This is because shower doors often are made of materials such as glass that can easily break and pose a danger.
Shower door height code.
A minimum space of 21 inches must be planned in front of lavatory toilet bidet and tub.
Threshold heights vary from 1 2 to 2 in many shower and pan designs though some have more or fewer options based on the shower or pan s size.
That is 30 inches by 30 inches.
A minimum space of 24 inches must be planned in front of a shower entry.
Shower floor minimum size is usually mandated to be at least 30 inches square.
As you enter the bathroom the door needs to be able to swing its width into the room without.
Shower controls should be placed at a height 40 50 102 127 cm above the shower floor and out of direct line of the water path to avoid being caught in extremely cold or hot water when operating.
Because shower doors are usually glass and can break and because of other access issues bathroom code states that shower doors need to have at least 24 inches of opening clearance.
This is also a safety issue because users who are forced to slip around narrow door openings are more prone to slipping on the floor.
The shower door needs to have an opening clearance of at least 24 inches.
So says the building code.
Shower maximum sizes are not mandated but minimum sizes are regulated.
For assistance with your specific situation contact your shower manufacturer.
There s no doubt threshold height can be confusing.