roof slope vs roof pitch

[Jerry Peck]

I know we started to discuss this once, then got side tracked, but ...

I was just looking through a 1939 4 volume set of Audels Carpenters & Builders Guide (only the 'Old Farts' here will remember those things) and came across the 'roof slope vs roof pitch' chart.

slope - pitch
2/12 - 1/12
4/12 - 1/6
6/12 - 1/4
8/12 - 1/3
10/12 - 5/12
12/12 - 1/2
14/12 - 7/12
16/12 - 2/3
18/12 - 3/4
20/12 - 5/6
22/12 - 11/12
24/12 - 1

You will notice that "pitch" is based on rise versus 2run.

With run = 12, that means "pitch" is rise vs 2run or 24

6/12 slope = 6/24 pitch = 1/4 pitch

This was based on the assumption that the roof started at the wall, rose to the ridge, then went back down to the other wall (2 runs for 1 rise).

If the roof rose 6 feet to the ridge, the ridge was 12 feet from the wall, then went back down 6 feet to the other wall 12 feet further, you had a rise of 6 feet over a run of 24 feet, or 6/24, reduced to the lowest common denominator = 1/4.

Remember, early buildings had roofs which were simple triangular structures, gable on one end, gable on the other, roof the same from gable to gable. Symmetry was the simplest and strongest way to build a roof.

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[Daniel Stone]

Hey Jerry...I have a complete set of 4 books that my father gave me...never could have framed without them.!

[Daniel Stone]

[Jerry Peck]

Daniel,

In COLOR too!

What year?

I got mine from my Dad too.

I've also got a 1951 4 volume set from him too. Alas, though, it also is still only the old black cover/binding.

Along with several old American Electricians Handbooks, from the 1940s and 1950s.

[Jerry McCarthy]

Carpenter's square is all you need. Mine (cica 1950) and the common pitch de jour in the San Francisco bay area tract homes (mostly ranch style) during the 50s, 60, and 70s was 4-1/2 & 12. Personally I liked either a 5 or 6 & 12 pitch.