Parts of a Roof: The Roof Deck



If you’re reroofing your home, all the elements to learn about can be overwhelming. There’s not only the roofing materials, there’s the underlayment, the decking under that, the flashing, and what on earth is fascia anyway?

It doesn’t have to be so complicated. At Joyland, we like to take the mystery out of roofing, and help our customers understand what we’re installing, so you can make informed decisions and feel secure in your roof.



When a roofer talks about “decking” or “sheathing,” they’re talking about the plywood or other wood under the shingles. The framing of your roof holds the decking up, but in a sense the decking is your roof. It’s a crucial part of your home that can get ignored by price-cutting roofers, but making sure that the roof decking is in good condition is one of the most important parts of any roof work.



Putting new shingles onto a rotting or damaged roof deck risks more damage to your home over time. The shingles you’re installing can be damaged, and won’t function as well as they should. Water can pool in sagging areas and create leaks.

If the roof deck is soft or damaged, the nails used to install the shingles won’t hold, and you can lose entire sections of shingles to wind or gravity.



If your roof decking is sagging between rafters, that’s usually a sign of poor ventilation. The repeated cycle of heat and moisture in an unventilated attic space will break down the strength of the plywood decking, leading to a weak, wavy-looking roof that struggles with snow loads.

Make sure to discuss proper ventilation with your roofing contractor, so that the new roof you’re installing stays strong for its entire lifespan.



Newer construction homes use plywood or OSB board for the roof deck, but if your home was built more than a few decades ago, you probably have more traditional lumber boards for your roof deck. Sometimes those boards are just fine, and can be reshingled with no problems. Often, though, the boards have large gaps between them that cause problems when shingling. If a roof deck isn’t solid and consistent, some of the shingle nails will miss the boards entirely, and over time you’ll lose shingles. These roofs require plywood or OSB decking to be added on top of the existing boards.

Slate and wood shake roofs were typically installed on wood lathe strips, instead of on a solid roof deck, so if you’re replacing a slate or shake roof with shingles, getting a good roof deck installed should be a priority.



If you’re getting your roof replaced, make sure to ask your contractor about your roof deck – not just about what goes on top of it. Make sure they’ll inspect the sheeting thoroughly and replace any sections that show damage.

An estimator should inspect your roof deck from inside, if you have an accessible attic space, to make sure that any decking that’s needed is included on the estimate from the beginning.

Basically, make sure your contractor has a plan for your roof deck, and stay in the loop so you know what’s going on.