The Basic Components of a Roof

What's Under My Roof?

It’s possible that one of the first things that distinguished early humans from other great apes was that when it rained they ran for cover while the chimps and gorillas sat out in the open and got rained on. Then, humans started to live in caves and eventually learned to use natural materials such as thatch to cover man-made structures. Now, the modern roof is a sophisticated part of every building. Here are the basic components of a modern roof:


Rafters are beams that extend from the soffit up to the ridge board. How they are angled determines the slope of the roof.

Ceiling Joists

These are horizontal pieces of lumber that are installed on edge to hold up the ceiling if the roof has an attic.


This is the horizontal board found at the highest point of the roof.

Plywood Sheathing

This is plywood that is installed over the ridgeboard, joists and roof rafters. The shingles are installed on top of it.

Roofing Felt

Roofing felt is a material that’s placed between the sheathing and the shingles. It protects against moisture and is also called roofing tar paper or underlayment.


These are sheets of lightweight metal such as aluminum or copper that are placed around a dormer window, a chimney or in the roof valley. Flashing is installed to keep out moisture. Some types of flashing are made of rubber asphalt.

Dormer Window

This is an upright window that projects from the roof and interrupts its surface. It adds space to an attic room.

Ridge Shingles

These are shingles that fit over the ridgeline. They are often cut from whole shingles, wrapped across the ridge and nailed down.


These are pieces of overlapping materials that are laid over the roof roofing felt. They can be made of many materials, including asphalt, wood, stone, concrete and tile.

Vent Pipes

Vent pipes allow fresh air to enter the attic and other spaces and allow stale air to escape. Some vents are actually part of the house’s plumbing. They allow water to drain easily, and allow sewer gases to leave the house.

Turbine Vent

Turbine vents have fan blades that pull air from the attic.


This is the board that runs along a wall on the underside of the rafter. It bridges the space between the wall and the fascia.


The fascia is a piece that’s nailed to the end of a rafter to form part of the soffit.