1 According to RD.com, the average safe room costs $2,000 to $5,000 to build. 2  FEMA.gov claims that the average safe room can cost anywhere from $6,600 to as much as $14,300.3  The size of the safe room will be the largest determining factor in the price. If you need to have a safe room installed by the professionals, consider getting multiple quotes from contractors in your area on websites like HomeAdvisor.com. 2  For example, a 8-by-8-foot room can cost $9,000, while a 14-by-14-foot room can cost around $15,000.