What Size Plywood Should You Use For Your Roof
The industry offers a thickness of anywhere from 5/16 inch to ¾ inch. So, what size plywood should you use for your roof?
There are several factors to consider:
- How the roof is designed.
- The spacing of the rafter.
- The expected load.
A half inch thickness is considered to be standard in a lot of areas and it should work just fine considering that its deemed okay by the roofing contractor after considering the things above. Its the standard for spacing of 24 inches in the rafter, although as mentioned, a 5/8 inch thick is more ideal. You might be tempted to choose a ¾ inch thickness although its unnecessary in most cases.
You can get plywood sheets with a length of up to 10 feet. The standard width is 4 feet.
Talk to a professional so that the factors will be properly considered so you can make the right choice on the best wood.
What Size Of Plywood Does Your Roof Need
The plywood thickness your roof requires depends on the load that the roof will need to be able to handle. If you have a flat roof, it will have a heavy load so you will need a thick plywood. By comparison, a pitched roof handles a lighter load as the weight gets evenly spread across the roof, so the plywood can be thinner.
Some older homes have -inch thickness but this is not the norm because its a bit too fragile. You therefore will have to settle for plywood thickness thats between ½ and inch thickness, both of which are suitable for standard loads with roof rafters being placed 24 inches apart.
Should You Choose ½-inch or -inch Roof Decking?
These are the most common thicknesses for roof decking, so you might wonder which one you should use and if it even matters. Basically, plywood thats -inch decking is stronger and more durable than ½-inch decking because of its extra thickness. It also produces a smoother finish as it hides any valleys between joists and trusses.
But, it takes more time and money to install. Its a good choice if your home is susceptible to hurricanes, a lot of snowfall, or other extreme weather conditions, because its thicker and therefore more protective.
What Wood Is Used For Roofing
Roofing is part of the building process. The roofing system involves the proper laying of wood planks or sheet to form the frame. With careful planning and orchestration and by choosing the right wood material for the deck, roof stability will be achieved. During construction, before placing roof tiles as the top covering of a structure, layers of work are involved, and this included building the roof foundation. Pillars, beams, rafters and ridges are joined together to form the frame.
Rafters are wood materials that are integral in finishing the decking. Here, decking or sheathing is laid before underlayment and tiles can be placed. The wood type for the decking will depend on tiles used. Tile materials have different weight specifications, and it takes smart engineering to build a sturdy roof deck.
You May Like: Skylights In Metal Roofing
What Is The Required Measurement For Roofing Plywood
Plywood comes in 4 b 8 feet sheets, but with varying thickness. For roofing, you need 3/8th of an inch thickness. The most common thickness is half an inch or 5/8th of an inch, which is the recommended size. Rafters are placed at a spacing of 24 inches, this accommodates the 5/8 thick plywood comfortably.
Permeability: Which Works Better Osb Or Ply :
The vapour permeance of building products is expressed in Nanograms in Canada , as in how many NGs of moisture can pass through a material, tested under specific conditions. In the US they go by ‘perms’, and 1 US perm is equal to 57 NG . So for simplicity, we’re going to roll with perms only from here on.
Between .1 perms and 1 perm, a material is classified as a type II vapour retarder, which is suitable for use as what is exclusively known as a ‘vapour barrier’ on a work site, the standard 6 mil polyethylene. And remember – a vapour barrier goes on the inside of a wall, NOT the outside. Since we intentionally contain water vapour on the interior of a building with a vapour retarder, the more vapour-permeable the exterior of your wall is, the less likely you will have moisture buildup inside.
The vapour-permeable elephant in the room?
The most commonly held opinion among building industry experts that we have read and spoken with, is that OSB has a perm rating of 2 and plywood has a perm rating of 10.
Those are the perm ratings you will find on many building information websites, though it conflicts with what is found in section 188.8.131.52 of the Canadian National Building Code, which rates the standard 7/16″ OSB at 44 NG and 3/8″ plywood at 57 NG, or 1 perm. Since anyone using plywood as sheathing will usually use 1/2″ , according to code, all sheathing is a Type II vapour retarder, the same classification given to 6 mil polyethylene.
Recommended Reading: Overhang Extension
Choosing Plywood For The Roof
Choosing the right type of plywood for the roof is one of the most important construction decisions that you will have to make. It determines how long your roof will last and how well it will protect the contents of your home. Both OSB and plywood for the roof have been approved for use, so it may come down to what you feel most comfortable using. Be sure to weigh the advantages and disadvantages of each option before you decide which way to go for your new home or your updated roof.
What Should You Look For In Using Plywood For Roofing
Among all the structures in your home, the roof is the most important so constructing it is given the utmost care possible.
While plywood may not be as crucial as roofing shingles, it still is an essential component and a big help in making the roof more durable.
