Door is hard to lift manually

The door is difficult to lift by hand. This guide covers spring balance, cable, roller, and track-friction causes.

First, if an operator is installed, ensure the emergency release has been pulled to disconnect the door from the operator. Now try lifting the door from the bottom. How would you describe the effort required?

Safety

Only pull the emergency release when the door is in the fully closed position. If the door is partially open and the springs are broken, the door may drop rapidly under its own weight.
Lift with your legs, not your back. If the door feels dangerously heavy (like lifting dead weight), stop immediately. The springs are likely broken. A falling door can cause severe injury.