The Black Diamond

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Moderator Post: > Reading the Tape by Handyman on 07/26/2005

The black diamond on the top scale starting at 19.2 inches is for truss layouts for 8-foot sheet goods—also referred to as the "black truss" markings. Originally the 19.2 was used in metric layouts. If you divide five into 96 inches (8 feet), it will give 19.2 inches—in other words, 5 trusses per sheet.

On the other hand, the "red stud" marking every 16 inches allows for a standard layout of six studs per 8-foot (96") section. Look at it this way: there are 5 black diamonds or 6 stud markings in an 8-foot width.

Truss Example:

Count the black diamonds and notice that the fifth one lands on 8 feet. Since an 8-foot sheet spans half the distance of its size, then the second course would start at the halfway point (4 feet) or, in this case, at the third diamond, which is slightly over 3' 2 3/8". The 19.2 black truss marking is just a better span if you don't want to span 24 inches on center with today's undersized plywood. However, I prefer 16-inch on center for truss layout—especially if ½" wallboard will be attached to the bottom cord of trusses. Even with 19.2 layout, I would recommend using 5/8" or 3/4" plywood and 5/8" wallboard.