Roof Coverings Flashcards
What is the most commonly used sheathing material?
OSB is the most commonly used sheathing material. Exterior grade plywood is also still used extensively, but it is higher in coat and has no major advantages over OSB. At one time, dimensional lumber was used extensively in residential construction, but increased costs in labour and material has made its use rare.
In Canada, is it permissible to use roof sheathing that is identified by United States markings only?
US marks are not applicable and should be ignored; only Canadian markings apply. Canadian building codes require sheathing meet Canadian standards and have a mark identifying one of those standards.
What grade and minimum thickness of plywood and OSB could be applied to trusses 600 mm on centre?
The truss spacing in residential construction is normally 600 mm and, for this spacing, 3/8” (9.5 mm) plywood or OSB 0-2 graded can be used if H clips or horizontal blocking is installed. If neither measure is employed, the minimum sheathing thickness is 1/2”.
Describe what each number and letter in the following grade marking means: 2R24
2: indicates the horizontal edges must be supported.
R: suitable for ROOF application
24: maximum rafter or truss spacing allowed
Do all of the edges of 18 mm fibreboard roof sheathing require support?
Asphalt-coated or impregnantes fibreboard may be used as roof sheathing provided the roofing consists of a continuous sheet or galvanized steel or aluminum. Framing or blocking must support all edges of fibreboard sheathing.
Describe a vented roof panel.
A composite panel of rigid insulation and oriented strand board that has a 1/2” to 3/4” ventilation space between them and that can be applied as a base for shingles or metal roof systems.
What are the primary functions of roof sheathing?
It is a structural element and is part of the framing. It has two primary functions: to strengthen the roof system by providing rigidity and preventing racking of the rafters or trusses and to provide a nailing base to which the roof finish can be attached.
Describe what conditions must exist in order for ice damming to occur.
Roof surfaces adjacent to heated interior spaces may experience surface temperatures higher than those of surfaces not adjacent to heated spaces (such as eaves). If conditions are right, snow melts on the warmer surfaces, but cools and freezes when reaching the eaves. An ice dam is created, which can cause water to back up under the roof covering and infiltrate the building.
What materials are used for asphalt shingles?
Asphalt shingles are constructed of heavy felt or fibreglass (which has a higher fire rating) that is impregnated with hot asphalt. The upper surface is covered with a finely crushed slate.
What materials are used for roll roofing?
Similar to asphalt shingles, roll roofing is an asphalt-impregnable do felt or glass may reinforced. The roofing comes in rolls rather than as individual shingles.
Describe the appearance of a wood hand-split shake.
A rough split face and sawn back. This produces an uneven surface appearance, with the butts of the shakes varying in thickness.
Describe the appearance of a wood shingle?
Smooth dawn on both surfaces and are uniform in size. These shingles can be applied to roofs and walls.
Does a standing seam metal roof have exposed fasteners?
No fasteners are exposed, resulting in a weather tight roof.
What are the two primary functions of roof sheathing?
Strengthen the roof system by providing rigidity and prevents racking of the rafters
And to provide a nailing base to which the roof can be finished.
How can you use 3/8 plywood or OSB 0-2 graded on the roof with 24” truss spacing?
H-clips or horizontal blocking. Otherwise 1/2” must be used
Asphalt shingles have a lifespan of 20 to 40 years. T or F
T
What is the most common type of shingle?
Three tab
Describe self-tabbing shingles?
It has a strip of bituminous material on the underside of the shingle. When heated by the sun, the strip softens and the tabs adhere to the shingles beneath.
When roll roofing is used, nails on the lower edge of the course can be concealed or exposed. What must be done to these nail heads?
Must be coated with an asphalt gun to prevent the penetration of moisture.
Double coverage selvage roofing is used for roofs that are almost flat. T or F
T
Roll roofing can provide good water protection but has a rather short service life. T or F
T
The top lap for roll roofing should be not less than ___.
75 mm (3”)
Roll roofing should overhang eaves and takes 10 - 12 mm (3/8 to 1/2). T or F
T
Fire retardants can be pressure-impregnated into shakes and shingles. T or F
T
What are three types of metal roofing products?
Standing Seam (used in commercial applications)
Corrugated galvanized steel roofing (common on agricultural buildings)
Pre-finished metal panel (resemble the appearance of a shingled roof)
Are the fasteners exposed in corrugated galvanized roofing?
Yes
Is corrugated galvanized roofing lapped and does it use washer screws. T or F
T