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Anatomy of a Roof

Last updated 6 years ago

Today we are going back to basics! Today’s post is breaking it down – we are going to talk about the different parts of a roof. There is a lot more to a roof than the shingles or TPO or other covering! In order to ensure that your home or building is protected adequately, there are many structures that must be constructed harmoniously in order to have a complete “roofing system”. We’ve included a couple of pictures, but today we are going to list definitions of each part of the roof structure so that you understand the terminology when you have us come out to take measurements and provide you with your free estimate!


Deck/sheathing: The board – usually plywood or OSB – that serves as the base for the entire roofing system.

Dormer: A dormer is a structure such as a wall that projects from a sloped roof, usually with a window.

Eaves: The is the edge of a roof that hangs over beyond the edge of a house.

Fascia: The board or trim that runs behind the gutter and eaves.

Felt: Paper used by the roofer under the shingles.

Flashing: Material used (usually sheet metal) that prevents leakage at junctions of a roof.

Counterflashing: This is flashing that is overlapped over flashing on a vertical structure, such as a wall. It is usually embedded in the structure.

Gable: The upper part of a wall that closes the end of a ridged roof (the triangular part).

Hip: The angle of a junction of two sides of a roof where the supporting walls join.

Joist: The horizontal structure of a flat roof to which the sheathing is nailed.

OSB (oriented strand board): Panels made of narrow bits of wood (4 X 8 feet) used as a substitute for plywood sheets as the sheathing of a roofing system. The panels are installed in layers, lengthwise and crosswise, and are held together with a resin.

Penetrations: Any area where a cut is made into the deck of a roof (such as a vet, chimney, swamp cooler, etc.).

Rafter: A slanted structure to which sheathing is nailed.

Ridge: The point where two sloping roof planes meet.

Slope: Also known as the pitch. It is the number of inched vertical rise per each foot of horizontal distance.

Soffit: The boards that run along the underside of the portion of the roof that extends beyond the walls of the exterior of the house.

Square: Equal to one hundred square feet of roof.

Underlayment: The material (usually felt) that is laid directly on top of the sheathing, before the shingles are laid.

Valley: The area where two sections of sloping roof come together. This is an area that forms a valley, or is equal to less than 180 degrees.


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