Septagon Construction Septagon Construction Visit Website 113 East Third St 113 East Third St Sedalia, MO 65301 (660) 827-5955 (660) 826-8058 (fax) Hours: Office Hours Monday thru Friday 8:00 am to 5:00 pm About Map About Septagon Construction, Co provides design-build, general contracting, and construction management to clients throughout Missouri and Iowa. What's Nearby? Distance: 5 10 15 20 25 50 mi.