Roofing 101 - Roofing System Components
The following are the basic components of a roofing system:
Eave protection is a layer of felt or plastic placed under the shingles on eaves, in valleys, along ridges, at roof perimeters and at joint flashings. Eave protection is important for the performance of a roof, acting as both a waterproofing membrane and as extra protection against-ice damming. It protects the roof against ice that builds up during winter freeze/thaw cycles.
What are the differences between eave protectors? There are many different types of eave protectors available. The following three meet National Building Code requirements for use on the eaves of roofs with slopes up to 8:12. PROGARD PLUS is a self-adhering waterproofing membrane designed to protect your roof - specifically on ridges, valleys, around chimneys, windows, skylights, and as an eave protector. It is installed directly on approved surfaces, by removing the detachable silicone film. This membrane can be installed under roofing shingles, metal roofs or used as air-barrier/vapour-barrier under a thermal insulation. It is made of SBS modified asphalt carried by a specially treated poly (non-slip) sheet. GRIPGARD, like PROGARD PLUS is a self-adhering waterproofing membrane created to protect your roof. It is installed directly on approved surfaces, by removing the detachable silicone film. Its core is made of fibreglass and SBS modified asphalt and it is surfaced with a fine granule. GLASSGARD is a coated glass mat product, coated with asphalt, and surfaced with sand.
Underlayment is an integral part of a roofing system. It is not required for use under all shingles. However, it is normally used as an element of a premium roofing system, offering backup protection against leaks. Underlayment acts as secondary protection against wind driven rain and as protection from moisture prior to shingle installation. It is also mandatory under all shingles to achieve a fire resistant rating. A minimum of two layers is mandatory on low slope application.
Do I need to install felt under my shingles? Felt underlayment is mandatory under the following conditions of application:
Advantages of using underlayment include:
- All glass-based shingles installed on slopes less than 8/12. It is optional for slopes greater than 8/12.
- Underlayment is required under Building Products of Canada's Eclipse laminated shingles on slopes less than 6/12. It is optional for slopes greater than 6/12.
- In order to achieve fire-resistant ratings (Class A or C), an underlayment must be used regardless of the type of shingle being installed.
- A minimum of 2 layers of felt is required for roofs with slopes less than 4/12. In such cases, the application must meet the requirements for low slope roofs.
- Reducing the risk of water infiltration due to wind driven rain, or if shingles are torn or cracked;
- Act as a buffer area between the shingles and the deck.
The proper selection and installation of roofing materials form the basis of a well-constructed roof that ensure the shingles selected perform to their maximum capabilities. But the shingles themselves determine the ultimate longevity of the roof. Premium shingles, with heavy-duty felt or fiberglass mats and thicker asphalt and granule coatings, provide longer life and, as a result, come with higher warranties. Learn more about Shingles here.
For efficient water shedding at the roof's edge, a drip edge of vinyl or metal should be installed on the eave and rake edges. The drip edge is installed under the eave protection membrane at the eaves. Along the rake, the metal drip edge should be installed over the underlayment or eave protection.
This is a common spot for snow and ice buildup, especially on roofs with lower pitches. In a premium roofing system, use of roll roofing material is required over the length of the valley.
Ice and water-proofing membrane rolls such as Progard Plus or Gripgard provide the optimum protection as the base for any valley construction and are critical in preventing problems with ice dams.
Ice damming develops as snow on the surface of the roof melts. Water runs under the edge of the roof creating a dam. Additional snow melts forming a pool against the dam causing water to back up, often getting under the shingles. Learn more about ice damming here.
Some of the roof's most vulnerable areas, with the highest potential for leaks include skylights, vents, chimneys, windows, and soil stacks, making waterproofing indispensable. Once again, ice and water membrane is a superb base underlayment for the flashing material. And don't forget to use roofing cements that meet or surpass CAN, CGSB or ASTM standards that are fully compatible with the shingle.
Proper air circulation will greatly reduce the chance of leaking, blistering, curling and many other potential problems. To tell if a home's ventilation is inadequate, several signs appear in the home's attic. Those signs include an attic that is hot and stuffy compared to the rest of the house, stagnant air, unbroken darkness indicating blocked or non-existent openings, and water stains/mold on the underside of the decking.
Why is ventilation so important? Ventilation is a crucial factor in the life of a roofing shingle. Heat build-up in the hot summer months, as well as the cold weather of winter will accelerate the aging process of your asphalt roofing shingles. Proper air circulation, regardless of the weather outside, will greatly reduce the chances of leaking, blistering, distortion, curling, rotting of wood structure, wet insulation and many other potential problems.
It is also important to note that adequate ventilation is required to validate the shingles manufacturer warranty. In Canada for example, minimum requirements prescribed in the National Building Code must be respected. In all cases, the most stringent applicable building codes must be followed.
Making sure the appropriate roof deck is under the shingles you have to install is critical to ensure optimal shingle performance. The roof deck should be in good condition: dry, clean, flat, smooth and securely nailed. Plywood decks at least 1/2" thick are best. If shingles are installed over an unacceptable roof deck, it may void the manufacturer's warranty. Any part of the deck that is rotted or warped must be replaced.
To view an interactive tour of a Premium Roofing System, click here.
Roofing 101 Article Source: