A. This is a question that may need to be answered by your local building department official, but depending on a couple of factors, I do not think that it would be necessary to move either the water or sewer line.

Things to consider are the age and condition of those lines and the required depth of the foundation footing for your locality. Here in Seattle the frost line for code purposes is 12 inches. That means that the bottom of the footing must be at least 1 foot deep. If you are sure that the water line is the required 2 feet deep, you should not have a problem. A properly constructed footing and foundation will disperse the load and the water line should be fine.

I’m a little unsure about requirements where the sewer line is concerned. Since interior plumbing waste lines are constructed differently from exterior ones, there may be some sort of requirement to replace the portion that will be under the house, but I don’t think so. If the existing side sewer (that portion that runs from the house to the city sewer line in the street) is old, or you have had problems with it in the past, you may want to deal with it now, before you build over it. Similarly, if the water line is old galvanized steel pipe, you may want to update that before you build.