I would just like to add a few thoughts for anyone that may be interested.
Prior to the early 1960's and the advent of the Stanley "Powerlock" Tape
the standard procedure used to lay out wall plates, was with the use of the
Carpenter's steel square, meaning a common framing square or rafter square.
The square would be slid down the plates and a line squared across at the
desired spacing, aligning one end of the square with the prior mark. A
slight error could creep in over longer distances, but it was minor.

The most commonly used center-to-center spacing in stick framing was  12",
16", 18" & 24". In the 1916 Stanley Catalog, the dozen or so Steel Square
models were offered with either a 16" or 18" tongue, the body length was a
standard 24". Vintage squares with a 18" tongue are uncommon but not rare.
In modern times the 18" spacing has been abandoned and the 12" spacing is
uncommon.

In 19th century balloon framing it was mandatory for floor joists to follow
stud spacing and in modern platform (or western) stick framing it is good
practice to locate joists directly over studs. The spacing of floor joists,
12", 16" or 24" is determined by the span, the width of the joist, the
species of wood and the type of flooring to be applied. The key factor is
the allowable amount of deflection, you want a fairly stiff floor. If you
were going to lay down a 2" thick subfloor, you could use a 24" joist
spacing, providing the overall span was minimal and the joists were wide
enough. To a lesser extent, the same is true of wall studs, ceiling joists
and rafters, the center-to-center spacing depends on the material to be
applied, the span and the width of the framing member.

Prior to the popularity of plywood, 1X wood sheathing was commonly used for
walls, floors and roofs. Interiors were lath and plaster. The popularity of
the 16" (or 18") stud spacing was based on the need for resistance to
deflection, to provide a firm finished surface. As an example, you wouldn't
put 5/16" lath over studs spaced 48" apart.

The main reason for the specific spacing of 12", 16" & 24" was also to
reduce waste. Construction lumber (sheathing) was generally supplied to the
job site in 2' increments, a mixture of 8',10',12',14' & 16' lengths.

Regards,
Tom

On Apr 19, 2014, at 1:18 AM, Judy Opfell  wrote:

> [snip] The spacing of floor joists,
> 12", 16" or 24" is determined by the span, the width of the joist, the
> species of wood and the type of flooring to be applied. The key factor is
> the allowable amount of deflection, you want a fairly stiff floor. If you
> were going to lay down a 2" thick subfloor, you could use a 24" joist
> spacing, providing the overall span was minimal and the joists were wide
> enough. To a lesser extent, the same is true of wall studs, ceiling joists
> and rafters, the center-to-center spacing depends on the material to be
> applied, the span and the width of the framing member.
> [snip]

        A thought just occurred to me.  When Aunt Tilly was waltzed across the
living room floor in 1910 she likely weighed 180-200 lbs.  Now she likely weighs
250-300, and Uncle Buck weighs 300-350.  That is quite the china-cabinet-
rattling dynamic load.  One sees items in the news about the need to increase
chair sizes in public spaces.  Has their been a need to increase joist sizes?

Regards,
Steve

I think the need to increase chair sizes has largely to do with changes
in average height rather than weight.  We've become much taller and the
average chair height has not.  Folding chairs tend to be 16 1/2 inches
high, others around 17 1/2 inches high.  That's too short for our taller
population.  Aunt Tilly was not much taller than five feet in 1910, 
while
women.  My grandmother (born in 1900) was thought tall at 5'4".  Now I
suspect 5'4" is below average.

Mike in Sacto


> 	A thought just occurred to me.  When Aunt Tilly was waltzed across
> the living room floor in 1910 she likely weighed 180-200 lbs.  Now she
> likely weighs 250-300, and Uncle Buck weighs 300-350.  That is quite
> the china-cabinet-rattling dynamic load.  One sees items in the news
> about the need to increase chair sizes in public spaces.  Has their
> been a need to increase joist sizes?
>

On 4/19/2014 7:54 AM, Steve Reynolds wrote:
> One sees items in the news about the need to increase chair sizes in public
spaces.


But not airplane seats eh? They seem to keep getting smaller.