be used for structural applications like floors, walls, roofs, and beams.
However, there are some aspects where one product is better suited than the other. The sections below identify key differences that should be considered when selecting the best material for your project.
Plywood is made using veneer-grade soft or hardwood logs. The layers of veneer are laid perpendicular to each other and bonded together with glue before being pressed and heated. The inner layers are typically softwood and may have voids, while the top and sometimes bottom are a higher grade or species of wood. The thickness and number of plys determine strength and use.
OSB is made of lower-grade soft and hardwood logs or scrap wood, so is more environmentally friendly. All flakes are soaked in a wax-resin adhesive. The inner layer is made up of smaller flakes of wood oriented in one direction, and the outer two layers are parallel to each other but opposing to the inner mass.
The mass of flakes is heated and pressed to bond all pieces together. The thickness of the mass determines the finished thickness, strength, and potential uses of the panel.
Shear strength is the ability of a material to resist shearing or breakage due to a chopping or striking-like force. The shear strength of various thicknesses of plywood is 4.14 MPa to 7.11 MPa or 600 psi to 1031.2 psi. The shear strength of OSB is 7.18 MPa to 10.34MPa or 1041.4 psi to 1499.7 psi. So, OSB has stronger shear strength than plywood.
Both plywood and OSB are extremely durable products. They are engineered and manufactured to resist loads perpendicular and parallel to their surfaces. The combination of different grain direction and adhesive make both OSB and plywood stronger and more durable than solid wood. They also have a more uniform strength too.
However, both tend to swell when wet, which can cause issues with fasteners, especially for OSB in hurricane or tornado-prone areas. Impact strength is another wind concern that can affect durability.
19/32” or about 5/8” plywood is able to withstand an impact force of a 9-pound length of 2×4 ‘fired’ at a speed of 34 mph. That would require OSB with a thickness of 13/16” or 26/32” for comparable strength in a similar ‘missile test’.
The grade, type, and finish of the plywood and OSB affect their appearance. Plywood typically has one smooth or good side (G1S) with any exterior voids filled with wood filler or football-shaped plugs. However, some plywood grades may be rough on both faces or they can have one or two sides finished in a hardwood or high-grade softwood veneer. All plywood shows the wood grain, looks like solid wood, and can be painted or stained.
OSB usually has a smooth sanded face and a rough or textured underside, and rough edges. There are no voids, so it has a solid surface, but the flakes or strands are visible and add texture. It can be stained or painted, however, since the flakes were soaked in adhesive and may be of different wood species or grain exposure, absorption can be less even.
Water and Heat Resistance
Plywood is made of sheets of veneer that can absorb moisture and swell, causing damp edges or cuts to separate. Moisture can also make the material less dimensionally stable, as well as more slippery to walk on.
Plywood is also considered more permeable to moisture, which also means it dries more quickly. Exposure to heat above 200°F will weaken the plywood and can cause charring.
OSB is made of wood strands or flakes soaked in adhesive, making them less susceptible to moisture. However, untreated cuts or edges expose raw wood, which will absorb moisture quickly, causing swelling, separation, or flaking. Plus, once wet, it will take longer to dry. OSB is more dimensionally stable and less slippery when wet. Like plywood, OSB is weakened and can char at temperatures above 200°F.
Plywood and OSB are engineered building materials. They will both last the life of the house or structure provided they are installed and maintained properly, and protected from the elements. Longevity also depends on vertical or horizontal orientation, and on interior or exterior application.
While the interior life span is the same for both materials, plywood has an exterior lifespan of up to 60 years and OSB of up to 30 years in similar conditions. If left unprotected from the elements, though, plywood usually will outlast OSB, but both lose their structural integrity quickly.
Installation of both OSB and plywood often depends upon orientation and application. Construction adhesive works well with both products as do screws, but nails hold better with plywood than OSB. Both panel materials can be installed vertically and horizontally in both longitudinal and latitudinal orientations.
Fasteners should be spaced 6” to 8” apart on the perimeter and 8” to 12” apart through the middle. However, the spacing of studs, joists, trusses, and rafters often determines orientation. Plywood is also lighter than OSB of the same thickness.
The finishing material applied over OSB or plywood can also dictate panel thickness, type of fastener, and which is a better substratum, subfloor, or decking. Many tile, hardwood, and shingle manufacturers recommend using plywood as a backer versus OSB due to its flexibility and nail-holding ability.
Some also recommend 5/8” plywood or 3/4″ OSB, since OSB is more flexible the thinner it is. Additionally, some building codes require plywood to be used for some applications instead of OSB as well as identifying panel thickness requirements.
OSB and plywood used for interior purposes should be protected from the elements prior to and after being installed. The quicker they are protected from the elements the better.
Both can be damaged by moisture, but once covered by roofing material, flooring, or wall finishes, they shouldn’t require any maintenance. Having said that, though, all cuts or holes made in both OSB and plywood should be protected with an appropriate sealant.
OSB and Plywood used for exterior purposes should be properly maintained to protect them from the elements. The wood should be painted, sealed, or stained to resist UV and moisture damage.
The frequency of reapplication will depend upon climate, exposure, and the quality of both the protective coating and the panel. All edges, cuts, and holes should also be well treated and protected, and fasteners should be checked and protected too.
