Understanding the Importance and Composition of Roof Decks


What do you think of when you hear the word “roof?” 

Chances are that you immediately picture the beautiful asphalt shingles, natural clay tiles, or metal roofing materials that cover most roofs — in other words, the portion of the roof that is visible from the street.

In truth, the components that make up the roof over your head extend far beyond its outer covering, and your roof deck is one of your roof’s most critical parts. This guide explores the importance of roof decks and walks you through the essential points to consider if you are preparing for a roof replacement or roof repair project.

What Is a Roof Deck? Look at the Anatomy of a Residential Roof

Understanding the role that your roof deck plays in protecting your home is easier if you’re familiar with the anatomy of your residential roof — so let’s get up close and personal! Each element of your roof has a unique function, and it all begins with your roof deck.

  • Roof decking:  Also called roof sheathing, is the frame that ensures your roof is structurally sound. Think of it as the foundation that provides the solid base on which shingles or roof tiles are laid. 
  • Underlayment:  Once the roof deck is in place, your team of roofers will install underlayment. Underlayment is a water-resistant membrane that helps to protect the roof deck and the rest of your property from rain and snowfall.
  • Roofing materials:  Asphalt shingles, wooden shakes, clay, concrete or slate tiles and even metal roofing solutions can only be installed after the roof decking and underlayment are in place. Roof decking ensures these roofing materials have a solid anchor point.
  • Finishing touches like flashing, drip edges, and ridge vents complete the roof. Together, they make sure that roof penetrations like chimneys and vents are secured, water easily slides off your roof, and the underlying structure is protected at all times. 

As you can see, residential roofs are complex structures — and we haven’t even touched on soffit vents, fascia, or gutters yet! Roof decking is the foundational element that makes everything else possible, but what are roof decks made of? 

What Are the Most Common Roof Decking Materials?

Roof decking materials have evolved a great deal over the years, and modern roof decks last longer than ever. You may not know what your current roof deck is made of, but if you’re getting ready for a roof replacement or you need roof repairs done, being familiar with the options will help you make an informed decision. 

Plywood Roof Decking

The fact that plywood is widely available, affordable, strong, and durable makes it a popular roof decking material. Plywood, a type of sheet decking, makes for a smooth surface on which skilled roofers can easily install underlayment and a wide variety of roofing materials. This type of decking is typically installed in 4 foot by 8 foot sheets.

Oriented Strand Board (OSB) Decking

The other common sheet decking you’ll come across is OSB, or oriented strand board. It consists of large sheets of compressed wood bonded with strong adhesives. It’s become extremely popular because oriented strand boards are amazingly budget-friendly, even compared to plywood, while being nearly as strong and durable.

Plank Decking

Plank decking — which looks a little like traditional hardwood flooring, but on your roof — is the oldest type of roof decking. As you can imagine, the cost of solid wood discourages most homeowners from even considering this option seriously. In addition, the extra weight makes plank decks unsuitable for some roofs.

Having said that, high-end modern plank decking with interlocking planks (a so-called tongue and groove design) is an excellent choice for some roofs. This decking outlasts many other types, making it a solid investment for the future of your home.

Other Decking Options

Concrete and metal roof decking materials are frequently used in commercial building projects. Even though you don’t see metal or concrete in residential homes very often, these types of decking are extremely long-lasting and flexible. They don’t just have the advantage of being fire-resistant but also make a good base for heavy roofing materials like slate and clay tiles

When Should You Consider Having Your Roof Decking Replaced?

Homeowners gearing up for a roof replacement may think they only need new shingles, and they may be right. In some cases, you can definitely get away with installing a new roof over existing deck materials. If that’s what you’re hoping for, the feasibility of that dream completely depends on the condition of your current decking. 

The most obvious signs that your roof decking may need to be replaced along with your shingles, include:

  • An uneven, wavy or sagging roof. 
  • A leaky attic. 
  • Signs of rot in the attic. 
  • Spongy or bouncy feedback when walking on the roof. 

If you’re getting ready to have your roof replaced, your roofing contractor will start their job with a meticulous roof inspection that includes a thorough look at the condition of the roof deck. From there, your roofers will be able to tell you whether it is possible to install new shingles or tiles over your existing decking materials. 

Your roofers will take local building codes into account as they advise you about the next steps you should take. Even if your decking is still in excellent condition, up-to-date regulations requiring decking to be fire-resistant may ultimately force you to have a new roof deck installed.

For Large or Small Jobs, Fortified Roofing Is the #1 Roofing Company You Should Call

Have you noticed any of these red flags which are leading you to believe that you may be dealing with a damaged roof deck? Do you already know you need a roof replacement and are you wondering whether new shingles can be installed over your current roof decking?

As a leading local roofing company in Middletown, NJ, we’ll send a seasoned expert to your home to conduct a thorough inspection that leaves no stone unturned. Partner with Fortified Roofing and get the answers to all your burning questions today!