Flashcards in Roof Coverings Deck (68):
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
What is the most common type of shingle?
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
Roll roofing can provide good water protection but has a rather short service life. T or F
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
Fire retardants can be pressure-impregnated into shakes and shingles. T or F
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?
Is corrugated galvanized roofing lapped and does it use washer screws. T or F
What is a visual characteristic of copper?
The copper oxidized and turns a characteristic blue/green colour.
Do copper roofs have a greater life expectancy than asphalt?
Why would additives be mixed with PVC roofing material?
To provide the panels with fire, microbial, and UV light resistance.
A cricket or a saddle should be provided at the top side (back) of the chimney, when it is ___ wide or greater.
750 mm (30")
When a cricket or saddle is not desired, a sheet of metal flashing must extend up the chimney a distance equal to ___ the width of the chimney or ____ " minimum
150 mm (6")
When a cricket or saddle is not desired, a sheet of metal flashing must travel up the ROOF a minimum of 1.5 times the shingle exposure. T or F
Open valleys must be flashed with a minimum of _____ wide sheet of metal or 2 layers of tool roofing.
The open valley is often cut slightly tapered as it approaches the bottom to handle the increasing water volume. T or F
If a rough fascia is not used, how could the lower edge of plywood roof sheathing be supported?
By the finish fascia
Which drawing in a set of house plans will provide the most information of the roof construction?
What are "H"-clips?
a bracket used to join edges of plywood roof sheathing
For what do "H"-clips act as a substitute?
Blocking between the rafters
Which drawing in a set of house plans will typically give information on the roof slope?
When re-shingling a roof what does "prepping the roof" mean?
Inspection of sheathing for damage and the resetting or replacement of loose nails after old shingles are removed
What is required for all items which penetrate through a roof surface, such as a chimney, fireplace, plumbing stack, etc.?
In standing seam roofing: Hidden clips are used to fix the leading edge of each sheet, no fasteners are exposed.
T or F
Wood shingles have two smooth sawn sides. T or F
Describe a built-up roof.
layer of asphalt felt paper hot-bonded and applied over rigid insulation board
When installing the starter course for wood shakes the butt ends should extend 1" to 1 1/2" past the roof edge. T or F
Vertical side joints in wood shingles should be offset from the joints in the previously laid course by a:
Minimum of 40 mm
What is the purpose of roof flashing?
prevent water seepage
Roll roofing joints must be lapped and cemented. T or F
Which type of flashing would you order to ensure a proper junction between a vertical wall and sloping roof, if asphalt shingles are to be used?
When a saddle is not used at the back of the chimney, the flashing must extend up the roof how much?
A minimum of 1.5 times the shingle exposure
Open valley flashing is exposed after the roofing is completed. T or F
An open valley shall be finished with not less than one layer of sheet metal at least 600 mm wide or two layers of roll roofing. T or F
The nails used to fasten asphalt shingles shall be located above the cut-outs a minimum of ___ mm.
What is the minimum width of flashing required for valleys?
600 mm (24")
Roll paper must overlap valley flashing __ mm.
150 mm (6")
Rolling paper must have atleast ___ top lap.
50 mm (2")
An open valley is tapered 1/8 of an inch every 12 inches. T or F
A closed valley requires that the top later of shingles are cut at the valley only on one side while the shingles from the other side run underneath at least ___ mm.
300 mm (1')
A woven valleys shingles are not cut at the valley but are woven or alternately lapped underneath each other at least 300 mm (12"). T or F
No fastener within 150 mm of centreline in a valley. T or F
Base Flashing is installed to shed water away from the wall and onto the roof covering. Sheathing membrane and wall finish must overlap the flashing by ___ mm.
75 mm (3")
When a roof meets a wall along its slope, the base flashing may take the form of a step flashing. This type of flashing is a pre-bent square of metal that is installed so that it extends up behind the sheathing membrane a minimum of ___ mm and extends away from the wall a minimum of ___ mm.
75 mm (3")
75 mm (3")
Counter flashing is required to cover the top edge of the base or step flashing where a masonry wall or chimney meets a roof surface and must be provided to all sides. T or F
Counter flashing must be embedded into the mortar joint of the block or brick veneer a minimum of ___. It must extend down the wall a minimum of ___ and lap the base flashing a minimum of ___.
150 mm (6")
A cricket or saddle should be provided at the top side of chimney, when it is ___ mm wide or greater.
750 mm (30")
Eave protection should extend from the edge of the roof a minimum of ___ up the roof slope to a line not less than ___ inside the inner face of the exterior wall.
900 mm (36")