I need to know where my last common rafter lies for my hip roof. I am putting my ceiling joists up and want to make sure that my last common rafter is in the correct location. I know that my last common should be at half of my total span but where exactly? For example if my total width from outside to outside wall is 30′ then I need to measure back from the corners 15′ for my last common and mark it but which side of the line does the last common fall?
Thanks
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Replies
You need to factor in half the thickness of your ridge.
Assuming that your ridge is 1 1/2", your run will be 14' 11 3/4". Mark that on your top plate and the X will be going away.
Place your common on the x.
Jim this may sound like a dumb question but why does the ridge thickness come into play? I can see that for the length of rafter but not where the last common falls on my top plate. What am I not seeing here?
There is more than one way to configure the cluster of rafters that occur at the end of the ridge. Most people converge at least three commons here (I don't conform to that thinking but it's most common). So, with that thought in mind, you may be right that my answer is not your answer. But, if you want the simplest solution, then you will make all your commons the same including all of them on the main sides of the roof and the middle one on the end that nails into the ridge. Keep in mind though that it's not necessary to have a common nail into the end of the ridge but 99.99% of the carpenters I've known does it.
Jim I think I may have confused you with my post. I am just talking about where to put a mark on my top plate as to where the last common rafter falls at the end of my ridge. Again if my span is 30' does my last common rafter center at 15' on my top plate?
yesI wish I didn't know now, what I didn't know then
Thanks
yes
Edited 9/21/2008 4:13 pm by Jim_Allen
Thanks.
I thought the span was 25' 5-1/2" or 25' 7-1/2"?? Something like that.
Anyway, Come in from each corner 14-11-1/4" and x away because 14' 11-1/4" is your rafter run if your now saying your span is 30' with a 2x ridge.Joe Carola
it would be the same, no matter what size ridge he has, or even if he had no ridge....what we're marking here, is the 1 1/2 inch rafter...
it would be the same, no matter what size ridge he has, or even if he had no ridge....what we're marking here, is the 1 1/2 inch rafter...
That's not true. It does matter what size the ridge is when figuring the run of the rafter because you have to deduct 1/2 the thickness of the ridge to get your run
I used a 2x ridge in the drawing. That gives you a 14' 11-1/4" run going from front to back and in on both side king commons of the roof.
If he used 5-1/2" ridge deducting 1/2 of that ridge, his run front to back and side to side would be 14' 9-1/4".
So, you measure in 14' 9-1/4" for the common he's talking about.
Joe Carola
I'm sorry, I thought we were refering to the last common rafter....the one that is in line with the ridge, and forms the center of the hipped end of the roof
now you have me really curious....wouldn't the end of the ridge, where the three rafters come together, at the end of the ridge, always fall at half the width of the building, off the end wall?
now you have me really curious....wouldn't the end of the ridge, where the three rafters come together, at the end of the ridge, always fall at half the width of the building, off the end wall?
No, it will fall where the run of the common rafter is after deducting half the ridge thickness. Look at both of my drawings. All the commons front back and side king commons are all cut the same length with the same run.
Joe Carola
it would be the same, no matter what size ridge he has, or even if he had no ridge....what we're marking here, is the 1 1/2 inch rafter...
It also doesn't matter what size the rafter is either unless it's wider than the ridge. You can have a 3-1/2" wide rafter with a 5-1/2" ridge the run will stay the same 14' 9-1/4"on the side king common rafter.
Joe Carola
joe, could you e-mail me privately at [email protected]
Yup.
Joe I was only using 30' as a example. If the span is 30' then the center of my last common should fall at 15'. Correct?
Joe I was only using 30' as a example. If the span is 30' then the center of my last common should fall at 15'. Correct?
Yes, if your ridge and rafter are the same thickness.
What is you REAL width and span?
Joe Carola
26'-5 1/2"
The edge of your common should fall at 15', in other words, the same run from the adjacent wall to the edge of the common, if there was no ridge beam.
All common rafters need to be backed off 1/2 the thickness of the ridge board/beam, therefore, in your example, if you are using a 2x ridge, then your run would be 15' minus 3/4" , and the layout would then be the same to the face of the common, or as you stated, 15' to the center.
Edited to clarify measurement
Edited 9/21/2008 7:53 pm by Heck
Thanks Heck. Lets say I had no ridge, would it change where the last common ended in relation to the corner of the building? I only need to know where my last common would fall from the corners. If for example the building was 30', then the centers of the end of ridge common and the two side king commons would be at 15'. Correct? Even if there was no ridge. I can see how the ridge thickness affects the length of rafter but not where it falls in the layout.
Well, it's somewhat of a simplification when describing layouts of 2x material that you can effectively disregard their thickness when laying out hips, but, in general you are correct to state that the adjacent commons are the same, therefore placing the face of the side commons at the same run from the corner.
