Measuring tapes are equipped with many different symbols to denote different meanings, one of which is a tiny black diamond. But exactly what these little signs mean is a question many internet users have asked over the years. Take, for instance, the Facebook post below:
Another post claimed that the black diamonds are used to “find the right position for wall studs” (archived here.)
On most measuring tapes, the black diamonds are spaced 19 3/16 inches apart to indicate the typical spacing of joists. Wall studs, on the other hand, are generally spaced either 16 or 12 inches apart.
We therefore rate the claim about studs as "False."
@jmg8tor Black diamond on tape measure #jmg8tor ♬ original sound - ??GATOR??
I-beam floor joists, or “I-joists,” are used in residential flooring and roof framing, according to the nonprofit trade association, APA – The Engineered Wood Association.
Tool manufacturer U.S. Tape further described the use of black diamonds on measuring tapes, writing on its website that:
The black diamonds which appear every 19 3/16” on metal tape measures are for spacing I-beam “timbers.” Several wood-product manufacturers offer I-beam “timbers” as a substitute for solid lumber floor joists.
The diamond marks on tape rule blades are for spacing these engineered floor joists in new construction. Because these beams can support more weight than their dimensional lumber counterpart, they often have different spacing requirements.
Span tables for these beams provide ratings for spacings of 12”, 16”, 19 3/16”, and 24”. If you multiply these dimensions by 8, 6, 5, and 4, respectively, you’ll find each comes to 96”, the length of the plywood panels used for sub-flooring.
Those diamond marks are there for builders who want to take advantage of the great strength of engineered I-beams by using fewer floor joists, with no loss of floor support.
Home Depot further confirmed that the black diamond or triangle shapes are called black truss marks, and are used to “indicate truss layouts of every 19 3/16 inches. This spacing is often used by some engineered joist manufacturers.”
Wall studs, on the other hand, are the boards that “function as framing elements” in a home to support its walls, according to the home improvement store Lowes. Measured on center, or from the center of each board, wall studs are generally spaced either 16 or 24 inches apart. On many tape measures, this is marked in red, noted Home Depot.
Measuring tapes are best used as a guide to determine where a stud may be, Montana-based contractor Chad Larrabee told Snopes.
Locating the studs in a wall is important for hanging heavy objects, as it provides support not offered by standard drywall found in homes. Though a measuring tape may be useful in mapping out where studs are located, it’s important to confirm their location using a stud finder, a device that scans the wall without penetrating it to find the edges of wood or metal boards and beams.
“Once you find your first stud, it usually is going to be on a 24- or 16-inch layout, so you can check your stud finder with a measuring tape. Stud finders [will] occasionally pick up things that aren’t studs,” Larabee told Snopes, adding that a combination of using a measuring tape and stud finder is a safe bet.