Everything You Need to Know About Roof Decking

When most people hear the term “deck” while discussing their home, they think of a lovely outdoor space with a grill, patio table, and maybe some unfortunate mosquitos. However, your home has a different kind of deck, which is essential to its ability to protect your and your belongings. That is your roof deck. Read on to learn about your roof deck, how it functions, and what signs of trouble you should keep an eye out for.

What is a Roof Deck?

You can think of your roof deck as the floor surface over which other roofing materials, like shingles or tiles, are applied. Also known as “sheathing,” roof decking provides a water-resistant layer between your home and the assault of nature.

Your roof decking isn’t visible once your entire roofing system is installed, but it is a critical component of your home’s structure. Sitting on the “trusses,” which are the roof’s frame, your roof deck holds the weight of the roofing materials most people consider their roof. Because it supports the weight of the overlaying materials, your roof deck must be strong. It also needs to be flexible enough to deal with heat, freezing temperatures, and whatever else nature throws its way.

What is a Roof Deck Made of?

Here are some common materials used for most roof decks:

Oriented Strand Board (OSB)

OSB is sheets of material made from shavings or strips of wood. These bits of wood are mixed with a resin material and pressed into thin, flat panels. The resin helps make OSB water-resistant. Because it is readily available, inexpensive, and reasonably sturdy, OSB is a popular choice for roof decking.

It isn’t without its disadvantages, however. Issues like missing shingles, improperly installed roofs, or simply roof degradation over time can cause water to seep into the OSB. While the resin helps repel water, it isn’t entirely impervious to extended contact with moisture. That can lead to rot or mold, which is detrimental to your home, and even health problems if you inhale the mold spores.


Plywood is made by gluing many thin layers of wood, known as “plies,” together to form panels. Each layer is rotated so that its grain runs at an angle compared to the layer below it, adding to the finished product’s durability. This cross-graining increases the strength of the wood, decreases splitting during nailing and cutting, reduces expansion and shrinkage, and resists warping. All of those features make it an excellent choice for roof decking.

Because plywood is more dense, it also repels moisture better than OSB, meaning it is less likely to have issues with rot and mold. That makes it safer and sturdier, but plywood is also more expensive than OSB. Your residential roofer will be knowledgeable about your local climate, the particulars of your structure, and other factors that guide the decision for the best roof deck material for your roof replacement. They will know best whether to use OSB or plywood for your roof decking.


Typically only used in commercial construction, concrete is another option for roof decking. Because it is extremely heavy, it can’t be used on all structures. Some building materials won’t withstand the weight of such a heavy roof deck. It is also the most expensive option. However, it is highly durable and more eco-friendly than wood-based materials like OSB and plywood, which are attractive features in some applications.

Plank Decking

While those are the three most common materials used for roof decking, you might occasionally see plank decking. This type of deck uses planks of wood rather than sheets. Plank decking is no longer a common type of roof deck, but you might still see it.

Roof Deck Problems

Roof decking’s number one enemy is rot.

While your roof is made to withstand daily abuse from the elements, it isn’t impervious to years or decades of intense sun, heavy snow, freezing temperatures, driving rain, and gusting wind. Once water gets underneath your shingles or tiles, it reaches your wooden roof deck. An occasional drop of water is unlikely to be problematic, but if the OSB or plywood deck remains wet, it may start to degrade or rot. You must catch this damage early and address it with quality roof repairs, which can keep an easy fix from becoming an expensive nightmare.

There is no time to spare if you see water spots on your ceiling or walls, warped boards in your attic, cracks, or loose boards. Contact a residential roof repair company immediately.

Even though you can’t see it, your roof deck works hard day in and day out to protect your home. It’s a critical component of your roof system and home’s structure. Keeping it in good condition and repairing or replacing it as needed helps your roof deck help you. Then you can sit back and enjoy a cold beverage on your home’s other deck without worries about what is happening overhead.

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