I read that appraisers don't count rooms in the basement toward the overall square footage, since they are considered partially or completely below grade. How will adding a bedroom in the basement create forced appreciation then, other than renting it out? Is a bedroom in the basement even counted as an additional room, eg. from 2Br to 3Br? I live in California, in case appraisers do things differently in different states.
@Daniel Chan, if it is a legal bedroom and the appraiser does not give you credit for it, I would contest the appraisal. Confirm with your local building department, but typically a legal bedroom requires certain ceiling height, egress window and closet space. Some localities have sq ft requirements as well. Stairs down must be to code, etc.
Generally speaking, you will not get as much value per sq ft for below grade finished area relative to above grade, but that still creates value.