The provided context is not relevant to the question of how to repair a sagging sofa base. The following answer is based on professional furniture repair knowledge.
Fixing a sagging sofa base typically involves identifying the source of the problem and addressing the specific structural failure. To begin, you will need to turn the sofa upside down or on its back to access the underside. Carefully remove the dust cover, which is usually a thin fabric stapled to the bottom of the frame. This will expose the sofa's support system.
Once the interior is exposed, inspect the support structure for damage. The most common causes of sagging are stretched or broken webbing, detached or broken springs, or a cracked wooden frame. If your sofa uses webbing, check if the straps have lost their tension or have detached from the frame. For sofas with serpentine (zigzag) springs, look for broken springs or clips that have come loose. If the wooden slats that support the springs or webbing are cracked or broken, this will also cause a significant sag.
For a permanent repair, you will need to replace the damaged components. Stretched webbing should be completely replaced with new material, using a webbing stretcher to ensure it is sufficiently taut before stapling it to the frame. Broken serpentine springs or their mounting clips can also be replaced; new parts are readily available online or at upholstery supply stores. If the wooden frame itself is cracked, you can reinforce it by gluing and screwing a new piece of wood alongside the damaged section.
If you are looking for a simpler, less invasive solution, you can add support directly under the cushions. A common quick fix is to cut a piece of plywood to fit the dimensions of the seating area and place it on top of the existing base but underneath the cushions. Alternatively, commercially available products known as "seat savers" or "sofa supports" are designed for this purpose. These rigid, often foldable panels provide a firm base for the cushions, immediately reducing the sag and improving comfort. While not a permanent structural repair, this method is effective, affordable, and requires no tools.
