The Three Main Components of a Roof

A roof is a large component of any house that serves an important purpose. It protects you and your family from the elements that can damage your home. This is why installing your roof requires professional assistance from Roofers Canton Ohio .

The structure of a roof starts with its frame. This includes joists, trusses and rafters. There are also other essential components that make up a roof, such as the drip edge, fascia board and gutters.


Rafters are the main structural beams of a roof and form the base on which the final roof covering is fixed. They’re part of the main framing of the roof and are also what give it its pitch, an angle that determines how much it rises from one end to the other. They come in two varieties, the principal rafters which sit at the center of the triangle formed by the king post and tie beam and the purlins which are placed over the principal rafters to add extra support.

They are normally made from wood although they can be fabricated out of metal, such as in steel-framed roofs. They are spaced evenly and meet at the ridge or apex of the roof, running along its length. They also provide a sturdy foundation for the attachment of roof boards and insulation.

Another important role that rafters play is to help in the distribution of weight over a large area, which reduces the overall stress on any single point and decreases the risk of structural damage. For this reason, rafters are usually joined together with horizontal beams called collar ties. This prevents the rafters from spreading apart and pushing on the walls of the building when there is downward pressure. The rafter ties are then tied to the ceiling joists which run between them.

An alternative to rafters is the use of trusses, prefabricated triangular structures that are popular in new construction and are ideal for roofs with a more complex design. Trusses are much lighter and are capable of covering a greater distance than rafters, making them more efficient to build. They can be constructed on-site or in a factory, and are able to handle more weight than rafters as they are designed to do so.

Ridge Board

Ridge boards are essentially the topmost part of the frame that defines a roof’s structure. They sit at the peak of the roof and the rafters attach to them to create a triangle that supports the roofing materials. A ridge board also plays an important role in distributing the weight of the roofing materials evenly across the roof.

For most modern homes, a ridge board is built out of LVL (laminated veneer lumber) – a wood product that’s made from strips of timber glued together with resin and a small amount of wax. The result is a lightweight, strong plank that’s used to form the foundation for the rest of the roof structure.

Another important component of a roof’s framing is a ridge vent that allows the roof to breathe. Without a ridge vent, the roof can become damp and humid and create the conditions for mold growth, which is one of the main causes of health problems in home interiors.

Other than a ridge vent, the most commonly seen element of a roof is the shingle or slate. These are placed in a layer that is then covered with a waterproofing underlayment, which helps to protect against leaks.

A ridge vent and underlayment are essential for preventing water and wind damage to the structure of a house. But there are other components that help to strengthen a roof, such as purlins and a sheathing that’s attached to the rafters or trusses.

Purlins are horizontal beams that sit on top of the principal rafters, providing additional support for the load. They can be wood, steel or even a combination of both. They can be installed in a variety of ways, but they’re most commonly used in conjunction with a ridge vent and an underlayment. The most common wood purlins are made out of plywood, but in recent decades, a more durable material called OSB has taken over as the standard for load bearing planks in residential construction.


Purlins are the horizontal beams that support a roof's decking and sheathing. They are an important part of the secondary framing in metal buildings and can replace closely packed rafters in wood-frame structures. Purlins are made of wood, steel or aluminum and can be in various sizes depending on the size of the building and the type of roof. They serve three important functions: they provide structural support, tie the rafters together and act as a sheeting support.

Moreover, they help transfer wind loads to the main frame and rafters, and they also prevent the roof from sagging. The sagging can give the building an ugly appearance and cause leakages in the interior. This is why it is crucial that the purlins are sturdy enough to withstand all the forces that they will encounter throughout their design life.

There are two types of purlins: C purlins and Z purlins. The C purlins have a C-shaped cross section and are usually used in smaller buildings, such as warehouses. On the other hand, the Z purlins have a cross section that resembles the letter Z and are often used in larger-scale structures such as warehouses.

Cold formed purlins are a great choice for most commercial buildings because of their light weight, high strength and stiffness, and ease of fabrication and installation. They are available in a variety of lengths and can be connected using a staggered sleeve or butted system. The design of a purlin depends on the load, span and building parameters like roof slope, wind speed, etc.

For metal purlins, you need to consider their corrosion resistance. To reduce the risk of corrosion, they need to be coated with a protective paint or zinc-coated. For example, if your building is located in a coastal or chemically reactive environment, you should choose steel purlins with a minimum coating mass of 120 GSM to avoid corrosion.


Roof sheathing, also known as roof decking, is the layer that sits beneath your shingles and other roofing materials. It offers a strong foundation for these external roofing materials to be nailed down and helps prevent leakage and other problems.

It’s typically made from oriented strand board or plywood. Oriented strand board is more lightweight than plywood but both offer similar durability and strength. It’s recommended to have a professional install your sheathing to ensure it meets local building codes and offers the necessary structural stability for your roof.

Plywood sheathing is more resistant to moisture and can help protect the rafters from warping or swelling over time. It also creates a more even surface for the shingles to be nailed down, which helps to ensure the longevity of your roofing materials.

Roof sheathing is typically installed in two different ways: plank sheathing and sheet sheathing. Plank sheathing was used before the invention of plywood and consists of elongated wooden boards that are either 1×6 or 1×8 in size. Alternatively, sheet sheathing consists of wide sheets of wood, most commonly made of plywood or oriented strand board (OSB).

Sheet sheathing is a more common option today than plank sheathing and is a stronger material. It’s a good choice for most roofs because it offers a more durable surface to nail down the shingles and other upper roofing materials. It’s also easier to inspect for damage to the sheathing and can be quickly replaced if it’s rotting. A rotted sheathing can be easily spotted by looking for water damage, puddles or staining in your ceiling or by using a flashlight to check for soft spots in the attic.

Ceiling Beams

A roof is a critical part of the overall structure of a home. It supports the live and dead weight of the building and provides a space for ventilation and insulation. It also creates a visual focal point that can have a strong impact on the design of a home. It’s important to understand the role that joists, beams, and trusses play in creating this frame of support.

In a conventional timber-framed house, the ceiling of a room is formed by a series of joists that support the ceiling cladding, or sheathing. The joists are supported by beams, which sit directly above them to reduce the amount of space they have to span. The ceiling beams can be made from wood or metal. They can be used to create a specific aesthetic, or they can simply be there to support the ceiling’s structure and to help with its insulating properties.

For example, reclaimed solid wood beams that still have visible crosscut marks from the saws used to cut them can be installed to add a rustic feel to a barn-style home or a mountain cabin. Or, modern steel beams can be used to give a lofty, industrial look to a modern living space.

Other elements that make up a roof can include dormers, which are structures that extend from the plane of a pitched roof to accommodate a window or other feature. Other parts that make up a roof can be called facets, which are sections of the roof that don’t extend to the ridge or pitch. These can include a chimney; skylights; and penetrations, which are holes for air, combustion, or plumbing vents; water pipes; and electrical wiring.

A roof is a large component of any house that serves an important purpose. It protects you and your family from the elements that can damage your home. This is why installing your roof requires professional assistance from Roofers Canton Ohio . The structure of a roof starts with its frame. This includes joists, trusses…