What Goes Under the Shingles on Your Roof

May 25, 2022

There’s more to your roof than just shingles. In fact, there are several layers underneath those shingles. The roof system is made up of these important layers:

  • Insulation
  • The Roof Deck
  • Ventilation
  • Underlayment
  • Ice and Water Shield
  • Flashing
  • Shingles





1. Insulation

Roof insulation is placed between the rafters of your attic walls and the beams of the roof. This insulation regulates the temperature of your attic by trapping warm air in the winter and cool air in the summer. Insulation helps improve your home’s energy efficiency rating as well as lower your electric bill. This insulation is vital in maintaining a consistent temperature.

2. The Roof Deck

The first layer is the roof deck, sometimes called sheathing, visible from the attic. This foundation is what the rest of the roofing materials are nailed down to. This deck is usually made of a thick plywood that can withstand the weight of the roofers as they install and repair roofs and heavy layers of snow or ice. These come in two thickness options, with the thicker usually being reserved for locations with heavy snow and icefall.

3. Ventilation

Roof ventilation allows for the flow of air underneath the roof deck. Proper ventilation allows for the warm, moist air that could damage wood and insulation to escape while dry, cool air remains in the attic. The moist, warm air escapes through the vents placed throughout your roof/attic. Not only does a vented roof remove this air, it prevents dramatic fluctuation in your home’s temperature, and your electric bills are lower. Finally, the ventilated roof prevents ice damming. With an attic full of warm air, the snow melts, collects in the gutters where the snow refreezes from being exposed to the elements. This ice causes a dam in the gutters, creates large icicles hanging from the gutters, and can tear gutters and roofing materials apart.

4. Ice and Water Shield

As the roof deck is made of plywood, this porous, wooden material requires protection from water. This shield is an entirely waterproof membrane that has an adhesive to seal against the roof deck.

5. Underlayment

The second line of defense to water is the felt layer of underlayment. It provides a breathable barrier and protective layer between the shingles and the roof deck. Too, it helps to prevent water from reaching the wood of the roof deck.

6. Flashing

Flashing is applied to the edges of the walls and chimneys of the roof. This includes the edge of the roof itself and the valleys where the seam of two angles of the roof meet. Flashing is usually made from steel, aluminum, copper, or stainless steel. Flashing bypasses water from the valleys of your roof so that it does not seep in past these edges.

7. Shingles

The final layer of your roof is the shingles. Asphalt shingles are the most common shingle used on homes. These shingles last approximately 20 to 30 years. They come in the largest range of colors, textures, and styles. Too, Asphalt is significantly more inexpensive than ceramic or slate roofing and is the main roofing style.