Roofs

Question 1

What are some common roof styles and features used in New Zealand?

Answer 1

Gable, Hip, Valley, Apron, Parapet, Skillion, Monopitch, Flat, Dormer.

Question 2

What is the basic difference between a rafter and a truss?

Answer 2

Rafters are individual beams that run from the ridge to the eaves, while trusses are pre-engineered frameworks with chords, webs, and nail plates.

Question 3

How is roof framing constructed to support roofing materials?

Answer 3

Roof framing is assembled with components like rafters or trusses that support the roof covering and transfer loads to walls or supporting structures.

Question 4

How is roof framing tied together and braced?

Answer 4

Roof framing is tied and braced with components like collar ties, strutting beams, and tension straps to ensure stability and prevent the roof from shifting.

Question 5

What precautions should be taken when making a penetration through an existing roof structure?

Answer 5

Ensure the penetration doesn’t affect structural components, is correctly reinforced, and doesn’t interfere with drainage. Larger penetrations may require consent.

Question 6

What is the purpose of fascia boards in roofing?

Answer 6

Fascia boards support gutters and seal the edge of the roof, preventing water from entering the rafters.

Question 7

What is a truncated truss?

Answer 7

A truncated truss is a modified truss used on roofs with hips, where the top portion is cut off to accommodate the hip.

Question 8

How are roof planes, ridges, and hips checked for straightness?

Answer 8

String lines, laser levels, and measuring tools are used to ensure the roof components are free of dips, humps, and “wobbles.”

Question 9

What are the typical spacing requirements for purlins according to NZS 3604:2011?

Answer 9

Purlins must be spaced between 900mm and 1200mm apart, depending on the wind zone and cladding type. However engineer design supersedes this.

Question 10

What are tension straps used for in roof framing?

Answer 10

Tension straps are steel straps used diagonally across the roof to brace trusses or rafters and prevent roof movement.

Question 11

What is the maximum size for a skylight penetration in long-run roofing?

Answer 11

The skylight area must not exceed 1.5m² or 1.5% of the roof area, whichever is greater.

Question 12

How should valley boards be set out for proper alignment with the roof?

Answer 12

Valley boards should align with the roof pitch, and their installation should ensure water runs off efficiently.

Question 13

What is the difference between a fascia and a barge board?

Answer 13

A fascia is installed along the eaves to support gutters, while a barge board is installed at the gable end to protect the roof’s edge and provide a decorative finish.

Question 14

How should fascias be cut around corners and gutter ends?

Answer 14

Fascia should be mitre cut at 45° for external corners, and flush cut for gutters to ensure a neat fit.

Question 15

How can soffit linings be fixed to prevent rattling in the wind?

Answer 15

Install foam tape, silicone, or scotia on the wall edge of the soffit, and ensure it’s nailed according to manufacturer specs.

Question 16

How is roof framing connected to the wall framing?

Answer 16

Roof framing is permanently tied together with components like collar ties and strutting beams, which are connected to the wall framing for stability.

Question 17

What is the purpose of an outrigger in roof framing?

Answer 17

An outrigger extends from the common rafter at the eaves to support the roof overhang beyond the wall.

Question 18

What is the purpose of a fly rafter in roof framing?

Answer 18

A fly rafter supports the gable end and extends beyond the main roofline to help form an overhanging roof.

Question 19

What is the role of sarking in roof construction?

Answer 19

Sarking is a protective layer installed under the roof cladding to prevent water penetration and provide thermal and acoustic insulation.

Question 20

How do purlins contribute to roof framing?

Answer 20

Purlins are horizontal beams that support rafters and distribute loads to load-bearing structures. They also provide a base for roof cladding.

Question 21

What is the purpose of an under-purlin in roof framing?

Answer 21

An under-purlin is located beneath the rafter to provide support and assist with transferring loads.

Question 22

What does an under-purlin strut do in roof framing?

Answer 22

It transfers loads from the under-purlin to the top plate of a load-bearing wall or a strutting beam when there is no load-bearing wall underneath.

Question 23

What is the function of a strutting beam in roof framing?

Answer 23

A strutting beam spans load-bearing walls to receive under-purlin struts where there is no load-bearing wall at the point of contact.

Question 24

What is a girder truss, and where is it located in roof framing?

