Use a screwdriver or chisel to pry the tacks from the burlap on the underside of the antique chair. Tap sharply with a hammer if necessary. Remove the old burlap, then the webbing.
Remove the fabric, stuffing and padding from the seat of the chair to reveal the top side of the antique chair springs.
Determine which antique chair springs are in need of repair or replacement. Examine the springs for rust, damage and excessive wear. Note how the springs are tied into place before proceeding.
Count the number of rungs on the chair springs with the open ends pointing away from you to determine the size spring you need. Purchase the right size spring for your upholstery project, taking the spring with you to the upholstery shop to buy new ones if possible.
Install new webbing. Lay the first strip into place, allowing a 2-inch overhang. Secure with two upholstery tacks, then fold the end over and secure with two to three more tacks. Continue with the remaining webbing strips, weaving the strips over and under one another until the webbing is secure and complete.
Clip the twine, securing the springs into place. Replace any damaged springs. Re-tie the springs into place with waxed upholstery twine, securing the springs to each other and to the webbing intersections. Choose the same tie style as used for the antique chair springs previously for a good result (see Resources) when you repair an antique spring bottom chair.
Apply a burlap cover over the springs on the top side of the chair, securing it into place with a staple gun, then replace the stuffing and upholstery fabric. Use new fabric and stuffing or reuse the old if you prefer. Staple burlap over the springs on the underside of the chair to complete your antique spring bottom chair repair.