A sagging or lumpy chair seat indicates the springs or the webbing have come away or the webbing has simply worn out; it also indicates the seat padding is in poor condition and needs replacing. Re-webbing a chair is a fairly straightforward job, but renewing the padding is slightly more difficult and is covered separately in the book.
Carrying out repairs
To examine the condition of the springing, turn the chair upside down and hold it steady by resting it on another chair or a workbench. Take off the hessian backing, using a chisel and mallet to remove the tacks which hold it to the frame; make sure you work very carefully in the direction of the grain to avoid damaging the wood. If the hessian is still in good condition, you will be able to use it again when you have completed the repair work. If, however, the backing looks worn or tatty, cut out a new one using the original as a pattern and allowing at least 25mm extra all around so you can make a neat, tucked-in finish.
When you have removed the hessian, check the condition of the webbing – and the springs if there are any; some chairs have only a padded base supported with webbing. Look to see whether any of the webbing has come away from the frame or become saggy and slack through wear; if this is the case, remove it using the chisel and mallet to knock out the tacks. Try not to enlarge the holes when you do this; if you do open them up a little, fill them with a fine wood filler and leave them to harden. Once the webbing is free from the frame, use a sharp knife to cut the spring twine which holds the webbing to the springs, disturbing the springs as little as possible.
Turn over the end of the new webbing l9mm and, using the original tack holes as a guide, fix the webbing to the front edge of the frame with five tacks, placed in the shape of a ‘W’, so the wood will not split. You will need to buy a web stretcher, or make one by cutting a deep ‘V’ across one end of a piece of 50x25mm wood. Stretch the webbing across the seat and wrap it around the stretcher from end to end. Pull the webbing across the frame and lay the V-shaped end of the stretcher onto the edge of the frame at about a 45 degree angle. Press it down firmly until you feel the webbing will not stretch any more. Hold the stretcher in place and fix the webbing with a single row of three tacks. Remove the stretcher and cut off the webbing about 25mm from the tacks. Tum the end over and secure it with two more tacks. Again using the old tack holes as a guide complete the webbing along the length of the frame. Fix strips of webbing across the width of the frame, weaving them through the lengthwise pieces then stretching and tacking as before.
To make sure the springs are secure and will not tear through the hessian, tuck each one under a place where two pieces of webbing overlap. If the springs tend to squeak, put a small piece of felt or some other kind of padding between the two parts of the spring which are rubbing together. When all the springs are in place, secure them to the webbing using spring twine and a half-circle or springing needle. Each spring should be fixed with four stitches equally spaced around it and caught at the same depth; finish off each stitch with a slip knot. Without breaking the twine, carry one stitch to an adjacent spring and stitch as before. When all the springs have been attached to the webbing in this way, finish off with a double knot and trim the twine.
Once you have renewed the seat padding, you can replace the backing. Fold in the edges of the hessian and tack it to the frame with three tacks in the middle of each side. Adjust any creases by taking out the tacks, straightening and retacking. When the hessian is flat, continue fixing it down with tacks every 50mm along the frame, avoiding previous holes if possible. Fold the hessian into shape around the legs and fix with tacks close together for a neat finish.