When designing a roofing job, most of the focus falls on what can be seen: the shingles, the color, and the gutters. But beneath, the real hero that protects your house is the structural paneling that forms the roof deck. Selecting the right roofing plywood is arguably one of the most important decisions you will ever make for the long-term health, safety, and structural integrity of your home. A weak or improper roof deck can lead to sagging, leaks, and catastrophic failure during severe weather. At Hawks Merchants, we believe an informed homeowner is the best customer, and this guide is designed to demystify the world of roof sheathing. We will explore why quality matters, what to look for, and how to ensure your roof is built on a foundation that lasts a lifetime.
This article is going to be your complete resource, breaking down technical jargon into simple, actionable information. We’re going to talk about the necessary differences in common materials, how to read those confusing stamps on the wood, and installation best practices separating a standard job from a professional one. Your roof is a complex system, and the plywood is its backbone.
What makes quality roofing plywood so crucial?
Defining Roofing Plywood: The Roof’s Foundation
Before we get into types and grades, it’s essential to understand what your roofing plywood does. This is a layer of wood panels that fastens directly to the trusses or rafters within the framework of your roof. It performs several non negotiable functions that are integral to your home’s structure.
First, it provides the solid, flat surface that your shingles or other roofing materials are nailed to. Without it, there would be nothing to attach the weatherproof layer to. Second, it distributes weight across the entire roof structure. This includes the heavy, constant load of the shingles, the temporary but immense weight of snow and ice, and even the weight of installers walking on the roof. Third, and perhaps most importantly, it provides shear strength and lateral bracing. This is what keeps your roof from racking, twisting, or collapsing under the extreme lateral forces of high winds during a storm.
The High Cost of Improper Roofing Plywood
Taking the shortcut with low quality, improper, or damaged sheathing will inevitably lead to costly repairs. You risk nail pull through, sagging between the trusses, and moisture damage that can rot the very structure of your home. That’s why selecting the right roofing plywood isn’t just a building code requirement; it’s an investment in peace of mind.
The 3 Shocking Differences Between Plywood and OSB
When you go into a lumberyard like Hawks Merchants, there are generally two kinds of roof sheathing that you see: Plywood and OSB, or Oriented Strand Board. Even though they can often be used for the same things, they aren’t the same product. The core differences come down to making the right choice for your budget and climate.
Understanding Plywood: The Classic Choice
Plywood is a sandwich of wood. It is made from several thin layers of wood veneer, known as plies, which are bonded together. The important thing to notice is that the grain of each layer is oriented at a 90 degree angle to the layer above it and the layer below. This cross-lamination is what gives plywood an exceptional strength to weight ratio and dimensional stability.
For roofing, this structure offers an enormous advantage: it holds fasteners such as roofing nails very well. If a nail happens to miss a rafter, the cross-grained layers grip the fastener firmly. In addition, plywood tends to tolerate moisture better during the short term. If it is exposed to water, it tends to swell evenly across the panel and then returns to its normal size as it dries, with less of a risk of permanent damage or loss of strength.
Understanding OSB: The Modern Contender
Is OSB Approved as Roofing Plywood?
OSB, or Oriented Strand Board, is an engineered wood product in which rectangular wood strands or flakes are compressed and glued in a very specific orientation. A true marvel in modern manufacturing, OSB allows large, consistent panels to be fabricated out of smaller, fast-growing trees and is generally less expensive in many applications.
OSB is structurally very strong and is approved by building codes for use as roofing plywood in most applications. But its main vulnerability is at the edges. If the edges of an OSB panel get wet and remain wet, they swell and flake, a problem that is often permanent. Sometimes, this swelling can telegraph through the shingles, creating small, visible ridges across the roof. Finally, it doesn’t hold fasteners nearly as well as plywood does when nailed between trusses.
Which One Wins for Your Roof?
Why Professionals Prefer Roofing Plywood
For most standard roofing jobs in moderate climates, either OSB or plywood will perform well if installed correctly. However, most professional roofers and builders prefer roofing plywood for its better moisture tolerance and fastener grip. If you live in a very humid or high rain environment or if you’re installing a high end, lifetime shingle the added resilience of plywood is often worth the modest extra investment.
How to Read Plywood Grades Like a Pro It’s Easy!
Walking down the aisle of lumber and seeing stamps on plywood can sometimes be a little intimidating. To the untrained eye, all these codes and numbers seem terribly complex; in reality, this is a simple, clear language that tells you precisely what the panel is for and where it can be used. Getting this right is non negotiable.
Decoding the Exposure Rating: Your #1 Priority
The most important stamp you will see is the Exposure Rating. For roofing, you will almost always see Exposure 1. This is an important term to know. It does not mean the plywood is waterproof. What it means is that the panel is bonded with a waterproof glue that can withstand normal, temporary exposure to moisture and weather during a standard construction cycle. It’s designed to get rained on a few times before the roof is shingled without delaminating, the layers peeling apart. Never, ever use an “Interior” grade panel for roofing, even if it looks the same.
