There can be several challenges associated with installing a half bath or a full bath in an attic.

The first problem will be getting the fixtures into the attic work area. Chances are that early in the project, you will have a small point of access to the attic. You will need to figure out how you will get the sink, toilet, tub or shower through that opening and up into the work space.

The second challenge is positioning the new bathroom in a location in the attic that is as close as possible to an existing bathroom on the floor below. The closer you are to existing supply and drain lines, the lower the cost of adding the bathroom.

The third major issue is determining the structural soundness of the house if that much additional weight is placed in the attic. Most homes are not built to support a large amount of extra weight in the attic. You might find that you need to reinforce the structural elements of the house to support the weight.

Adding a bathroom also requires (in most locations) the addition of some kind of ventilation system for the bathroom.