Porch Roof Rafter Framing Question

1064 Views 13 Replies 3 Participants Last post by rlrigsby, May 13, 2020

rlrigsby

Discussion Starter · May 12, 2020

We are remodeling a cabin in the mountains and are presently expanding the porch and house roof out over the deck. I replaced the railing posts with columns and installed double 2x beams. I had to build a small knee wall above a cross member to support the continuation of the porch rafters and the house roof rafters on one side. The other end will be supported by bearing walls for a mudroom that stops at the roof peak and extends outward the width of the deck.

I ran into a problem as I began running the porch rafters to match the pitch and overhand of the existing porch rafters. All was fine until I reached the 45 degree section of the new porch beams. As I turned the rafters 90 degrees to cross the 45 degree angle, each successive rafter became increasing higher from the top of the beam because the point where the rafter crossed the beam naturally moved closer toward the knee wall and causing the distance between the bottom of the rafter and the top of the beam to increase. By the time I reached the far end where the 45 met the outside beam, the distance between the rafter and top of beam was 3-1/2" inches. So in order for the top of the roof to remain level across the width of the roof expansion, I found it necessary to gradually raise the rafters over the 45 degree area.

The roof is level but when viewing the overhang from underneath, there is a very obvious increasing space from the farthest point of the 45 from the knee wall to the nearest point to the knee wall where it meets up with the outside beam. I realize that it's occurring because the rafters are crossing over the 45 degree area of the beam at different points and their pitch is producing the increasing space in relation to the position of the beam under them. The question is how can this area be framed to avoid such a circumstance? I tried running the rafters both 90 degrees to the 45 in that area and then just running them straight across it but it obviously makes no difference because the rafters nevertheless cross the 45 area of the beam at different points that produce a gradually increasing space. I've attached a drawing that is not to scale but generally depicts what I'm working with at this area of the house.

The roof obviously has to remain level and the rafter problem described is also going to produce a sub-fascia and fascia that will rise from one end of the 45 to the other end, a height differential of 3-1/2 inches and making it out of level with the beam below it. There obviously must be some way to frame this area to avoid the problem but I'm overlooking it.

Any help here would be much appreciated.

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de-nagorg

· #2 · May 12, 2020

You're working and thinking too hard.

You take your long rafter, and place it where you want it, then mark where it needs to be cut, and go cut it.

Voilla, you have created a perfect rafter for each spot, without all the fuss.

ED

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rlrigsby

Discussion Starter · #3 · May 12, 2020

de-nagorg said:
You're working and thinking too hard.

You take your long rafter, and place it where you want it, then mark where it needs to be cut, and go cut it.

Voilla, you have created a perfect rafter for each spot, without all the fuss.

ED

Thanks for the reply. I typically use the process that you describe. The problem is not the mark or the cut, but the fact that the 45 angle of the beam causes each rafter to be increasingly higher above the beam due to the pitch of the rafters. I've drawn out what I think will be the solution in running the rafters in the opposite direction by first doubling up the existing porch rafter and then using buckets at 16" o.c. up to the knee wall. That will allow all the rafters to cross the beam equally from end to end and also serve as the overhang on the outside both at the front beam as they cross the gable end above the beam at the far end. I think that may be my best approach at this point.

Thanks again for your advice.

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Nealtw

· #4 · May 12, 2020

rlrigsby said:
Thanks for the reply. I typically use the process that you describe. The problem is not the mark or the cut, but the fact that the 45 angle of the beam causes each rafter to be increasingly higher above the beam due to the pitch of the rafters. I've drawn out what I think will be the solution in running the rafters in the opposite direction by first doubling up the existing porch rafter and then using buckets at 16" o.c. up to the knee wall. That will allow all the rafters to cross the beam equally from end to end and also serve as the overhang on the outside both at the front beam as they cross the gable end above the beam at the far end. I think that may be my best approach at this point.

Thanks again for your advice.

Did you want to turn the corner like a hip roof?

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Nealtw

· #5 · May 12, 2020

It looks to me like a section of octagon.

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rlrigsby

Discussion Starter · #6 · May 12, 2020 (Edited)

Nealtw said:
It looks to me like a section of octagon.

