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What Size Plywood Do You Use On A Roof

Plywood Size For Roofing

OSB vs. Plywood: Which Should You Choose for Your Roof Deck?

Plywood is defined as an engineered wood sheet made up of fine strands or layers of wood veneers glued together. The adjoining layers are placed 90-degrees to one another through a procedure called cross-graining. Roof loads vary with the slope of the gable. Types of Plywood come in different thicknesses ranging from 5/16 to 3/4 inch.

For rafters spaced 20 and above inches apart, 1/2 to 5/8-inch plywood is recommended. In most cases, the rafter spacing is 24 inches, and 5/8-inch plywood is recommended. This plywood will accommodate any roof load for most environments and is the most common roof application plywood standard. However, for any roofs with cumbersome roof loads, 3/4-inch Plywood will be required. Regardless of the plywood thickness, it should be a type suitable for exterior purposes. They are usually graded as Exposure 1 or Exterior.

What Type Of Nails For Sheathing

If you need to install new roof decking or OSB, youll need to nail it to the roof truss. There are fewer requirements for these nails than those used to secure shingles. Common nails, or even wood screws, may be acceptable nails for OSB roof sheathing. You should check with your building code and local bylaws to confirm.

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When Nailing 26 Inch Joists What Size Nail Should Be Used

In a 2×6 joist Id use a total of 8 8d or 10d nails, 4 per side, typically 8d in size or in some cases 10d these are the most-commonly-used nail sizes when toe-nailing 2x framing lumber as unless youre using box nails, larger nails tend to split the lumber, especially when, as in your photo, theyre nailed too close.

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Types Of Plywood Used For Roofing

There are multiple types of plywood available in the market like shuttering plywood, general plywood or structural plywood.

Shuttering plywood is used to hold concrete, while general plywood is used for non-structural roles. Like its name, structural plywood is used for structural purposes.

Structural plywood is put through tests to prove structural integrity and meets building regulations, while general plywood doesnt go through the same process.

CDX is the grade of plywood most commonly used for roofing .

The wood is graded on each side from A to D, depending on the level of imperfections, .

One side of the plywood could be A grade with the other side a D grade. This works if the lower graded side is used on the inside of the roof, while the high grade faces the outside.

The C in CDX represents the grade given to the front of the plywood, the D represents the grade given to the back of the plywood and the X represents the type of glue used to bond the layers together.

There is one more type of plywood that has been known to be used in roofing, which is Fire-Retardant Plywood or FRT Plywood. This kind of plywood can be life-saving in the time of a crisis and is sometimes required in certain areas.

What Size Osb Should Be Used For Roofing

Roofing Plywood Size

Typical types of wood used for roof sheathing are oriented strand board, known as OSB, and plywood, the most popular being OSB. Sheets of 7/16-inch thick, with no edge support, can be used in an area where the snow load is 30 pounds per square foot. With edge support and the same snow load, 3/8-inch OSB can be used.

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Plywood Thickness For The Roof

One of the most important factors when selecting the plywood for your roof is how thick each piece should be. Like most other things, there is no one right answer for the plywood thickness of your roof. The answer depends mostly on how far apart the rafters are and the roof loads, which vary based on the pitch of your roof.

The most common scenario is a home that has rafters set approximately 16 inches apart. In this case, plywood should be a minimum of 3/8 inch thick. However, you may need to consider bolstering the plywood thickness for a roof that has a higher load. A roof that lays practically flat will have a much heavier load than a steeper roof that allows rain, snow, and ice to roll right off.

Rafters that are slightly farther apart might require ½ inch or 5/8-inch-thick plywood. Many homes have rafters that are even wider at 24 inches apart and will require a thicker sheet of plywood. When this is the case, experts recommend a 5/8-inch-thick sheet. Keep in mind that the load of the roof still plays a role in the plywood thickness. A flatter roof with rafters farther apart may need a thickness of up to ¾ inch.

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Benefits Of Roof Sheathing

Roof sheathing helps distribute the weight of the entire roof evenly. Due to the sheathing boards attached to the roof system, it makes sure that heavy rain and snow do not cause sagging or bowing.

Since most sheathing boards are weatherproofed, having roofing sheathing helps prolong the lifespan of the roof and is safe from water leaking.

