I am doing some planning for an addition to my somewhat small 50's ranch home. The current plan is to lay the new foundation over the sewer main line. We don't have many other options since the sewer line come out in the middle-back of the house. It seems like this could be a real problem if the line ever needed to be replaced. Especially, since many homes in my neighborhood, and possibly mine, have orangeburg main sewer pipes. Would it be reasonable to replace the line before the slab is poured, since a new line would be much less likely to fail? Here are pictures of the current and proposed floorplans with the sewer line drawn in. Thanks for any help!