The reality is that rafter thickness (as well as ridge thickness) is a component of the layout. Consider 4x rafters. The layout would be moved toward the end wall by 1/2 the thickness of the rafter, solely due to the width of the rafter on the end of the ridge wanting to shoulder over the side commons and peaking at a point too far into the building. This end rafter needs to be clipped shorter, therefore made to intersect lower, in order to preserve the actual points of intersection and the corresponding slopes of each side.
Edit in blue
Edited 9/21/2008 8:12 pm by Heck
Edited 9/21/2008 8:12 pm by Heck
I gotcha now Heck. Thanks
This conversation is really confusing.
And your drawing did zip to help me understand ... although I'm fairly certain it made sense ... to yourself.
Ditto
From:
Clewless1 <!----><!---->
10:34 am
To:
Framer <!----><!---->
(26 of 33)
110219.26 in reply to 110219.11
This conversation is really confusing.
And your drawing did zip to help me understand ... although I'm fairly certain it made sense ... to yourself.
View Image Options
View ImageReply
From:
Jim_Allen <!----><!---->
11:08 am
To:
Clewless1 <!----><!---->
(27 of 33)
110219.27 in reply to 110219.26
Ditto
Jim,
What's so hard for you of all people to understand a basic hip roof common rafter run?
The rafter run front, back and side commons are half the span minus 1/2 the thickness of the ridge. They are all the same run and same length.
Whatever the run is front to back, it's the same on the sides. Your ridge starts at the side with the common run measurement.
You have a 4' span with a 2x ridge and 2x rafters, your run is 1' 11-1/4". Come in 1' 11-1/4" from the outside of the wall and make a mark and go. That's where you king common starts if you want to use one and that's where your ridge starts regardless if you use a king common or not.
If you use king commons the 1' 11-1/4" measurement has to be the same front to back and side to the ridge because it's 45° .
Look at this drawing, I used a 4' span with 2x ridge and 2x commons.
It's simple and basic Jim.
Joe Carola
Edited 9/22/2008 11:04 pm ET by Framer
Your preaching to the choir Joe. I cut my first irregular roof, with a handsaw after laying it all out back in carpenter school in the 70's. They made us do all the math without a calculator, including the square roots LOL! No speed squares either....only speedier squares (framing squares). The thing that didn't make sense was your drawing that showed some lines with a few dimensions. It looked like nice lines but it didn't show any rafters.
The thing that didn't make sense was your drawing that showed some lines with a few dimensions. It looked like nice lines but it didn't show any rafters.
Jim,
Alright, you didn't realize the lines were the rafters, but you did see the measurements and you obviously know that the side king common rafter and where the ridge starts has the same run and rafter length as the rest of the commons.
I'm sure my last drawing cleared that up.
Joe Carola
yes
You did it w/out a calculator??? how'd you do that? LOL Back 'in the old days' they really did make you work.
I agree w/ Jim ... first drawing a bit sketchy (I'm being polite, now) ... we ain't your wife and we can't read your mind ... only what you put on paper ... if you make us fill in the blanks we may or may not 'get it'. The new drawing was much better ... glad you ain't no architect ... hate to have to build to your drawings.
If so many people are confused, I usually look w/in myself to see the error of my communication. I'm no framer by trade and the topic was interesting, but by the same token, it seemed like different people were talking about entirely different things (to me, the lay person) ... just thought it amusing. Sorry 'bout the miscommunication ... no offense intended in any of my prose.
Clarification (for my benefit as I ain't no expert framer, Framer) ... the end roof plane has only one common rafter, right? And you cut the ridge length so that rafter is identical to the side roof rafters, right? Or is the length of the ridge that critical (i.e. minor variations in the end roof slope are relatively meaningless?)?
Oh ... and it is clewless, not clueless ... there IS a difference (although I don't expect you to 'get it' ... it's pretty dry humor ... although I've been known to also be clueless more than just a few times).
so dry we are all parched :-)
I agree w/ Jim ... first drawing a bit sketchy (I'm being polite, now) ... we ain't your wife and we can't read your mind ... only what you put on paper ... if you make us fill in the blanks we may or may not 'get it'.
What didn't you get, the numbers were right there. So I didn't write rafters next to the lines, the numbers were right there for the runs.
The new drawing was much better ... glad you ain't no architect ... hate to have to build to your drawings.
Still being polite? Glad you ain't no framer because you wouldn't know how to frame from any drawing.
If so many people are confused, I usually look w/in myself to see the error of my communication. I'm no framer by trade and the topic was interesting, but by the same token, it seemed like different people were talking about entirely different things (to me, the lay person) ... just thought it amusing.
