When you are looking for the bug, remember that it will be in a corner of the glass, very small, and barely legible because it is a light etching of the glass surface. When a door or window has multiple small glass panes, at least one pane must have the full bug, and the others only need to have a “16 CFR 1201” marking. In some cases, the bug will be partially or completely concealed by the frame.


    Laminated glass is more difficult to identify. It may not have a bug, because most building codes don’t require it and, If there is a bug, it may reference a DOT (Department of Transportation) approval code. Also, laminated glass can be cut to size after manufacturing, and the bug may have been cut off. Tempered glass will shatter if cut or drilled after manufacturing, and must be tempered to the exact size required, so the bug is there somewhere.

    Industry professionals identify unmarked laminated glass by the multiple reflections visible when you put an object next to the glass. Glass that is not laminated shows only two reflections from the two surfaces of the glass.

     A federal law mandates safety glass for areas that have the possibility of impact by a person, such as sliding glass doors and low windows in walking areas. The stained glass panel at foot level at a stair landing, shown below, is an example of a window that should be safety glass. Pretty, but very dangerous.

     The law did not go into effect until July 6th, 1977, so earlier windows and doors may not be safety glass. Older sliding glass doors are considered so dangerous by some building departments, such as Los Angeles, that they are required to be replaced or protected with safety film when the property is sold.

ScotchShield®, manufactured by 3M, is one of several brands of safety film that can be applied to old doors and windows to provide shatter protection. An installer typically adds a small label indicating that the glass now meets the CPSC standard for safety glass after completing the work.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection. -


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Glass is tempered during the manufacturing process by rapidly cooling the outer surfaces with chilled air, but leaving the inner core still viscous. When the glass has completely cooled, the core is in tension and outer layers are in compression. This makes it four times more resistant to impact than regular (annealed) glass and, when shattered, it fractures perpendicular to the face of the glass into small pebble-size pieces.

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