Picking Plywood for Your Roof: What’s Out There?
Over time, it’s common for houses to develop sagging and leaky roofs. To prevent excessive spending on roof repairs and extend the lifespan of your home, it’s not recommended to opt for the same thickness of materials across different types. Investing in quality roof sheathing is particularly crucial for homes in cold climates or areas prone to frequent weather fluctuations.

This article will guide you on choosing the right sheathing thickness for your roof based on your material, application, and environment and Explore the essentials of roof plywood, its types, benefits, and installation tips to ensure a durable and sturdy roof for your home. Perfect for builders and DIYers

Roof plywood refers to a type of sheathing or decking material used in the construction of roofs. It’s typically made from thin layers of wood veneer, known as plies, that are glued together in a cross-grain pattern to improve strength and durability. Roof plywood provides a stable base for roofing materials such as shingles, tiles, or metal panels. It helps to distribute the weight of these materials evenly across the roof structure and provides a solid surface for attachment. Roof plywood also plays a crucial role in supporting the roof’s load and resisting the forces of wind, snow, and other environmental factors.

Peeking Under the Shingles: What’s There?

The surface of the roof, the one visible from the curb, is just one part of your home’s entire roofing system. In truth, your home is more complex and not just a simple layering of shingles. Knowing the different parts of the roof is important as it will help you understand roof replacement and better repair practices.

Pro Exteriors discusses the parts of the roof underneath the shingles
Pro Exteriors discusses the parts of the roof underneath the shingles

Decking Explained

Also known as the wood sheathing, this is the base on which everything else is laid on. It’s essentially the foundation of the roof. This is typically made with OSB or oriented strand board or plywood that’s attached with nails onto the rafters. Since it’s made of wood, it will require general roof repair if there’s a leak or water intrusion coming from the shingles.

The Lowdown on Underlayment

This durable paper is saturated with asphalt and installed on top of the decking, right underneath the shingles, hence its name. It serves as the roof’s last line of defense when water leaks from the shingles occur due to cracking or tearing.

Drip Edges Demystified

Also known as eave flashings, these angled aluminum strops are nailed over sides of the underlayment at the edges. They prevent water from building up at the sides and redirect them to the eaves and, eventually, to the gutters.

Flashings: What and Why

These are the thin metal strips located at the most vulnerable parts of the roof, such as the hips and valleys. They essentially act as a barrier to prevent water leakage and pooling on the surface. Although they extend the life of the roof, they are susceptible to wear and tear, too. As such, it’s important to regularly check if the flashings on your roof are still in good condition.

Picking Plywood for Your Roof: What’s Out There?

When it comes to plywood for roofing, there are many options available in the market. Bases on your particular requirements and budget, you can choose from the following types of plywood for roofing:

Picking Plywood for Your Roof: What’s Out There?
Picking Plywood for Your Roof: What’s Out There?

CDX Plywood: A Solid Choice

CDX is a type of plywood. Basically, Plywood derives its strength from layers of wood that are bonded together.The wood grain alternates from layer to layer, adding significantly to the strength of the plywood sheet. A special grade of plywood called “CDX” is a popular choice for roof sheathing. CDX plywood can withstand temporary exposure to rain and other moisture sources. For both roofers and homeowners, this characteristic of CDX plywood provides essential peace of mind. With CDX plywood, the three letters represent:

  • C: The grade of the front of the plywood sheet
  • D: The grade of the back of the plywood sheet
  • X: The type of glue used to bond the layers
  • There are different grades/classes of plywood which are represented by letters A, B, C and D. As you would expect, A is the most expensive and the best quality, in terms of the number of knots on it. The less the number of knots, holes and repaired defects the more expensive the plywood.

“A” grade plywood has no knots or defects, making it the top grade. A surface graded as C is suitable for use under shingles and roofing felt. The D grade is suitable for the underside of the plywood sheet. In terms of roof sheathing, CDX plywood offers a good balance between cost and performance.

CDX plywood and OSB plywood
CDX plywood and OSB plywood

ZIP Wood

ZIP wood is an engineered product known for its strength and durability. A key to ZIP wood is the use of a water-resistant barrier that still breathes. This vapor permeable barrier eliminates the need for roofing felt. All five layers of ZIP system insulated sheathing are moisture-resistant, making it easy to work with in places like Montgomery County known for such variable weather.

The simplified two-step installation reduces labor costs by as much as 40% when compared to traditional plywood sheathing and felt installations. Roofers simply install the panels and tape the seams. The final result is a continuous, rigid air barrier that greatly reduces air leakage. Homeowners enjoy greater energy efficiency, lower utility bills, and a reduced carbon footprint.

FRT Plywood

Because a fire can spread from townhouse to townhome, building codes often require the use of fire-retardant (FRT) plywood for roof sheathing, depending upon the design of the structure. Fire exposure to FRT plywood initiates a process of acid hydrolysis that increases fire resistance at a critical time.

However, In the 1980s, an estimated 1 million housing units were built with potentially defective FRT plywood. Although today’s sheathing does not present the same challenges, FRT plywood from several decades ago may degrade prematurely. Roof replacements are often the solution in such cases.

FRT Plywood
FRT Plywood

Constructional structural plywood

Created specifically for the purpose of exterior use. This type of plywood is very strong, durable and high performing. It is ideal for all types of building and construction applications. Marine Grade plywood is one of the most popular examples of construction plywoods

Shuttering plywood

Is a structural plywood used primarily to hold concrete. It’s strong and built through multiple tests to check its strength and structural integrity.

