average cost to add a dormer
Step 4. Add a shed roof dormer to create an attic bedroom for one of the most beneficial additions. Figure dormer additions at $80 to $120 a square foot, usually a total of between $5,000 and $20,000, depending on the size and roof style.reate a family room for $80,000 or more, a sunroom for slightly less, but expect to gain only 50 to 60 percent of the cost in added value. Add or expand a master suite for $100,000 or more and you will enjoy more comfortable living, but will increase the home value by only about half the cost.