What Is Roof Decking? (& Which Material Is Best For You)

While you might only see the shingles or tiles on your roof, a roofing system actually comprises many parts working together. Roof decking is one of the foundational layers that provide structural integrity and increase the longevity of your roof. 

At McClellands Contracting and Roofing, our goal is to help homeowners understand all the elements that go into a durable, high-performing roof. Read on as we dive into the importance of roof decking and explore the different materials available to help you make an informed decision.

In this blog post, we’ll cover the following topics:

• What is roof decking?
• Types of roof decking
• Different roof decking materials
• Estimated cost of roof decking
• Tips for choosing the best roof decking material

What is Roof Decking?

Roof decking, also known as roof sheathing, is the layer that sits right above the roof trusses or rafters. Its main function is to provide a flat, sturdy surface and to support the roofing materials like shingles, tiles, or metal panels. The roof deck essentially forms the base of your roofing system.

Uneven or damaged roof decking can cause drooping, leaks, or even premature collapse of the entire roofing structure. A properly installed and well-maintained roof deck is crucial for ensuring the overall strength, weather resistance, and longevity of your roof.

Types of Roof Decking

Roof decking is primarily available in two types:  

Sheet Decking

Sheet decking consists of large panels or sheets covering the entire roof area. These sheets can be made from various materials, such as plywood, oriented strand board (OSB), or cementitious boards. Sheet decking is the more prevalent choice today as it provides a continuous surface, better spanning capabilities, and improved resistance to moisture and weathering.

Plank Decking

Plank decking, as the name suggests, consists of long, linear wooden planks or boards laid side-by-side across the trusses or rafters. These planks are typically made of rough-sawn lumber or tongue-and-groove boards. While plank decking was a common choice in the past, it has largely been replaced by sheet decking in modern construction due to ease of installation and better performance.

Different Roof Decking Materials and Their Pros & Cons

When it comes to roof decking materials, there are several options available, each with its own set of advantages and drawbacks. Let's explore the most common materials used for roof decking:

1. Plywood

Plywood is one of the most widely used materials for roof decking. It is made by layering and gluing thin sheets of wood veneer in alternating directions, resulting in a strong, rigid panel. Plywood roof decking offers good structural strength, moisture resistance, and a smooth surface for installing roofing materials.

Pros

• It has a proven track record and widespread availability.
• Plywood roof sheathing has an excellent strength-to-weight ratio.
• It is relatively inexpensive in comparison to some other decking options.
• It is easy to work with and install.

Drawbacks

• It is susceptible to moisture damage and delamination if not properly treated or installed.
• Plywood decking has limited spanning capabilities when compared to some engineered wood products.
• It has environmental concerns due to deforestation and sustainability.

2. Oriented Strand Board (OSB)

OSB is made from wood strands or chips arranged in layers and bonded with resin. It is a popular choice for roof decking due to its strength, dimensional stability, and cost-effectiveness.

Pros

• OSB roof sheathing is strong and tough and is suitable for long spans.
• It is comparatively more affordable than plywood.
• When properly treated, OSB sheathing is resistant to delamination and moisture damage.
• It is an environment-friendly roof decking material option as it utilizes wood waste and by-products.

Drawbacks

• OSB can swell or delaminate if exposed to excessive moisture during installation or leaks.
• The surface of the OSB can be rough and may require additional underlayment to create a smooth surface for some roofing materials.

3. Metal Decking

Metal roof decking is made from steel, aluminum, or other metal alloys formed into corrugated or ribbed panels. It is a popular option in industrial and commercial buildings but can also be used for residential roofs, especially in areas prone to wildfires or termite infestations.

Pros

• It is an excellent fire-resistant and durable roof decking material option.
• Metal roof decking is resistant to moisture and insect damage. 
• It is a lightweight yet strong roof decking option, and it is suitable for long spans.
• Metal is a recyclable material, making it an eco-friendly option.

Drawbacks

• Metal is a comparatively more expensive roof decking option than other materials.
• Metal has the potential for condensation and humidity issues if the attic or roof space is not properly ventilated.
• This roof sheathing certainly requires specialized installation techniques.

4. Cementitious Boards

Cementitious boards, such as fiber cement or cement-based panels, are made from a mixture of Portland cement, wood fibers, and other additives. These boards offer excellent fire resistance, moisture resistance, and durability.

Pros

• These are highly resistant to moisture, rot, and termite damage.
• Cementitious roof sheathing boards have excellent fireproof and thermal insulation properties.
• These boards have a long lifespan and low maintenance requirements.
• Cementitious roof sheathing boards provide smooth surfaces suitable for various roofing materials.

Drawbacks

• These boards are comparatively heavier than wood-based options.
• These are more expensive than plywood or OSB.
• Cementitious boards require specialized cutting tools and techniques
• These boards have limited availability and selection in some areas.

Estimated Cost of Roof Decking

The cost of roof decking can significantly vary depending on the material chosen, the roof's size, and the installation's complexity. Here are some approximate cost ranges for common roof decking materials:

• Plywood: $0.50 - $2 per square foot
• Oriented Strand Board (OSB): $0.30 - $2 per square foot
• Metal Decking: $3 - $7 per square foot
• Cementitious Boards: $2 - $10 per square foot

These are not exact estimates, the real cost will be determined by material quality, local availability, and the need for extra components or underlayment. It is always advisable to consult with a professional roofing contractor to obtain an exact price for your project. 

Choosing the Best Roof Decking Material for Your Needs

The best roof decking material for your roof depends upon certain factors, so when you select the suitable roof decking material for your home or building, consider the following factors:

1. Climate and Weather Conditions

Consider the weather patterns in your region. If you live in an area with high humidity or frequent rainfall, moisture-resistant materials like cementitious boards or treated plywood may be the better choice. 

2. Structural Requirements

Evaluate the span between the trusses or rafters and the anticipated live and dead loads. Some materials like OSB or metal decking can span longer distances without additional support.

3. Fire Resistance

If fire safety is a significant concern, consider non-combustible options like metal or cementitious boards. These materials have a much lower risk of contributing to the spread of flames and serve as an extra layer of protection against the potential risk of fire hazards. Metal and cementitious boards can be especially beneficial in areas with high wildfire risk or for buildings that require stringent fire codes.

4. Durability and Longevity

While some materials like plywood may be more economical upfront, investing in longer-lasting options like metal or cementitious boards can save you money in the long run by reducing the need for frequent replacements.

5. Ease of Installation

Depending on your skill level and available labor, some materials, like plywood or OSB, may be easier to work with and install than metal or cementitious boards. Metal and cementitious boards often require professional installation for optimal performance and longevity.

Call Us For Roof Replacement Services in Pittsburgh

At McClellands Contracting and Roofing, we pride ourselves on our expertise in all aspects of roofing, including the selection and installation of high-quality roof decking materials. If you’re looking for roof replacement services in Pittsburgh, we’re here to assist you. We have a team of roofing experts who can walk you through the process and ensure that your roof's foundation is built to last. For free consultation feel free to call us at (412) 353-5660.