Dumb Question About Division Marks

joasis

Ok, I am new here, but didn't see anything relevant about this in a search, so here goes: My metal building salesman called me a few days back and asked me to look at my tape measure, then asked why there is a "diamond" @ 19-3/16" and it repeats every 19+ inches til 8 feet, which it is exactly in the red above 8? I have done construction and steel a long time and have never known what these divisions are for, specifically. They divide 8/5 but for what? A search on the internet said rafters can be spaced this way to save material and still keep in 8 ft and 16 ft material, but really? So what do you guys think? I bet it is something I should have known and will look stupid when answered, but at least I can call my steel guy and say, see???

MJW

It could be a spacing for rafters, not sure. I have seen it on floor trusses. They are normally spaced 19 diamond on center.

maj

The black diamonds are @ 19 2/10" (nineteen, two tenths), It is another equal division of 8', which is the common sheathing size(4'x8').Alot of floor trusses and even dimensional floor joists are being spec'd @ 19.2, rafters and even studs can be layed out at 19.2(although it would be tough to insulate).Every 8' you are saving one joist, so for a whole house x 20 houses a year, well, you can see the savings.

Glasshousebltr

It's for floor truss with 3 1/2" cords. It leaves 15 1/2 inches for the underlayment to span.

Bob

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Bob

N.E.Bldg&Rest.LLC

This is from the stanley company

”The black diamond marks every 19.2" on our tape rule blades are for spacing joists and studs. Several wood product manufacturers offer Engineered Lumber as a substitute for conventional lumber. Span tables for these lumber products provide ratings for spacing of 12in., 16in., 19-3/16in., and 24in. If you multiply these dimensions by 8, 6, 5 and 4, respectively, you'll notice that you come up with 96in., the length of the panels that will be used for sub-flooring or sheathing. Engineered Lumber is usually specified by the architects and engineers who draw the plans. They take advantage of its strength by using fewer joists or studs where codes allow.”

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karma_carpentry

Yeah, I've been learned that it's for laying out 19.2" O.C. for 8' sheet materials. Only ever used it once, in a furred-out ceiling to improve the insulation value of the sprayed in foam - wanted more than 16" spacing but couldn't go to 24" with 1/2" rock on the ceiling.

Funny how I never noticed those marks until someone told me about it.

joasis

Me too Karma, until I was asked cause my steel guy thinks I should know, i never knew either...since my main business is steel buildings, roofing, and spec homes, I would have never guessed...and since everything we do is on slabs, I have never laid a joisted floor except on a basement, and we didn't do it with 19-2/10 spacing....