When most homeowners think about their roof, the first thing that comes to mind is probably shingles. But underneath those shingles is a critical component that’s just as important—roof decking. Also known as the roof sheathing, this structural layer forms the foundation for your entire roofing system.

At Finley’s Roofing, we believe informed homeowners make better decisions. So in this post, we’re breaking down what roof decking is, why it matters, how to know when it needs replacing, and how it fits into the overall cost of a roof replacement.

What Is Roof Decking?

Roof decking (or sheathing) is the flat surface layer that your shingles are nailed to. It’s attached to your home’s trusses or rafters and acts as the structural base for the rest of your roofing materials.

🔨 Common Types of Roof Decking:

  • OSB (Oriented Strand Board): Most common today, made from compressed wood strands and adhesives.
  • Plywood: Slightly more expensive but stronger in high-moisture areas.
  • Plank decking: Often found in older homes, made of individual wooden boards laid side by side.

No matter which type you have, its job is to provide a smooth, strong, and secure surface for your underlayment and shingles.

Why Is Roof Decking So Important?

Though it’s out of sight, roof decking plays a huge role in your roof’s performance and longevity.

✅ Structural Support

Decking acts as the backbone of your roofing system, holding everything in place—from nails and underlayment to shingles and flashing.

✅ Moisture Protection

When installed correctly and in good condition, decking helps keep moisture out of your attic and insulation.

✅ A Flat Surface for Proper Installation

Wavy, rotted, or warped decking can make your roof look uneven and cause shingles to fail prematurely.

✅ Safety

Strong decking supports the weight of roofing materials and contractors working on your roof. Compromised decking is a hazard.

What Causes Roof Decking to Fail?

Decking is built to last, but it’s not immune to damage. Here are the most common culprits:

💧 Water Intrusion

Leaks from damaged shingles, flashing, or clogged gutters can soak the decking, leading to rot and mold.

🐿️ Pests

Animals like squirrels and raccoons can chew through decking to get into your attic, especially if it’s already weakened.

🌬️ Poor Ventilation

Hot, humid air trapped in your attic can create condensation on the underside of the decking, eventually leading to warping or mold.

🕰️ Age

Over time, even the best decking materials degrade—especially if your roof is over 20 years old or has had multiple repairs.

Signs Your Roof Decking May Be Compromised

While most homeowners won’t see their decking directly, there are some telltale signs of trouble:

Inside the Home:

  • Water stains on your ceiling or walls
  • Sagging areas in your ceiling
  • Musty smells in your attic
  • Wet or moldy insulation

Outside the Home:

  • A sagging or uneven roofline
  • Shingles that curl, buckle, or fall off prematurely
  • Evidence of roof leaks or soft spots
  • Roofers having trouble nailing new shingles (a major red flag!)

If you notice any of these issues, it may be time for a full roof inspection, especially if it’s been more than 10–15 years since your last one.

Does Roof Decking Need to Be Replaced with the Roof?

Not always—but in many cases, yes.

When we replace a roof at Finley’s Roofing, we carefully inspect the decking once the old shingles and underlayment are removed. If the decking is in good condition, we re-use it. But if we find:

  • Rotting wood
  • Soft spots or sagging
  • Widespread water damage
  • Code violations (especially in older homes)

…then replacing all or part of the decking is essential to ensure your new roof lasts as long as it should.

How Decking Affects Your Roof Replacement Cost

Decking replacement is typically priced per sheet of plywood or OSB. If damage is localized, we may only need to replace a few panels. But if widespread issues are found, it can significantly increase the cost of your project.

💡 Good to Know:

At Finley’s Roofing, we’re always transparent. We’ll explain what we find, show you photos if needed, and never do extra work without your approval.

Why Finley’s Roofing Takes Decking Seriously

Some roofers cut corners by installing new shingles over questionable decking. We don’t.

We believe every part of your roof—not just the shingles—should be done right. Here’s what sets us apart:

  • 83+ years of experience in Georgia roofing
  • GAF Master Elite® Certified Contractor
  • Every job includes a full decking inspection
  • We don’t ask for payment until the job is complete—and done to your satisfaction
  • Backed by our 10-year workmanship warranty

Your roof protects everything underneath it. The decking protects your roof. It’s that simple.

Final Thoughts: Don’t Overlook What’s Underneath Your Roof

When it comes to roof replacements, what’s underneath matters just as much as what’s on top. Roof decking may be hidden, but it’s a crucial part of your roofing system.

Ignoring it can lead to leaks, mold, higher energy bills, and premature roof failure.
Paying attention to it now can save you thousands later.

Need a Roof Inspection or Estimate in Georgia? We’re Here to Help.

At Finley’s Roofing, we don’t just slap on new shingles. We inspect every layer of your roofing system—starting from the decking up.

📞 Call us today at 770-262-7375 or
🌐 Visit finleysroofing.com to request your free, no-obligation roofing estimate.

We want you to look up at your roof and say, “Oh wow”—not “Oh no.”