Both plywood and OSB are traded as commodities, so their price will vary with location and the time of year. The quality, thickness, and grade also determine its cost. Cabinet or Grade
A plywood is sanded smooth and has no defects, while construction or Grade D plywood isn’t sanded, so has defects and is rougher but is suitable for subfloors or roof decks. Plywood with hardwood veneers is even more expensive.
OSB can be used for most building applications that plywood can be used for and like plywood, there are different types, thicknesses, and qualities. Standard OSB is used for subfloors, walls, roof sheathing, and much more, and may be square-edged or tongue and groove (T&G).
Zip OSB has a waterproof facing and is ideal for exterior walls and roof decks. There is also Subfloor OSB that is stronger, smoother, T&G-edged, and better than standard OSB. However, the price varies, so shop around.
A 7/16” 4×8 sheet of OSB sheathing is $11.80 in my local home building store, and a comparable 15/32” plywood sheathing is $25.55, so more than double.
Both OSB and plywood are interchangeable in most building applications. They can be used for subfloors, roof and wall sheathing, shelving, and numerous other purposes. The type, grade, thickness, and quality often determine use.
Due to its solid wood look veneer, plywood is also used for cabinetry, furniture, interior paneling and wall finishes, painted floors, crafts, toys, and much more. Additionally, plywood looks better when painted or stained than OSB, plus it holds fasteners better.
OSB has a more unfinished or raw look, so even when painted, the texture of the flakes or strands is still visible, which may make it less aesthetically appealing for some uses.
OSB is available in 4×8, 4×9, 4×10, and 5×9 sheets as well as in 1/2 sheets or 1/4 sheets in a variety of thicknesses from 15/64″ to 1-1/2”. It can also be ordered in 4’, 5’, or 8’ widths by 20’, 22’, 24’, or longer panels too.
Plywood is commonly available in 4’x8’, 4’x4’, 2’x8’, 2’x4’, 2’x2’, 5’x10’, 5’x5’, 4’x7’, 3’x7’, 3’x6’, 4’x6’, 3’x8’, and other dimensions in a dozen or more thicknesses ranging from 1/8” to 1-1/8”. It is also available in larger lengths and widths, similar to OSB.
Pros and Cons of Plywood
Plywood is a common construction material that has been in use for more than 60 years, so has a proven track record. However, like everything, it has some positives and negatives to consider when choosing building materials. Here are some points to consider.
- Available in different thicknesses and dimensions
- Multiple grades and types of finishes
- Used for construction, cabinetry, furniture making, and more
- Solid wood look that can be left exposed and finished
- Better nail-holding ability
- Layers can separate, bubble, or warp if exposed to moisture
- Adhesives contain urea-formaldehyde, so off-gassing and dust are issues
Pros and Cons of OSB
OSB is a widely used building material that is used for floor, wall, and roof sheathing. Like any product, OSB has some strong characteristics but it also has some flaws. Below are some points to consider when selecting your building materials.
- Greater shear strength
- 30% to 50% less expensive per 4×8 sheet for equivalent thickness
- Available in long panels up to 24ft or more
- Has a uniform density with no voids or soft spots
- More environmentally friendly
- The adhesives contain formaldehyde, so off-gassing and dust are a concern
- Exposed raw wood will swell and flake if exposed to moisture
- Has a rough texture so not a good finishing product
Is OSB Better Than Plywood for a Shed?
The argument for which is better when building a shed, plywood or OSB, will never be won. It comes down to personal preference, budget, and how long you need or want the shed to last. Both materials require regular maintenance and should be painted or stained if left exposed to the elements.
Neither handles moisture well if left untreated. There are millions of sheds made of both types of materials, but since plywood has been around longer than OSB, it currently has a better record of longevity.
Plywood has a smoother finish, which makes it easier to paint or stain and slide boxes on, making it a better choice for the floor, especially if pressure treated. Plywood is also lighter, so may be easier for one person to manage.
Most shed roofs are covered with shingles, shakes, or metal, so the less expensive OSB is definitely the better pick there.
Aesthetically, plywood finished walls look better than OSB if left exposed and stained or painted. However, if the walls will be sided or otherwise covered, use OSB and put the savings toward the cost of the siding.
OSB or Plywood for Outdoor Use
Both OSB and plywood can be used for exposed outdoor uses, however, they both need to be stained or painted to protect them from the elements. Both are available in exterior grade or rated panels, but only plywood comes pressure treated. However, properly treated and maintained OSB will withstand similar conditions to plywood, provided it isn’t in contact with the ground.
If you want an exposed, smooth, solid wood-like finish, though, then plywood is the better choice. If budget is a bigger concern, go with OSB.
Which Is Better OSB or Plywood?
The use of proper building techniques and practices is as important as the type of building materials. Selecting the best material for your project usually depends on what the project is and the budget. For most building construction, OSB and plywood can be used interchangeably.
Plywood has better nail-holding ability and is less likely to produce squeaky floors. However, the use of construction adhesive and screws make OSB a quiet option too.
Both plywood and OSB meet the building code requirements in most areas for walls, floors, and roofs with little difference in thickness. They have similar performance in most test environments and in the field.
However, while plywood has been around longer, OSB presently accounts for 70% of the sheathing materials being used for wall, floor, and roof construction. However, if you’re building cabinetry or furniture, plywood is better. As to which is best for your project, we’ll leave that for you to decide.