Exactly, and thanks for taking your time to provide an alternate drawing. As mentioned in my original post, I had originally ran the rafters at the 45 section more or less at 90 degreed to the beam as shown in your drawing, but had tried to run the rafters on either side of that section in the same direction as the original porch rafters. I think I was trying to combine a shed roof with a section of an octagon so that the metal roofing would travel in the same direction as the original. I finally realize by your drawing that the metal roof unavoidably has to remain perpendicular to the beam at each section for it all to turn out level at the fascia, which creates yet another issue not encountered with a true octagon roof.

Unlike the octagon, I have 2 different pitches, the porch roof at 3/12 and the house roof at 7/12. The 7/12 pitched roof section above the porch roof will naturally be shedding water more than 12' directly down and against the upper metal cap on the 45 that basically rises at only 3/12, so it would oddly enough end up needing a cap for symmetry but a valley to channel the water off the roof at that point. Even the lower side may need to be treated differently because of the overall roof configuration and force of water coming down from the 7/12 roof section.

Again, thanks for the time to re-sketch my drawing. It has me much closer to what I need to do. My only dilemma at this point is making the metal roof water tight where it breaks on either side of the 45.

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rlrigsby

Discussion Starter · #7 · May 12, 2020

Nealtw said:
It looks to me like a section of octagon.

I also think I may be misreading your drawing to a certain point, though. In reviewing it again, it appears that you're showing the section beyond the 45 heading toward the back of the house to be framed such that it is lower than the house roof? Do I understand that correctly?

It did, however, just make me realize a way to possibly solve the issue. I mentioned that there is a mudroom being built with the front wall starting at the peak of the house roof. If I'm going to build the porch roof like an octagon section, it seems perfectly reasonable to simply maintain the 3/12 pitch of the porch onto the back side of the 45 all the way to the new mudroom wall. I'd simply run a ledger along the original wall from the point where the 45 rafters all meet up and extend it along the original house wall to the new wall and maintain a 3/12 pitch over to the beam. I'd then use a shed roof over the new mudroom that is a continuation of the original house roof at 7/12.

Would that work?

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Nealtw

· #8 · May 12, 2020

rlrigsby said:
I also think I may be misreading your drawing to a certain point, though. In reviewing it again, it appears that you're showing the section beyond the 45 heading toward the back of the house to be framed such that it is lower than the house roof? Do I understand that correctly?

It did, however, just make me realize a way to possibly solve the issue. I mentioned that there is a mudroom being built with the front wall starting at the peak of the house roof. If I'm going to build the porch roof like an octagon section, it seems perfectly reasonable to simply maintain the 3/12 pitch of the porch onto the back side of the 45 all the way to the new mudroom wall. I'd simply run a ledger along the original wall from the point where the 45 rafters all meet up and extend it along the original house wall to the new wall and maintain a 3/12 pitch over to the beam. I'd then use a shed roof over the new mudroom that is a continuation of the original house roof at 7/12.

Would that work?

I am not sure I understand where you are seeing a problem with water sealing. Both hip rafters at the 45 would be ridges and they wouldn't be subject to the water from the house roof.

There are other ways you could do the roof

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Nealtw

· #9 · May 12, 2020

Like this

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Nealtw

· #10 · May 12, 2020

de-nagorg said:
You're working and thinking too hard.

You take your long rafter, and place it where you want it, then mark where it needs to be cut, and go cut it.

Voilla, you have created a perfect rafter for each spot, without all the fuss.

ED

Ed, I am still not sure I understand all the details here. :wink2:

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rlrigsby

Discussion Starter · #11 · May 12, 2020

Nealtw said:
Like this

My first choice would be a hip roof but my budget just won't allow it. Still have the garage to build. It would look the best. I think I'm going to settle for what I depicted in the attached drawing, with a ledger against the house and just run the rafters at the same 3/12 pitch as the original porch back to the new mudroom.

Your first drawing solved my nightmare. I had it all taken out and re-assembled this morning to the 45 and everything is now level with the beam all the way around. The ledger is on and I put a rafter in place to test it and all is going to work fine. Rain spoiled the rest of my day. Looks like everything should fall into place now.

Can't thank you enough for your time and assistance. It's put me back on track.