OK, I am in the process of building a large log home. My Garage sets @ a 22.5º angle attached to the house. When running my valley rafter between the house and the garage I cannot get it to come out right. My garage is 28′ wide and the house is 24′. I have a 4′ section which sets outside the main portion of the house, setting @ the angle. I have read multiple articles and tried using String and trial and error (mostly error) methods. I have tied all of my other valleys in I just cant figure out how to tie this angle in………any suggestions will be greatly appreciated.
<!—-> <!—-> <!—-> I am attaching @ rough drawing of the layout to give anyone an idea…..<!—-> <!—->
Replies
Can you post a quick sketch of the roof in plan view?
I cannot read the roof lines into your posted drawing.
I do not have a drawing the roof line does transition from a 12/12 to a 10/12 over the garage. I have a friend that could probably draw it up and I could post tomorrow.
Jake,
Are the top plates at the same height in the garage and in the main house.... are you starting from an equal plane? And does the front wall of the house really extend all the way to the corner of garage as drawn.... creating that triangle of dead space between the two in the front?
Any additional information would be a big help....actual photos or scans of your plans. If I have my head around this correctly, you're going to be left with some odd looking tapered rakes because of the how the roofs plane in with one another. The big problem is that if you plates are at equal heights, you've got a 4" difference in ridge height to make up somewhere.
Really need more information here.....
Edited 2/25/2008 9:05 am ET by dieselpig
jake ... i can see where i think your valley is going to be
and it sounds like the intersecting roofs already exist
i don't understand why you can't plane them in with string linesMike Smith Rhode Island : Design / Build / Repair / Restore
Jake... even if you're not great with math, you can always figure out odd ball rafters if you have the space to snap it out, full scale, in place, on the deck. This way you end up with a full scale, plan view set of drawings right in front of you. I use this method often for odd situations in roof framing and usually find it to be faster in the long run than working through a lot of complicated trig. Especially once you figure in human error at the calculator.
All you really need to get going is to find the point where the two roof intersect in two places.... the first at the lower end of the roof and the second at the upper end of the roof..... then connect the dots. This will also give you any cheek cut angles in plan view.
My guess is that you are attempting to create the valley in the wrong spot. I suspect that you are using the wall intersection as your reference points, which could be theoretically correct depending on wall heights and overhang sizes. Theoretically possible, but not probable.
Heres a picture that shows where your major components land. The overhang is drawn in red, the ridge is blue and the hip and valley is a dark green.
I can't even begin to answer your questions without a few answers that the others have asked, but this pic will offer a basis for discussion.
Bob's next test date: 12/10/07
one of the things i love about cad ( especially Chief )
is dragging those roof planes , it allows me to visualize complex roofs so easily
View Image
i think you hit it right on the head.. instead of planing the roofs , he was using the wall intersections
of course this assumes the gable ends are right and left, whereas the wingl on the left, the gables could be front and back
who knows. ?... 20 milkbones to the correct answer !!!Mike Smith Rhode Island : Design / Build / Repair / Restore
Hehehe, Mike, I didn't use CAD! His file was a doc file. I did a cntrl prtscn and pasted to Paint. I then cropped it and added the simple lines. I'm 99% sure that his problems are that he's trying to line up over the wall intersections which would be a nightmare. Bob's next test date: 12/10/07
no... i nu u didn't use cad....
i was just jawing about how neat cad is
when i was on a drawing table, i could draw things that couldn't be done in real life
in cad3-d you can only draw reality...
i think your analysis is spot onMike Smith Rhode Island : Design / Build / Repair / Restore
Yes...I know what you mean. It's easy to draw, impossible to build.Actually, Chief would create the intersection on those roofs rather easily: I think. If I wasn't busy, I'd sketch it up for the OP but I dont' have the time. Bob's next test date: 12/10/07
Jim/Mike
your line is about where I have the valley now and I do have aprox. 4 ft of dead space the angle to the valley is very steep. Would I be better off to take the area of dead space straight down to my existing wall @ least 4 ft in to where my intersection of my house and garage takes place. My Gables are on the ends ( to answer some of the questions).
Any and all comments are appreciated.
