Roof Decking and Roof Replacement

Is Roof Decking Replaced During a Roof Replacement?

There are layers of materials that form a complete and properly functioning roof. One of the most important layers is the roof decking; it is the foundation for the entire roof system.

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Is Roof Decking Replaced During a Roof Replacement? Learn More Here.

When you think of the roof on your home you probably think about the shingles and vents that you see when you look at it. But, your roof is much more than the shingles you see. It is a combination of materials and components that, in totality, protect your home from the weather and elements outside.

At Allied Roofing Solutions, your professional New Jersey roofers for roof replacement, we have extensive experience replacing roofs with the knowledge of when roof decking should be replaced. In this article, we will explain exactly what roof decking is, why it is important, different types of decking, and some of the most common reasons for replacing it.

roof decking

What is Roof Decking?

First, let’s define roof decking. Roof decking is the wooden frame beneath the shingles and other materials that make up the entire roof. The decking provides the load-bearing foundation for your roof just as the foundation of your house does. All the shingles and roofing components are installed on the roof decking. If the decking is not in proper functioning condition, the roof won’t be either.

Why Is Roof Decking Important?

Being that the roof decking is the foundational component of the roof, it must be in good shape. When moisture has infiltrated the roof deck from loose shingles, torn shingles, and so forth, the roof deck will need to be repaired. If the damage is extensive, the roof deck should be replaced.

Strength and stability

Roof decking provides a solid and stable foundation for the roofing structure so the other materials have a strong base. The decking helps to distribute evenly the weight of the roof and any other loads from snow and wind.

Enhanced structural support

As a stable platform, the roof decking helps to support the structure of the roof and prevent it and other roofing components from sagging or collapsing over time. These structural components are critical in avoiding costly roof repairs or a full roof replacement.

Protection from the elements

Roof decking is a barrier against excess moisture and a potentially damaging weather event that can harm the roof, causing leaks or other issues that need to be replaced.

Improved insulation

A properly installed roof deck can improve the energy efficiency of your house by adding a layer of insulation that keeps the home warm in the winter and cool in the summer.

Easy to install

Roof decking is relatively easy to install and can be done quickly and efficiently.


Roof decking materials can come from a variety of different roofing material options. The roof deck can be customized to suit the specific needs of the home.

types of Roof Decking

Types of Wooden Roof Decking

There are two basic types of wooden roof decking: plank decking and sheet decking.

Plank Roof Decking

Before plywood was invented, plank decking was the primary type of residential roof decking. Plank decking, as the name implies, is made up of wooden boards (planks) that come in two different sizes, 1×6 or 1×8.

Sheet Roof Decking

Sheet decking is made with flat sheets of wood that are one of three types: 1) plywood, 2) CDX plywood, and 3) OSB roof decking.

Plywood Decking

Plywood decking is made from thin layers of wood veneer plank decking that are glued together, creating a strong, durable, and lightweight material. Plywood is available in a range of grades from high-quality panels with a smooth surface to lower-grade panels with visible knots and other imperfections. Plywood is a popular choice for roof decking because of its qualities in strength, durability, and versatility.

CDX plywood is commonly used for roof decks but has some differences as compared to regular plywood. The term “CDX” stands for “C-D Exposure1,” which indicates that the plywood has a C-grade front veneer and a D-grade back veneer. It is designed to be used where it is exposed to some moisture but not directly exposed to the elements. CDX plywood roof decking is affordable, durable, and versatile.

OSB stands for “Oriented Strand Board” and is a type of roof decking commonly used for residential roofs. OSB is made by compressing and gluing together strands of wood planks that are arranged in alternating layers, creating a strong and durable panel. It is a cost-effective alternative to plywood roof decking. OSB is available in a range of thicknesses and grades, making it a versatile option that is easily customized to suit the specific needs of the home.

Main Reason for Replacing Roof Decking

Replace the roof decking

The primary reason for replacing roof decking is when it has been compromised by moisture and has begun to rot. When the roof decking becomes saturated with moisture, it will begin to rot and deteriorate over time. This destroys the structural integrity of the roof and can lead to damage to the other roofing materials and the interior of the home. In most cases, a roof inspection will show whether your roof decking needs to be replaced.

Common Causes of Rotting

The most common causes of roof deck rot include:

  • Poor ventilation
  • Leaks
  • Condensation
  • Exposure to the elements

Here are some common signs of roof decking rot:

  • Sagging or dipping sections of the roof
  • Soft or spongy feeling when walking on the roof
  • Moisture or water stains on the ceiling or walls inside the home
  • Discoloration or dark spots on the roof decking
  • Roof leaks and water infiltration
  • Cracks and/or splits in the roof decking
  • Visible mold or mildew growth on the roof decking
  • Roofing materials that appear loose or unstable

When any of these signs are found, the issues need to be addressed as soon as possible to prevent further damage to the roofing system and the home.

Does the Roof Deck Need to be Replaced when Replacing the Roof?

Usually, at least some roof decking needs to be replaced during your roof replacement. Most of the time, only a few boards have to be replaced. However, there are some reasons why the entire roof deck should be replaced. Learn more about roof replacement with our homeowner’s guide to the roof replacement process.

roof deck’s structural integrity

When the Roof Deck Has Rotten or Broken Boards

If any of the roof deck’s structural integrity is compromised by rotting or broken boards, the place that is impacted must be replaced. Not only is replacing the affected part of the roof deck critical for proper roof functionality, but it is also a building code requirement. Code R905.2.1 of the 2018 International Residential Code stipulates that your roof decking must be able to withstand and hold your new roof when it is installed. This requires asphalt shingles to be fastened to solidly sheathed decks.

Plank Roof Decking Has Gaps

When the Plank Roof Decking Has Gaps

Another building code deals with the shingle manufacturer’s specific installation instructions. Code R905.1 of the 2018 International Residential Code stipulates that roof coverings shall be applied following the applicable provisions of this section and the manufacturer’s installation instructions. As of 2021, per shingle manufacturers’ installation instructions, plank decking must be replaced if there is more than a ⅛” gap between the planks. If there is a gap larger than ⅛”, the plank boards must be replaced after the old roof is torn off. This is because the roofing nails will be in the gaps and lead to roof leaks. Learn more more about why proper roof installation is important.

Contact Us to Learn more about Whether Roof Decking Replaced During a Roof Replacement

When you suspect that your roof is deteriorating with loose and missing shingles that can let moisture infiltrate your home or are experiencing leaks, call Allied Roofing Solutions. Our team of roofing professionals and experts can inspect your roof and determine if you need roof repairs or a total roof replacement. We are committed to providing the top-quality work that you are looking for! We serve much of New Jersey, including Bergen County, Essex County, Hudson County, Middlesex County, Morris County, Passaic County, and Somerset County. To schedule a free roof inspection, please call us at  (201) 773-0633 or fill out our handy free estimate form.