Interpretation #8825

Original Request

Code Version: 2021
Code: BUILDING
Code Description
Chapter
Section: 202 - Definitions
Topic: HEIGHT, THRESHOLD BUILDING

Question

Please explain how to apply the definition of Threshold Building Height to 2 buildings on the same lot. One roof is an existing low slope roof with a height of 34-ft. The other is a new addition with a low slope roof at a height of 53-ft. Would this not be a threshold building because the mean height between the two roofs is 42'-6" or does the measurement go to the highest point on each building, the mean of the highest roof or some other calculation?

Answer Published 09/26/2023 at 10:25 AM

The 53 ft tall building may fall under the definition of THRESHOLD BUILDING. Please refer to the definition of a threshold building found in Chapter 2 of the Florida Building Code, Building volume and attached in the commentary for convenience. The other does not appear to be a threshold building, based on height. It is important to look at the definition as there are 3 criteria that can establish a threshold building, height is only one of them. If the buildings are structurally independent, the smaller building cannot be considered a THRESHOLD BUILDING based on height, unless it falls into the other portion(s) of the definition. Mean Roof Height is determined per building and not by combining two independent buildings. It is also important to note the number of stories in the building as defined for a threshold building, along with the use of the structure.

Commentary

Definitions pertinent to this interpretation from the Florida Building Code 7th Edition, Building volume: GRADE PLANE. A reference plane representing the average of finished ground level adjoining the building at exterior walls. Where the finished ground level slopes away from the exterior walls, the reference plane shall be established by the lowest points within the area between the building and the lot line or, where the lot line is more than 6 feet (1829 mm) from the building, between the building and a point 6 feet (1829 mm) from the building. HEIGHT, BUILDING. The vertical distance from grade plane to the average height of the highest roof surface. HEIGHT, THRESHOLD BUILDING. The height of the building is at the mean distance between the eaves and the ridge of the roofing structure. If the distance from grade to the line which is the mean distance between the eaves and the ridge of the roofing structure is more than 50 feet (16 240 mm), the building is to be considered a “threshold building” within the contemplation of the Threshold Building Act. THRESHOLD BUILDING. In accordance with Florida Statute, any building which is greater than 3 stories or 50 feet (15 240 mm) in height, or which has an assembly occupancy classification that exceeds 5,000 square feet (464.52 m2) in area and an occupant content of greater than 500 persons.