Most people that want to have a project built do not know if they need an architectural drawing or not. Depending where the project is located and what you are building has a determining factor in deciding what you will need. Commercial buildings or commercial projects typically require an architect or engineers stamped drawing. Residential tends to be more lenient on drawing requirements. Regardless, having a drawing is a benefit for everyone involved. It keeps everyone on the same page and what you are wanting. The less detailed the drawings, the more room for interpretation.
However, drawings are not cheap and do not add to the buildings actual value. If this cost is a concern, it would be recommended to talk with a general contractor or the city/county building department where the project is located. Then discuss the requirements, to see what is the most cost efficient solution to move forward.