Asphalt shingles are commonly weatherproofing treatments and adding sheathing to this gives them an additional layer of protection.

When a massive snowstorm or typhoon goes near your home, roof seething assures your roof of no sagging or bowing.

Roof sheathing also has a fire-retardant treatment that helps prevent attic fires. Attic fires are prone to homes that are heat-insulated and exposed to extreme heat during the day.

If a roof has also passed its time of prime, it will be prone to breakage and damage from environmental changes.

For homeowners who opt to seldomly check up on their roof, roof sheathing will be a sustainable solution to secure the roof system in your home.

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What Is Roof Sheathing And Why Is It Important

How To Install OSB Roof Sheathing

Roof sheathing is composed of hardwood or metal covering that provides a flat, uniform, and stable platform for nailing or screwing the roofing material. It also acts as an additional layer between your house and the external roof materials, preventing water from going inside your house.

Sheathing reinforces your roof by equally distributing any weight or load applied. Roof sheathing serves the purpose of strengthening your ceiling and preventing it from collapsing upon itself. It is often connected to your roofs seams and trusses to keep your shingle from sagging or bending due to the changing environment. Roof sheathing provides additional fire protection by making it much harder for fire to spread to the rooftop.

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What Types Of Plywood Are There

There are two types of plywood used in roofing construction structural and general plywood. Structural plywood has proof of strength performance provided by the supplier and indicates it has passed the building regulations to be used for structural use in a building. General plywood does not have this proof of strength performance so should not be used for structural applications. Shuttering plywood is another type of plywood but it generally isnt used in roofing. Instead, it is used to hold concrete whilst it sets.

Generally, plywood comes in 4 by 8-foot sheets, and in a variety of grades. Each side is rated A to D, with A being of the highest quality and with no imperfections or knots, which can potentially lead to weaknesses in the sheet, and D grade is generally unsanded plywood that can have defects and knotholes of up to 2.5 inches. A-grade plywood is the most costly but can be combined with D-grade plywood if the side graded D is on the underside. CDX is the most common form of plywood, with a C-grade side and D-grade side, and the X stands for the glue that bonds the sheets together. Although not made of the highest quality sheets, it is often considered the strongest due to the glue used to seal it together.

Whether youre looking for plywood, pitched roofing materials, flat roofing materials, or accessories, weve got everything youll need, and if you have any questions give our experts a call on 01752 692 760.

Will Cold Climates Require A Thicker Roof Sheathing

Whether youre sheathing a house or a shed, you should always keep the weather in mind while deciding on the suitable thickness for the roof sheathing, especially in the winter.

This is because winter is where the majority of the rain and wind occur, which are the true test of the structural integrity and durability of the roof sheathing.

Moreover, in northern states, winter is often accompanied by snow, which puts a tremendous load on the roof in terms of sturdiness and moisture resistance.

Another specification that the APA includes on the label of the roof sheathing is the maximum load it can support, which is usually measured by pounds per square foot or psf.

If you live in an area where snow falls regularly, its always better to err on the side of caution and go for a roof with a load tolerance of about 50 psf or higher.

Of course, panels rated at 50 psf or higher are usually thicker than average roof sheathing options, and they usually cost a bit more, so you have to keep that in mind.

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How Much Does Mdo Weigh

MDO: Medium Density Overlay is a type of exterior plywood specifically designed to be painted easily, holding the paint better, and looking better after painting, than other types of engineered wood panels.

The wood plies are typically softwood, and a thick, smooth layer of a highly water-resistant resin is applied to one or both sides of the panel.

A typical 4 x 8 sheet of 1/2-inch MDO weighs around 48 lbs.

Is 1/2 Inch Plywood On Mobile Home Considered Thin

How to Install a Plywood Subfloor

Sooo an insurance hired engineer made a comment in his reportfrom his inspection of my mobile that the roof had thin plywood.He made this assertion without seeing the actual wood thickness.I have just found out for certain via a roofer that my roof plywood thicknessis 1/2 inch.Firstly I would like to ask if this thickness is considered thin.Also I am wondering if different thickness has been used in recent years on newermobile homes.Mine was built in 1988.Thanks for the info!

