BCGBC4010A Apply structural principles to residential low-rise constructions

Roof systems

Topic activity
Question 1 of 23
Ceiling joists are spaced according to the material they support. True or false?
A.	True
B.	False 
The correct answer is A - True. Typically joists support plasterboard which can span 450 mm.

Question 2 of 23
Which of the following is correct?
A.	Strutting beams do not transfer the roof load to load bearing walls.
B.	Strutting beams do not support roof members.
C.	Strutting beams do not transfer the roof load to a ceiling joist.
D.	Strutting beams are not often subject to wind pressure acting on the roof.
The correct answer is C - Strutting beams do not transfer the roof load to a ceiling joist. Strutting beams must not rest on the ceiling joist or transfer loads to them.

Question 3 of 23
Why are strutting beams chamfered?
A.	To avoid interference with the ceiling joists
B.	To avoid interference with the roof cladding
C.	To avoid interference with the underpurlins
D.	To avoid interference with ceiling battens
The correct answer is B - To avoid interference with the roof cladding. This is at the point where they meet the rafters.

Question 4 of 23
What can be used to fix ceiling joists to hanging beams?
A.	Timber battens only
B.	Metal joist hanger brackets only
C.	Hoop iron straps only
D.	All of the above
The correct answer is D - All of the above. All of these can be used. The metal ones are purpose made.

Question 5 of 23
A hanging beam increases the span of the ceiling joist. True or false?
A.	True
B.	False
The correct answer is B - False. The span of the ceiling joist is reduced by a hanging beam.

Question 6 of 23
What is a birdsmouth?
A.	A type of cut
B.	A type of timber batten
C.	A type of wall plate
D.	A type of chamfering
The correct answer is A - A type of cut. It is a type of cut that looks like a bird’s open beak.

Question 7 of 23
The closer that struts are to vertical, the more efficient they are. True or false?
A.	True
B.	False
The correct answer is A - True. Struts are more efficient the closer they are to vertical.

Question 8 of 23
Why are underpurlins so named?
A.	They are fixed under the struts
B.	They are fixed under the ceiling joists
C.	They are fixed under the rafters
D.	They are fixed under the overpurlins
The correct answer is C - They are fixed under the rafters. 

Question 9 of 23
What do collar ties have to be fitted with?
A.	Every second pair of rafters
B.	Every pair of rafters
C.	Every third pair of rafters
D.	Every pair of ceiling joists
The correct answer is A - Every second pair of rafters. They help the rafter pairs to resist spreading.

Question 10 of 23
What fraction of a rafter’s depth might a rafter be birdsmouthed?
A.	Half of the rafter’s depth
B.	A third of the rafter’s depth
C.	A quarter of the rafter’s depth
D.	None of the above. A rafter is not birdsmouthed.
The correct answer is B - A third of the rafter’s depth. A rafter may be cut in this way so that it rests directly on top of the plate.

Question 11 of 23
Ridgeboards make sure that rafter pairs meet at a consistent height. True or false?
A.	True
B.	False
The correct answer is A - True. This results in a horizontal ridge line.

Question 12 of 23
Roof trusses are more affected by weather than timber beams. True or false?
A.	True
B.	False
The correct answer is B - False. Roof trusses are less affected by the weather than timber beams. This is one of the advantages of roof trusses.

Question 13 of 23
What is a 'web tie' in a roof truss? 
A.	A perpendicular bracing for the webs
B.	A corner occupied by spiders
C.	A lateral bracing for the webs
D.	A tie for the top chords
The correct answer is C - A lateral bracing for the webs. If the truss is heavily loaded the webs may need to be laterally braced using web ties

Question 14 of 23
Which of the following truss types is most suitable for a sloping ceiling?
A.	Creeper truss
B.	Scissor truss
C.	Hip truss
D.	Bowstring truss
The correct answer is B - Scissor truss. It is a modified standard truss. Most scissor trusses have equal pitch each side of the apex.

Question 15 of 23
The house style known as ‘homestead’ has a bell truss. True or false?
A.	True
B.	False
The correct answer is A - True. The ‘homestead’ house style has a bell truss. The top chord has two pitches where the lower pitch is usually the verandah.

Question 16 of 23
Downward loads on a roof cause compression in the top chords. True or false?
A.	True
B.	False
The correct answer is A - True. Because top chords are long and slender, they tend to buckle sideways when in compression.

Question 17 of 23
Bracing is required for which of the following?
A.	Top chords only
B.	Bottom chords only
C.	Web elements and top chords only
D.	All of the above
The correct answer is D - All of the above. Roof battens, steel braces and web ties are all methods used for this bracing.

Question 18 of 23
In areas subject to high winds which of the following answers gives the correct upgrading for truss connections?
A.	Strapsnailsnail plates
B.	Nail platesstrapsnails
C.	Nailsnail platesstraps
D.	Nail platesnailsstraps
The correct answer is C - Nailsnail platesstraps. Straps are the strongest connection.

Question 19 of 23
Roof trusses can be modified on-site to suit different needs. True or false?
A.	True
B.	False
The correct answer is B - False. It is important that roof trusses are not modified in any way.

Question 20 of 23
Which of the following tiling material is a naturally occurring rock?
A.	Fibre cement shingle
B.	Shakes
C.	Slate
D.	Steel-pressed
The correct answer is C - Slate. Slate is rock. 

Question 21 of 23
At what pitch is most metal sheet roofing watertight down to?
A.	5 degrees
B.	10 degrees
C.	1 degree
D.	None of the above
The correct answer is A - 5 degrees. However, some decking profiles are watertight at 1 degree.

Question 22 of 23
Rainwater falling from copper pipes onto galvanised sheeting is likely to cause corrosion. True or false?
A.	True
B.	False
The correct answer is A - True. Using different metals together will cause corrosion.

Question 23 of 23
What is the usual side lap for corrugated roofing? 
A.	Two laps
B.	One lap
C.	One and a half laps
D.	Two and a half laps
The correct answer is C - One and a half laps. One and a half laps is the generally accepted practice.

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