Anatomy of a roof. Have you ever wondered about all the elements of your roof that keep you safe from rain, snow, ice and other forms of moisture?


Broadly speaking, those elements can be considered the anatomy of a roof. While every house is unique in some way, all roofs have certain basic elements in common that help to define their basic anatomy.

A system of layers

Probably the most helpful way of thinking about your roof is that it is a system of layers specifically designed to maximize the protection of your home.

From the outside you might only see the roof shingles, but there is a lot that goes into a roof under this layer.

Moreover, there are many different features found along the edges of the roof, as well as along vulnerable joints, which are also specifically designed to keep your house safe. With that in mind, let’s take a closer look at each of those roof layers.



Every roof needs a base, and in this case, the base is known as the decking. Decking is also known as wood sheathing. It is the basis for everything that goes into the composition of the roof, including the final layer of shingles.

Typically, the decking is made of plywood (or other wood composite, such as OSB). But the decking can also be made of materials like polystyrene, concrete or metal.

The roof decking (when made of plywood) is nailed onto the wooden rafters of your home.


The next layer of your roof system is the underlayment of the roof. This is what goes on top of the roof decking, and it is the layer before you add the asphalt three-tabs. The roof underlayment is usually quite thin, and is made of a felt-like material that includes durable paper and asphalt for bonding onto the top roof layer.

Think of the roof underlayment as an extra barrier of protection against snow, rain and wind.

If any shingles come off the roof, it is the underlayment that provides the next layer of protection.


The shingles are then added on top of the roof underlayment. This is the very top coating of the roof, and what is visible to the human eye when you are looking at a roof from street level.

The most popular (and most affordable) type is asphalt shingles, which is further divided into two other classes: 3-tab and architectural. In addition to asphalt, there are wood, shake, metal, and tile shingles.

Think of this layer as the outer protective shell of your roof. Often, you have tremendous flexibility in how you use shingles on your roof, with some of them being used for aesthetic purposes as much as protective purposes.

Still, always consult your local building code about them, because there might be very specific rules about what types of shingles are allowed in your local area. For example, if you live near the ocean, they might need to be of certain strength or size in case of violent storms.


The flashing is another way to protect your roof from moisture. Flashing is really just a piece of sheet metal (such as a sheet of aluminum or steel) that is then secured in place on your roof wherever there are vulnerable joints, such as along the base of a chimney.


The chimney is usually made of stone or brick, and rises above the top of the roof. If you have a fireplace, then you have a chimney of some sort.

Other key parts of the chimney include the chimney cap, which is a metal or stone top to keep out rain, and the chimney flue, which is a series of fire-resistant clay pipes designed to transfer smoke and fumes away from your fireplace.

Gutters and downspouts

Gutters are typically aluminum structures designed to carry water away from your roof. In order to ensure that this water does not carry into your foundation, the bottom part of a gutter, known as the downspout, is usually angled.

This is just to make sure the water is sent away from the foundation.


This is the lower edge of the roof that extends beyond the exterior walls of your roof. It is the eaves where the gutter pipes are attached.


The soffit is the under part of the eaves that projects over the exterior wall. It is typically fitted with vents, and these vents are then used for ventilating your attic space.


The fascia is attached to the edge of a roof and is designed to hold the gutter.

Drip edge

The drip edge is also known as the eaves flashing, and refers to the metal flashing along the edges of a roof which transfers rain away from the house into the gutter.


The gable helps to form a peaked roof, and can be visualized as an A-framed sidewall that gives a typical residential roof its distinctive shape.

Vent pipe

This is a pipe, typically made of plastic or cast iron, which protrudes from your roof and is connected to your home plumbing system.

It is useful in making sure that all parts of your plumbing system – sinks, tubs, toilets and bath – work properly.


The ridge is the peak at the highest point of a sloped roof. In order to ensure the protective quality of the roof, the ridge will often have a ridge cap added as the last stage of a roofing project.

Sometimes there is a vent running along the entire length of the ridge to help with ventilation.

Final notes

As you can see, there are many elements to a roof. When a roof is constructed properly, every element works together to maximize its weather protection qualities.

As you add each layer to the roof, you need to make sure that they are properly aligned and attached. That way, even if one element of the roofing system is somehow damaged by wind or rain, all of the other elements can work together to keep you safe and dry.



Last update on 2023-07-04 / Affiliate links / Images from Amazon Product Advertising API

Founder & Editor

Hi, I’m Jim. I was a roofing constructor for 20 years, before deciding to start and gather the best content about roofing. I love woodworking and construction and it was only natural for me to start this passion project of mine. Thank you for visitng.