Construct pitched roofs (CPCCCA3007C)
- Working drawings for domestic construction will often only show the proposed roof in elevation and plan, it is therefore heavily reliant on the carpenter’s skills and knowledge to cut the members to allow the roof to be pitched. What is the Australian Standard which governs the structural requirements of timber framing?
AS 1684 - Code
It is an Australian standard that is also known as Timber framing code. It covers the design criteria and is made up of four parts.
- Refer to the building plans at https://derbyshire.com.au/wp-content/uploads/2016/03/Construction-Document-Sample-1.pdf, to complete this question.
What is the size of the site area?
The area of any land on which development is to be carried is known as site area.
Awhole or part of one lot is included in land.
For finding the area of rectangle, multiply the height with the width.
What are the corrosion protection requirements for built-in structural members?
Exposure to the atmosphere needs to be reduced. From dissimilar metals should be stayed away. Water should be prevented from building. Surface irregularities should be avoided.
What type of roof cladding will be used?
OSB is most used for sheathing and subflooring material.
What is the pitch of the roof above the garage?
By the pitch, the gable roof is described.
- Below is a plan view of a building on which a hip and valley roof is to be constructed. Sketch in the plan of the roof shape, using the following principles to determine the position of plan roof members:
- All angles formed by the external wall plates must be bisected;
- Only one member is drawn from any one corner;
- Hips are formed where the wall plates create an external corner;
- Valleys are created where an internal corner is formed by two plates;
- Rafters are always set at 90° to the wall plates; and
- A ridge will always be level and parallel to the external wall plates.
Below is a plan view of a building on which a hip and valley roof is to be constructed. Sketch in the plan of the roof shape, using the following principles to determine the position of plan roof members:
· All angles formed by the external wall plates must be bisected;
· Only one member is drawn from any one corner;
· Hips are formed where the wall plates create an external corner;
· Valleys are created where an internal corner is formed by two plates;
· Rafters are always set at 90° to the wall plates; and
· A ridge will always be level and parallel to the external wall plates.
Select The Largest Rectangular Area And Mark Its Outline
Lightly Draw The Outline Of A Hip Roof On This Area
Bisect All External And Internal Corners
Draw In Ridge Positions For Each Extension
Remove any unwanted lines
Firm in the roof plan to ensure correct intersection connections
- What code of practice must be followed when working on roof framing?
The working at height code of practices must be followed.
- Detail 3 safety measures critical to construction work undertaken at heights.
Proper PPE needs to be selected when working at heights. The selection needs to be of right quality. Daily inspection of PPE’s should be done before people rose to higher heights.
For working at heights, make use of proper equipment. Involvement of lifts and ladders is in the equipment.
Some equipment such as carbineers and retractors should also be used. Safety in working at higher heights is also provided by such equipment.
- Outline 4 safety measures to be taken to avoid objects falling from the area where the work is being carried out onto the persons below.
1) Follow the general rule of wearing hard hats.
Always bear in mind that it is necessary to keep wearing hard hats when work is being performed overhead or when there are other work conditions that call for it. It is important to know that hard harts do not just simply bring protection for your head.
2) Always check the items on the loose.
One of the most important things that need to be consider is to always check the items on the loose. Keep in mind that checking all of the things and equipment will help to ensure safety in the workplace and avoid accidents from happening.
3) Make sure to wear recommend PPE
Before doing the tasks in the worksite, one have to make sure that are wearing the correct and recommended personal protective equipment.
4) Know the importance of communication
Communication is one of the most important key factors in every work environment. Effective communication is vital to achieving the successful completion of any particular construction project. When there is good communication, it can improve teamwork and lead to better project collaboration.
- Every week, 50 Victorian construction workers are injured seriously enough to stop work because basic site safety and housekeeping is not up to scratch. For each area below, provide at least 2 examples of housekeeping requirements.
Area- Housekeeping requirement
Ground/Flooring- Timber and concrete floor is suspended.
Delivery and storage of equipment and materials- There should be cash registers, various bags of different size.
Access and movement around the site- Driveways and footpaths are clear
Waste-Are empty bins/skips adequate?
Work areas- As the traders go, do they clean?
- As you gather the tools you’ll need for the workday, you come across the below. What does this mean?
As the person is speaking, conduct the interview, this will set the tone on how one will be perceived throughout the interview.
- Pitched and loudness should be used
- Learning skills should be responsive.
- One must be clear and concise
- Humor should be used
- If the side of the house (from front to rear) is 8 m, determine the area of the roof. (Assume that the roof does not overhang the walls in any direction.)
cos 28 = adj./hypot.
xcos 28" = 4
x = 4/(cos 28 degrees)
= 4.5 m
Area of roof = 10.8m x 4.5m x 2m
- How do screws differ from nails? When would you use nails and when would you use screws
Resistance is offered by the screws for breaking under tension.
