Roofing terminology Explained

Common Roofing Terminology

How well do you know your roof? If you had to call someone to repair a part of your roof or look at a specific part, how would you describe it? Here are some of the more common terms that are used most often along with a description of them.


The most used material is half inch plywood which is nailed to the roof trusses. This offers a surface for the roofing material to be attached to such as shingles being nailed down.

Roof Edge/Eave Edge

These boards run along the edge of the roof and seal off the air space between the roof and the eaves. These boards are also referred to as fascia boards.


This is the line that runs horizontally along the top of the roof.


This is the empty space that is located below the roof. This area must have adequate air flow (ventilation) so that it protects your home from excessive heat in summer and cold air in the winter.


This is a structure which sits on the upper side of a chimney or vent and diverts water around the projection so that it will not ingress under the roof.


This is the angle cut in a “V” which is located where the two slopes of the roof meet.

Roof Vents

Enclosed structures which are constructed of plastic or metal and have fins and openings which allow for the space in the attic to receive proper ventilation. The best vents are open on all four sides and sit above the roofline to take advantage of wind from every direction.

Plumbing Vent

These are small pipes that can be seen poking out of a roof.  Air moves through these pipes to move wastewater to the septic tank or the sewer.

Drip Edge

This moulding covers the roof’s edge to lower the risk of water ingressing under the surface of the roof.


A small piece of cardboard or polystyrene which sits between the rafters to ensure that air can flow freely over the insulation around the soffits.


Shingles can be wood, fiberglass or asphalt and are used to form a roof, protecting your home from weather. These are usually available in a wide range of colors and styles.

Eave membrane

A protective membrane that sits under the shingles to prevent water from getting through the roof when ice dams form.

Underlay membrane

A coating created from felt usually saturated with asphalt or some type of synthetic fabric which protects the shingles on your roof from any resin which can be released by wood decking.


Flashing is sometimes flexible, but it can also be very rigid. It can be made from plastic, aluminum or galvanized steel and covers the joints of the roof. It prevents water from getting into openings on the roof or from seeping under any other parts of the roof. It is generally used in any valleys of the roof or around bases or chimneys, vents and plumbing stacks.

Shingle Choice

Asphalt shingles are a popular choice in North America because they are easy to install and are very affordable. They provide a solid waterproof surface by allowing water to flow over them, with a generally lifespan of between 20 and 40 years.

New shingle roofs are often installed right over top of old shingles to save time and money, but it is not a recommended practice because this can lead to distortion and defects that can compromise the performance of the new roof.

Thicker and heavier shingles provide better resistance to bad weather. There are two main types of fiberglass-based shingles:

  • Shingles that have two to three layers, reinforced or laminated (architectural) shingles
  • Shingles that have one layer and three tabs.

Laminated shingles cost more money but last for much longer. If you plan to replace your roof, it is important to keep some extra shingles handy if small repairs are needed.  Make sure that you know the brand, model number and color of your shingles should the need arise. Your old roof shingles can be recycled. There are many places to purchase shingles, including online, but remember to check that the materials used meet the local building codes in your area.


Most asphalt shingle companies will offer a warranty of 100% for the first five years on single layer shingles and 15 years for laminate shingles. As the singles age, the portion that you will recoup lowers and eventually the warranty will come to an end. Some manufacturers will also offer protection against the development of blue-green algae or damage that can be caused by storms.

If you want to have an extended warranty, many roofing systems offer these, but they will cost more money than a standard warranty. These more expensive, more lengthy warranties also are only in place if the roofer carrying out the work is certified by the manufacturer to perform that work. If the decking of the roof is not in good condition or there is not sufficient ventilation in the attic, it can void the warranty.

How do Roof Types Affect Ventilation?

The type of roof you choose will have certain standards to comply with ventilation. For example, the design and shape of a roof can cause ventilation issues in your attic. The slope of your roof can also affect they type of materials that are used on it. Asphalt shingles, for example, must be installed on a 4/12 pitch. The materials used must always be compatible with the roof grade to remain waterproof.

To ensure adequate airflow, the ventilation openings that are required will be completely dependent upon the type of roof that is installed. The ventilation openings have a direct ration to the surface of the insulated ceiling of about 1 to 300 or one square foot of ventilation openings for every 300 square feet of insulated ceiling.

Types of Roofs

Roof with Dormers or Gables

If an attic space has dormers added in this means, there is less room for soffits. This means that the soffits that are installed must allow for more air intake (or have higher perforations).

Asymmetrical Roof

The air intake near the top of the roof must be balanced when it contains asymmetrical slopes. This means that the percentage of ventilation openings located along the base of the long side of the roof need to be increased while the ventilation openings located along the shorter side of the roof should be decreased.

If a roof has an accessible attic together with a cathedral ceiling, then the accessible side needs ventilation openings to the insulated ceiling at the rate of 1:300 and on the cathedral side ventilation openings need to be 1:150 at a minimum.

Flat Roof

If the roof slope is less than 2/12 it is referred to as flat. Ventilation openings in this situation should be a minimum of 1:150.

Roof with no Attic (“Cathedral Ceiling”)

If a roof has no attic it should have a ventilation ratio of 1:150. There should be openings along both the base and the peak of the roof.

Mansard Roof

The lower part of this type of roof needs no ventilation but the attic section should have ventilation like regular standards of normal attic roofs.