25+ Parts Of A Roof And Their Functions (Explained and Pictures)

Last Updated on October 10, 2021 by Kimberly Crawford

With all the recent trends in architecture right now, it will be hard to keep up especially if you do not have the slightest clue of how each structure works, what they are composed of and the respective functions of these parts.

I mean, would it be nice to specifically know which part needs maintenance or repair when the time comes? Aside from that, it will always come in handy for future home improvements. 

For these reasons, we will be focusing on the parts of a roof and their functions today. 

Related: Parts of a door and door frame

Parts of a roof and their functions

parts of roof diagram

For sure, you would know a thing or two like the gutter, the chimney, the vent pipe, the beams and the rafters.

But aside from these, we do not know more and that is why we just look at the roof as one of the final pieces in constructing a house or a building not knowing that there are other small, equally important pieces inside it that should work for it to become stable.

Here is a rundown of the different parts of a roof and their functions. 

Related: Types Of Roof Vents

Rake of a roof

1. Shingles


It is essentially a roof cover that comes in flat and rectangular shapes. They are installed at the roof’s eaves after the roof decking is placed.

Depending on the location and design of your house, it is made of various weatherproof materials such as flagstone, slate, plastic, wood, metal and other composite materials.

At present, solar shingles have also become a trend. Its main function is to prevent water from entering the eaves. To make it ultimately waterproof, shingle underlayment is also applied after. 

Related19+ Different Types Of Roof Shingles (Materials, Brands, Pros, Cons, Cost)

2. Ridge


It is technically known as the ridge board. It is the horizontal wood or metal resting at the roof’s peak creating the roof’s triangle.

In technical terms, it is the highest peak on a roof. In terms of function, the ridge is connected to the rafters and trusses to make the roof’s frame. Interestingly, it is also used to refer to a roof board or beam used in building the roof’s ridge entirely. 

3. Valley


It connects two pitched/sloped roofs, forming an angle of 90 degrees. It supports the valley rafter which in turn supports an internal roof gutter where water and small debris will fall and trickle down to the external gutter.

Essentially, it is the roof valley that collects the water that will fall off the roof. This is the reason why choosing the right installation type for the valley is one of the most crucial steps in roofing or else you would have serious leaking problems. 

Related: Alternatives to Gutters

4. Eave


It is considered as the lowest point in a pitched/gabled/mansard roof. They are also called roof edges overhanging from the wall’s face projecting from the side of the house.

It is the one that connects the gutters to the roof. Technically, it functions to clear the wall with water trickling down the surface. 

5. Soffit


It is a fixture considered to be both aesthetic and functional. This is the roof structure that you will see when you straighten a roof up. It is located in between the wall and the roof’s eaves.

It basically conceals the ceiling joists and the rafters. Its basic function is to protect the rafters from natural elements such as moisture and molds. Through this, it also helps preserve the longevity of the roof materials. 

6. Rake


While it is considered as one of several roof sections, the rake is not exactly found on the roof. It is used to describe the sloped sides at the ends of a gabled roof. It can be flat or with overhangs.

Rake with overhangs can be left open or can be closed with the fascia or soffit. It can also be customized for roof aesthetics. 

7. Sidewall

It is one of the types of walls used in roof flashing (which is a waterproofing material to prevent water infiltration), specifically in base and step flashing.

Sidewalls like its front wall counterpart are vertical walls intersecting with the roof deck’s surface. It connects the edges of a sloping roof deck. 

8. Flashing


It can be made with different materials including aluminum, galvanized steel and plastic.

Its main function is to prevent water from passing through roof openings and other critical areas in the roof where water could pool. Thus, it is typically mounted in roof valleys, vents, chimneys and skylights.

Through the various types of roof flashing, ponding water is redirected in many parts of the roof. 

