I have read your post and understand your question to be in relation to opening protection only when it comes to glazed or non-glazed openings. This is an interesting question as many parts of the Building Code are misinterpreted or falsely referenced, and this happens to be one of the sections that gets the most attention and is improperly understood. I’ll walk you through the process and try to explain:
Specifically, the first order of business is to understand the purpose and design of windows and non-glazed openings (operable and inoperable). Windows and exterior doors are structural, they distribute loads laterally throughout the exterior envelope and are a direct part of the mitigation of the structure, on an existing structure this sends us directly to chapter 5 in determining what and how the repair/replacement should be carried out. See reference below:
***2010 Florida Building Code: Existing Building 506.1 General. ***
Structural repairs shall be in compliance with this section and Section 501.2. Regardless of the extent of structural or nonstructural damage, dangerous conditions shall be eliminated. Regardless of the scope of repair, new structural members and connections used for repair or rehabilitation shall comply with the detailing provisions of the Florida Building Code, Building for new buildings of similar structure, purpose and location.
As you can see, any repair or alteration of a structural component in an existing building requires compliance with the Florida Building Code: Building for new buildings of similar structure, purpose, and location. What this is telling you is there is more to consider than just opening protection, design pressure must also be considered, and for this we go to the exact title code being referenced:
***606.4 Replacement of windows and doors. ***
The replacement of garage doors, exterior doors, skylight, operative and inoperative windows shall be designed and constructed to comply with Chapter 16 of the Florida Building Code, Building.
1. Opening protection exception: For one- and two-family dwellings constructed under codes other than the Florida Building Code and located in windborne debris regions, the replacement of garage doors and exterior doors with glazing, sliding glass doors, glass patio doors, skylights, and operable and inoperable windows within any 12-month period shall not be required to have opening protection but shall be designed for wind pressures for enclosed buildings, provided the aggregate area of the glazing in the replaced components does not exceed 25 percent of the aggregate area of the glazed openings in the dwelling or dwelling unit.
2. Opening protection exception for High Velocity Hurricane Zones: For one- and two-family dwellings constructed under codes prior to September 1, 1994 the replacement of exterior doors with glazing, sliding glass doors, glass patio doors, skylights, and operable and inoperable windows within any 12 month period shall not be required to have opening protection provided the aggregate area of the glazing in the replaced components does not exceed 25 percent of the aggregate area of the glazed openings in the dwelling or dwelling unit.
The code specifically tells us that the structural alteration must consider the design pressure of the building envelope as part of the “enclosed building”, the opening protection is the only part of the exemption that is limited by glazing area. With that in mind, if the in-place glazing does not meet the requirements of design pressure, it is not in compliance with the Florida Building Code: Building as required.
As you can see, impact protection is not required provided less than 25% of the glazed openings are replaced. But, the openings AND structure must be in compliance with like new structure of similar construction and be design pressure rated. This means all windows that are part of the exterior structure must be in compliance with the Florida Building Code: Building for design pressure as stated in the first code reference.
Once you alter the structure of an existing building, it is required to be in compliance with the provisions of the Florida Building Code: Building….the exception is for opening protection only, not for design pressure. Many of the things you see happening at the building department that seem to alter or give permission to alter the stated code are false. And, building departments and officials can actually be held accountable for this.
The AHJ is allowed to alter chapter 1 of the Florida Building Code only, they can allow local approval and must show compliance with minimum code standards to do so. I recently had a building official tell me they allow 30% of the glazing to be altered without impact protection, I bit my lip and decided it wasn’t worth the argument as the inspector was helping me with a structure I had just inspected.
In closing, the restriction on percentage to require opening protection has nothing to do with design pressure, which is required. You can’t alter a structure and make it less safe than previous, and any alteration to the structural components requires compliance with the Florida Building Code: Building. The only exemption is opening protection……
I hope this helps……good luck
Robert R. Sheppard