When it comes to roofing, most homeowners think about shingles, flashing, or gutters. But there’s one layer that’s just as essential, roofing plywood. It’s the foundation your entire roof depends on.

If you’re planning a new roof or replacing an old one, understanding roof sheathing also called roof plywood or roof sheeting, is key. This often-hidden layer supports everything above it, from underlayment to shingles.

Whether you’re tackling a full roof replacement or need expert roofing services, knowing your plywood options can make all the difference. In this guide, we’ll walk you through the different types of plywood, how to choose the best one for your home, and why this decision impacts your roof’s long-term durability.

What Is Roof Plywood?

Roofing plywood, also called roof sheathing, is a flat wood panel that forms the deck of your roof. It’s fastened to the framing and supports the layers above. The most common sizes are 4×8 feet, and the standard thickness is ½ inch, though some projects may need thicker sheets.

Why Plywood Roofing Is So Important

The plywood under your shingles isn’t just there for support – it adds strength, helps protect against leaks, and keeps your roof sturdy during storms. A weak or poor-quality roofs plywood can lead to sagging, mold, and expensive damage down the road.

So, picking the right material means investing in the life of your home.

Types of Plywood Roofing

Different homes and climates require different types of plywood. Let’s explore the most common choices, along with their pros, cons, and best-use cases.

CDX Plywood

CDX plywood is the most widely used type for residential roofs. It’s made from softwood layers bonded with waterproof glue. The “C” and “D” grades refer to the front and back surfaces, which may have visible knots or blemishes, but don’t affect performance.

Why it’s popular:

• Durable and moderately water-resistant
• Readily available and affordable
• Meets most residential building codes

However, CDX shouldn’t be left exposed for long. If it’s not covered quickly, it can warp or weaken under heavy rain.

OSB (Oriented Strand Board)

OSB is another commonly used material in roof construction. Instead of wood sheets, it’s made from compressed wood strands and adhesives, which gives it a consistent texture.

Benefits of OSB:

• Budget-friendly option
• Uniform surface makes installation easy
• Suitable for dry climates

On the downside, OSB is more sensitive to moisture. It tends to swell when wet and dries slowly. In regions with frequent rain or snow, this can be a problem.

Pressure-Treated Plywood

This type of plywood is chemically treated to resist moisture, rot, and pests. It’s ideal for environments with high humidity or where water exposure is common.

Advantages include:

• Long-lasting under wet conditions
• Resistant to mold and termites
• Great for areas prone to leaks or poor ventilation

Though more expensive than standard plywood, the added protection can pay off over time—especially in areas like Maryland where seasonal weather can be unpredictable.

Hardwood Plywood

Hardwood plywood is made from high-density wood like oak, maple, or birch. It’s more often used in commercial roofing or high-end custom homes.

Why choose hardwood plywood:

• Exceptional strength and durability
• Ideal for heavy roofing materials
• Long-term investment for premium builds

However, it’s overkill for most residential roofs due to its cost and weight.

Different Types of Roofing Plywood Comparison Table

Here’s a quick side-by-side to help compare options:

Type	Moisture Resistance	Cost	Durability	Best Use
CDX Plywood	Good	Moderate	High	Standard residential roofs
OSB	Fair	Budget-friendly	Medium	Dry climate, budget builds
Pressure-Treated	Excellent	Higher	Very High	Humid or rainy climates
Hardwood Plywood	Good	Expensive	Very High	Premium or commercial roofing

How Thick Should Roof Sheathing Be?

Roof plywood must be thick enough to support weight and weather conditions. Here are some general rules:

• ½ inch thick: Standard for homes with 16-inch rafter spacing
• ⅝ to ¾ inch: Best for wider spacing or heavy roof loads
• ¾ inch or more: Used in commercial roofs or where snow accumulation is high

Check your local building code and talk to a roofing professional for the best recommendation.

Factors to Consider When Choosing Plywood Roofing

Not sure what to go with? Here are some key factors that can help you decide:

1. Climate Conditions

If you live in a humid or rainy state like Maryland, moisture resistance is crucial. CDX or pressure-treated plywood is better suited than OSB.

2. Budget

OSB is a budget-friendly choice, but it’s not always the best long-term investment in wet climates.

3. Roof Pitch and Design

Steeper roofs shed water faster, so they might do fine with standard CDX. Flat or low-slope roofs benefit from added water protection.

4. Roofing Material

Tile and slate roofs are heavier than asphalt shingles. They require stronger sheathing—typically ¾ inch or thicker plywood.

5. Rafter Spacing

Wider rafter spacing means your plywood needs to handle more pressure between beams. Thicker plywood helps prevent sagging.

Signs Your Roof Plywood Needs Replacement

Already have a roof but wondering if your sheathing is still holding up? Here are some signs of trouble:

• Sagging or uneven roof surface
• Water stains in the attic or ceiling
• Visible mold or mildew under the roof
• Shingles that don’t sit flat
• A musty smell in your upper floors or attic

If you notice any of these, your roof sheathing may be compromised and should be inspected right away.

Maryland Roofing Services You Can Trust

If you’re planning a roof installation or replacement in Maryland, it’s important to work with professionals who understand the local climate, building codes, and material options.

USA Builders and Developers specializes in roofing services across Maryland. From roof inspections to full decking replacements, we ensure your home is protected from top to bottom.

We proudly serve the following areas:

• Bethesda – 20814
• Chevy Chase – 20815
• Kensington – 20895
• Silver Spring – 20910, 20912, 20902, 20911
• Baltimore City – 21218, 21230, 21231, 21211, 21224, 21210, 21212, 21213, 21215
• Gaithersburg – 20886

Final Thoughts

Choosing the right roofs plywood doesn’t have to be stressful. Most homeowners find that CDX plywood offers the best balance of cost, durability, and moisture resistance. For areas with high humidity or rain, like Maryland, pressure-treated plywood may be worth the investment.

Need help making the right call? Talk to experienced contractors who can guide you based on your roof’s structure, climate, and future plans.

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