silly math question to find the pitch of a roof... I should know this!

[MulePacker]

I didn't measure my roof pitch correctly... I feel so silly..

lets say top plate line is 0" (interior measurements)

From top plate to center of ridge is 16'6" at a Level line.

From plate line to ridge at a PLUMB line is 23"

What is the Pitch? Ha

[Levis]

23" / 16'-6" (or 198") = 0.116162 x 12" = 1 3/8 in 12

[MulePacker]

ahh yes.. dont laugh!

[Joe Carrick]

Another way to put this is:

x/12 = vert/horiz
x/12 = 23/198
x = 12*(23/198)
x = 1.3939

close enough to 1.375 to call it 1-3/8"

just a simple algebraic ratio - and solve for x

[gawdzira]

sohcahtoa.

[mgabriel]

Not entirely correct....if your plumb measurement is from the top of the top plate to the top of the ridge. You would need to subtract your heel height (at the point of measurement at the top plate) from your plumb measurement to get your true pitch. Will it make a significant difference in your calculations, probably not, but you asked....

[sutcac]

Heh, heh. He said "sohcahtoa". Heh, heh.

[Allen42acj]

You can just draw the lines in Chief and open the line to check the angle..

[Texian]

Or......

(Smartphone + Roof Pitch App) X (Learning Curve Time + Ladder Setup Time) = Roof Pitch

I use the free app called Pitch Gauge and calibrated with a couple of triangles

[alan11]

Based on your dimensions, the answer is Roof Pitch (Theta) = arctan (23 / 198), which means roof pitch = 6.625 degrees.

Alan

[gawdzira]

Alan11, I did not realize you could turn it up to 11?

[perryh]

Do what I do , just get a digital level and put it up against the rafter and set it to show the pitch.

[Glenn Woodward]

Perry,

You can get apps for the iphone or ipad that do that as well.

[perryh]

Perry,

You can get apps for the iphone or ipad that do that as well.

Yes, even my Disto laser measurer has an angle meter built in.