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A dining area has a flat roof section which projects 1.6 metres from the rear wall of a house, as shown - Leaving Cert Construction Studies - Question 1 - 2022
Question 1
A dining area has a flat roof section which projects 1.6 metres from the rear wall of a house, as shown. The flat roof is covered with a waterproof membrane, on 150 ... show full transcript
Worked Solution & Example Answer:A dining area has a flat roof section which projects 1.6 metres from the rear wall of a house, as shown - Leaving Cert Construction Studies - Question 1 - 2022
Step 1
To a scale of 1:5, draw a vertical section through the external wall of the dining area, the flat roof and the rear wall of the house.
Answer
To create an accurate vertical section at the scale of 1:5, begin by plotting the external wall and flat roof outline. The external cavity wall section should be indicated with a thickness of 450 mm, and include both the external and internal renderings.
- External Wall: Draw a cavity wall with the external leaf (100 mm) and internal leaf (100 mm). Add insulation where necessary, showing it as a full-fill cavity.
- Flat Roof: Continue the drawing with the flat roof; indicate layers:
- Waterproof membrane on top
- 150 mm rigid insulation
- OSB or plywood decking, measuring 18-40 mm thick, with appropriate supports (200 mm x 50 mm joists).
- Insulated plasterboard (50 mm insulation + 12.5 mm board) fixed underneath the joists.
- Abutment with Rear Wall: Finish the section by illustrating the abutment at least 400 mm above the roof line, ensuring that the details are interconnected properly to show continuity.
Step 2
On your drawing, indicate the typical design detailing to prevent the formation of a thermal bridge at the junction of the flat roof and rear wall.
Answer
To effectively indicate measures against thermal bridging at the junction:
- Insulated Block: Show the placement of an insulated block where the flat roof meets the rear wall, distinctly labeled in your drawing.
- Thermal Break: Illustrate a thermal break material between the roof and wall junction to mitigate heat loss.
- Wallplate: Include a continuous wallplate that extends above the insulation, ensuring that it doesn’t bridge to the external wall uninsulated.
- Flashing: Indicate a lead flashing and a tilting fillet to ensure proper water drainage and to maintain a continuous insulation layer without thermal bridging risks.