What Is Roof Decking, And How Do You Know When It’s Bad?

Oct 15

Shingles and coatings get all the attention, but your roof’s real strength starts beneath the surface, with something called roof decking.

If you’re not in the roofing world, it’s probably a term you’ve never heard. But it’s one of the most important parts of your roof system. And when it starts to fail, the rest of your roof can go with it.

Let’s break down what roof decking is, what it does, and how to know when it needs attention.

What Exactly Is Roof Decking?

Roof decking (also called sheathing) is the flat surface layer that sits on top of your trusses or rafters and under your underlayment and shingles.

In most homes, it’s made of:

Plywood
OSB (oriented strand board)

This is what your entire roofing system is built on; your shingles or metal roof don’t just float in space. They’re fastened directly into this layer.

Why It Matters

Think of roof decking as the foundation of your roof. If it’s solid, everything else performs better. If it’s damaged or weak, you’re going to have problems, even if your shingles look great.

Your decking provides:

Structural support
A base for waterproofing layers
Stability for fasteners and flashing
Resistance to wind uplift

Signs Your Roof Decking May Be Bad

Most homeowners don’t see their roof decking; it’s hidden. But here are red flags that suggest something underneath is failing:

1. Sagging or Soft Spots on the Roof

If your roofline dips or feels bouncy when walked on, the decking may be deteriorating or water-damaged.

2. Leaks or Water Stains Inside

If water gets past your shingles and underlayment, the decking is the next to go. Stains on ceilings or in the attic are warning signs.

3. Mold or Rot in the Attic

Decking that's been wet too long may show signs of mold, rot, or mildew along the underside.

4. Aging Roof with No Decking Inspection History

If your roof is 15–20 years old and has never had a full tear-off or decking check, it might be time for an evaluation.

Can You Repair Roof Decking?

Sometimes, yes. If only a small section is damaged, it can be cut out and replaced. But in many cases, especially when paired with a roof replacement, we’ll assess whether full replacement is the safer, longer-lasting solution.

Don’t Let What’s Under Your Roof Go Ignored

Roof decking issues are a silent killer. They don’t always show up until major damage is done, and by then, it’s costing you more than it should.

At Superior Contracting, we don’t just cover up problems. We fix them from the inside out.

Call us today for an inspection and let us give your roof a solid foundation, literally.

hillary hyslope