What is that new pitch?

[Bob Dylan]

Go here and watch and listen. What you are seeing is Chief Architect software figuring the roof for an "Arizona hip."

http://www.lfcompany.com/louis/chief...a_Hip.viewlet/

The two side planes coming out to the bumpout have a pitch adjustment.

What is the math here, and how is it figured with the CM Pro?

[Jon Blakemore]

Re: What is that new pitch?

I don't use a CM, but wouldn't the pitch be 10/16.97?

[shadyike2007]

Re: What is that new pitch?

Go here and watch and listen. What you are seeing is Chief Architect software figuring the roof for an "Arizona hip."

http://www.lfcompany.com/louis/chief...a_Hip.viewlet/

The two side planes coming out to the bumpout have a pitch adjustment.

What is the math here, and how is it figured with the CM Pro?

I'm on dial up and having a hard time viewing this could you post a diagram of it?

[Joe Carola]

Re: What is that new pitch?

Go here and watch and listen. What you are seeing is Chief Architect software figuring the roof for an "Arizona hip."

http://www.lfcompany.com/louis/chief...a_Hip.viewlet/

The two side planes coming out to the bumpout have a pitch adjustment.

What is the math here, and how is it figured with the CM Pro?

Bob,

That tutorial is hard to listen too. Takes way to much time to draw. His drawing changes the pitch because he changes the location of the side hips. If he frames that roof like it's an octagon roof because all three walls are the same size, the pitch wouldn't change. The pitch would stay 10/12 and the hips would be 10/13. The side hips should go to the corner and that way all three walls have the same pitch, same common and hip lengths.

[Joe Carola]

Re: What is that new pitch?

Here's a drawing. Look where I put the side hips in the corner. This would be the right way to frame it if it was a cathedral ceiling also.

The second drawing is the way he did it where the blue is.

[kpatrix]

Re: What is that new pitch?

Go here and watch and listen. What you are seeing is Chief Architect software figuring the roof for an "Arizona hip."

http://www.lfcompany.com/louis/chief...a_Hip.viewlet/

The two side planes coming out to the bumpout have a pitch adjustment.

What is the math here, and how is it figured with the CM Pro?

That tutorial is missing one important piece of information.

For that roof to really work right, It has to be 5 sided . Overlapping the hip and valley shingles as they converge on the fascia at a centered point create an imperfect intersection. The hip ridge shingle has to be cut/covered as it laps the valley.

With a five sider projected right, the hip ridge shingles outside edge die into the valley, This roof is pretty involved to make "just right". Space is required at the hip/val intersection.

Make those bump outs always have at least 5" perpendicular to the main, and that way the hip ridge shingles outside edge doesn't have to be clipped at the fascia intersection.

[Richard Birch]

Re: What is that new pitch?

That tutorial is missing one important piece of information.

For that roof to really work right, It has to be 5 sided . Overlapping the hip and valley shingles as they converge on the fascia at a centered point create an imperfect intersection. The hip ridge shingle has to be cut/covered as it laps the valley.

With a five sider projected right, the hip ridge shingles outside edge die into the valley, This roof is pretty involved to make "just right". Space is required at the hip/val intersection.

Make those bump outs always have at least 5" perpendicular to the main, and that way the hip ridge shingles outside edge doesn't have to be clipped at the fascia intersection.

I agree. His looks good on paper, but it's not the way I prefer to do them. (As Joe C shows)

[kawendtco]

Re: What is that new pitch?

i frame a lot of these, but there is a lot of trial and error if the bay walls arent framed on a 45. how do i determine hip and valley pitch on odd angled bays? finding the ridge length isnt a problem, as the depth of the bay,(assuming it is parallel to the main roof wall line), determines this. again assuming the bay is framed at the same pitch as the rest of the roof line. also how do i determine the span and run for the commons on odd angled bays? i usually set up a set of strings but this is time consuming. my reichers rafter bible doesnt show this stuff. though it is the best book for all pitches equal on both planes and or setting 90 degrees from each other. i use a computer level which helps but this is more of a scribe in method. it works but isnt the most efficient. i find myself framing these things in my head at 3 a.m. any help out there?

what we run into is a bay that cannot be framed any deeper than twice the height of joist as per our code, and flanker windows that determine the length of the walls on either side of center. so sides of bay can truly end up at any angle.

so many lumber-putter-together-ers (my way of being nice to the not so conscientious builders) simply put the roof up without any regard to overhangs lining up or pitches matching. it becomes a matter of 'just get it done so we can close this house up and go to the next one'. i want it to be right, not just done.

