A bathroom renovation is one of the few times you can change the plumbing layout for the cost of a few extra metres of pipe. After tiling, it's a major job. These are the decisions to lock in before rough-in.
Toilet: floor pan or wall-hung?
Wall-hung looks great and frees up floor space, but the in-wall cistern needs framing reinforcement and a serviceable access panel. Decide before the plasterer's quote.
Shower: rail or rainfall?
Rainfall shower roses need a ceiling-fed water line and adequate pressure (>250kPa). On a 2-storey home you may need a pressure pump.
Vanity: single or double?
Double vanities need a second waste outlet and hot/cold set — easy to add at rough-in, awkward later.
Laundry sharing the wall?
Renovating one wet area is the perfect time to refresh the next. Shared stack work and waterproofing only get done once.
Don't forget compliance
All new fixtures need WaterMark certification. Your plumber must issue a Notice of Work and a Certificate of Compliance — keep them for resale and insurance.