What Are the 2 Main Components of a Roof?

A roof protects the inside of a house or building from weather elements like wind, rain, snow, heat, cold, and sun. A roofing system also provides insulation and sheds moisture.

Builders start with a wooden frame called a roof truss, which supports the weight of the other roof components. These include the ridge, valley, dormer, skylight, and chimney.


Rafters are a critical part of a roof. These internal beams, shaped like triangles, run from the ridge (the peak of the roof) to the eave (the edge). They support the roof decking and structure. They also help distribute weight throughout the building, helping prevent excessive stress on outside walls.

Rafter frames are typically made of wood, but some buildings use metal rafters for extra durability. Rafters come in various sizes and shapes to suit different roof types and building designs.

The two most common kinds of rafters are principal rafters and struts. Principal rafters create the sides of the triangle that the king post sits in the middle of, while struts extend outward to increase stability. In a traditional timber frame building, a ridge board rests at the top of the rafters and ceiling joists connect them to the exterior walls.

To increase potential roof spans without increasing rafter size, builders sometimes use purlins to bridge between rafters. These are perpendicular to the rafters and connect them with cleats that secure them in place. When a rafter is in need of additional strength, joists can be added on either side.

Another key component of a roof is its drainage system, which helps to prevent water from collecting around the base of a house. The drain system is comprised of a gutter and downspout, which carry water away from the roof and down the sides of the building. It also includes an ice and water barrier, which prevents ice dams from forming and helps to prevent moisture damage to the roof’s internal structure. An ice and water protector is a thin membrane that can be placed under shingles to help defend against leaks caused by wind-driven rain.


In a building, purlins are horizontal beams that provide support for a roof. They also help to stabilize and strengthen the secondary framing. In fact, they serve three important structural functions:

First, they create a horizontal diaphragm that supports the weight of the roof deck (whatever material you choose for your roof). Second, they help to make the entire roof structure more rigid by tying the rafter beams together. Third, they increase the span that can be achieved by the building’s trusses. This allows for a larger building to be created with fewer trusses.

Purlins are made of galvanized steel or cold-formed steel, which makes them durable and reliable. They can withstand many kinds of weather conditions, including snow and high winds. They can be used to build any kind of roof, from a flat to a pitched look. They can even be combined with wood joists to construct a wooden roof.

There are 2 main types of purlins: C and Z purlins. C purlins are in the shape of a letter C, and they often replace rafters fitted closely to each other in wood frame buildings. Z purlins are in the shape of the letter Z, and they are stronger and studier than C purlins. They are mostly used in metal buildings, but can also be used for walls and flooring.

It is not recommended that purlins be welded or hot-cut, as the heat from welding will affect their material properties and may cause stress concentrations. They should also not be stacked tightly together, as this can lead to premature corrosion. Ideally, they should be stacked openly and left to air out. It is also important to wear fall protection when walking on a roof, especially before the roofing sheets are fastened down.


In the most basic sense, a roof protects you and your family from the elements. But a roof is actually more complex than it seems, with a variety of components that work together to create a strong and durable shelter for your home.

The rafters and trusses form the skeleton of your roof, but there are other parts that help to make it water-proof and resistant. Underlayment is one of these components, a waterproof layer that is installed directly on top of the sheathing/decking of your roof. It provides a second line of protection from rain and snow, and it helps shed water.

Sheathing, also known as roof decking, is the flat wooden boards that are attached to your rafters and trusses. It serves as the nailbed on which shingles and other roofing materials are applied, and it is essential to your roof’s structure. You can find sheathing in the form of plywood or oriented strand board (OSB).

Another crucial component is the fascia, which is located along the bottom of your rafters and trusses. The fascia provides a finishing touch to the edges of your roof, and it is often installed with soffit vents in order to provide adequate ventilation.

The eaves and ridge of your roof are important as well. The ridge is the highest point of your roof, and it connects the different sections of your roof. The eaves are the edges of your roof that run horizontally; they can be finished with wood trim or a metal drip edge, and they are sometimes fitted with soffit vents. You can also find roof valleys, which are where two different slopes of your roof meet at an internal angle. You can see roof valleys at the corners of your roof and also in areas where your roof abuts a wall, such as at chimneys.


Gutters are metal troughs that take rainwater from the lower edge of your roof and channel it through downspouts to drain away from your home. They are essential for water management on a house, helping to prevent foundation and crawl space issues. In addition, they help reduce erosion on your property and stop moisture problems like peeling paint or rotted siding. The gutter system also helps protect the fascia, soffit, and rafters from rotting and water damage.

A soffit is the flat board that runs along the underside of your roof at the eaves, covering rafters and providing a base for attaching gutters. Soffits are a critical component for the integrity of your roof, protecting against rot, insect infestations, and mold. They are usually made of wood, but can be made of a variety of materials to complement your roof’s style.

The eaves are the sloped edges of your roof, often the most visible part to passersby. Without a gutter system, rainwater cascades in heavy sheets off the roof and can be destructive to your property. Without gutters, water can erode soil and batter tender plants and flowers. It can also saturate shingle underlayment and leak into your home, damaging the structure and creating an unpleasant mess.

The ridge of the roof is where the two sides meet and create a peak. A roof valley is where a sloped section meets another sloping section of the roof. A dormer is a structure that projects out from the side of a roof, often holding windows. It can be small, housing just one window, or large, with several windows.


A roof’s shingles protect the rest of the structure, including the interior living space, from rain and other elements. They also add to the home’s curb appeal and make it more energy-efficient. But there are other roof parts that are important to the function of a house. These parts stop leaks, redirect water flow and keep wood from rot.

The roof’s underlayment and decking are essential to the overall strength of a roof. Underlayment is a thin material that goes over the decking and under the shingles, acting as an insulation and helping to prevent moisture from damaging the framing underneath. Decking is usually made from plywood or oriented strand board and acts as the base for all other roofing materials.

Shingles are the main roofing material used in most homes. They are a durable, cost-effective, long-lasting product that can withstand a variety of weather conditions and a variety of architectural styles. They are available in a wide range of colors and styles, including laminate or architectural shingles that mimic the look of wood shakes, with deep shadow bands to add character.

Some shingle roofs include ice and water shields to help protect against damage from melting snow. These flat sheets of waterproof material go over vulnerable areas like valleys, around vents, skylights and roof edges, and where the roof meets a wall. They can also be installed by Roofers Akron Oh over the chimney flashing to help protect against leaks.

Roof valleys are the indented areas where two sections of the roof meet. They are often prone to leaks, but they can be protected with metal flashing in open or woven styles. Chimney flashing is a flat piece of steel that goes around the chimney and helps to keep rainwater from leaking into the house.

A roof protects the inside of a house or building from weather elements like wind, rain, snow, heat, cold, and sun. A roofing system also provides insulation and sheds moisture. Builders start with a wooden frame called a roof truss, which supports the weight of the other roof components. These include the ridge, valley, dormer,…