It seems like you're the one that is confused obviously because your not a framer. Any framer would pick up on the run measurements I gave and understand it in 2 seconds.
Sorry 'bout the miscommunication ... no offense intended in any of my prose.
Sure about that? There's no miscommunication on how you write.
Clarification (for my benefit as I ain't no expert framer, Framer) ... the end roof plane has only one common rafter, right? And you cut the ridge length so that rafter is identical to the side roof rafters, right? Or is the length of the ridge that critical (i.e. minor variations in the end roof slope are relatively meaningless?)?
Really want to know, or are you still trying to be a d!ck?
Oh ... and it is clewless, not clueless ... there IS a difference (although I don't expect you to 'get it' ...
Really! still just being a d!ck!
Joe Carola
Joe,
Sorry, dude. I REALLY did not mean to offend you. Being too glib, maybe trying to make a point. My apologies. And I really was trying to understand. Communicating in this manner can be tough ... especially w/ a topic like this ... like instead of having drawings, you have an audio tape telling you how to build it.
I'm outta here ... let you guys discuss this on your own.
This conversation is really confusing.
And your drawing did zip to help me understand ... although I'm fairly certain it made sense ... to yourself.
Your name fits. What's so hard to understand, it's a simple hip roof and the drawing is simple.
Joe Carola
This is how I think of it. The common that comes off the end of the ridge should be exact same length as all the rest of the commons.
If the run is the same, the height is the same and the diagonal is the same, then it is the same pitch as the main roof.
So if we cut rafters minus 1/2 the thickness of the ridge, then the ridge needs to "grow" 1/2 its thickness. This way ALL commons are exactly the same length.
Does that help at all?
"So if we cut rafters minus 1/2 the thickness of the ridge, then the ridge needs to "grow" 1/2 its thickness. This way ALL commons are exactly the same length.Does that help at all?"Yes and no.Should that ridge grow 1/2 the thickness on both ends? What if one end is gable?
Only on the hipped end and only if we want all the kings to come together a the end of the ridge and the hip fit between them.
View Image
From Shufflebotham's Place
View Image
From Shufflebotham's Place
Let me in on this, I say 14'-11 1/4". That will be the run of your King Commons, assumming a two by ridge.
I can see an opportunity here for a model home builder - Instead of paying for new plans for a different house, just hire a different framer.
Just kidding, folks.
Let me in on this, I say 14'-11 1/4". That will be the run of your King Commons, assumming a two by ridge.
That is the run of your king common because that's the run on your front and back commons and the rest of every single common on the entire roof. There's no mystery here. The side king commons and where the ridge starts has the same run as the common rafter.
Joe Carola
Edited 9/23/2008 8:16 am ET by Framer
Tim I think I may have confused some of the people in my o.p. by the way I worded it.Sorry to those. I believe some people are thinking that I am asking how long my rafter should be, I am not. I'm just asking where it should fall in relation to the corners of my end walls. If I have a building span of 30' then the center of the last common rafter should be at 15'. Even if I have a ridge that is 1' thick and rafters that are 8" thick the center of the last common will still be at 15'. Correct?
Not it wouldn't if you wanted all your commons the same length.
It would be 15' minus 1/2 the ridge thickness. The distance along the plates to the rafter is the same as the adjusted run of the main common rafters. So if you calculate your rafters as 30' minus the ridge/2 to get the adusted run, then it would be the exact same thing coming in from the end.
This way you have a 45 degree plan view hip.
Here is what you should have with a 30' wide building.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Thanks Jon. Now what would be my measurement to the center of the last common rafter? You have 14'-11 1/4" from the face of the last common to the corner of the wall. Would it not be 15' to the center?
Yes, assuming you're using conventional 2x lumber.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Yes. That's your third yes to that exact question.
Thanks Jon. Now what would be my measurement to the center of the last common rafter? You have 14'-11 1/4" from the face of the last common to the corner of the wall. Would it not be 15' to the center?
Did you not believe me when I told you your answer in this post?
http://forums.taunton.com/tp-breaktime/messages?msg=110219.20Joe Carola
Joe,everything you said made sense from the first post..... you're too old and too
good a framer to have to put up with any depricating posts....for some of us who
have read your very informative posts in the past,in many different forums,keep up
the good work...I've been doing construction for 34 years and am still learning. kweaver
Appreciate the kind words.
I've been doing construction for 34 years and am still learning.
I here you.The day I stop learning is the day I die.
Joe Carola
Joe I believed all of you. The point I was trying to make was... never mind.Thanks
Joe I believed all of you. The point I was trying to make was... never mind.
The point you were trying to make was what? Was it that you wanted to know if 15' was to the center of the common? The answer was yes, IF you were using the same size common as the ridge. The answer was no, if you were using a bigger ridge like I showed you in the drawing with a 5-1/2" ridge.