[Joe Bartok]

Re: What is that new pitch?

Go here and watch and listen. What you are seeing is Chief Architect software figuring the roof for an "Arizona hip."

http://www.lfcompany.com/louis/chief...a_Hip.viewlet/

The two side planes coming out to the bumpout have a pitch adjustment.

What is the math here, and how is it figured with the CM Pro?

Gene, I don't have enough Internet time to watch the entire tutorial, but skipping ahead to the last image it looks like your roof is similar to one of the "Joe Carola" Bay Window Calculators at SBE Builders Roof Framing Online Tools. (Attached are a couple of pics of a roof like what I'm seeing in the tutorial, the photos were taken from a distance so the image quality leaves something to be desired).

Just guessing here but is this the math or adjustment you are looking for: General Plan Angle Formula? There were a few bay window and bow window threads about a year ago and the math played a role in common and Hip pitch adjustments for these roofs. As I recall Sim has incorporated this in the code in many of his bay and bow window calculators.

[Joe Bartok]

Re: What is that new pitch?

The two side planes coming out to the bumpout have a pitch adjustment.

I don't understand what "pitch adjustment" is being made with the side planes. The calculations for this Arizona Hip with Unequal Pitches were standard procedure. This was calced from the fascia so the 10/12 bay roof triangles remain a regular nonagon (40° central angles) in plan view. The main roof pitch is 8/12.

There is more than one resolution here. I made another drawing of the same roof but started at the plate line, then moved the Hip rafter feet to fit the equal overhangs. (Same as the adjustments in the "Bow Bay Window" thread, using the "General Plan Angle Formula" for unequal pitches, irregular plan angle.) The calculations were to ten decimal places and I cannot find fault with them.

This doesn't seem that difficult. Or am I missing the point of the original question? Maybe there's a mistake in my math?

[Tim Uhler]

Re: What is that new pitch?

Just a couple of pictures of the framing from a few years ago.

http://picasaweb.google.com/PioneerB...75930511876562

http://picasaweb.google.com/PioneerB...75922434467954

http://picasaweb.google.com/PioneerB...76172217053170

http://picasaweb.google.com/PioneerB...76758172413026

[Richard Birch]

Re: What is that new pitch?

Joe C.

I have never seen a bay roof with unequal pitches as shown on the unequal pitch bay, over at

http://www.sbebuilders.com/tools/joe...-baywindow.php

I didn't see it in plan view looking right at it either. (I have never seen a local plan detailed that way.)

That is a very interesting solution to bring the HAPs on the wing walls up to equalize them on the wing walls. Change (Minor) the face roof’s pitch to bring the hap up there. Novel idea! (I missed it and hence the edit) But does it work?

It seems to me to work the roofs over the 45 walls would have to have equal HAPs to meet at the valley as shown and keep the overhangs equal. That would make the overhang’s plan view valley angle 67.5* as shown, but the Hip’s angle should be 67.5* too, as on an equilateral Octagon, shouldn’t it?

I still think there is an error in your bay roof solution as shown, but I’m known for making mistakes and if I’ve made one here, tell me what I do not understand.

Are the wing roofs also steeper than the major pitch? Can't be.

Third edit;

OK, I got it, (I think) The wing pitches are equal to the main roof (not specified) and the Bay's hips are commons to that pitch and meet at a 90 at the ridge. (The gray triangles are not to scale.) I think I have seen these before.

Fourth edit;

OK. Back to the drawing board.

Your hip-commons don't meet at a 90. Wouldn't they need too to work?

Sheesh! I can't see the geometry.

[Joe Bartok]

Re: What is that new pitch?

Another example Arizona Roof with unequal pitches, the Hip rafter feet have been shifted to accommodate equal overhangs. All rises are calculated from the level plane passing through the fascia line.

This is the simplest case of a radial shift to produce equal overhangs. The Hip rafter peak remains fixed while the foot moves; the common slope is adjusted to reflect the new position of the Hip.

