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willcmjr 09-14-2009 05:58 PM

Question: Altering One Side of a Gable Roof to a Shed Roof
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I'm currently designing an addition for my friend. She currently has a Cape Cod, with with a gable roof on the second story, approx 9:12 pitch. (Almost identical to white house)

She wants to raise the rear side of the roof up. Initially we had discussed doing a full shed dormer (small drawing). But raising the entire side would give just a little more space inside, make drywalling a little easier, etc.

So basically it would end up a salt box with a ridge line centered on the house (bottom pic). I can't find any designs or mention of people doing this. Either I find shed dormers, or a saltbox with the ridge line off-center.

Any ideas, help, etc?

Much obliged! Billy :)

Aframe 09-15-2009 10:09 PM


This is more of a carpentry issue than roofing. You may get a better response over there.

But here goes it.

For either set up you will need an engineered framing plan that takes into account the loads of the new and existing roof frames.
By keeping the new roof pulled in at the gable ends even if just 6" or so will save you the trouble of tying in the new to existing siding.

Other way would be to make a reverse salt box. Just need to mdify roof plan for pitch and ridge location.

Either way is fine

Scuba_Dave 09-15-2009 10:35 PM

I don't see a Pink house ?

willcmjr 09-15-2009 11:40 PM

Aframe... Thanks for the help! Your right about the carpentry thing, I did post a link over their to this thread. And thanks for the pic of the reverse saltbox, I couldn't find one with a center ridgline. What type of connections would I be looking at to resist the change in lateral loads. We had thought about the siding part. Still on the fence, but leading towards doing the whole thing, not a dormer.

Dave, the smaller drawing looks pink to me that's why I called it that. I'm referring to the small drawing.

Scuba_Dave 09-16-2009 07:28 AM

I thought maybe a picture didn't make it
I raised the back of my Cape, I have about 6' 4" at the back wall
I did the entire back/sides
It's easier as far as siding, roofing & loads
Prior roof was 2x10's, new roof was the same
Inspector wanted a 2x12 as a ridge beam
Other then that I drew up my own plans & submitted them
No engineering was required since all loads remained the same

Most of the 2nd floor back windows were replaced with additional construction
Roof is on the far left addition & I'm working on residing & finishing the exterior
I did all the plans & work
Beams for the addition on the far left were engineered for Load

willcmjr 09-16-2009 04:19 PM

Everything you said it about what we're expecting. The only thing I'm worried about is, long term there can be some 'push out' of the walls that a gable rest on. On the raised side, how did you tie that in the resist that push?

Scuba_Dave 09-16-2009 04:43 PM

The rafters tie in the top part of the wall
I also have rafter ties/collar ties between the front rafters & the back rafters
The floor ties in the bottom part of the wall
The wall also sits directly on the top plate of the wall below
A 2x6 was nailed into the bottom part of the new wall
Then the floor sheathing cut back some & a 2'+ piece ties in existing floor joists with the new floor joist/wall

For support along the ridge beam I had existing support approx 10' in from each side that extends all the way to the basement

Gary in WA 09-16-2009 06:32 PM

Here are three ways to add a dormer:
1. double or triple up the common rafters to carry the loads imposed there: supporting side shed walls and double header joist that carry the common rafters between side walls;

2. Install a bearing beam (as in Dave's new big addition) across the span to carry the roof's loads; (strongest of all three)

3. update the ridge and install ceiling joists to act as collar ties to keep walls from spreading and ridge from sagging. ( as Dave's old house) Ending with a low rise per foot which puts more load on the ridge and may bring a code into play: Supports such as ridge for <3/12 slope designed as beams not rafters... IRC 802.3

Check with your local Building Department for their specific requirements.
Be safe, G

willcmjr 09-16-2009 10:07 PM

Hey GBR. Thanks for reading and replying! Actually, we're leaning towards doing what's in the bottom picture in my post, raising the whole roof.

Any framing advice for that, with regards to the lateral loads on that new wall?


Gary in WA 09-16-2009 10:48 PM

That will be quite the undertaking! This site has some good books with limited previews, with many good tips on framing.
After reading that article, hit the search books button on top, go through any/all other books as a quick look will tell if it's what you want. Or be more specific in the search box.
I suggest hiring a Structural Engineer to draw your shear and load paths once you settle on a design to present to your building department. I was at your City's site and noticed it mentioning Historic Area or not. You may want to search their requirements first, before continuing. This is the best way for securing loved one's safety and helpful if the house is ever sold. We are here to help answer any further questions.
Be safe, Gary

Scuba_Dave 09-17-2009 08:33 AM

OK, the bottom picture changed to basically what I did to my house?

Is that what you were planning on doing or the old Pic?
The old Pic looked like a lot of work

willcmjr 09-17-2009 04:32 PM

GBR, the house is not in the same municipality, it's actually my friend's house. But thank you for your thoroughness! Actually I have several framing books, including textbooks. None of them seem to tackle this type of roof.

Scuba, the new pic is what we're talking about. The old one was just a saltbox, because I couldn't find a pic that was a good representation. The new pic is identical to what we're looking to do. The vertical loads on the 1st floor would remain the same. But the lateral loads on that new raised wall would be different, so that's what I'm just trying to check into.

Thanks for all your input guys!

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