My wife and I are planning on adding on to our home to accomidate our 6 growing children. The addition is an open great room with 20 foot open celings. 1/2 of the area will be floored and coverted to a bedroom and bath. The addition is 28' X 50 foot meaning the beams withh be open and exposed on 30 feet. Were can we find these trussed and how much is the cost going to be?