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The slated roof of a new house is constructed using prefabricated trussed rafters and has a pitch of 45 degrees - Leaving Cert Construction Studies - Question 7 - 2017
Question 7
The slated roof of a new house is constructed using prefabricated trussed rafters and has a pitch of 45 degrees. The internal span of the house is 4.0 metres. The ro... show full transcript
Worked Solution & Example Answer:The slated roof of a new house is constructed using prefabricated trussed rafters and has a pitch of 45 degrees - Leaving Cert Construction Studies - Question 7 - 2017
Step 1
To a scale of 1:10, draw a vertical section through the roof structure.
Answer
Begin by sketching a vertical section that clearly indicates the 45-degree pitch of the roof. At the center, draw the trussed rafters with a span of 4.0 meters, adhering to the scale of 1:10. Ensure the eaves detail is well represented, showing the typical design at the junction with the wall. Include the necessary battens, which should be drawn as slats of 50 x 40 mm positioned appropriately. Additionally, illustrate the breather membrane that is sealed and taped, creating space for ventilation.
Next, display the insulation layer consisting of PIR insulation board, ensuring to indicate that it is fixed to the rafters at a distance of 600 mm centers. Reflect the plasterboard with bonded polystyrene or similar to enhance fire protection. Finally, label all components properly, including the ridge level and ceiling details, to meet the requirements.
Step 2
Show the typical design detailing at one of the eaves and include battens, membranes and four courses of slate at eaves.
Answer
For the eaves detail, illustrate the configuration of the roof precisely at its lowest section. Begin with the trussed rafters extending down to the wallplate, where the wall interacts with the roof. Include the battens placed horizontally (50 x 40 mm) over the rafters, showing their function in holding the slates in place. Draw the layers of membranes sealed for waterproofing, indicating the placement of at least two layers.
Finally, represent the four courses of slates at the eaves, demonstrating the overlap from each course to ensure proper water runoff. Label each course of slate clearly, with dimensions if necessary.
Step 3
On your drawing show the typical dimensions of three roof members.
Answer
Indicate the dimensions of the three primary roof members:
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Trussed Rafter: Sketch details specifying the dimensions, typically 150 mm width by 200 mm height at the web sections, spanning 4.0 meters.
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Batten: The battens should be depicted as 50 mm x 40 mm, installed horizontally at regular centers, usually every 600 mm, to secure the roof covering.
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Wall Plate: Represent the wall plate as 100 mm x 75 mm, resting on the masonry of the wall to support the trussed rafters.
Use the same 1:10 scale to ensure accurate and proportional representation.