Hi Im back Sooo an insurance hired engineer made a comment in his reportfrom his inspection of my mobile that the roof had thin plywood.He made this assertion without seeing the actual wood thickness.I have just found out for certain via a roofer that my roof plywood thicknessis 1/2 inch.Firstly I would like to ask if this thickness is considered thin.Also I am wondering if different thickness has been used in recent years on newermobile homes.Mine was built in 1988.Thanks for the info!

He was probably assuming that it had 3/8 plywood which is common.

1/2 is thick enough, standard.

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Plywood Resists Moisture Well

Thanks to its impressive performance upon exposure to water for extended periods, plywood makes for a handy material in outdoor uses such as roofing.

Even if it does expand or swell due to moisture, this happens uniformly across the entire deck so that it doesnt affect the overall structure of the roof. Additionally, plywood quickly dries out, which minimizes the risk of mold building up and other moisture issues.

Types Of Roof Sheathing

There are many different types of roof sheathing, the main ones are:

  • OSB uses adhesives compressed with layers of wood chips that alternate direction between each layer
  • Plywood compresses large, ultra-thin sheets of wood into a sandwich using adhesives and heat to form one board
  • Dimensional Lumber an older way to sheath a house, in which tongue and groove lumber was frequently used or 1 lumber butting up against one another

Today the most common types of sheathing are plywood or strand board. Plywood is more expensive but slightly stronger. Dimensional lumber is not used because it would be much more expensive and provides a lesser surface for nails or screws due to gaps between all the boards.

Many builders who are redoing a roof that has original dimensional lumber as a roof deck will put plywood or OSB over the top before finishing the roof with new roofing material as it is simply a more reliable substrate than many pieces of lumber on end.

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Weight Of The Covering Material

The amount of weight on the roof is greatly affected by the number of shingle layers installed. Some building codes will only allow not more than two layers of shingles as a third can put on too much weight, resulting in the roof collapsing. Typically the heavier the covering material, the greater the thickness of the plywood to be used.

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If you want a strong, durable roof, you have to ensure you have installed the correct roof decking.

This is made up of sheet materials that produce a flat surface so that shingles can be nailed onto it securely, and decking is usually made out of plywood.

What is plywood, exactly?

Plywood is a wood-based material thats constructed from thin layers of wood. These are glued crosswise along the grain to prevent shrinkage and swelling from occurring.

With this in mind, lets explore what plywood is used for in roofing, and why its a good choice. Well also explore what you need to know about the different types of plywood.

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Recommended Thickness Of Shed Roof Sheathing

The recommended thickness for roof decking on a shed is . At that thickness, you can economically sheath your shed while still getting an extremely solid roof substrate that will stand the test of time.

OSB board is preferable to plywood for sheathing a shed. Strand board that is tongue and groove makes for a very straightforward install on your shed. If your rafters or shed trusses are widely spaced, or uneven then the tongue and groove give the edges additional strength, particularly if they arent supported by framing at every edge.

The strand board, besides being cheaper, also works extremely well with tar paper. The rough surface of OSB as compared to the smoother surface of plywood allows the tar paper to hold better and makes installation much faster.

And while plywood may dry faster than strand board, its important to note that all strand board roof decking you buy these days has blue edges. That means the edges have been waterproofed, which makes it much less likely water will penetrate the board. The adhesives that bond the strand board are also waterproof.

You could always opt for thicker roof deck panels, but for a shed there is no need to go thicker if your framing is of standard width. Once you start buying panels that are greater than thick, youll notice the cost rise significantly.

Plywood Has Its Strengths

Plywood also has a slight advantage in stiffness, which means that subflooring panels do not need to be as thick. With 24-inch truss/joist spacing, the National Wood Flooring Association recommends 1-inch OSB underlayment, compared to 7/8-inch plywood. Depending on thickness, plywood is also approximately two pounds or more lighter per sheet.

Perhaps, plywoods biggest feature is the homeowners perception of higher quality. Unlike OSB, plywood actually looks like wood, and is familiar to customers. This altered perception is one of the reasons plywood has survived and dominates the market for DIY home remodeling projects.

However, after selecting one of these two for the roof system substrate, the more challenging choice will be what should cover it. Atlas Roofing makes a nailable OSB board that is bonded to insulation with an aluminum foil radiant barrier on the underside of the OSB surface. A complete description of all these substrate cover choices can be found at Atlas Roofings website:

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