Dear Philip: The best practice when doing work on your house that involves plumbing or electrical changes, gas connections, structural work, and roofing, among other things, is to get a permit. Not only does it ensure that the contractor’s work will meet the city or county codes, it establishes a review process for the work that is done. Not every job needs a permit, e.g., refinishing floors or installing carpeting, buying a new appliance to replace an old one. But it is the best practice and if you ever want to sell your house, buyers are more assured that the work you did complied with the building codes.