What Size Window Has to Be Tempered? A Florida Code Guide

If you’re asking what size window has to be tempered by code, size is only part of the answer. The Florida Building Code also looks at where the glass sits, how high its bottom edge starts, and what is nearby. This guide explains those pieces in plain words for South Florida homeowners, buyers, and renovators. It’s general information, so your local building department decides how the rules apply to your project.

Short answer: tempering depends on where the glass sits, not only its size

Window size alone doesn’t settle the question. The code treats certain spots as hazardous locations, which it defines in Section 2406.4. So start with the location of the glass, then look at height and area. Florida’s code has more than one edition, including the 8th Edition (2023) and the 9th Edition (2026). Confirm which one applies to your project with the local building department.

Bottom-edge height: where the glass starts matters most

The bottom edge of the glass is the height to measure, not the top of the window. Start from the finished floor, which is the surface you actually walk on. That means the tile or carpet, not the subfloor beneath it. A window with a low bottom edge can raise a glazing question even when the window looks ordinary. Write down the bottom edge and top edge for each pane. Those two numbers, plus the pane size, are the core inputs. Having them written down before you call makes any plan review easier.

Glass area: measure each pane on its own

Glass area is the width times the height of each pane. A pane 3 feet wide and 4 feet tall is 12 square feet. Measure the glass itself, not the outside of the frame, because the frame takes up space the glass does not. A large picture window may be one pane, while a double-hung window has two sashes with separate glass. Area works together with height and location, so one number rarely answers the question alone. Keep a simple list with each pane’s width, height, bottom-edge height, and area.

Location triggers: doors, stairs, and wet areas

Location can matter even when a window is small. Glass near a door, a stair, or a tub or shower is worth raising with the building department before you order glass. Exterior doors need extra attention too. The Florida Building Code, Residential analysis of changes notes a revision to the water intrusion testing exception for doors that an overhang protects. A door with a short overhang may not qualify for that exception. Ask your installer to show how the overhang measures against the code figures.

How tempering differs from egress sizing and impact glass

Tempering, egress, and impact glass are three separate rules, and people often mix them up. Tempering is a glass safety rule. Egress is about an opening you can use to get out in an emergency. A tempered window is not automatically an escape opening, and an escape opening is not automatically tempered. Impact glass is a third rule. A Miami-Dade product approval notice shows one impact product tested and accepted for Florida Building Code compliance, including Miami-Dade and High Velocity Hurricane Zone requirements. An impact-rated unit can also be tempered. In a multi-pane unit in a hazardous location, every pane must meet the safety glazing requirements.

What to check on your window or project before you decide

Start with five measurements: bottom-edge height, top-edge height, width and height of each pane, distance to the nearest door or stair, and whether the window sits in a bathroom or shower area. For impact products, note the product approval number. Under a Florida Building Commission code supplement, certain projects in existing one-family or two-family dwellings or townhouses may be exempt from some requirements when listed conditions are met. Flashing must also meet the code when windows are replaced, per the Existing Building analysis for Section 707.4.

Talk through your window situation with our team

You might be reading this because an inspector flagged a window, a home you’re buying has glass nobody can explain, or a renovation is already underway. A project can stall while the question stays open, and that’s stressful. Knowing what size window has to be tempered by code starts with the location, height, and area of each pane. If a window in your plans may need tempered glass, contact ASP Superhome for a free, confidential first consultation with no obligation to continue.