This is when you get your plumber to install all your pipe work. Before this you need to have a good cabinet design completed. This will tell you exactly where your sinks are going. Now if you are going straight of plans its not such a big deal. But if you plan on making modifications in your bathrooms you need to have that figured out before you rough in the plumbing. A plumber likes to have a cabinet design on hand to make sure everything will work out. I have friends that are plumbers and they "helped" me do the rough in. I pulled my own permits for this. Now they were experienced plumbers so they gave me a list of materials to get. Once the materials were onsite the work was mostly completed in a weekend. You will need to have a rough in plumbing inspection done before any covering. I installed hot water faucets outside for car and dog washing. A I also planned for future ideas and installed some pipe work for an outside sink. Something I will complete when I have the money, but eventually I would like to have an outdoor kitchen on my patio. Make sure you think of these kind of things. It is much cheaper to do now rather then later. We want the rough in plumbing done before the roof. This way your plumbing vents are installed for roofer. Lets now get this house roofed. After your rough in is complete for plumbing you will need to have inspection before any covering of walls. My inspections were done through Seattle and King County Public Health.