Everything You Always Wanted to Know About Lumber Thickness

The thickness of kiln dried hardwood lumber is determined by measuring the distance between the two faces of a piece along the board's edge. Hardwood lumber is produced and sold rough sawn (prior to planing). Standard thickness refers to the rough sawn measurement, expressed in 1/4 inch increments, beginning with 3/4 inches. The number of 1/4" increments, or "quarters" is commonly used to describe lumber thickness. For example, a rough sawn board 1" thick is referred to as being "Four Quarter" because there are 4 - 1/4" increments in one inch. Hardwood lumber can be purchased planed or "surfaced" on two faces to customer specifications. The finished thickness, or thickness whereby all rough saw marks are eliminated, is 3/16" less than the rough thickness. The illustration below shows the standard kiln dried rough thicknesses offered by ITL.