When choosing plywood for your roof, here are the attributes you should look for:
Don’t Miss: Roofing Cost Los Angeles
When Was Plywood Invented Who Invented It
The earliest idea for plywood was conceived in 1797, when Samuel Bentham first applied for patents that covered the machine production of veneers. In those patents, he described laminating layers of veneer with a specialized glue in order to form a single thick piece. Roughly 50 years later, Immanuel Nobel realized that several thin layers of wood could be bonded together to establish a single durable piece of laminated wood, known now as plywood.
Below Are Some Comparisons
1. The Oriented Strand Board is considered more structurally consistent than plywood as it compacts more strands of wood in a sheet of the same thickness as that of plywood.
2. While OSB absorbs less moisture, plywood absorbs more but dries out more completely and faster.
3. The Oriented Strand Board does not delaminate, affecting plywood, but it is mainly prone to swelling at the edges when exposed to water.
4. Oriented Strand Board is cheaper than plywood.
Read Also: How Do I Know If My Roof Is Leaking
Why Use Plywood For The Roof
First, plywood is made of an inexpensive material that is water-resistant with structural stability. For this reason, most builders consider it one of the best and favorite option among other materials used for exterior parts of the house. Despite the roof structure being taken by its brunt, plywood is naturally strong and can be relied on to support the entire roofing system. Its strength is from the make and the materials used for the plywood. It is made up of wood that is layered together. These layers run in an alternate direction, making them more compact and firm.
Plywood is also made so that its strength is equally distributed, which is enhanced by the layering of materials used. Layering minimizes the shrinking and expanding of wood in case of temperature changes or splitting when nailed into. It is also known to do well even when exposed to moisture over a long period from the way it is made. It has an even expansion and ability to dry fast, causing it to retain its original size.
Such features do not apply in other wood types as some will either decompose or weaken when exposed to moisture over an extended period. Plywood has a short drying time, and for this reason, it does not affect the roof.
Plywood For Roof Sheathing
Roof sheathing or roof decking involves installing a layer of plywood or OSB to cover the joists and trusses, the beams that make up the skeleton structure of a roof.
The sheathing is placed below the roofs shingles and above its framework. It provides the roofing tiles and shingles with a support layer to rest on.
The purpose of sheathing is to:
- Provide support as it prevents the direct attachment of shingles to joists and trusses by evenly distributing their weight shingles.
- Provide extra protection by incorporating an additional layer of insulation to resist leaks and reduce the spread of fires.
Roof sheathing is typically made out of wood, either plywood or OSB. While the latter is less expensive, its more fragile and lightweight, so many roofers go for plywood.
Don’t Miss: Adding Eaves To Gable End
What Are The Advantages Of Plywood
There are advantages of hardwood plywood over other options like wood veneer, hardwood veneer or even solid wood. You may not know it, but plywood is actually stronger than solid wood . Plywood material also often cheaper than solid wood, and can look just as attractive if you go for a decorative plywood or plywood veneer.
However functionality sometimes trumps design, particularly when comparing commercial plywood with other types more suited for furnishings and decor. Commercial ply is not known for its aesthetic appeal, and which makes it even more important to know the different plywood types before you buy. This is something to keep in mind the next time you purchase a plywood product
What Kind Of Plywood Do You Use On A Flat Roof
4.7/5plywoodveneershould be usedflat roofs
Accordingly, does a roof need plywood?
Sometimes referred to as roof sheathing or a roof deck, this plywood acts as a foundation for the layers of underlay and the shingles on your roof and connects the roof to the frame of the house. Even though it isnt visible, it is very important to the structure of your home.
Also, what thickness OSB should be used for roofing? 7/16-inch
Also, is OSB better than plywood for roofing?
OSB takes longer to get wet than plywood but also takes longer to dry out. When used as a roof sheathing, this tendency to hold moisture means it can degrade faster than plywood when exposed to chronic leaks. Swollen edges have been known to telegraph visible ridges called ghost lines through asphalt roof shingles.
How thick should Roof plywood be?
Most Common ThicknessFor rafters spaced 20 or more inches apart, 1/2- or 5/8-inch plywood is recommended. The most common rafter spacing is 24 inches, and 5/8-inch plywood is recommended for that. It will support roof loads for most situations and is the standard for most roof applications.
You May Like: Can You Use Flex Seal On Camper Roof
Read Also: Roof Replacement Cost California
What Is Roof Decking/sheating
Also known as sheating, decking is basically where the roofer attaches the shingles or whatever your chosen roofing material is. Obviously, it should be graded for exterior use meaning it should be able to withstand rain especially during the construction of the roof. The waterproofed coat of plywood makes it a top choice along with OSB, planks and wood boards.
What is plywood? Plywood is made out of laminated sheets of veneer. Its a top choice because of its characteristic wherein it expands evenly when exposed to water unlike OSB wherein only the edges expand.
