Tourmaline is a one-stop shop to design and build your ADU. An ADU, or Accessory Dwelling Unit, is a complete and separate living space, typically built in the backyard of a property that already has a single-family home. An ADU can be a guest house, accommodate parents or grown children, or be a great source of rental income, and can increase the value of your home. New state and local laws make it easier than ever to build an ADU on your property. Let us show you how.