There are also some radial shift or offset drawings in this Bay Roof to a Point Double Bumpout 45° thread.

EDIT ... forgot to upload images of the 3D model of this roof; also added the pics to the "Arizona Roof with unequal pitches" link above. The calcs for this roof were originally executed to ten decimal places in order to test the "fit" of the intersecting planes.

[Richard Birch]

Re: What is that new pitch?

Another example Arizona Roof with unequal pitches, the Hip rafter feet have been shifted to accommodate equal overhangs. All rises are calculated from the level plane passing through the fascia line.

This is the simplest case of a radial shift to produce equal overhangs. The Hip rafter peak remains fixed while the foot moves; the common slope is adjusted to reflect the new position of the Hip.

There are also some radial shift or offset drawings in this Bay Roof to a Point Double Bumpout 45° thread.

Well, my last post was a calamity. =)

Joe B.

Please check my assumptions on the geometry. Joe C.’s Unequal pitched bay roof has a geometric flaw as I understand it.

True or False?

1. The Main Roof (the structure's roof the bay roof protrudes from that is not shown) and the wing walls (45* s) must have the same pitch to keep the HAP’s equal with equal overhangs. (Not keeping the pitches equal will change the HAP and the major span)

2. The plan view’s triangle of the bay’s face roof (minor pitch) will be a right triangle with the fascia length as the hypotenuse and the two right angle legs will act as both commons and hips to the wing wall roofs.

3. The hip-commons described above determine the ridge height.

4. The major and minor pitches as described in the online calculator cannot be selected values. They will be defined by the ridge height.

a. Major Pitch = Ridge height/Effective Run((Major Span – ridge thickness)/2)

b. Minor Pitch = Ridge height (from top of fascia)/Effective Run, or((Fascia length-ridge thickness)/2)

The Sketchup model I did seems’ to rely on these assumptions. I have attached it. Just click on the “Comes back” view tab to see the model version of Joe C.’s roof. (Roof at right w/ dogleg valley). For some fun, play the animation. To skip the kaleidoscope tornado effects, click the views you want to look at. (The view tabs between Zoom and tilt, and the “Comes back” tab.)

[Bob Dylan]

Re: What is that new pitch?

Thanks to all who contributed. I am the one who originated this thread.

The question I posed in the OP, ("what is that new pitch?"), was generated as I said, from seeing a video tutorial in Chief Architect software.

I could expand upon the question some more, now that I have modeled solutions in Sketchup, and seen some replies.

The problem was solved by the guy who did the CA tut, using these set-up facts: 10:12 main, bumpout three equal sides of an octagon, desired o'hang 1'6", desired pitch on all five planes 10:12.

Your solution with the radial shift to accommodate the equal o'hang is the same, solved with math, as that solved with the Chief Architect tools as used by the tutorial author. Or is it?

Using Sketchup, and not math, I solved it in another way, ending up with the same ridge height, but with the three front pitches at 10, and the pair flanking the ridge as about 10.75. All five planes have three sides, and the valleys are straight lines.

Also I SU, I modeled the JoeC solution, with all five planes pitched at 10, but with the doglegged valleys. Since he springs his roofs for the reachout ridge from the wall points, he ends up with the lower ridge.

The question most in my mind, sitting here and about to receive and work through using this new software, is "would a framer do it the way Chief has shown, or not?"

I sort of got the impression after reading a lot of posts on Chief Architect users forums that most users of the software are plans drawers who have no real interest or experience with roof cutting.

I don't think there are more than the three ways I have seen now, to do this five-plane array of roofs for the bumpout as specified. Clearly, if you throw in the additional language to the setup, "all five planes must be equal pitched," then the JoeC method is the only solution.

If you say, "make as many planes as possible at 10:12, but the valleys must be straight lines," then there are two.

So, the question still stands, and I guess you would have to give it a fair test by giving it to a whole crowd of diverse roof cutters, "what is the best way to build this, valley geometry notwithstanding?"

The comment about roof shingling, with this bumpout, no matter how framed, having a valley converging with a hip right at the eave, is a valid concern. How many roof cutters would think ahead to that downstream issue? I don't know.