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# Determining rafter length

## Determining rafter length

#1
10-21-10, 08:09 PM
Member
Join Date: Jun 2005
Location: VA Beach
Posts: 25
Determining rafter length

I'm adding a small bathroom to the back of the house (10x14) and am coming up with three different numbers for rafter length (one by hand, two using online calculators). It's a simple roof 4/12 pitch, 14'1" outside to outside, 2/6 ridge board and 2/4 rafters.

Any advice/tips for figuring out length? I want to pre-cut so I can start nailing away once I have the joists hung.

Thanks,

Tim

#2
10-21-10, 10:01 PM
Group Moderator
Join Date: Dec 2004
Posts: 26,825
Well, I don't claim to be much of a framer, but if I just quickly do it by hand, I am coming up with a hair over 87 3/4", from the long point of your plumb cut at the ridge to the point on top of the rafter that is plumb above the outside wall cut of your birdsmouth.

What are you coming up with? Or are you going to leave us in suspense as to the various numbers you are coming up with?

#3
10-22-10, 07:03 AM
Member
Join Date: Jun 2005
Location: VA Beach
Posts: 25
X,

Using an online calculator (here Rafter Angle Calculator)

I get

95 7/8"

Using my excel spreadsheet I get 16' (I'm doing something wrong there.....)

The online calculator asks for overhang but I'm not sure if that means each overhang added together or just one side...

What I mean is, my overhang is 3" so I'm not sure if the calculator expects 3 or 6.

I'm sure I'm overthinking this, just want to make sure I get it right.

Thanks,

Tim

#4
10-22-10, 07:29 AM
Member
Join Date: Feb 2006
Location: USA
Posts: 6,380
Rafter

I get 91 7/16 in. for the top edge of the rafter(including overhang).

For total rafter width 14' 1" + 6" - 1.5" = 14' 5.5" /2 = 7' 2.75".

12.65/12 = 1.054 x 7' 2.75" = 91.43" rounded to 91 7/16"