A comment sometimes voiced about patio doors is the height of the door sill – and the concern that it could be a hazard if someone were to trip on it. Sliding patio and other doors of this nature are designed to meet specific performance guidelines in accordance to testing regimens created by the American Architectural Manufacturers Association (AAMA) and accepted by the American National Standards Institute (ANSI) and various building codes.
To achieve what the industry recognizes as "high performance” and to manufacture doors with the water resistance level homeowners need, a higher sill height is required. This is necessary to resist water penetration – especially in heavy or severe rain and storms. Virtually all comparable products that are designed to have similar performance have a high sill height.
Unfortunately there just is no other way to achieve the necessary performance levels. I, too, have high-performance patio doors in my home, with four small grandchildren who use the doors regularly. Fortunately we've never experienced a tripping problem.
For homeowners who believe the sill height is a concern, I'd suggest perhaps some sort of bright tape at the sill when the door is in the open position to attract the attention of visitors. It would be nice to have high-performance doors with a lower sill, but the science just doesn’t allow it.
I hope this adequately explains the need for higher sill designs on high-performance doors.