View Single Post
  #5   Report Post  
Posted to alt.home.repair
marson marson is offline
external usenet poster
 
Posts: 478
Default Angle Cut for Facia on Gable Rake Side

On Feb 29, 8:52 pm, "Pat" wrote:
wrote in message

...

On Feb 29, 8:35 pm, "Pat" wrote:
wrote in message


...


I have a 3/12 pitch roof (3 inch's of rise for each 12 inch's of
run). I am installing Facia Board (1x8 pine) and my question concerns
the proper angle cut at the ridge of the roof. The right angle
triangle by definition of the 3/12 pitch has a 90degree angle at the
top plate center, a 14degree angle at the eave and a 76degree angle at
the ridge (for a total of 180degrees in the right triangle)


Vision a gable roof and the two right triangles would fit against each
other and form the gable. The two 76degree angles would be together
at the ridge of the roof. What would the plumb cut be in degrees for
the facia board on the ridge? I thought that with two 76degree angles
combined that I would split that in half for the cut, but obviously
that is wrong. The angle cut is not 76degrees and my miter saw
wouldn't cut that anyway. I think the angle cut may be 14degrees for
each of the facia boards joining at the ridge on the two 76degree
angles, but I don't know why I think that or how the angle is actually
calculated.


Thanks for any assistance with the angle cut.


David


90 minus 76 = 14


14degrees makes sense, but why am I subtracting from 90degress when
the angle is 76 degrees? Guess I should have paid more attention in
school huh?


Probably need a blackboard so I can draw you a picture. A miter saw makes a
90 degree angle with the fence. To cut a 76 degree angle on the board you
set the saw to 14 degrees.


What most carpenters would do is hold their speed squares on the 3/12
mark, and look down and see what angle the plumb cut corresponds to.
Mathematically orientated carpenters can use a scientific calculator
and enter 3 / 12 INV TAN. Which I guess is technically the angle of
the rafter to the ceiling joist, but it is also the angle that you set
your miter saw to. Like Paul said.