Roofing Systems Flashcards

What is the minimum roof slope generally recommended for asphalt shingle installation in Canada?

Answer: 4:12

Most asphalt shingle manufacturers recommend a minimum slope of 4:12 for standard installation. Slopes between 2:12 and 4:12 require special low-slope application techniques including full ice and water shield underlayment.

What is ice and water shield membrane and where is it required in Canadian roofing?

Answer: A self-adhering waterproof membrane applied at vulnerable areas like eaves and valleys

Ice and water shield is a self-adhering rubberized asphalt membrane applied to the roof deck at areas vulnerable to ice damming and water infiltration. The NBC requires it at eaves (extending at least 900 mm past the interior wall line), valleys, and around penetrations.

What is the standard exposure (amount of shingle visible) for a typical three-tab asphalt shingle?

Answer: 127 mm (5 in.)

Standard three-tab asphalt shingles have a typical exposure of 127 mm (5 inches), meaning each course overlaps the one below by approximately two-thirds of the shingle height, providing triple coverage.

What is the purpose of a ridge vent on a sloped roof?

Answer: To allow warm, moist air to exhaust from the attic at the highest point

A ridge vent runs along the peak of the roof and allows warm, moist air to naturally exhaust from the attic. Combined with soffit vents providing intake air, it creates continuous ventilation that prevents moisture buildup and ice damming.

What is a roof truss and how does it differ from conventional rafter framing?

Answer: A truss is a prefabricated triangulated framework that spans the full building width without interior bearing walls

A roof truss is a pre-engineered, prefabricated triangulated framework typically made from 2×4 or 2×6 lumber connected with metal connector plates. Unlike conventional rafters that may require interior bearing walls, trusses span the full width of the building.

According to the NBC, what is the minimum attic ventilation ratio for a residential roof in Canada?

Answer: 1:300 of the insulated ceiling area

The NBC requires a minimum ventilation ratio of 1:300 of the insulated ceiling area when ventilation is provided at both the soffit and ridge/upper area. If ventilation is only at one level, the ratio increases to 1:150.