Why Restrictions are Needed
The stairway is a dangerous area where a slip can mean serious injury. Windows around stairs have specific height and glass requires based on that height to prevent a slip on the stairs from becoming a fall through the window. Tougher glass requirements for low windows ensure that a person falling against the glass cannot break it.
Tempered Safety Glass
Tempered glass has been heat-treated making it stronger, but it must be tempered after cutting. You cannot cut a tempered glass pane down to size because it breaks. When tempered glass breaks, it does not shatter like regular window glass. It breaks into small nuggets. To determine if your windows are tempered, look for what is known as a "bug." This stamped image on the windowpane says the glass is tempered and it gives the thickness.
Distance from Stairs
The height of the window will not matter if the window is within 36 inches of the stairs. In such a case, install safety glass on the window to prevent an accident. Windows located within 60 inches of the bottom tread in any direction must also have safety glass, according to "Code Check Complete: An Illustrated Guide to the Building, Mechanical, and Electrical Codes," by Redwood Kardon, et al. Portions of the window higher than 60 inches above the stairs do not need safety glass.
Minimum Height from Floor
As with other windows in the house, the minimum height windows are from the ground is dictated by code. Measured from the landing or the highest stair under the window, there must be 24 inches of space, according to “Code Check Complete: An Illustrated Guide to the Building, Mechanical, and Electrical Codes." If your window has openings of less than 4 inches or guards covering it, you can install it lower.