What are the main components of a roofing system?

Roof decking (also known as sheathing), underlayment, roof flashings, ventilation products and shingles are the five main components of a residential roofing system. Below you will find a brief description of these five components.

  • Decking: Usually made from ½-inch plywood. The decking is fastened to the roof rafters, it reinforces the roof structure and provides a nailbed for the shingles. Some roofing materials, like wood shakes, are installed over skip sheathing; when replacing this type of roof plywood needs to be installed over the skip sheathing.
  • Underlayment: Roof underlayment is a sheet of felt or synthetic material installed over the roof’s plywood deck before the shingles are fastened. The underlayment is an added layer of protection and is designed to prevent rain and moisture from penetrating the deck, which could result in attic leaks and wood rot.
  • Flashings: Roof flashing is one of the most critical parts of a roof. Flashing secures joints in the roof and places that tend to receive a lot of water, like valleys between slopes. Flashings are secured to direct water away from vulnerable areas of the roof and into the gutters. The main roof flashings are drip metal, rake metal, valleys, step flashing, roof to wall flashing, chimneys / skylights and roof pipes.
  • Ventilation products: Attic ventilation is essential for the performance and lifespan of a roofing system. Proper ventilation consists of two parts: intake and exhaust. There are different products available for both. The main products used in the industry for intake are undereave vents (also known as soffit vents and bird blocks) and edge vents. The most common products used for exhaust are ridge vents and roof louvers.
  • Roofing material: The most common residential roofing material used in the United States is asphalt shingles (also knows as composition shingles). There are many other options available; for example, metal roofing, wood shake, and slate roofing. The shingles (or any other material) is what protects the rooftop from the sun, rain, hail and snow as well as improve the physical appearance of your home.