Speaking of OSB, its a top choice of homeowners looking for something more affordable than plywood. As a warning, its considered by some to be inferior in quality as compared to plywood. Well discuss plywood vs OSB more later.
Recommended Reading: How Much Does A Roof Cost In California
Sealing The Roof Sheathing
How does sheathing stop leaks if its just a bunch of boardsplaced on the rafters and joints?
The key is sealingit. Plywood and OSB have seams between the sheets of sheathing. This canpotentially allow water to seep through the cracks and cause indoor leaks,especially in severe weather. When you seal those seams, you make it harder forwater to leak through and cause damage to your home or business.
Sealing the sheathing on your roof is an affordable thing todo. The materials used to seal the seams generally some form of roofers tape are easily accessible, and most professionals in the field practice thisprocedure.
Takingthis little step has the potential to save you thousands of dollars in damagesafter a severe storm. Check out this short video for a demonstration on whysealing the roofs sheathing or decking is important if not necessary:
Recommended Reading: Roof Overhang Extension
Mastering Roof Inspections: Asphalt Composition Shingles Part 38
The purpose of the series Mastering Roof Inspections is to teach home inspectors, as well as insurance and roofing professionals, how to recognize proper and improper conditions while inspecting steep-slope, residential roofs. This series covers roof framing, roofing materials, the attic, and the conditions that affect the roofing materials and components, including wind and hail.SUBSTRATES
Substrate is a generic term that refers to an underlying supporting material. In addition to roofs, a substrate can refer to walls, floors, and even soil. When discussing roofs, the substrate can be the wood roof sheathing or, if new shingles are being applied over old, the old shingles could be considered part of the substrate.
Sheathing is a more specific term used to describe boards or panels that form the roof deck. Since sheathing also describes rough wall and floor coverings, well use the full terms roof sheathing and roof deck.
In older homes, the roof sheathing is usually wood boards. Over the years, plywood replaced boards, and oriented strand board, or OSB, has gradually replaced plywood.
Typically, older homes were originally roofed with wood shakes or shingles.
To encourage drying, they were laid over wood-board roof sheathing, with spaces left between the boards to improve air flow. When the original wood shakes or shingles failed, they were typically replaced with asphalt shingles, which require solid sheathing.
Plywood and OSB
Can Plywood Be Bent
Although plywood can be bent, it has to be of a specialized variety, as most other types of plywood will splinter and break if they are bent. The best variety of plywood available for bending has to be close-grained so that the surface does not separate with bending. Close-grained hardwood faces are ideal, which include plywoods that are made from mahogany, poplar, and birch.
You May Like: How Much Roof Overhang On Shed
Should I Use Cdx Or Osb For Roofing Plywood
When planning to redo your roof or repair some damages, you might come across different grades and types of wood, such as OSB and CDX and start wondering what those abbreviations mean. What are the differences? Is one better for roofing than the other? Should I use CDX or OSB for roofing plywood? OSB and CDX do not only look different, but they have unique characteristics that make one better than the other in specific applications.
Lets learn the differences between CDX and OSB so you can make a more informed decision when it comes time to choose one or the other for your roofing project.
What Type Of Plywood Is Used For Roofing Size And Thickness Guide
A roofing system consists of a variety of materials and parts, which are interconnected to protect the inside of your house from harsh weather conditions and elements.
The materials used may vary, depending on the location of the building to the shape of the roof and even the surrounding climate. The materials can range anywhere from asphalt, wood, metal, clay or even glass.
On more modern homes, roof decks are more often seen with laminated panels of plywood, or non-laminated oriented strand boards .
Don’t Miss: Roof Cost California
What Is Roof Sheathing
Roof sheathing, also known as roof decking, is a layer of plywood or OSB that covers the trusses and joists, which are the beams that make up the roofs skeleton shape.
Roof sheathing goes above the roofs framework but below its shingles. That is because roofing shingles and tiles need a layer of support to rest on.
The purpose of roof sheathing is to support the roofs structure by evenly distributing the weight of the shingles, instead of directly attaching them to trusses and joists.
It also provides additional protection by adding an extra layer of insulation against leaks, slowing the spread of fires, and more.
Usually, roof sheathing is made of wood. It can come in the form of plywood or oriented strand board . OSB is less expensive, but lighter and far more fragile, which is why many roofers rely on plywood.
The Thickness Of Plywood For Roofing
When it comes to selecting an appropriate thickness of plywood for roofing, a few factors come into play. The choice will mainly depend on:
- The space between rafters.
- The slope of the roof.
- The weight of any other material that you plan on installing on top of the deck.
- The load of the design is the stress that the roof is expected to endure due to weather elements and various forces, especially the weight of ice or snow build-up.
As a rule of thumb, the wider the space between rafters, the heavier the shingling. This lowers the roof slope, which causes the weather load to be heavier. Consequently, the thicker the plywood youll need to use.
Recommended Reading: Hydrostop Cost Per Square Foot