If your couch is caving in upon sitting, the couch springs are the likely culprit. Springs that have popped out of the bottom of your couch may be completely broken or just loose, with the latter being easily fixable. While broken springs or other extreme damage will require the help of a professional, many couch spring issues can be remedied without spending money on repair services. Understanding the type of spring you are dealing with and what to look for when repairing broken springs will make such repairs a simple DIY task.
Flip the couch on its side so you can easily work with the broken springs. Have a friend or family member help you if the couch is on the heavier side. Remove the gauzy fabric covering the bottom of the couch, which is generally attached to the couch with either glue, thread or staples. Carefully peel back the fabric if glued and use a staple remover to avoid tearing the fabric if stapled. Use a seam ripper if the fabric is sewn to the bottom of the couch. Torn fabric resulting from springs popping out of the couch bottom can be either taped or sewn back into place.
Identify the type of spring you are dealing with. Couch springs are usually serpentine or sinuous, meaning they are either coil or zigzag-shaped, respectively. Note how the springs are attached to the couch as well, as this will tell you if the springs are either sagging or just loose.
Reconnect loose springs with their fastening brackets if applicable. If springs are held in place with string, use twine or other sturdy string or thin rope to place springs in their correct space. Springs that are attached to the couch via clips should be checked for clips that are broken, loose or missing. Use a drill or screwdriver to screw clips back into place, though you might have to re-order clips from your couch's manufacturer if you find a clip or two is missing or damaged beyond repair. Springs that are completely broken will also have to be replaced.
Place the gauze fabric back on the bottom of the couch with either glue or a staple gun.