What Is Roof Decking? (And How Often Should You Replace It?)
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What Is Roof Decking? (And How Often Should You Replace It?)

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Posted By: Roof Troopers

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You may think that your roof is just the shingles, but there are actually numerous components that work together to create a protective roof, such as:

  • Flashing
  • Ice and water shield (underlayment)
  • Soffits
  • Fascia
  • Roof decking

You simply wouldn’t have a roof without a roof deck! If you have a roof replacement coming up, it’s wise to learn about the different parts of a complete roofing system. That way, if your roof decking needs replacement, you’ll know what questions to ask.

What Is Roof Decking & Why Is It Important?

The roof deck is the structural foundation of your roof. It’s what the shingles or other roofing material attach to, providing stability and protection from the elements. Roof decking (or roof sheathing) is important because:

  • It provides a stable base for roofing materials.
  • It helps to protect the roofing materials from weather and wind damage.
  • It can help to insulate your home, keeping it cooler in the summer and warmer in the winter.

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There are two types of roof decks:

  • Plywood: The most common roof decking, plywood is easy to find and relatively inexpensive.
  • Oriented strand board (OSB): A newer option, OSB is made of wood chips that are pressed and formed into sheets.

If your roof is more than 20 years old, it’s likely made of plywood. Many homes built before 1980 have 1/2-inch plywood, while those built after 1980 may have 3/4-inch plywood.

Plywood vs. OSB

While plywood has been the standard roof decking for many years, oriented strand board is becoming more popular. Here’s a look at the pros and cons of each:


  • ✅ PRO: Inexpensive, easy to find
  • ❌ CON: More likely to warp or crack than OSB

Oriented strand board:

  • ✅ PRO: Stronger and more stable than plywood, less likely to warp or crack
  • ❌ CON: More expensive than plywood

Should Roof Decking Be Replaced?

Unfortunately, roof decking isn’t invincible. Over time, it can become damaged and will eventually need to be replaced. But how do you know when it’s time for roof deck replacement?

Here are a few signs that you may need a new roof deck:

  • There is cracked or missing plywood or OSB.
  • The roof deck is sagging or soft in spots.
  • There are visible water stains on the roof decking.
  • There is mold or mildew on the roof decking.
  • The roof nails are popping up through the roof decking.

Typically, your roof deck should get replaced every 20 to 30 years, depending on its condition and the type of roofing materials you have.

If you’re not sure whether your roof deck needs to be replaced, it’s always best to have a professional roofer take a look. They’ll be able to assess the damage and give you an expert opinion.

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How Does Roof Decking Affect Ventilation?

Your roof needs proper ventilation to function properly and last a long time. In fact, roof ventilation is one of the most important roofing components!

Proper roof ventilation helps to:

  • Regulate the temperature inside your attic
  • Minimize condensation and mold growth
  • Extend the life of your roofing materials

There are two types of roof ventilation:

  • Passive: This type of ventilation relies on natural forces, such as wind, to create air movement.
  • Active: Active roof ventilation uses fans or other mechanical means to force air movement.

Both types of roof ventilation are important, but active roof ventilation is often more effective, especially in hot climates.

Roof decking affects ventilation by providing a stable base for the roofing materials and by helping to insulate your home. If your roof deck is damaged, it can affect the ventilation of your roof and lead to problems down the road.

What Are Signs of Rotted Roof Decking?

If your roof deck is rotted, it’s important to have it replaced as soon as possible. Rotted roof decking can lead to a host of problems, including:

  • Leaks: Water can seep through cracks and holes in rotted roof decking, causing leaks in your roof.
  • Mold and mildew: Rotted roof decking is the perfect breeding ground for mold and mildew. Not only is this unsightly, but it can also be harmful to your health.
  • Structural damage: Rotted roof decking is weaker than healthy roof decking, which means it’s more likely to collapse under the weight of heavy snow or debris. This can cause serious damage to your home.

There are a few signs that you may have rotted roof decking, including:

  • Water stains on your ceiling: If you notice water stains on your ceiling, it’s a good indication that your roof deck is leaking.
  • Mold or mildew growth: As we mentioned before, mold and mildew love to grow in damp, dark places. If you see mold or mildew on your roof deck, it’s a sign that it’s beginning to rot.
  • Sagging: Rotted roof decking is often spongy or soft to the touch. This can cause the roof deck to sag, which puts unnecessary stress on your roofing materials.

If you suspect that your roof deck is rotted, it’s important to have it inspected by a professional roofer. They’ll be able to tell you for sure and recommend the best course of action.

Sometimes, no one notices a rotted roof deck until you’ve scheduled a roof replacement. As the roofing contractor tears off your shingles, they may notice deck rot once the decking is exposed. In this case, they will need to replace the decking because it’s unsafe to continue living with rotted decking.

How Much Does Roof Decking Cost?

It can be frustrating to have to pay for new roof decking if you weren’t originally planning for that expense. To be fully prepared, roof decking usually costs between $2 and $4 per square foot.

This price range will depend on a few factors, including:

  • The type of roof materials you have: If you have asphalt shingles, for example, the roof decking will be different than if you have metal roofing.
  • The size of your roof: A larger roof will obviously require more roof decking material than a smaller roof.
  • The condition of your roof: A roof that’s in good condition won’t need as much work as a roof that’s in bad condition.

We Put Care Into Your Complete Roofing System

We hope that this guide on roof decking has helped you feel more informed about this essential component of your roof. Here at Roof Troopers, we prioritize installing high-quality roofing systems so that our customers have long-lasting, protective roofs that last for decades.

If you’re experiencing issues with your roof, reach out to our friendly team! We’ll perform a detailed roof inspection and give you a free estimate.


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