Jake
Edited 2/27/2008 1:21 am ET by jake101
Jake. Your post is directed to Blue and Mike, so I don't really know if I'm welcome to post here or not, but here goes. I have read your plea, and really wish I could help you out. But for the life of me, I cannot decipher this sentence: "I have a 4' section which sets outside the main portion of the house, setting @ the angle."
The other two sentences I cannot grasp are "your line is about where I have the valley now and I do have aprox. 4 ft of dead space the angle to the valley is very steep."
and "Would I be better off to take the area of dead space straight down to my existing wall @ least 4 ft in to where my intersection of my house and garage takes place."
Your sketch is too rough for me to make heads or tails of, and it looks like a floor plan, not a roof plan. Are you building this from a set of blueprints? Can you post a pic of the roof plan? How about some photos of the roof itself?
I'm guessing there are others out there who would offer help, if you could present a clearer picture of the problem.
I do appreciate your sense of humor - a vital quality for a builder! "I have read multiple articles and tried using String and trial and error (mostly error) methods."
I have never built a log home, so my imput here would be limited, but I enjoy the challenge of a tricky valley rafter problem.View Image “Good work costs much more than poor imitation or factory product” – Charles GreeneCaliforniaRemodelingContractor.com
jake ... any kind of pic would be helpfulMike Smith Rhode Island : Design / Build / Repair / Restore
I will go along with everyone else, picture, print please.
I dont know if this helps or not but typically, if you are planing two different pitches together, the hip or valley pitch will be the difference between the two. You are going from a 10 to a 12 so the valley pitch will be an 11. also the seat cut of your valley will not sit at the intersection of the two walls, it should be thrown to the side of the steeper plane.
Edited 2/27/2008 1:50 pm ET by seek1970
Edited 2/27/2008 1:51 pm ET by seek1970
"if you are planing two different pitches together, the hip or valley pitch will be the difference between the two. You are going from a 10 to a 12 so the valley pitch will be an 11."That seems like such an easy formula to remember. I wish my teachers had taught me that back in apprentice school. Instead, they taught me a very convoluted method for determining the rise and runs of the valleys and hips that took about a dozen steps. I wonder why they didn't just give us that simple explantion....?....! I have a theory.... Bob's next test date: 12/10/07
That's cuz it aint right...
Rabble rouser! Bob's next test date: 12/10/07
BS it aint right Ive been doing it like that for 10 years and my roofs
ALWAYS plain out ! you can plugit into all your formulas and cad programs all you want . Do you guys even cut rafters or just tell other people to do it ? Back when I came up in the trades we all used carpenters squares . Im guessing you dont know what that looks like.
Edited 2/27/2008 9:04 pm ET by seek1970
So you're admitting that you don't know how to use a scientific calculator. No crime in that, as long as you don't use incorrect and oversimplified formulas that won't get you what you want.
I'm no architect. I've been a carpenter and builder for more than 25 years, and I teach building science, math for builders and engineering for the home builder.
And I teach a segment on the history and multiple functions of the carpenter's orginal analog computer - the framing square.
Sign up for one of my classes - you might learn something.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Edited 2/27/2008 10:19 pm ET by Riversong
You are going from a 10 to a 12 so the valley pitch will be an 11.
I don't think this is correct.
The irregular valley rafter angle is calculated from:
Valley Pitch Angle = arctan(tan Major Pitch Angle × sin Major Plan Angle)
and
Major Side Plan Angle = arctan(Minor Pitch ÷ Major Pitch)
arctan (10/12) = 39.8°
arctan (tan45° x sin39.8°) = arctan (1 x .64) = 32.6°
32.6° = 10-7/8 : 17 valley pitch
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
Gee 10 7/8 x 17 is pretty close to an 11 . My post was made assuming the roof was being framed with conventional lumber and I admit to putting my foot in my mouth with regard to anything concerning log roof systems with which I have no experience. Conventional roof systems in my opinion dont require a scientific calculator to frame. I also realize that the valley member is an expensive piece of timber and the angle needs to be established before cutting , but you have to admit that using the difference of the two pitches got front row seats in the ballpark by your calculations. I believe using some string and a template for the plumb cut and seat cut would get the angles needed to cut the timber.
