Upholstery Repair

Replacing Foam

Foam can be about 4 inches thick and rarely comes in the exact size you need. There are several ways to cut and trim it.

The foam is often polyurethane so you do NOT want to use a hot wire because of the fumes and also because it melts into stickiness rather than basically evaporating like polystyrene foam. Hotwire cutters are for polystyrene foam.

Professionals often use an old fashioned electric carving knives. It is faster and easier than a sharp serrated bread knife which also works. A hacksaw with a big toothed blade works as well.

We have heard about a “soft materials blade” you can get for a jigsaw that will do the job.

For 2" foam you could use a snap off utility blade. Extend the blade and make sure it is really sharp.

Use your off hand (the one not holding the knife) to gently spread apart the foam above/behind the blade to keep it from gripping the blade.

There is absolutely skill involved in getting a clean cut and the stuff is not very forgiving. Don’t imagine you’re going to get that factory edge with whatever you do, but you can absolutely get it clean enough that when it’s done, you won’t be able to tell which edge you cut, assuming you get it pretty square. That’ll be the trick.

Remember you want your foam a tad bigger than your cover. You want the foam insert to be under some compression in the finished cushion. So don’t go too small.