House construction: this was the part that had us all the most nervous. Dropping the last ~100kg piece of stone bathroom floor into place with like 0.7cm of clearance all around. Went as smoothly as it could have, though.
@steve I used to live in a rental with a window that was right next to the shower head. I guarantee you that there is mold under the window sill and the blinds the landlord put in had completely rusted.