Rule of thumb: if it opens for a car, it's residential; if it opens for a truck, forklift, or loading dock, it's commercial — and that single difference changes almost everything about the door, from the steel gauge to how often the springs need attention. The exceptions are the homes that blur the line: oversized RV garages, detached workshops, and hobby barns often use commercial-grade doors even though they sit on a residential lot. So if your spouse points at a thick steel door on a neighbor's workshop and says "that's basically what we have," they might actually be right — it depends on the building, not just the zip code.