What are the Small Black Diamonds on Tape Measures?

Ever noticed the little black diamonds or triangles on your tape measure? The diamonds start at the 19.2 inches mark on the tape and can be utilized to help correctly space the floor trusses for a 4×8 T&G sub-floor with a span rating of 20” o.c. The black diamonds provide a visual cue to help you work faster.

Of course there is a joist or Rimboard to start the framing but after that there are 5 open bays and 5 joists for each 4×8 sub-floor panel. So if you divide 96 inches (8 feet) by 5 (open bays), you get the required 19.2”o.c. for the 20”o.c. span rating on the sub-floor.

There are also marks to help you layout correct spacing for wall studs but we will put that in another post.

Tape Measures

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