Final answer:
The maximum height difference without a guard in a Part 9 building is usually 30 inches, but one must consult the local building code for precise regulations as this can vary by region.
Step-by-step explanation:
The maximum height difference you can have without a guard in a Part 9 building, which refers to the building code requirements typically related to residential construction, is dependent on specific regional building codes. However, in many regions governed by the International Building Code or similar regulations, the typical maximum height difference allowed is 30 inches (76 centimeters). It is important to consult the local building code for the exact figure as it can vary, but the general rule of thumb is that any elevation change greater than this requires a guard or railing to prevent falls and ensure safety.