need help with shed roof framing!


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Old 10-09-08, 07:14 PM
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need help with shed roof framing!

I am finishing my shed this weekend and I need help calculating the correct pitch of the roof. I have found all sorts of information but nothing that correctly tells me how long to make my rafters. The shed is just over 8 feet wide and 13 feet long. Please any information would be great or just a point in the right direction!

-Lucas
 
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Old 10-09-08, 07:53 PM
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let us know a little more info? do you want an over hang? if so will you put soffit ventilation, or in that case what type of ventilation will you use? here is a site that gives an easy example.

roofgenius.com/roofpitch.htm
 
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Old 10-09-08, 07:58 PM
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Originally Posted by Im trying
let us know a little more info? do you want an over hang? if so will you put soffit ventilation, or in that case what type of ventilation will you use? here is a site that gives an easy example.

roofgenius.com/roofpitch.htm
Yes some sort of overhang would be ideal, probably about 8 inches and i would use soffit ventilation

-Lucas
 
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Old 10-10-08, 04:01 PM
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For aesthetic reasons only, how tall are the walls on the shed?

I'm assuming you have 4 walls up right now? Do you know their exact length?
 
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Old 10-10-08, 05:05 PM
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Originally Posted by Rob_C
For aesthetic reasons only, how tall are the walls on the shed?

I'm assuming you have 4 walls up right now? Do you know their exact length?
Walls are 83" high, shed is exactly 146" long and 108" wide

-Lucas
 
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Old 10-10-08, 11:44 PM
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I had nothing else to do on a Friday night, so i decided to work out your roof. I ended up cutting up beer boxes to do layouts.

Hopefully these numbers will work out for you, but always measure and check everything before you cut, nothing is ever perfect. I made sure to show all my work, so it’s easy to switch out any numbers that may change.

I will refer to many of these terms:




First you have to decide on the pitch of your roof. For a shed like yours, i would go with a 6/12 pitch

The front is 108” wide, so 54”, or 4.5’ to the center.
The best boards to use for the rafters will be 2”x4”x12’

Take a board, and as close to the end as possible, draw a line as shown:



This line will be the ridge plumb cut (1). Since the rafters meet in the middle on a ridge board, we will have to make another mark to cut the rafter back for this (but don't cut anything yet). Make a parallel line 3/4” inside the first line you drew. (3/4” is half the width of your ridge board, assuming you’re using 2x4s)

Now take your framing square, and find the common rafter table (don't worry if it doesn't have one, i'll do the math anyways). Look under the 6” mark, and you should see 13.42

Multiply 13.42 by the length of the total run 4.5’, which comes out to 60.39, or around 60 3/8”. This is the Determined Line Length(3) in the reference picture

Measure down 60 3/8” from the top of your ridge plumb line (1). draw a line parallel to your ridge in the same way described before that will meet this mark. This will be your seat cut plumb line(4) From this mark. Draw a square line 1 1/2” from the bottom of the plumb line, forming the notch where the rafter will sit on your wall.

I wouldn’t worry about the soffit/fascia cuts until your rafters are all cut and in place.

I tried this layout on a number of different pitches, and this is the one that i was most comfortable with, but by all means experiment with what you think will look best

It is also worth noting that i used the front measurement you gave me (108”) in my calculations. If you haven’t put your sheathing on yet, you need to adjust this number accordingly

I hope this helps you make sense of how to build a roof.

I have never personally used this method before, so please, good or bad, come back and let me know how it goes.

good luck!
 
 

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