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Will My Roof Decking Get Replaced During a Roof Replacement?

June 14th, 2023 | 7 min. read

Will My Roof Decking Get Replaced During a Roof Replacement?

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Homeowners usually only think about their shingles when getting a new roof. However, you’ll not only be replacing your old roofing material but also the old components. 

But one component that’s a little different than the others is your roof’s decking. That’s why a common question I get asked after an inspection is, “Will my roof decking get replaced during my roof replacement?”

For over 30 years, the team at Bill Ragan Roofing has taken pride in providing transparent and honest information to homeowners investing in a new roof. Because of this, I’ll help you understand what you need to know about replacing your roof decking. 

In this article, we’ll cover the following:

  • Quick overview of what roof decking is and the types.
  • If roof decking gets replaced during a roof replacement and why.
  • How a roofing contractor includes replacing roof decking on your roof estimate.

What is roof decking?

Before we get to whether or not your roof decking gets replaced during a roof replacement, let’s do a quick review of what roof decking is and the types. Roof decking (also called roof sheathing) is the wooden frame of your roof that your shingles and other roofing components are installed on.

osb roof decking

There are 2 types of roof decking: plank decking and sheet decking.

Plank roof decking

Plank decking was the main type of roof decking used in residential roofing before the invention of plywood. This type of roof decking is made up of elongated and rectangular wooden boards that come in two different sizes, 1x6 or 1x8.  

plank roof decking

While it’s not as commonly used today, plank decking is still on plenty of homes. 

Sheet roof decking

Sheet decking (or sheathing) are flat sheets of wood that are either plywood or OSB. 

osb roof decking(OSB roof decking)

OSB (oriented strand board) sheet decking is the most commonly used on roofs today. It’s made up of wood chips/strips compressed together to form a flat 7/16” sheet.

plywood roof decking(Plywood roof decking)

Plywood comes in several different thicknesses (⅜”, ½”, ⅝”, and ¾”) depending on the span of the rafters. Both types of sheet decking are great options, but which one you get depends on your budget and the availability of the wood. 

Will your roof decking get replaced during a roof replacement?

There’s a good chance that some roof decking will need to be replaced during your roof replacement. Most of the time, a few boards have to be replaced, but it’s uncommon to need the entire roof decking replaced. 

sections of plywood roof decking that were replaced before roof replacement(Sections of roof decking that were replaced)

With that in mind, there are two reasons why roof decking will need replacing: rotting and building codes.

Replacing roof decking from rotten or broken boards

A new roof needs a solid foundation before the materials and components can be installed. If any of your roof decking’s integrity is compromised by rotting or broken boards, the impacted piece(s) of wood must be replaced. 

rotten roof decking around a skylight

While replacing compromised roof decking is crucial for proper roof installation, it’s also a building code. According to code R905.2.1 of the 2018 International Residential Code: asphalt shingles shall be fastened to solidly sheathed decks. 

This code simply means that your roof decking must be able to withstand and hold your new roof when it’s installed. 

Replacing plank roof decking due to gaps

While replacing compromised roof decking is required by codes, another code impacts plank roof decking specifically. However, it has to do with following the shingle manufacturer’s specific installation instructions.

According to code R905.1 of the 2018 International Residential Code: roof coverings (roofing materials) shall be applied in accordance with applicable provisions of this section and the manufacturer’s installation instructions. 

This code means your local roofing contractor must follow all installation instructions provided by manufacturers. As of 2021, per shingle manufacturers’ installation instructions, plank decking must be replaced if there is more than a 1/8” gap between the planks. 

gap in between roof decking planks that need to be replaced per building codes

If there’s a gap larger than 1/8”, the plank boards will need to be replaced after your old roof is torn off. The main reason is that roofing nails fit between these gaps, leading to roof leaks and leaving the shingles prone to wind damage

nail that came through the gap in between plank roof decking

However, failing to follow these installation instructions also voids the roofing material warranty on the shingles. 

How does a roofing contractor include replacing roof decking on your roof estimate?

Unfortunately, your roofing contractor won’t know how much of your roof decking needs to be replaced until they finish tearing off your old roof. Because of this, there’s a chance there won’t be a fixed price on your original estimate.

Some roofing companies include it as a line item that specifies how much it will cost per sheet to replace the roof decking. If this happens, they should tell you how much needs to be replaced and that it’ll show up on your final invoice at the already agreed price.

On the other hand, some roofing companies automatically include roof decking replacement in their estimates, which means you’ll pay for the wood whether they use it or not. Both ways are right, but the important thing is that there’s a line-item in your estimate stating what happens with the compromised roof decking.

If a roofing contractor has nothing in their estimate about replacing decking, it’s probably a hidden fee to keep their original price lower than other companies. That’s why you should always compare your roof estimates to learn if a roofing company left something off that’ll show up later as a hidden fee.

What else gets replaced during a roof replacement?

Now you know what roof decking is, if it gets replaced during a roof replacement, and how a roofing contractor handles it on an estimate. Remember, there’s a good chance you’ll at least have a few boards that need to be replaced.

However, you won’t actually know until your roofing contractor finishes the tear-off process. The important thing is to make sure you know exactly how replacing compromised decking is handled. 

But did you know that roof decking is the only roofing component that may not need replacing? If you don't, you're not alone. 

Some homeowners just think the shingles they can see is their roof. However, a roof is a combination of materials and components that fit together to form a complete leak-free roof system. 

If even one is left off your roof during your replacement, I guarantee you’ll have costly problems. That’s why it’s crucial to know everything that should be included in a roof replacement. 

Check out 9 Materials Included With Your Roof Replacement to learn all the components and materials that get replaced when getting a new roof.

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