  • Chimney flashing: It is another waterproofing material installed in the intersection connecting the chimney and the roof. It is mainly used to prevent moisture penetrating the home through the roof. 
  • Vent pipe flashing: It is externally installed on the roof. It acts as a sealant to the vent pipe to prevent water from seeping through surrounding openings where water could enter. 
  • Valley flashing: It is installed in the roof’s valley line, hence, the name. It’s also functions as a waterproofing material for the roof. 
  • Skylight flashing: It is also a waterproofing fixture applied in between the skylight’s glass and frame. It is applied on top of skylight sealants to contain moisture on the glass surface. 
  • Dormer flashing: It is essentially used to add more protection to the roof against water damage. It is installed under the sides and on top of the roof’s steel or at the dormer’s bottom or end wall. 

9. Hip


It is the external angle functioning as the intersection where adjacent sloping sides of a roof would meet.

An associated term is the hip end which refers to the triangular sloping surface usually formed by the intersecting hips in the roof’s edge/eaves.

It is associated with a hipped roof, a roof design known for its slants and inward slopes on all of its sides. Hipped roofs are commonly used in snowy and windy areas as the ice would easily slide off from the slants. 

10. Flat roof

Flat roof

It is a type of a roof structure considered as one of the most ancient roof types. It provides an additional usable space in the roof that is why it is also called a living roof.

They are commonly used in locations with arid climates and on commercial buildings. It is economical because it is easy to install and it is not prone to many damages, hence, costing less on repair. 

11. Dormer


It is also called the dormer window because it provides a space where the skylight is housed. It projects out of the roof surface or beyond the plane of a pitched roof.

Functionally, dormers work to increase usable areas in compact rooms/lofts. For example, if you are thinking of converting your attic to an additional room, a dormer will be good because it will provide natural light and added ventilation, allowing better air flow and fresh air. 

12. Abutment


It is a term used specifically in bridge construction and in roofing. In building roof systems, abutment refers to the spaces in the roof where the roof’s slope intersects to a vertical area such as chimneys or walls.

They can be found on the side, top or around these vertical areas where they connect with. 

13. Low pitch areas

They are also called low slope areas or just low spots. They are common among flat type roofs. Low pitch areas are basically the lower slopes in the whole roofing system. However, it is in low pitch areas that ponding usually occurs.

When left without high quality putty, ponding can damage the roof sheaths and the wood rafters over time. 

14. Downspout


It is the pipe installed vertically from the roof down to the ground. It is the pipe connected to the external gutter and channels the expelled water down to a designated point.

While it is usually made of PVC, downspouts can also be made of galvanized steel and other plastic materials. 

15. Drip Edge

It is a type of metal flashing used to protect underlying roof fixtures. It is installed along the eaves to re-route water flow away from the fascia. In structure, it hangs from the roof’s sides.

It has a small metal flange bent away from the fascia. Some people would say that the drip edge is no longer essential since you have the gutter to work almost the same job. But it is a functional feature, nonetheless, and if you need visuals on how to install one, you can check this tutorial from Your Average Roofer

16. Fascia


It is also called roof lines. The fascia would be the boards running the points where outer walls of the house meet the roofs.

It is also nailed to the rafters to work as support for the gutters or essentially the main board where the gutters are attached. It is also considered to improve the roof’s aesthetic value especially if you used hipped roof and flat roof designs. 

17. Gutters


It is an important external roof fixture. It is a duct functioning as a water discharging system for the house. For the gutter to serve its purpose though, it has to be installed in an angle where the water it pushes off would not fall directly around the house grounds.

Water falling too close in the house’s foundation could weaken it and can also damage the basement entirely if you have one.


18. Rafter


It is essentially the wood/metal frames that work as the frame/skeleton of the roof. Thus, it is one of the most important parts of a roof because without it, there will be no structure to the roof entirely.

It is a diagonal shaped structure that is included in the truss. It meets at the apex and its main function is to support the roof deck from heavy loads. 

Generally, it is where everything is attached, hence, you will need to brace it further to be more stable. For visuals, you can check this video from NSM Construction

19. Underlayment


It is also called as underlayment membranes. It offers a blanket or a protective cushioning to the entire roof decking to protect it from too much moisture.

