Tyrell Nelson added 11 points and Adonis Burbage finished with 11 points and nine rebounds for Gardner-Webb (11-12, 6-5 Big South).
Charleston Southern (8-14, 4-7) got 17 points from Armel Potter.
Burbage's 3 at the 7:45 mark of the first half triggered a 22-8 run allowing the Bulldogs to take control of the game.
Leading 35-22 at the half, Nelson hit a layup and a jumper, and a Poston 3 pushed the lead to 42-26. Gardner-Webb then went scoreless for nearly five minutes, but the Buccaneers shot just 1 for 7 from the field during that same stretch and trailed by 10.
The Bulldogs finished 22 for 33 (66.7 percent) from the free-throw line while Charleston Southern (15 for 22) shot 68.2 percent. Both teams shot just 35 percent from the field.