How to Install a New Roof: Start by Choosing a Roof System

Choosing a new roof system is simplified as you understand the basic mechanisms that make up a roof. According to the National Roofing Contractors Association, a steep slope roof system of 25% or more is made up of the following components:10


  • Covering: This includes materials like slate, tile, shingles, or metal that will protect sheathing from the outer elements.
  • Sheathing: Sheet material or boards fastened directly to roof rafters to cover a building.
  • Structure: Trusses and rafters manufactured to support sheathing components.
  • Flashing: Sheet metal or other materials installed directly into the joints and valleys of a roof system to prevent water leakage.
  • Drainage: Design features that include flow, shape, and layout to allow a roof to effectively shed water.

As you select a new roof system for your home or business, you can review the materials listed in detail in the previous chapters. For steep slope roofs in the US, asphalt shingles are most commonly used since they can be effectively reinforced with fiberglass or organic materials.

Asphalt shingles are classified by their fire resistance as Class A, B, or C, with Class A offering the most fire protection.

In comparison, wood shingles are popular in certain areas of the country, like California, although some local building codes may prohibit the use of wood shingles and shakes if fire resistance is a concern.

Wood shingles and shakes are often rated at Class C for fire protection or may have no rating at all; some wood shingles are reinforced with a factory treatment for fire resistance, offering a Class A rating.

Other durable roofing materials for steep slope roofs include tile, slate, and metal. Clay or concrete tile is heavy and may require additional structural supports to reinforce materials; slate is an expensive roofing material that is virtually indestructible; metal shingles are lightweight, weather resistant, and may have a Class A fire rating.

When taking the five components listed above into account to choose a new roof system, insulation and ventilation remain a top priority. Without adequate ventilation in a roof, heat and moisture will build up over time in the attic of a structure to cause buckling shingles, rotting rafters, and corrupted insulation.

The proper ventilation in an attic can prevent moisture accumulation to reduce the risk of structural damage. This will greatly increase the life of roofing materials.

Well-installed ventilation in a roof structure will meet the following criteria:

  • Vapor retarder installed under insulation and next to the ceiling to prevent moisture from accumulating in the attic.
  • Gap-free insulation layer on attic flooring to protect a structure from heat loss or gain.
  • Ample vented spaces to permit air to move in and out freely.
  • At least 1 inch between roof sheathing and insulation.

While exact ventilation requirements can vary, the NRCA recommends at least 1 ft.2 of free venting per 150 ft.² of attic flooring. Roof vents should be installed proportionally at roof eaves or near roof ridges.

Insulation can be installed as part of your DIY project; for any questions or concerns, make sure to contact a professional contractor for help.