I lifted mine but probably shouldn't have. I kept sticking stuff under it, a crate, a stool, until I was able to put two step ladders under. The higher it goes, the lighter it becomes since now the horizontal roller starts to take on some of the weight. But it's super dangerous.

When the spring broke, one of them snapped, and the quickly dropping door snapped the other one as well. Surprisingly it didn't damage the door itself. It's a double door so had two springs.

I toyed with the idea of replacing the springs myself but after asking around doing a few searches decided it's best I pay a professional to do it.

I guess it depends what you make it of, doesn't it? Growing up I had a typical corrugated roller door, it was very easy for me as a kid to open it with some of the weight supported by the roller. I think they have springs but they're not as extreme as the tilt/section doors. Apparently you can throw a motor on the end similar to roller blind kits, and they wouldn't have to deal with as much weight as a spring-based door. Of course, I do not live in an extreme weather area (yet).

Could it be made of lighter material. Ironic how the garage door is perhaps the most armoured part of a house

450lbs but because it is not straight up but up and back that probably gives a 2-1 leverage so 225lb or 100kg. using your legs to lift it would be in the realm of a regular male weight trainer but not the average jo or jane.

The opener doesn't support the weight of the door, that's the springs.

That's why it's surprising how heavy the doors are. Springs make it very easy open and close the garage doors with one hand, so we get used to it. When springs snap, (they all have a limited lifetime) the doors suddenly feel surprisingly heavy.

Don't know your situation but I'd dare to suggest fix the opener, simply because it means not standing right underneath, you or your kid, when the springs snap. It was quite startling when that happened.

Are the springs still in place? If yes, then they are still doing most of the work.