They are typically made of felt and rubber strips but the trend has shifted to reinforced fiberglass and synthetic materials. 

They are essentially waterproof materials that work as barriers for water and moisture and are installed directly in the roof deck. It comes in different types placed in different key areas in the roof where water ponding could be a problem. 

  • Rafter underlayment: Its function is to provide additional protection for the rafters by adding a water-resistant layer where moisture could not infiltrate. 
  • Valley underlayment: Roof valleys structurally channel a lot of water. It is the reason why they need to be applied with valley underlayment. This one is a waterproofing layer whose function is to add protection to the roof valleys and inhibit it from leaking. 
  • Felt underlayment: It is the traditional underlayment made of felt paper. Its main function is waterproofing the roof. It is stacked above the solid decking board usually covered by shingles. 
  • Synthetic underlayment: As the term suggests, it is a type of underlayment membrane made of synthetic material and not felt. It is considered as a high-tech protective layer installed before the roof shingles. It is applied on the areas in a roof decking that are not covered by water and ice shields. 

Vent Pipe: It is also called as plumbing vents. They usually extend from the building’s waste pipes and are installed through the roof. Through vent pipes, sewer gases are released outside the house/building instead of being trapped inside it. These pipes also allow more oxygen in the waste pipes lessening the bad smell that comes from them. 

20. Collar beam

Collar beam

It is usually used in domestic roof construction. It is horizontal in shape and it connects two rafters intersecting at the ridge to provide more stability to the roof structure. Basically, a collar beam is used to frame the ceiling’s structure. 

21. Chimney


It is a popular structure but a lot of us might not know that it is a part of the roofing system.

It is this vertical structure connected through the roof used as ventilation by exhausting smoke and other combustion gases coming from the stove, boiler or fireplace through the atmosphere.  

22. Ice and water protector

Ice and water protector

They are more commonly called ice and water shields. They may not be necessary but particular states require them in their building codes.

These shields are basically types of underlayment used to prevent ice dams and heavy, wind-driven rains.

They are installed in three specific parts of the roof: in the eaves and rakes to protect roof interior due to frost, roof valleys where water could pond as well as in the flashings and chimneys to allow wind-driven rains to flow back up. 

23. Skylight


If it is part of the original roof construction layout, it is considered as part of the common roof area. This must be clear because it is not often considered as part of the roof. It is both aesthetic and functional.

Aesthetically, provides additional lighting and sky views. Functionally, it offers more ventilation and acts as egress during emergencies. It comes in the form of a window or ceiling installed directly in the roof. It is housed by a dormer. Check out these beautiful skylight designs from Decoist and Home Designing

24. Lookout


It is also called a roof outlooker or a lookout rafter. Structurally, it is a wooden joist from a building’s wall plate extending to the cantilever.

Functionally, it provides a surface where the fascia boards will be nailed and a support structure for the roof sheathing. It is also used as a joist where finished materials of the eaves are fastened. 

25. Solid decking

It is more popularly called roof decking.  It is a composite decking made of solid materials. It is like real wood but it is actually made of sturdier components for the purpose of carrying heavier roof load.

It adds additional protection between the roof and the home and adds an extra surface for underlayment and shingles for further weatherproofing. Structurally, solid decking is composed of flat boards attached firmly in trusses and are stretched on joists across the roof. 


roof parts

The common homeowner would not have the time and fascination to know all of these in ordinary days. But it does pay to know the major parts of the roof if not all because whether you like it or not, annual maintenance is here before you know it.

As the cliché goes, knowing where it hurts will save you from prolonged pain. In the case of roofing, knowing the parts of a roof and their functions will lessen the cost of future repairs because you already know where to look.

As a matter of fact, you can do the maintenance work on your own if you know these things. It does not hurt to know the parts of a roof and their functions. Aside from adding a whole new knowledge set to your credential, it will come as a life-saver in the future.