Roof sheathing is a part of roofing that you may well have no idea even existed. You’d be forgiven for your ignorance, given that most people could live their whole lives in a home and never even see it.

Nestled neatly under the outer layer (shingles, tiles, sheets of metal) and above the main structure of the roof is where you’ll find the roof sheathing. Without this critical layer, your roof would quickly become defunct. You’d face a multitude of problems. Leaks. Condensation. Draughts. The list continues.

First, it’s important to understand precisely what roof sheathing is. We’ll cover that now before we share details on the various types of sheathing, the functions it provides, and some installation tips.

The Evolution of Roof Sheathing

Many people refer to roof sheathing as decking. If you think of your roof structure as a human body, the trusses and rafters are the skeleton. These give your roof the shape. The outer part of the roof, the tiles and shingles, is the skin. Between the two are the muscles of the body. This is your sheathing.

Sheathing ties everything together and stops elements from coming loose or falling away. Historically, property builders would run boards perpendicular to the rafters or trusses. They’d leave gaps for expansion and contraction, as well as ventilation. Nowadays, there has been a shift away from wooden boards and towards oriented strand board (OSB).

OSBs provide more durability and wider coverage in a far more cost-effective way. Roofs have evolved over the years, so it’s no surprise that sheathing has too.

Roof sheathing provides a flat surface to which you can affix outer materials, but there’s much more to it than that. Roof sheathing also provides:

  • Structural Integrity: Sheathing braces the outer material and the trusses and rafters. It’s another level of rigidity that your roof requires to maintain sturdiness. As inclement weather hammers onto your roof, sheathing helps keep it from buckling.
  • Weatherproofing: Of course, the outer layer is your first line of defense from the elements. Should that fail, you’ll be happy that your sheathing is in place as backup.
  • Insulation: Adding another layer to your home adds another section of insulation. It might be thin, but every little helps. It all helps to reduce cold or heat transfer from your home.

Types of Roof Sheathing

We’ve mentioned a couple of options above. Now, we’ll share further details on each option presented to roofers and DIY enthusiasts.


Plywood is a very popular choice and was the leading choice for many years before OSB was created. Plywood is created by gluing together veneers taken from larger sheets of wood. The grains are glued perpendicular to each other to build strength. You’ll pay more for stronger versions of plywood. It’s a great choice if you want a balance between weight and strength.

Oriented Strand Board (OSB)

Many people see plywood and OSB as the same thing. The crucial difference is that OSB is made from compressed wood strands. These wood strands are intertwined and then bonded together to form a strong board. It’s a very affordable material and is very consistent in strength. It’s not always a great choice in humid climates as it can be compromised after prolonged exposure to moisture.


If you live in an older home, you might have plank sheathing on your roof. As you’d expect, these are wooden planks secured to the rafters. Few modern homes use planks, and many roof restorations and roof repairs lead to their replacement.

Particleboard or Fiberboard

Both of these are created in the same way as OSBs but with wood particles or fibers instead of strands. They aren’t as durable as the other options on this list, plus they suck up moisture. Few people opt for these on their roofs.

Installation Tips for Roof Sheathing

These tips will prove useful for any budding DIY roofer. Remember that DIY roofing is incredibly challenging and not without safety risks. If you’re ever in doubt, make sure that you call a professional for assistance. Even if only for a thorough roof inspection before you start work.

Pick Your Material

Go for the best selection that you can afford. That doesn’t mean the most expensive. It means the best option for your roof and its situation. That might mean choosing plywood or OSB. There might even be a reason that you’d choose planks.

Leave Gaps

It might seem counterintuitive to leave gaps, but it’s a necessary part of the process. The boards need space to breathe as they expand and contract depending on the temperature and humidity. OSB, in particular, requires gaps to avoid buckling and swelling.

Look For Nail Patterns

When you purchase the boards, look for the recommended nail pattern that the manufacturer provides. Almost all of them will. This will ensure that your boards are secured properly with even weight distribution.

Allow For Ventilation

You need your roof to have good airflow if you want to avoid moisture build-up between your exterior materials and your sheathing. If air can’t remove the moisture, you’ll face problems such as mold, mildew, and even rot.

Be Safe

Safety should always be your top priority. If you’re ever accessing the outside of your roof, make sure that you have appropriate harnesses, headgear, and non-slip footwear. Ladders should be entirely stable, and you should try to have someone working with you at all times.

Key Takeaways

Roof sheathing is definitely an unsung hero of the roofing world. Rarely seen, barely talked about, but there it is, securing and protecting your home. If you’re installing your own, understand the materials and nuances of your home, then follow our tips for success.

  • Regardless of the type you choose, always leave gaps and allow for ventilation.
  • Pick the best board you can that’s appropriate for your roof structure.
  • If in doubt, call in a professional to complete a roof inspection.

Are you looking for some professional, impartial advice on your roof sheathing or anything related to your roof at all? Contact Trenton Roofing, and we’ll be happy to answer your queries and help you with your project.

Alex Valentino

Alex Valentino – Vice President

Leading the way for the company’s second generation of family and employee ownership, Alex’s mission is to create lasting relationships built on trust and respect by providing uncompromising workmanship and unparalleled customer service. With a focus on safety and consumer education, Trenton Roofing strives to set the bar for the advancement of the roofing industry and the betterment of our local communities. When he is not working, Alex can be found traveling with his fiancée, watching football or playing a relaxing round of golf with his friends.