Decking or Sheathing

Welcome back to another exciting roofing blog from Professional Roofers! In our last two blogs, we discussed what roof rafters, joists, and trusses are: a series of evenly spaced parallel beams that support the structure of your roof and walls, as well as providing a space for ventilation and insulation in your home. For this post we are now going to be discussing what goes on top of those beams to allow easy movement on a roof, and to block the elements from your home: the “sheathing”, which is also sometimes referred to as “decking” of a roof. A roof’s sheathing is simply a board that is nailed to rafters, trusses, or roofing joists, covering them from the elements. If you know what wall decking is, roof decking is similar, but generally made from thicker and stronger materials than your wall.

Essentially, this sheathing provides a flat surface that adds a certain amount of stability to a roof, while also creating the first layer of defense from the elements. Since roof decking tends to be made from wood and wood can rot when mixed with moisture and heat, after being laid, this layer of defense should be protected quite quickly with waterproofing membranes. That said, it is nonetheless still one more layer of protection and stability for a roof, and an incredibly important part of the roofing process, as roof decking provides the foundation for all other protective membranes and materials like shingles, flashing, or membranes to be applied. It must therefore be strong enough to support the materials that are attached to it, and durable enough to cope with the stresses of the elements and its constant use. Your sheathing, if applied correctly, will significantly increase the rigidity and strength of your roof.

In residential roofing, a roof’s sheathing is generally made from a layered wooden board (usually plywood or oriented strand board); however, it can be made from metal, concrete, or even cement depending on the home or how much weight the decking is needed to hold. Sometimes homeowners opt to install radiant barrier sheathing, which is a wooden board that has aluminum on one side. When installed, the aluminum side of radiant barrier sheathing will face down into an attic space and reflect the heat coming off the roof, preventing additional summer heat from entering your home. This type of sheathing is particularly useful in hotter climates and can reduce the need for air conditioning.

Sometimes at Professional Roofers we run into a home that is having roofing problems caused by improper sheathing installation. If your roof is made with wooden decking (as it likely is), it should be applied with approximately 1/8 of an inch distance between each board, to allow for the expansion and contraction of the boards as the seasons change. Moisture and heat can cause wood to expand, and if your contractor didn’t space out your decking properly then the boards might push up against each other as they expand, causing ripples along your roof or shingles that might break off or lay incorrectly. It is absolutely a recipe for disaster, and is something that is easily avoidable with proper installation.

Hopefully you have found this blog as informative and helpful as our last blogs, and we look forward to sharing more of our roofing insight with you next time!

Joists, Rafters and Trusses Part 2

Welcome back to the Professional Roofer’s blog, where we are discussing all the important structural elements and materials that make up roofs. In our last blog, we discussed the importance of roofing joists, ceiling joists, rafters, and trusses; and explained what roofing joists and ceiling joists were. If you haven’t already read that blog, we highly recommend you go back and read it now, as we will be building off of that information for this blog piece, where we will be introducing rafters and trusses.

From last week’s blog, we know that roofs with a slope of less than 2 in 12 have parallel planks of wood called roof joists that are spaced at specific distances apart for load-bearing purposes. These planks are called joists because they are relatively horizontal to the ground, and are therefore categorized within the “joist” family of building terms. However, since steeply sloped roofs of more than 2 in 12 are raised up too high for the parallel planks to be considered joists, they go by a different name, and are instead called “rafters”. Roof rafters are typically joined where the two slopes converge along the ridge of your roof, running all the way down to the eaves. They too are spaced at specific intervals apart for load bearing purposes, and are parallel to one another. The only difference between joists and rafters are the amount of load they must be designed to carry, and their angle – that is generally it. Raftered roofs have a great deal of attic living or storage space beneath their planks, as insulation is generally fitted in between individual rafters, leaving the rest of the space open for personal use.

If you have a sloped roof, but your attic space is nonexistent or uninhabitable, you likely have trusses, the most common roofing support system used in North America today. Trusses are lightweight, pre-fabricated, and specifically engineered roofing support systems. Trusses are created from straight structural components (like pieces of wood) that are interconnected into a roughly triangular shape. They primarily use lighter, smaller pieces of wood in their construction that allow them to be cheaper than traditional rafters. Trusses cannot be disassembled or altered in any way without drastically reducing their structural integrity, so they do limit construction to a certain degree and prevent a home from having usable attic space. However, since they come pre-made, are typically cheaper than rafters, and are much easier and faster to install than regular rafters they tend to be the preferred choice for builders. They can also span long distances, by as much as 60 feet, which allows for a more open housing floor plan and a reduction in load bearing walls for most homes.

We hope that you’ve enjoyed learning about the various plank-like structural elements that make up your roof, and feel a little bit better informed about your home and some of the technical jargon your contractor or roofer may use. Until next time Toronto!


Joists, Rafters and Trusses Part 1

In today’s Professional Roofers blog, we have chosen to go “beneath the shingles” a little to discuss some important structural terms that relate to your roof, but that you certainly won’t see on the outside of your home: roof joists, ceiling joists, rafters, and trusses. Depending on the style and slope of your home roof, you will likely have one or two of these structural elements integrated into your house. These structural components are all a little bit different, which we will explain in more detail soon, and yet they all share the same jobs: carrying the live and dead loads of your roof, supporting the walls of your home, preventing the walls of your home from spreading or racking (shaking), and creating a space for ventilation and insulation. In other words, they’re incredibly important and completely necessary for any modern house.

Continue reading “Joists, Rafters and Trusses Part 1”