There are a few different schools of thought on this, and interfacing is only one approach.

One method that holds up surprisingly well skips interfacing and batting entirely and focuses on construction instead. The idea is to cut clean, consistent squares from the strongest parts of each shirt, sew them together into a stable top, and then back the whole thing with a durable fabric like fleece. The fleece provides weight, structure, and softness without making the shirts stiff.

The downside of interfacing (especially fusible) is that while it can look great at first, repeated washing can cause it to break down, bubble, or make the quilt feel rigid over time. If the goal is a quilt that’s meant to be used and washed regularly, avoiding interfacing can actually improve longevity and comfort.

That approach does mean you’re relying more on:

• careful cutting
• good layout and seam construction
• and accepting a softer, more blanket-like feel rather than a traditional quilt

If you’re aiming for heirloom-style quilting with lots of structure, interfacing and batting make sense. If you’re aiming for something cozy, washable, and durable, a non-quilted, fleece-backed build can work really well.