Beneath every strong roof is a solid foundation—and that foundation is the roof decking. Also known as roof sheathing, this structural layer is crucial for supporting your roofing materials and maintaining the overall integrity of your home.

Whether you're planning a roof replacement or simply want to understand your roof’s structure better, here's everything you need to know about roof decking.

Roof decking is the base layer of wood or board material installed over your home’s rafters or trusses. It serves as the platform onto which all other roofing materials—underlayment, shingles, flashing—are attached.

Without proper decking, your roof lacks the stability and structure needed to withstand weather, weight, and wear over time.

Types of roof decking

There are two primary types of roof decking used in residential and commercial construction:

Plank decking

Made from solid wood planks, typically 1x6 or 1x8 boards. This older method is found in homes built before the 1970s and offers a rustic, sturdy build, but is less common in modern roofing.

• Best for: Historic homes, restoration projects

• Requires: Even spacing and structural reinforcement when adding modern roofing materials

Sheet decking

The most common modern option, sheet decking is made from:

• Plywood (typically ⅜" to ¾" thick)

• OSB (Oriented Strand Board) – made of wood chips bonded with resin

Sheet decking offers a smooth, uniform surface, is cost-effective, and works well with today’s roofing systems.

• Best for: Most modern homes

• Offers: Lightweight strength and consistent performance

Understanding the layers of a roof

Roof decking is just one part of a multi-layered system that includes:

• Underlayment

• Ice & water shield

• Shingles or roofing material

• Flashing

• Ridge vents and more

Each layer depends on the decking as its base of support—so any damage or weakness here affects the entire roof system.

When should roof decking be replaced?

You should consider replacing roof decking when:

• Your roof is being replaced, especially if the decking shows signs of rot or water damage

• There’s a roof leak, and water has compromised the wood underneath

• The decking feels spongy or soft when walked on

• You notice sagging or unevenness on your roof’s surface

A thorough inspection by a roofing professional can determine whether full or partial replacement is necessary.

Signs of damaged roof decking

Watch for these red flags:

• Water stains or mold on ceilings or attic

• Musty odors or mildew

• Warped or soft decking when inspected

• Leaks after rainstorms

• Visible sagging between rafters

Ignoring these issues can lead to costly repairs, structural issues, and safety hazards.

How to install roof decking? 6 steps

1. Remove old roofing materials and inspect the existing deck

2. Remove and dispose of damaged or rotten decking

3. Cut and measure new decking (plywood or OSB panels)

4. Lay panels over rafters, stagger seams for strength

5. Secure decking with nails or screws per local code

6. Install underlayment and continue roofing process

Note: This process should only be done by licensed roofing professionals for safety and performance.

How much does roof decking cost?

Costs vary based on material type and roof size. On average:

• OSB or plywood decking: $2 – $5 per square foot (materials only)

• Labor & disposal: Additional $1.50 – $3 per square foot

• Full replacement on a 1,500 sq ft roof: Typically ranges from $4,500 – $10,000

Prices may vary based on local rates, roof accessibility, and structural needs.

What is the difference between roof decking and roof sheathing?

There is no real difference—these terms are used interchangeably. Both refer to the layer of boards or panels that form the base of the roof, supporting shingles and underlayment.

What is the best decking for a roof?

For most homes, OSB and plywood are the best choices due to their affordability, durability, and compatibility with modern roofing systems. Plank decking may still be used in specialty or historic renovations.

Need expert guidance on your roof decking?

At Masterpiece Roofing, we assess the condition of your decking with every inspection or replacement, ensuring your new roof has the strong foundation it needs. From replacing damaged wood to complete deck installation, our team delivers quality craftsmanship and peace of mind.

Contact Masterpiece Roofing today for trusted roofing services in New England.