How to Fix a Sagging Couch Cushion in 15 Minutes

Why Couch Cushions Sag (and How to Spot the Cause)

A sagging couch is not only an eyesore but also a major pain for your back. Before you run out to buy an expensive new sofa, you should know that cushion sag is incredibly easy to fix. Over time, the inner foam core of your cushions naturally compresses, or the underlying support springs begin to stretch. In just 15 minutes, you can restore your sofa to its former plush glory using a few inexpensive materials.

What You Need

• Polyester fiberfill (Poly-Fill): Perfect for restoring soft, rounded edges and filling out empty corners.
• High-density upholstery foam (1-inch thick): Ideal for structural support if your cushions are severely flattened.
• A piece of sturdy cardboard or 1/4-inch plywood: (Optional) Used to reinforce stretched couch springs.
• Bar soap or candle wax: (Optional) To lubricate stubborn cushion zippers.

Step 1: Inspect the Cushion and Couch Base

Remove the sagging cushion from your couch. Sit directly on the empty couch frame to test if the underlying springs or webbing are sagging. If the base feels firm but the cushion feels flat, your problem is compressed foam. If the base itself sinks deeply, you will need to reinforce the support system beneath the cushions as well.

Step 2: Unzip and Access the Foam Core

Locate the zipper on the back of your cushion cover. Unzip it carefully to reveal the inner foam block, which is usually wrapped in a thin layer of white batting. If the zipper is stubborn or stuck, rub a piece of dry bar soap or a candle wax stick along the teeth to lubricate it before pulling.

Step 3: Stuff the Corners with Poly-Fill

Most cushion sag occurs in the front-center and the corners where your body weight rests the most. Take handfuls of polyester fiberfill and gently stuff them between the existing foam core and the fabric cover. Focus heavily on the front edge and the corners to restore a sharp, plump, and professional look. Smooth out any lumps with your hands as you go.

Step 4: Add a Foam Booster Layer (For Severe Sag)

If your cushion is still too flat after adding fiberfill, you need to add a structural booster. Cut a piece of 1-inch high-density upholstery foam to match the dimensions of your cushion. Slide this extra foam layer inside the cushion cover, placing it directly underneath the existing foam core. This provides a fresh, firm foundation without altering the softness of the top seat.

Step 5: Reinforce the Couch Base (If Necessary)

If your couch springs are stretched out, stuffing the cushions won't fully solve the sag. Measure the seat platform beneath your cushions. Cut a piece of heavy cardboard or 1/4-inch plywood slightly smaller than the platform, sand the edges to prevent fabric snags, and place it directly under the cushions. This distributes weight evenly and stops the cushions from sinking into the gaps between the springs.

Step 6: Zip Up and Fluff

Zip the cushion cover back up. If the cushion is now very full, pull the fabric edges closely together with one hand while pulling the zipper with the other to avoid tearing the seams or catching the inner batting. Once zipped, give the cushion a few firm pats to distribute the filling evenly, place it back on your couch, and enjoy your revived, ultra-comfortable seat!