Roof Framing Question

snuddenstang

I am building a 18x22 family room addition. This will be going on the right side of my 1 story ranch.
My current pitch is a 5/12 gable roof.
I have never done a roof system, 2 of my framing friends will help.
The addition will be tying into the original roof with a reverse gable. I am not going to frame the roof on both new top plates. I am going to make a more dramatic roof line. The outside right will lay on the new top plate but the left side will lay on the existing 5/12 roof.
The span will be 26'
12" soffit overhang
2x10 ridge beam
2x8 roof rafters
2x6 walls
The new roof will also be a 5/12
I would love some assistance on laying out the common rafters and ridge beam height.

Ntxnaildriver

If you can show me a drawing I will give it a shot.

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Joe Carola

For a 26' span herev is your rafter length and overhang length. I don't know where you got 26' span though.

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Joe Carola

snuddenstang

I got the span from the outside of the right top plate to the location on the existing roof where I want the new roof to land on the existing roof.

How do I figure how high to put the ridge beam?

snuddenstang

Joe, Thank you very much for your assistance. That is a HUGE help. I see you are also from NJ, small world.
How do I also figure out the lengths of the rafters where they fall on the 5/12 existing roof? I would also have to lay out the valley on that side of the roof.

osborn

I think hes talking about an overlay.

Tom R

I'm not really following exactly what you're doing here, - - but the height of your ridge would be exactly how it sounds, - - 5" of heigth for every 12" of length, - - so if for instance, - - your ridge is perpendicular to the 18' wall, - - that would be '9' (half of the 18) X the 5", - - so it would be 45" high.

If the ridge is running perpendicular to your 22' wall, - - it would be '11' (half of the 22) X 5", - - which would be 55" inches high (above your top plate) . . .

Jack Rafter

If you need a quick way to figure your roof try my calculator I just finished it

http://www.josephfusco.org/Roof_Fram...ulator_V1.html

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Tom R

Bastard hip, - - err, - - I mean, - - hip bastard . . . J/K Joe

Nice . . .

Joe Carola

You don't have to figure out the ridge height. All you have to do is set the two rafters on each end of the building nailed into the top plates and then slide your ridge up into it. The rafters set the ridge height.

In your case the ridge height would be 5' 10-1/2".

You have a run of 12' 5-3/4" from the inside of the 2x6 wall and the rise to the bottom of the rafter is 5' 2-3/8". Now you add the plumbcut of the 2x8 and that is 8-1/8" to the rise and that's 5' 10-1/2" to the top of the ridge.

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Joe Carola

snuddenstang

Here is a very crude pictue of how I plan to have the addition look like. I literally cut and pasted this picture with my house and another house.
My current house ends on the right side where the stone on the right side of the front door ends. This is not to scale, but you can get the idea of what I am trying to accomplish. As you can see the new gable roof is not going to end on the left side of the new top plate. I am extending the new gable roof over to the existing roof to make a more dramatic look.

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snuddenstang

Here is a picture of my existing house.

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Tom R

Not questioning your knowledge by any means, Joe, - - and maybe it's me that's reading it wrong, - - but I think when he's saying 26' span, he's talking about the length of the ridge (including where it dies in to the existing roof). He did say the addition was going to be 18' X 22', - - so that's what I was basing his potential ridge height(s) on . . .

snuddenstang

The span I am talking about is the distance from the outside right top plate of the new addition to the spot on the the existing roof, just above the window.
I chose that spot because there is a similar ranch house like mine in my neighborhood that has this similar roof line. This is why I am having difficulty figuring out the rafter layout. It is not just as simple as figuring out the addition span which would be 18', that is the addition width. I am trying to make the house look bigger by framing the reverse gable over the existing roof. Hopefully the pictures will shop what I am taking about.

snuddenstang

Can I still use 2/8 roof rafters? That is a long span? It will be almost 16'.
Would I also need to add any additionla support under my existing roof where the new roof lands on it. The existing roof is framed in 2x6 roof rafters.

JustaFramer

I don't think 2x8 can be used for 16' spans at 2' on center. As for supporting the existing roof. What would you support the rafters too the ceiling joists? that in effect would be building trusses. By doing that a engineer would have to be consulted because you are using the cj's to distribute the load which could cause drywall cracking in the future.

Personally if it were me I would go with trusses and have a girder built to catch the opposing side from the new wall. A package could be designed were you dont' even have to tear off the other roof. Of couse some over framing woud have to be done probably with 2x6's
In these parts trusses are cheaper than stick framing.

snuddenstang

My rafters are 16" on center.

snuddenstang

Joe Carola, Can I ask you a few questions? Can you e-mail me msnudden@optonline.net
Thanks, Mike

emersonhomes

If you dont know how to frame a roof you should consider finding a job and gaining more experince

RED HORSE 554

(- half the ridge board if not the rafter will be 3/4 to long)If measureing from center of ridge board to the outside of top plate perfict dead on A+B=C pythagoras theory