Lumber size is often referred to as 4/4 (pronounced FOUR-QUARTER), 5/4 (FIVE-QUARTER), 6/4 (SIX-QUARTER), etc. This refers to the thickness of the lumber when it is first sawn and in its rough dimensions. 4/4 lumber is sawn in the rough to a full 1 inch. The size increases in 1/4″ increments. 5/4 lumber is sawn at one and one-quarter inches, or five 1/4 inch increments, 6/4 lumber is sawn at 1 1/2 inches, and so on.
When surfaced on both faces, the lumber typically measures approximately 1/4 inch less in thickness as compared to when it came from the sawmill. Goosebay’s 4/4 dressed lumber typically measures 13/16 inch. 5/4 is dressed to a full inch.