What Do A, B, C, and D Grades Mean?
The Best Grade for Roofing Plywood: CDX
The letter grades on plywood refer to the visual quality of the front and back veneers. A is the highest quality smooth, sanded, and with no knots. D is the lowest, allowing for large knots and unpatched holes.
For roofing plywood, you don’t need a pretty finish that will never be seen. The most common grade you’ll find is CDX.
C: The face veneer. It can have some knots, knotholes, and splits that have been repaired with patches. This C side faces up for the roofers to walk on.
D: The back veneer. It can have larger, unrepaired knots and holes. This D side faces down into the attic.
X: This is the abbreviation for Exposure 1 glue, as described above.
CDX plywood is the workhorse of the construction industry: strong, durable, and cost effective for a job where structural performance matters far more than appearance.
Span Ratings Explained: Don’t Get This Wrong
The last code to understand is the Span Rating, which consists of two numbers separated by a slash, such as 24/16, 32/16, and 48/24. This is the key to matching your plywood to your home’s structure.
First Number: Maximum recommended spacing, in inches, for roof rafters
Second Number: The maximum recommended spacing, in inches, for floor joists.
Matching Roofing Plywood Span Ratings to Your Trusses
Plywood is always rated stronger in the direction of its long axis, so its roof rating is always higher. For an average home with trusses spaced 24 inches on center (O.C.), you would want a panel with a first number of at least 24. The most common roofing plywood panels for this application are rated. Using a panel with a lower span rating than your truss spacing-for example, using a 16 O.C. panel on 24 O.C. trusses will yield a soft, sagging, and unsafe roof.
5 Proven Best Practices for Roofing Plywood Installation
Getting Your Roofing Plywood Installation Right
You can purchase the best roofing plywood in the world, but if it is installed incorrectly, the value of that plywood is lost. Installation is what ensures the roof acts as a single, monolithic system.
Stagger Your Seams: Never install plywood so the seams line up. Like a bricklayer, the seams between panels should be staggered. This locks all of the panels together and dramatically increases the roof’s ability to resist wind and shear forces.
Leave the Gap: This is the most common mistake amateurs make. Plywood, like all wood products, expands and contracts with changes in temperature and humidity. A small 1/8-inch gap must be left between all panel edges to allow for this movement. This is often accomplished by using a 10d nail as a temporary spacer. Without this gap, panels will buckle and warp, creating ridges under your shingles.
Use H-Clips (When Needed): If you’re using standard 1/2-inch plywood on 24-inch centers, code requires you to support the unbraced edges between the trusses. Small “H-Clips” are a fast and easy way to do this. They snap onto the edges of two panels, tying them together and preventing them from sagging independently.
Follow the Fastener Schedule: Do not guess with the nailing. Building code gives a specific “fastener schedule.” This usually means 8d (2 3/8-inch) common nails at 6-inch intervals along the panel edges and 12 inches “in the field” (middle of the panel, over the trusses). This pattern is vital to achieving the roof’s full wind-uplift rating.
Run the Grain Perpendicular:
Always Install Roofing Plywood Perpendicularly
Always install roofing plywood panels with the long axis-the 8-foot side-running perpendicular to the rafters or trusses. This ensures the panel’s “Span Rating” is being used correctly, as it is strongest in this orientation.
Why Settle? The Hawks Merchants Advantage for Your Project
Choosing the Right Roofing Plywood at Hawks Merchants
Choosing the right roofing plywood doesn’t have to be as complicated as it seems. This is where partnering with a knowledgeable supplier like Hawks Merchants makes all the difference. We don’t just sell lumber; we provide solutions. Our team understands local building codes and the specific demands of our regional climate. We’ll look at your plans and, in an instant, identify the correct grade, thickness, and span rating you need for a safe and durable project.
Our Commitment to Quality Roofing Plywood
At Hawks Merchants, we carry a deep inventory of high-quality, APA-stamped panels. We take the time to store our roofing plywood properly so that when it arrives at your job site, it will be flat, dry, and ready to be installed. Unlike a big-box store, where you might be on your own, our experts are here to help you load up, answer your questions about fastener schedules, and make sure you have the right H-clips and underlayment to complete the job correctly the first time.
Your roof is the most important part of your home. Don’t build its foundation on guesswork. Trust the experts who have been supplying professional contractors and discerning homeowners for years.
Your Home’s Secure Foundation Starts Here
The Undeniable Importance of Roofing Plywood
The roof over your head is a complete system, and its strength begins with the sheathing. From providing a nail-base for shingles to bracing your home against severe winds, the role of roofing plywood is too important to overlook. By understanding the difference between plywood and OSB, knowing how to read a grade stamp, and following proper installation techniques, you are taking a professional approach to your project.
Your Investment in Quality Roofing Plywood
Buying high-quality roofing plywood, for instance, from a reputable supplier like Hawks Merchants, is not an expense but rather a direct investment in your home’s structural integrity, safety, and long-term value. Don’t leave your project to chance.
