Everything You Need to Know About Roof Decking

Your roof features several different layers of materials that all work together to form a complete roof system. While every layer is required for a healthy roof, one of the most crucial is roof decking. It’s the foundation for your entire roof system.

In our 30+ years of roofing experience, we’ve always walked homeowners through a thorough explanation of their roof so they know exactly what they’re paying for when they get a replacement. That’s why we’re going to break down everything you need to know about roof decking.

By the end of this article, you’ll learn what roof decking is, what it’s made of, and how/when your decking needs to be replaced. Let’s get into it.

What is Roof Decking?

Roof decking, also called sheathing, is the foundation of your roof that connects it to the frame of your home. It’s the base that lays on top of your attic’s structural trusses to cover the rafters and support the weight of shingles and other roofing materials.

What is Roof Decking Made Of?

Roof decking is typically made with one of four materials, some of which are more ideal for certain residential roofing systems:

1. Oriented Strand Board (OSB) - Pictured above, this is by far the most common type of roof decking material used today. That's because it’s durable, readily available, and relatively inexpensive. OSB is made by compressing layers of wood strands together with adhesives. The strands are oriented to overlap each other, creating a stronger board. 
   
   
2. Plywood - Construction-grade plywood is another common roof decking material. They follow the same installation methods as OSB roof decking. 
   
   
3. Tongue and Groove - This type of decking is built out of two-by-six boards. Each board has a “tongue” on one end and a “groove” on the other that locks into each other during installation. Because of their aesthetic effect, this type of decking is typically used on roofs are going to be visible from the inside once the home is complete. 
   
   
4. Plank Sheathing - While not as common as OSB and plywood, plank sheathing is used for certain types of roofs, such as wood shakes. This decking features wood planks spaced about one and a half inches apart.

When Does Roof Decking Need to be Replaced?

When you get a roof replacement, you might have to replace sections your roof decking. Because it lays under the shingles, it can be difficult to tell its condition until the old roof has been torn off.

There are a number of signs of roof rot, such as moldy smells, wet walls, and consistent leaks when it storms. If your contractor finds that the decking is rotten, sprinkled with black mold, or shows heavy water damage, it will need to be replaced. However, decking isn’t usually completely replaced; only the sections with such conditions will need replacement.

What Causes Roof Decking to Rot?

When it comes to your roof, water or any form of moisture is enemy number one. Roof decking is particularly susceptible to water damage since it’s made from wood and wood composites.

Water can make its way into your roof in a variety of ways. Old or worn out shingles, clogged gutters, improperly installed flashing, snow or ice dams, a buildup of humidity and heat in the attic, and improper roof ventilation can all let water and moisture into your roofing system and lead to rotted decking.

What Are the Signs of Rotted Roof Decking?

Here are some common signs that you might have rotten roof decking:

• Wet spots on the ceiling
• Stains on interior walls
• Peeling wallpaper
• Water stains on rafters
• Mold and mildew in your attic
• Sagging ceiling or roofline

All of the signs we just mentioned are primarily caused by roof leaks. A quick inspection of the attic might uncover dark water stains on the rafters or in the insulation, or even light passing through holes in the roof. If left undetected, mold and mildew will develop in the walls, ceilings and insulation.

A sagging ceiling or roofline is another clue that there are major problems with a roof’s decking and the roofing structure. Soaked or waterlogged decking can warp, which can lead to a bowed or wavy roofline and ceiling.

Because it’s consistently exposed to various weather conditions, you should have your roof inspected twice a year—once in the fall, after hot weather has subsided, and once in the spring, after the danger of ice and snow is behind you. You should also have your roof inspected after a big storm, hurricane, or other potentially damaging weather event.

What Else Should You Know About Your Roof?

Now that you know what roof flashing is, what it’s made of, and the seven different types of flashing, you should feel confident knowing that your roof and all of its components are designed to protect your home.

Remember, making sure your roof decking is in good condition is vital to getting the most life out of your roof. However, it isn’t the only material that works to extend your roof’s longevity. You can check out our article on the ten materials included in your roof replacement to learn more about the other components that make up your roof.

If you live in Raleigh and need help with your roof, give us a call! On average, we work with over 900 homeowners a year who are looking for a high-quality roofing experience, just like you. If you want a free roof inspection or to learn more about your roof decking, don’t hesitate to fill out the form below. We’d be happy to help.