VU22026 Construct a basic roof frame
Student name: Page 6. VU22026 – Construct a basic roof frame
INTRODUCTION The primary object of a roof is to protect the building and contents from the elements. Roofs must be made strong enough to withstand the dynamic force that comes with high winds.
TYPES OF ROOFS The most common types of pitched roof construction are the gable, the hip roof, hip and valley, hipped roof with Dutch gable and the skillion roof. A roof may consist of a combination of various styles.
Gable roof A gable roof has a ridge at the centre and slopes in two directions. This type of roof has a triangle on the rear or front of the facade, which is formed by the straight slope declining from the ridge to eave.
Gable roof
Hip roof The hip roof has four sloping sides. It is a strong type of roof because it is braced by four hip rafters. The hip rafters run at 45° from each corner of the building to the ridge when viewed from directly above.
Hip roof
Hip and valley roof This type of roof is used for an L or U shaped building. The valley is formed at the internal junction of the two roofs.
Hip and valley roof
22338VIC – Certificate II in Building and Construction Pre-apprenticeship ©Copyright L.A.P.tek Pty. Ltd. VU22026 – Construct a basic roof frame Page 11.
Hip rafter Hip rafters are on the hip end. Both hip rafters are equal in length and in plan view they are at 45º to the walls. The plumb cuts and birds mouth are very different from that of the common and creeper rafters.
The difference is caused by the rake of the hip. Hip rafter
Common rafters A conventional hip and gable roof has common rafters opposing each other on each side of the ridge, pitched at the same angle or rake.
The rafter is fixed to the ceiling joist and the top plate.
Common rafters
Fixing common rafters Common rafters are fixed to the top wall plate and also the ridge board.
Collar ties Collar ties are fixed below the ridge at the top third of the roof on Common rafters joined to the top plate and ridge board every second pair of opposing rafters
Creeper rafters Creeper rafters are on the hip end and oppose each other on each side of the hip rafters. Creeper rafters are pitched at the same angle as the common and jack rafters. Each pair is equal in length with opposing side cuts, known as left and right.
Fixed at 90º In plan view, common, jack and creeper rafters are all fixed at 90º to the top plates and have the same plumb cut. Creeper rafters
©Copyright L.A.P.tek Pty. Ltd. 22338VIC – Certificate II in Building and Construction Pre-apprenticeship Page 24. VU22026 – Construct a basic roof frame
PATTERN RAFTER
Calculate ‘Actual rafter length’ How: To calculate the actual rafter length. Half span – Half ridge board thickness, then use the roof table to determine the rafter length.
......
......
......
3. Refer to the roof table to determine the rafter length. 4. Mark out and cut a pattern rafter.
22338VIC – Certificate II in Building and Construction Pre-apprenticeship ©Copyright L.A.P.tek Pty. Ltd. Page 34. VU22026 – Construct a basic roof frame
ROOF SETOUT – STEP 14 TASK 21: UNDER PURLINS AND STRUTS
How: Study pages 163 – 172 and 195 – 197. Building a House: Framing Practices. After teacher lesson on under purlins, struts and collar ties, complete the following tasks. 1. Cut and fix the under purlins to the rafters. 2. Cut and fit the timber struts to the under purlins. 3. Cut and fit the timber struts to the ridge board. 4. Cut and fit collar ties to the under purlins and rafters.
NOTE: All struts to be fitted to the specifications as set out in AS.1674. Residential timber framed construction.
Assessment criteria: All joints must be tight. (e.g. stud to top and bottom plate maximum gap 2 mm) Set out to plans +/- 2 mm. All work must be in accordance with 1648 Residential timber-framed construction. All work practices adopt current OHS requirements.
Example: Under purlins and struts
22338VIC – Certificate II in Building and Construction Pre-apprenticeship ©Copyright L.A.P.tek Pty. Ltd. VU22026 – Construct a basic roof frame Page 37.
ROOF TRUSS COMPONENTS A “truss” is formed when structural members are joined together in triangular configurations. The major components of a truss are as follows
TASK 22: IDENTIFY TRUSS COMPONENTS AND ROOF TRUSS SHAPES
How: Locate a complete roof truss in the workshop that has the above components, then identify the various components to your teacher, then identify the various truss shapes below
©Copyright L.A.P.tek Pty. Ltd. 22338VIC – Certificate II in Building and Construction Pre-apprenticeship VU22026 – Construct a basic roof frame Page 39.
Student Learning Guide & Record
ACHIEVED TASK PAGE TASK TITLE Yes No
Task 1 7 Identify various types of roofs
Task 2 9 Roof framing components
Task 3 13 Identify and explain roof framing components
Task 4 15 Identify roofing definitions
Task 5 16 Build a support frame for a hip and gable roof
Task 6 17 Mark the position of the three jack rafters
Set out the common and creeper rafter Task 7 18 positions
Task 8 19 Mark the ridge board rafter positions
Task 9 20 Estimate quantity of materials required
Task 10 21 Pre-cut ceiling joists
Task 11 22 Cut and fit the hanging beam
Task 12 23 Make a roof boat and a pattern rafter
Task 13 25 Cut and pitch roof
Task 14 26 Fit the remaining common rafters
Task 15 27 Cut and fit hip rafters
Task 16 28 Cut and fit creeper rafters
Task 17 29 Gable end raking plate
Task 18 31 Fit remaining infill gable studs
Task 19 32 Assemble gable end
Task 20 33 Fit fascia and barges
©Copyright L.A.P.tek Pty. Ltd. 22338VIC – Certificate II in Building and Construction Pre-apprenticeship Page 40. VU22026 – Construct a basic roof frame
ACHIEVED TASK PAGE TASK TITLE Yes No
Task 21 34 Under purlins and struts
Identify types components and roof truss Task 22 37 shapes
22338VIC – Certificate II in Building and Construction Pre-apprenticeship ©Copyright L.A.P.tek Pty. Ltd.