Base Line Height


Korel_Design
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6 minutes ago, Korel_Design said:

If you were drawing a hip roof that had a combination of two different roof pitches, such as 12:12 on the left to right slopes and 8:12 on the front to back slopes, shouldn't the Base Line Heights be the same? 

 

This would depend entirely on WHERE your baseline is located.  If your baseline is located out at your fascia then the answer is probably yes.  If your baseline is located above your exterior wall than the answer is probably no.

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Think of the baseline as the teetering point for your roof plane.  If you start to drop the portion of roof above this teetering point (lower the pitch) then the portion below will raise up.  If you raise the portion of roof above that teetering point (increase pitch) then the portion below will drop down...

 

Baseline 1.jpg

Baseline 2.jpg

Baseline 3.jpg

Baseline 4.jpg

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3 minutes ago, javatom said:

If the eave depth and fascia heights match, the roof edges will seam together nicely.

If the eave (overhang) of a 12:12 roof is the same as the eave of a 8:12 roof then they have to be on different plate heights. The intersecting roofs the are 90° apart. The left to right pitch is 12:12. The front to back is 8:12. Therefore, the eave depth and the fascia height can not be the same.

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7 minutes ago, Korel_Design said:

If the eave (overhang) of a 12:12 roof is the same as the eave of a 8:12 roof then they have to be on different plate heights. The intersecting roofs the are 90° apart. The left to right pitch is 12:12. The front to back is 8:12. Therefore, the eave depth and the fascia height can not be the same.

 

This is only true if your wall heights, rafter depth, and seat cut are all identical.  There are obviously a lot of variables. 

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9 minutes ago, Korel_Design said:

The term "Base Line" takes getting use to. I grew up framing houses where the bottom of the rafter was notched (Bird's Mouth) where it was teetering on the inside of the plate height. 

 

You can always move your baseline to get what you're after or manually set the Birdsmouth Seat to the depth of your wall.  I was just showing how Chief has it set up by default.

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21 hours ago, Korel_Design said:

....... the framers in the field will just call me a knuckle head and do it their way. ;)

I wish!! Usually you are right, but a few weeks ago a framer/builder called me because I had used a bastard hip on the rear of a porch to tie into the rear main roof line. He couldn't figure out how to do. Kept telling the client he would have to redo all of the porch framing to make it work. To keep the client from exploding (which he was on the verge of) I did a 3D overview of the framing and sent him a couple of jpg's to his cell phone. So that's the way you do it? :wacko:

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