Every part of a roof has a specific purpose to ensure protection of a house from the elements. Like a puzzle, each part works with the others to enhance the strength and security of the roof while providing flexibility for design options. Depending on the style, components of a house roof may vary beyond the basic parts. Once the foundation of the roof exists, then shingles, tiles or other types of materials complete the house roof.

Roof Truss

House roof

Common in the 21st century, the roof truss frames the rafters. Offering more strength than the traditional piecework framing method, the roof truss allows a greater variety of shapes in designing roofs because of the flexibility of the method. Built from wood, roof trusses provide renewable resources in environmentally friendly construction.

Rafters

Wooden rooftop

Making up the main skeleton of a roof, sloping rafters support the other layers of the roofing process. Spaced 16 to 48 inches (depending on roof design) rafters lay atop building walls. Typically, rafters extend beyond the outside wall, creating eaves, which help protect the building sides and windows from rain and snow runoff from the completed roof.

Ridge Board

Exterior of house with dormer

The ridge board runs horizontally across the top of the roof formation where the tops of the rafters securely fasten, forming an angle. To prevent moisture from entering the attic or crawl space between the main building and the roof, the ridge board must have ridge caps or ridge cap shingles.

Sheathing or Decking

USA, House under construction

Secured to the rafters and used as the base for nailing the other roof coverings, sheets of sheathing or decking normally consist of wood materials such as oriented strand board or plywood. Sheathing acts as another roofing barrier to protect against the elements.

Underlay

Roof of house under construction

Placed on top of the decking, the heavy felt paper underlay (sometimes called tar paper) attaches to the surface of the decking, adding another protective layer against moisture.

Flashing

Construction worker on roof

Galvanized metal flashing protects the roof against leaks by molding around chimneys, roof vents, skylights and where heavy moisture runoff gathers. Flashing secures atop the underlay before attaching the shingles or other final roofing materials