Joe Carola
Joe I guess I still don't understand. I don't understand how ridge thickness affects where the last common falls. I guess there is something i'm just not following. I know you are busy but could you draw up a hip with a 5" ridge and 2x ridge with 2x rafters? Thanks
Think of it this way, "The run of your common rafter from the plate to the side of the ridge needs to be the same run for your king off the end of the ridge.
Joe I guess I still don't understand. I don't understand how ridge thickness affects where the last common falls. I guess there is something i'm just not following. I know you are busy but could you draw up a hip with a 5" ridge and 2x ridge with 2x rafters
The thickness of the ridge HAS to effect the run because you are deducting half the ridge thickness, therefore the run of the common rafters front to back HAS to be the same coming in from the sides(King Commons) to the first rafter that you're talking about.
if you have a 4' wide piece of plywood and laid out this hip roof using a 5" ridge, your common rafter run is 4' - 5" = 3'7"/2 = 1' 9-1/2". That is the common and King rafter run. Every single rafter front to back and the two side king common rafters are the same size and have the same run. It has to in order to create a 45° hip.
I drew this showing you on the left side using a 2x ridge and on the right side using a 5" ridge like you asked. The 5" side I used two king commons to show you how you create an EXACT square where the runs are front to back and on the side.Joe Carola
Just to clarify-
"If I have a building span of 30' then the center of the last common rafter should be at 15'. Even if I have a ridge that is 1' thick and rafters that are 8" thick the center of the last common will still be at 15'. Correct?"
If your ridge is 12" thick and your rafters would start at 14'6" from the outside of the wall plate. The center of the first common rafter would be 14'10" from the outside of the wall plate.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Close enough.
I shrunk the picture.
I just changed the left side of the drawing using a 12" wide ridge. Look at the exact square the common runs make and where the hip is.
Thanks Joe I see it now. Can you give me the formula again? I want to write it down in my notes. I can see where it was not clicking for me. Half the width of the building-half the ridge thickness. What about rafter thickness? Where does that come into play? Thanks again.Edited 9/25/2008 9:09 am ET by blownonfuel
Edited 9/25/2008 2:28 pm ET by blownonfuel
Half the width of the building-half the ridge thickness.
Yes, that's your rfater run for all commons including the side king commons.
What about rafter thickness? Where does that come into play?
Rafter thickness doesn't come into play when it's the same thickness as the ridge, or if the ridge is wider than the rafters. It's comes into play if the rafter is thicker than the ridge, which you won't have to worry about. I've been framing for 25 years now and have never once in my lifetime seen that before.
Joe Carola
Thanks for helping me out Joe and your patience. Joe funny that you should mention about rafters being thicker than the ridge. Take a look at Tim Uhler's pics in this thread, post 31, he has some massive hip rafters and a doubled 2x ridge.
Edited 9/25/2008 7:01 pm ET by blownonfuel
The only thing hip rafter affects is how much it weighs and how much load it can carry. Layout is practically unaffected, common rafter is 100% unaffected by hip thickness.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Interesting. Only the commons and ridge then?
Here's the thing. It's just a simple square.If the common rafters have a run of 12', the first common rafter will be 144" to the inside face (145-1/2" to the outside face) every time. It doesn't matter what the ridge thickness is.If the common rafters have a run of 16', the first common layout is at 16'.You can substitute any number you want and it will work. All you have to know if the run of the common and you're practically done.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
I got it now Jon. Thanks
Take a look at Tim Uhler's pics in this thread, post 31, he has some massive hip rafters and a doubled 2x ridge.
The engineer spec'd the double 2x12 ridge and 5 1/8" x 12" LVL hips, but we put in 14" deep hips so that the hips would hang lower than the finished ceiling. Last time we did this house, we used the 12" hip and there was/is some cracking in the drywall.
If you look here
View Image
Lot 30 Muirkirkyou will see that we had single 2x12 ridge, double, triple, glulam and LVL ridges :-)
Are the 12" sagging Tim? What is causing the cracking?
The cracking was due to the the kitchen, fireplace and it being a cathedral hip. At least in my opinion.
Joe funny that you should mention about rafters being thicker than the ridge. Take a look at Tim Uhler's pics in this thread, post 31, he has some massive hip rafters and a doubled 2x ridge
I'm talking about th common rafters being thicker than the ridge when you nail all three king commons like we're talking about. The hips can be any width and not matter. I put up 28' double 1-3/4" x 11-7/8" lvl hips today on one section of the house with a double 1-3/4"x 11-7/8" ridge and double 2x12 hips on another section of the house. Joe Carola
I bet Lil Joey hoisted them himself :-)
Got any pictures? What have you been up to? How's work going for you?
I got it in my notes now Joe. Thanks