It is the most extensively used type of glass for windows in all types of buildings. A variety of classes, classifies quality according to defects. The most commonly used grades are A and B. Grade A is used for the better class of buildings where appearance is mandatory, and B is used for industrial buildings, residences, basements, etc.

Comparing to thickness, clear window glass is classified as ‘‘single-strength’’ about 3⁄32 in thick; ‘‘double-strength’’ about 1⁄8 in thick; and ‘‘heavy-sheet’’ up to 7⁄32 in thick.
Maximum sizes are as follows:
single-strength, 40 x 50 in;
doublestrength, 60 x 80 in; and
heavy sheet, 76 x 120 in.

Because of flexibility, single strength and double strength shall never be used in areas exceeding 12 ft2, and for appearance areas should not exceed 7 ft2.

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