Answer 24

A girder truss is a large truss that supports one or more smaller trusses. It is located at the center of the roof or along the longest span.

Question 25

What is a truncated truss, and why is it used?

Answer 25

A truncated truss is a modified truss used in hip roofs, where the top portion is cut off to accommodate the hip and allow the roof to fall in a different direction.

Question 26

What are the key components of a truss?

Answer 26

The key components of a truss are the chords (top and bottom members), webs (internal members), and nail plates (joins).

Question 27

What is the first truss to be installed on a roof with hips and valleys, and why?

Answer 27

The truncated girder truss is installed first, as it carries more weight and establishes the intersection of the hips, providing a reference for other trusses.

Question 28

How can you ensure that roof planes, ridges, and hips are straight?

Answer 28

Use string lines or lasers to check for straightness, and check levels and plumb to ensure trusses are installed properly.

Question 29

How do you set out fly rafters to ensure they are straight?

Answer 29

Use a string line or laser from one end of the roof to the other, ensuring the fly rafters sit the same distance from the string line.

Question 30

What factors influence the spacing of purlins in roof framing?

Answer 30

The type of cladding material and the wind zone can influence the number and spacing of purlins.

Question 31

What is the minimum length for purlins according to NZS 3604:2011?

Answer 31

Purlins must be at least 1.2m in length to span at least three trusses.

Question 32

What is the purpose of dragon ties in roof framing?

Answer 32

Dragon ties are used for ceiling bracing and to prevent walls from spreading. They are fixed diagonally across ceiling joists or bottom chords of trusses.

Question 33

What are wire dogs used for in roof framing?

Answer 33

Wire dogs are Z-shaped nails used to hold down trusses or rafters, attaching them to the top plate.

Question 34

What is the purpose of cyclone straps in roof framing?

Answer 34

Cyclone straps are used to secure trusses or rafters to the top plate to prevent roof movement during strong winds.

Question 35

What are multigrip plates used for in roof framing?

Answer 35

Multigrip plates are used to secure trusses or rafters to the top plate, providing a strong connection to resist forces.

Question 36

What factors influence the choice of materials for roof hardware?

Answer 36

Material compatibility with environmental conditions, load-bearing requirements, ease of installation, cost, and availability are key considerations.

Question 37

Can nails be substituted with bolts or screws in roof framing?

Answer 37

Yes, depending on the project requirements and engineer/council approval, nails can sometimes be substituted with bolts or screws for stronger connections.

Question 38

When is stainless steel hardware preferred over galvanized hardware?

Answer 38

Stainless steel is preferred in high-corrosive areas such as coastal environments due to its superior resistance to rust and corrosion.

Question 39

Why is the location of a roof penetration important?

Answer 39

It must avoid interfering with structural components, drainage systems, and ensure water runoff is properly managed to prevent leaks.

Question 40

What should be considered when framing out a skylight opening?

Answer 40

The framing must include upstands and reinforcement to support the skylight and ensure it is sealed correctly against the weather.

Question 41

How should valley flashing be installed?

Answer 41

Valley flashing should be installed over both exterior purlins, ensuring it is properly sealed and protects against water penetration.

Question 42

How far should roof cladding and valley flashing overhang the fascia?

Answer 42

The roof cladding and valley flashing should overhang the fascia by at least 80mm.

Question 43

Where is the barge board installed, and what is its function?

Answer 43

The barge board is installed at the gable end of the roof, securing the roofing material and providing a finished, neat appearance.

Question 44

How should fascia be cut for external corners?

Answer 44

Fascia should be mitre cut at 45° to ensure a tight fit at external corners.

Question 45

How should fascia be cut for internal corners?

Answer 45

Fascia can either be mitre cut or square cut at internal corners, depending on the angle.

Question 46

How should fascia be cut at the ends of spouting?

Answer 46

The fascia should be cut flush with the end of the gutter for a clean finish.

Question 47

What is one method of joining an angled soffit to a level soffit?

Answer 47

A transition trim can be used for a tidy finish when joining angled and level soffits.

Question 48

How can soffit linings be fastened to prevent rattling in the wind?

Answer 48

Soffit linings can be fixed using foam tape, silicone, and nails according to manufacturer specifications.

Question 49

What is one common method for joining soffit boards?

Answer 49

Soffit boards can be joined using silicone or custom flashing for a seamless look.