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Roof Decking is Critical to Performance

• April 1, 2020

It’s What’s Under the Shingles that Count!

Roof Decking is Critical to Performance!


We often encounter problems to roof decking during replacement. Especially, in older homes. Althoughwe try to prepare customers for the cost up front, it can still be a shock when the necessaryreplacements are tallied. We do our best to estimate deck replacement before every job, butsometimes it is just not possible. If you are facing costly roof deck replacement, think about the costsyou will face if you do not proceed with the necessary repairs…Roof decking is the support for the waterproof covering of your roofing system. For residential roofs it istypically constructed using plywood or OSB in newer construction, and plank sheathing or tongue andgroove material in older homes. Each material has its’ own advantages and disadvantages, but what isimportant is that no matter what material is used, it must be solid and capable of supporting the roofcovering, reasonable live, wind and snow loads, between rafters/trusses. Since this material is notwaterproof and can be compromised by storm damage, and/or failure of the cover material, it isimportant to assess and replace damaged or out of compliance decking when replacing the roofingsystem.Manufacturers of roofing systems and building compliance authorities have specific requirements forroof decks to ensure safety and performance of the roof. There are two things you should do whenbuilding or replacing a roof.First, you should check with your local Planning and Zoning authority or a state compliance office forguidance on decking requirements. Typically, requirements are set to protect individuals working onyour roof, and occupants inside of the home, from construction activities and weather that is commonfor the area. Parts of the country that receive lots of snow for instance will have greater supportrequirements for roof structures and coverings than areas that do not. However, snow load is not theonly factor to consider in framing and decking requirements. If using a heavier material, such as claytiles in South Florida for example, the roof structure and decking will need greater support than anasphalt shingle roof.Second, you should make sure that the roof deck material meets the requirements of the manufacturerof the roofing system you will be using. For reference, Owens Corning® requires the following:• Solidly-sheathed roof decks: – Minimum 3/8-inch plywood sheathing, rated by TheEngineered Wood Association (APA).1 – Minimum 7/16-inch Oriented Strand Board (OSB),rated by The Engineered Wood Association (APA).1 – Installed with minimum 1/8-inch andmaximum 1/4-inch spacing at all panel edges and end joints. Sheathing thickness andinstallation must follow the sheathing manufacturer’s and local building code requirements.• Decks constructed with spaced deck boards: – Minimum 6 inch wide – Minimum 3/4-inchthick – Installed with maximum 1/4-inch spacing between boards – Holes or gaps greaterthan 1/4-inch must be repaired or boards replaced. All roof deck surfaces, regardless of type, should be clean, dry, and free of debris,protrusions, dust and oil prior to the installation of underlayment or asphalt shingles. Owens


Corning® asphalt shingles should never be installed directly over insulation board of anytype.


If you fail to follow these recommendations by the manufacturer, you may be voiding coverage underthe warranty of the manufacturer, or insurance coverage for a loss in the future.When replacing roofing systems contractors should evaluate and provide you with evidence of the needfor decking replacement. Whenever we perform a tear-off we properly clean the deck surface, takepictures of areas where boards/sheathing has been water damaged, spacing between boards is notcompliant, boards are broken, have holes, or are deformed, and we show those to the customer sothere is no confusion about the need for replacement. It is common for roof decks on older homes toneed partial to full replacement due to one of more of these issues, but even newer homes can requirethe same, due to poor workmanship and damage caused by previous contractors.Make sure to protect yourself by hiring a contractor that knows, explains, and does these all of thesethings!


That is what we do at Roof It Right, LLC. We invest into our people to make sure we do the job RIGHT! I’m James Hannon, the assistant general manager, and I would like to say thank you for checking out our BLOG at Roof It Right, LLC. We are a Louisville, Ky based company that specializes in exterior home products, insurance claim services, and most importantly educating our community about what we do!

James Hannon
Assistant General
ManagerRoof It Right!

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