General plywood

is the most common type of plywood and is used for general applications such as furniture, doors and other interior use. This type of plywood may not always suitable for exterior applications such as roofing and may need more maintenance than others.

How to Choose the Best Plywood for Your Roof

Plywood are nowadays most popular material use for roofing. This is because plywood is strong and provides good durability to the rood and it quite affordable than many alternatives such as slate, metal, rubber slate, solar, plastic polymer, etc.

In this post we will suggest how to choose the best plywood for roofing. Let’s start with the basics.

Material Matters: Picking Your Sheathing

Wood Boards

Plywood weighs less than OSB, and liquid takes time to degrade the wood board’s overall strength. However, if this phenomenon occurs, your rooftop deck may sink over time, costing you hundreds of dollars in repairs.

For rooftop sheathing, the chipboard must be at least 1/2 inch thick. At the rafters, the plywood can span up to 32 inches and between ground joints, it can span up to 15 inches.

Consider consulting an engineer to ensure proper structural integrity when determining rafter spacing and dimensions for your new roof.

Oriented Strand Board Rocks

OSB is ideal for those on a budget who desire larger boards than the conventional plywood panels. OSB is more resistant to moisture and has a higher tensile strength than hardwood.

Half-inch OSB is acceptable for rafter band gaps of up to 24 inches. Panels must be attached to the rafters with appropriate fasteners and should have at least 1/8-inch expansion space among each layer. An OSB roof plank’s minimum depth is approximately 15/32 inches.

Sizing It Up: Panels & Trusses

When comparing If there are wider intervals between the framing, choose a thicker foundation

Type of Roof Application

The thickness of your roof covering is determined by a variety of factors, including the type of roof, roof’s inclination, climate condition, and material design codes.

What Thickness of Plywood Should You Go For?

The recommended thickness for your roof depends on the materials you are using and the roof’s slope. For example, an ideal thickness for roofing plywood is at least 5/8 inches for a standard asphalt shingles roof. This standard thickness provides enough support for the weight of the shingles and the typical loads a residential roof should expect.

Minimum Roof Sheathing Thickness

Minimum sheathing requirements dictate that ⅜” thick is the lowest you can go in terms of thickness.

What happens if your roof sheathing materials are too thin?

Wrong dimensions will lessen the integrity of the overall structure of your roof. Thin layers of roof covers are more prone to bend between the foundation, thus compromising the outer roof system. When additional weight is applied to a ⅜” board, the panel will sink over time.

Maximum Roof Sheathing Thickness

It is essential to pay close attention to the markings on the panel boards because various materials with the same thickness are rated for different spans.

For a metal roof, you should use thicker plywood, usually a minimum thickness of 3/4 inches. This is because metal roofs are generally heavier than asphalt shingle roofs and require more support to prevent sagging and warping.

For a low-slope roof, the recommended roof sheathing thickness is also 3/4 inch. Low-slope roofs are more prone to water pooling. A thicker sheathing plywood will provide extra protection against water damage.

It is important to note that the recommendations above are general guidelines and that the best way to determine the actual thickness you need is with a professional or the manufacturer’s specifications. Additionally, consider the right sheathing thickness to ensure adequate protection if you live in a region with heavy snow loads or high winds.

Installing Plywood Like a Pro: A Few Tips

Installing roofing plywood is crucial in ensuring a solid and durable roof. Here are a few tips to keep in mind when installing plywood for your roof:

Getting Sheets Aligned Just Right

Proper alignment and spacing between plywood sheets are essential when installing roofing plywood. Well-laid plywood ensures that the roof is structurally sound and that there are no gaps or overlaps in the plywood.

When you align the sheets correctly, the edges of each sheet fit together seamlessly, providing a smooth surface to apply the roofing material. This creates a strong and stable base for the roof, helping to prevent leaks and other problems.

Picking the Perfect Roof Decking

Using the correct roof decking ensures that support your roof appropriately and that there are no weak spots in the roof, which can lead to leaks and other problems. It is also essential to use a high-quality roof deck, as low-quality or inappropriate roof deck can lead to failure or damage over time, costing you more in the long run.

Thickness Check: Making Sure It’s Just Right

Using the correct sheathing thickness is crucial for the roof’s structural integrity. If the sheathing is too thin, you may need to provide more support for the roofing material, as a lack of support can lead to warping or sagging roofs. On the other hand, sheathing that is too thick may not be necessary.

Don’t Skimp on Fasteners

High-quality fasteners are typically durable materials, such as stainless steel or hot-dip galvanized steel. These materials can withstand the elements and provide a strong and secure connection between the plywood and the roof decks. These fasteners also have a better resistance to rust and corrosion, which is vital for the roof’s longevity.

Maybe Call in the Experts?

Installing plywood on roofs can be a complex and challenging task. If you are not comfortable with the process, it is best to consider hiring a professional. This will help to ensure that the roof installation is correct and structurally sound. That the reason why our team is here to help you choose the best option for your home.

Whether you need a budget-friendly solution, increased moisture resistance, or optimal strength for steep-slope roofs, our roofing contractors have you covered. We understand the unique challenges posed by different roofing applications, and our recommendations will ensure you get a roof that stands the test of time.

Get in touch with our team of roofing specialists today to schedule a comprehensive roof inspection by calling us at +84-83-333-2333 or filling out the contact form below to get started.