For structural joining,the nails are preferred as they are more flexible.
If more holding power is needed than nails, screws are helpful.
- List 2 types of timber commonly used for roof framing.
Following are the 2 types of timber that are commonly used:
Kiln-dried Douglas fir wood
- With what material should ceilings be constructed, to provide a resistance to the spread of fire? Give 5 examples.
- 2 layers of 16mm GyprockFyrcheck plasterboard
- Perforated gypsum lath with a normal paper finish
- 12mm fibrous plaster reinforced with 13mm X 13mm X 0.7 galvanised steel wire mesh located not more than 6mm from the exposed face
- Fibre cement sheeting
- Pre-finished metal sheeting not exceeding 1mm thick
- 12mm cellulose cement flat sheeting
- What is the purpose and function of temporary fencing around a building site?
The main aim of temporary fencing is to prevent the runoff from soil and also helps in minimisation of the dust level. The sites where buildings are built can be a dusty place and nearby protection of environment is important.
- Outline the 6 steps involved in setting out a pattern rafter.
- Scale drawing should be produced for finding the true length.
- Pitch line on the rafter needs to be marked.
- Adjustable level needs to be set for marking a plumb cut.
- True length of the pitch needs to be marked on the rafter.
- Bird’s mouth should be marked.
- Plumb cut should be remarked. This becomes the pattern rafter.
- In 4 steps, describe the process to erect a simple hip roof over a rectangular building.
- Cut/test pattern rafter
- Mark out last common / jack rafter
- Cut ridge to length
- Erect ridge, measure hips and cut erect complete roof
- There are 3 main principles related to roofing, which are critical to the accurate construction of roofs in general. What are they?
- Ridges level should be parallel to wall plate.
- Rafters needs to be placed at 90 degree to the wall plates.
- External/internal corners must be bisected for allowing the correct placement of hips and valleys.
- What is the difference between the ‘theoretical length’ and the ‘actual’ or cutting length of the rafter?
The entire length of the rafter is devoted to the ‘actual length’. The ‘theoretical length’ is devoted to the length of the rafter that is used for testing the purpose.
- How can you determine the quantity of rafter lengths required for a build?
In the ‘Australian roof building manual’, the length of the rafter is found.
- There are 8 bevels and proportions required to pitch a hip roof. List the 8 bevels and proportions required.
- Plumb bevel common rafter
- Level bevel common rafter
- Edge bevel creeper
- Edge bevel purlin
- Plumb bevel hip
- Level bevel hip
- Edge bevel hip
- Face bevel purlin
- There are 4 methods used to establish hip length. List the 4 methods.
Following are the 4 methods that is used to establish hip length:
- Measured in-situ
- steel square set out
- On the diagram below, shade in the birdsmouth cut out.
22. Building has a span of 5000 mm and ridge thickness of 50 mm. The true half span is 2475 mm.
Use the below formula to determine rafter length for the following scenarios:
Rafter length = 1 divided by (cosine x roof pitch) x half span
Slope of 26 degrees- Rafter length = 1 divided by (cosine x roof pitch) x half span
= 1/cos26 x 2475
= 1/0.8988 x 2475
= 2753.67 mm
Slope of 42 degrees- Rafter length=1 divided by (cosine x roof pitch) x half span
=1/cos42 x 2475 =1/0.7431 x 2475
Slope of 17.5 degrees- Rafter length t = 1divictedb (cosine x roof pitch) x half span
= 1/cos17.5 x 2475 Slope of 17.5 degrees
=1/0.9537 x 2475 = 2595.16 mm
- What is the purpose of under purlins, where are they positioned, and how are they supported?
- List the 2 methods to determining the length of the first creeper.
Method 1- setting from the centring rafter
Method 2- setting from the outside of the wall plate corner.
- What is the purpose of collar ties, and where are they located?
What is the main function of a collar tie?
The main function of a collar tie is that it helps in preventing rafter sag.
What is the ideal location for a collar tie?
The ideal location for a collar tie is that it should be located halfway up the rafters.
- How are gable rafters supported?
Gable end framing uses the vertical studs when the rafters are in place. It is positioned directly over the wall studs and is supported by the end top plates.
- What is the function of valley boards?
It is essential to use the valley board for supporting the dry valley.
- From where can you obtain the storage requirements for materials?
For specific storage requirement, refer to SDS.
29. Teamwork includes open communication and everyone contributing to improve the workplace to safely and successfully achieve the construction goal. Good communication means that everyone can voice their opinion. Building trust ensures that workers are comfortable sharing their suggestions and concerns.
How are workers empowered on the construction site? Provide 5 examples.
- In safety training, participation needs to be done and there should be identification of hazards.
- When it is necessary, timeout for safety should be called.
- Removal of defective tools and equipment needs to be done.
- Hazards should be corrected immediately when it is safe to do.
- If the questions are of concern, ask for the training or guidance.