This is when the excitement begins. Now you finally get to see the physical manifestation of your project as it moves from paper to reality. Foundation: If you’re building a slab home, the plumbing will most likely be set up prior to the pouring of the concrete slab. You’ll have water and drain pipes that will need to go through the slab and under the house, so the pipes have to be in place before the slab gets poured. If your home is on pier and beam that is not the case;