Hello there! The provided links didn't have specific instructions on how to repair sofa foam, but don't worry, it's a very common and manageable DIY project. I can certainly walk you through the process.
Giving new life to a sagging sofa usually comes down to revitalizing the foam inside the cushions. The easiest method is to add extra padding. You can unzip your cushion covers, take out the foam insert, and wrap it with one or two layers of polyester batting, which you can find at most fabric or craft stores. This adds plumpness and helps fill out the cover, giving your cushion a fuller, more comfortable feel. You can use a light-duty spray adhesive to keep the batting in place while you work.
For a more permanent and effective fix, especially if your foam is old and has lost its spring, your best bet is to replace the foam insert completely. First, you'll need to measure the old foam insert for length, width, and thickness. A good tip is to add about half an inch to the thickness and width measurements to ensure the new cushion fits snugly inside the cover.
Next, you'll need to buy new high-density foam, which is ideal for seat cushions because it's durable and supportive. You can often have it cut to your exact measurements at the store, or you can cut it yourself at home using an electric carving knife for a clean edge. Just like with the quick fix, it's a great idea to wrap this new foam core in a layer of polyester batting before putting it back in the cover. This protects the foam and gives the cushion a soft, rounded look. Getting the new, larger insert back into the cover can be a bit of a squeeze, but a helpful trick is to fold the foam like a taco to slide it in, then let it expand into place.
These steps can make a huge difference and bring your comfy sofa back to its former glory without the cost of buying a whole new one. Happy repairing
