I’m looking at a set of historic building plans.
They call out a 1/3 pitch roof. But, if I calculate the pitch using the rise and run shown on the plans, I get an 8/12 pitch.
Was there an old style of roof call outs, that I should be aware of?
I’m looking at a set of historic building plans.
They call out a 1/3 pitch roof. But, if I calculate the pitch using the rise and run shown on the plans, I get an 8/12 pitch.
Was there an old style of roof call outs, that I should be aware of?
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Replies
Definitely old style. The number is an argument against 24.
i.e. 1/3 of 24 is 8, so a 1/3 pitch is 8/12.
Or 12 is half of 24, so a half pitch is 12/12. A "full pitch" is 24/12.
It's a pain in the neck - Guess that's why they quit using it.
On the other hand, it tells you how tall the roof is. The 1/3 pitch is one third as tall as it is wide.
One of the guys explained it a bit.
One of the guys that works for me explained it a bit. He also said that it is easier on the old framing squares, as some of them had a direct scale for it on the 18-inch leg.
Roof pitch and roof slope are the same but they are expressed differently. Pitch is described as a fraction, slope is described as rise per foot of run. A roof that has a rise of 4" per 1' of run, 4/12 would be a 1/3 pitch.
Hammer look at the original post, they arent the same.
That is what caused me to post, If I calc the rise/over the run based on the dimension, I get an 8/12, or 2/3 pitch.
The stated pitch drawings is 1/3.
If you read the first post I did in this thread it explains it. It's a very old way of expressing roof slopes, and has nothing to do with conventional ratios expressed as a number over 12.
Yeah, as I suggested, I'd bet that it comes from observing the finished roof and noting that the height is, eg, 1/3rd the width.