Hi,
I am planning to add an ensuite and a powder room to our existing home, and I intend to manage the project myself instead of hiring a builder. To make room for these additions, we’re reducing the living/dining area. We’re working within a tight budget, so we’re aiming to avoid cutting into the concrete slab.
One of the Solution provided by plumber is to
1. Instead of building a regular wall to enclose the area, build a Cavity wall, allowing plumbing and sewerage lines to exit the house at the nearest opening, avoiding concrete cuts and achieving the necessary 1:60 fall.
2. For shower minor cutting at the edge will be required.
3. Digging a trench to the ORG (overflow relief gully) to connect the drainage to existing sewer line and adjusting the ORG accordingly.
4. Using in-wall toilets to maintain the fall to the nearest exit point, with all toilets positioned on the plumbing wall.
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Questions
1. Does running sewerage lines through the wall meet Australian standards and codes?
2. Are there any foreseeable issues with running plumbing through a wall, such as potential damage to timber framing over time due to moisture or anything?
3. Should we consider insulation around the plumbing to protect against potential leaks or any other issues?
4. What methods can we use to protect the plumbing from accidental damage, like someone driving a nail into the wall and damaging plumbing?
5. How should framing be handled? With standard 90 mm studs, would we need two frames and 110+ mm cavity between 2 frames ? or 2 studs can be joined together to create wider. depth.
Thanks in advance for all the help

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