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Tape measure markings #62733
02/25/06 01:46 PM
02/25/06 01:46 PM
e57  Offline OP
Joined: May 2003
Posts: 2,876
Found a GC holed up in his trailer trying to figure out this one: (Wracking the brain and internet)

What are the triangle, or diamond markings every 19.2" or 19-3/32" for?

Mark Heller
"Well - I oughta....." -Jackie Gleason
Work Gear for Electricians and the Trades
Re: Tape measure markings #62734
02/25/06 02:00 PM
02/25/06 02:00 PM
SolarPowered  Offline
Joined: Jul 2004
Posts: 625
Palo Alto, CA, USA
19.2" makes five joists every 8 feet. It's the intermediate density between 16" centers (six joists per 8') and 24" centers (four joists per 8').

Re: Tape measure markings #62735
02/25/06 02:01 PM
02/25/06 02:01 PM
wis-sparky  Offline
Joined: Jul 2005
Posts: 16
I've heard this one before, the measurement is for spacing floor joists - not seen too much in part of the country

Re: Tape measure markings #62736
02/25/06 10:40 PM
02/25/06 10:40 PM
Peter  Offline
Joined: Jun 2004
Posts: 92
San Diego
Those black diamonds are the cubit marks. You remember the story of God and Moses and the Ark? The cubit is God's pwesonal measure ment system and is based on the length of the forearm.
When Horatio Stanley, a very devout Christian, invented the tape measure in 1926, he included these cubit marks just in case someone might need to build another ark.
It so happens that an 8' plywood or gypsum board panel divided by 8 os exactly equal to 19.2" which is pretty close to 19 3/16ths".
This has proved useful in construction since it provides more joists that 2' on center but less than the traditional 16" on center.

Re: Tape measure markings #62737
02/26/06 12:29 AM
02/26/06 12:29 AM
Sandro  Offline
Joined: Dec 2001
Posts: 444
Stoney Creek, ON, Canada
Er, Moses and the ark?

Re: Tape measure markings #62738
02/26/06 01:14 AM
02/26/06 01:14 AM
JoeTestingEngr  Offline
Joined: Nov 2005
Posts: 800
Chicago, Il.
That's certainly different than the way Bill Cosby told the story! Riiiiiight. I'll have to dig out the record and give it another spin.

Re: Tape measure markings #62739
02/26/06 01:43 AM
02/26/06 01:43 AM
Larry Fine  Offline
Joined: Feb 2005
Posts: 693
Richmond, VA
Pete, I don't know what you've been doing tonight, but do you have enough to go around?

Larry Fine
Fine Electric Co.
Re: Tape measure markings #62740
02/26/06 04:03 AM
02/26/06 04:03 AM
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Pete I think someone has been pulling your Christin leg. [Linked Image]

From Stanley Tools knowledge base.

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.

No mention of a cubit.

I did find that 'cubits' range from 16 to 26 inches depending on who is doing the measuring.

Bob Badger
Construction & Maintenance Electrician
Re: Tape measure markings #62741
02/26/06 04:43 AM
02/26/06 04:43 AM
Alan Belson  Offline
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
Marks show the distance over ones head that a joke goes? [Linked Image]

Wood work but can't!
Re: Tape measure markings #62742
02/26/06 11:22 AM
02/26/06 11:22 AM
e57  Offline OP
Joined: May 2003
Posts: 2,876
Good answers gents!

Personally, I don't know the real answer...

So far, though:
  • 5 joist or stud layout alternative to 24"(4), or 16"(6) per 8' (Most logical answer)
  • Truss layout (Not mentioned here)
  • And the "Stanley Cubit" (Pete was not alone on this, there are many who prescribe to the same therory. *More on this in a minute...)
  • My favorite so far, and related to the one above. "It's a Masonic Order thing... You wouldn't understand." [Linked Image]

*Asked around to a bunch of old framers who note that it must have been around for some time, because they only ever see this lay out used in baloon frames in the early 1900's and prior. Well before plywood and sheet-rock, back when '2X4's' were 2X4".

Anyway, at this point, I think this is a Myth Busters Issue.

Mark Heller
"Well - I oughta....." -Jackie Gleason
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