Your methods would indeed work and your formula might be classified as a "rule of thumb" if it works for all pitches. I've never considered it, so I can't comment on it. Does it work for a 2/12 and 12/12?In any event, it's important to remember to qualify the formulas. No ones trying to bust any ballz but it is important to get the stuff technically right or qualify it with a brief explanation. Thanks for sharing. Bob's next test date: 12/10/07
Well I guess I should have clarified that it is "get you in the ball park method " . It seemed like the man just couldnt make it work. And yeah , its necessary to make an adjustment to the angle at times. Not all carpenters went to school to learn how to build houses. Some of us came up in the trade by learning from guys who didnt have expensive calculators or maybe even a high school diploma. They taught us old school methods that are effective in fabricating a well built structure , And we do it without a working knowledge of trig. or calc. I hope someday I will have the opportunity to take a class or two in construction math if for nothing else but to understand what the hell you guys are talking about. For now though, I can only go to work every day satisfied in the knowledge that my houses will be standing for as long as the adhesives in the LVL hold . As for the 2/12 to a 12/12 Im not sure. I dont think that ive ever had to build a "bastard" hip or valley with such a dramatic difference. Im not trying to bust ballz either but but I got somewhat of a swelled head snyd remark kind of vibe from a couple of replies when I was only trying to help.
Edited 2/28/2008 9:32 pm ET by seek1970
seek... you don't need trig or calc to get the most accurate results
just a Construction Master calculator
and a good book showing all the keystrokes and diagrams.... like Will Holladay's
" A Roofcutter's Secrets"
http://www.amazon.com/Roof-Cutters-Secrets-Framing-Custom/dp/1928580149
between your old school knowledge, that book, and a CM... you'd blow right by most of these guys
me... i thought it was pretty cool that you came up with 11:17
and the trig calc came up with 10.875 : 17.
... that's gotta be a dull pencil line off
Mike Smith Rhode Island : Design / Build / Repair / Restore
Edited 2/28/2008 9:39 pm ET by MikeSmith
That was my point. I use a cm calc when I dont have a minute but I still like to keep the old noodle oiled and do the math with the rafter tables on the square. I figure someone spent tons of time inventing it so I might as well pay them some homage as it is an ingenious tool. As long as it doesnt cost me boss too much jack. Thanks for the comment.
Mike
The very first roof I framed without my mentor had an irregular valley. I just avg'd the pitches and it worked ok. The bigger the difference in pitches, the farther off avg'ing them will get you.
Then I got a CM and it takes about 4 seconds to get the exact angles.
For the valley in this picture http://picasaweb.google.com/TimothyUhler/Bernies/photo#5150886026807559314 it took about 2 minutes to figure the length and the angles. It is just a series of right triangles. I used no trig at all. You just need the rise and run of the valley and that all comes off that garage roof.
Tim, your roof photos are like what I'm thinking the OP is trying to describe. (Edit ... also like the recent diagrams posted by Huck). I hope the OP has a look at these photos an drawings, maybe he can tell us if they are on the right track toward what he is describing.
Joe Bartok
Edited 2/29/2008 12:03 pm ET by JoeBartok
It stands to reason that the actual pitch for an irregular valley will be somewhere between 10 and 12 and 11 would be as good as a guess as any. I've built many irregulars where the pitches were 8/12 and 12/12. Lots of 7/12 and 12/12. Several slightly lower than that. Never a 2/12 12/12. I wonder if our construction master gurus will tell us what the valley rafter would be for a 8/12 and 12/12. I've got a Construction master in the drawer behind me but I don't have the slightest inclination of how I'd find that valley. I can do it with good old fashioned geometry but I'd rather not. Lets see....some rules of thumb I was taught. "Cantilever 3 to 1 ratio". I've known carpenters that thought that applied to all situations including carrying a bearing load out there in cantileverland. Another: "When finding the angle of the roof pitch multiply the slope x 4 and add 2". That rule of thumb used to work fine for us when all the roofs were 4/12, 5/12 or even 6/12. That rule doesn't work so well as the pitch steepens. I've had to prove it to the old timers by asking them what a 12/12 would be if I used the rules of thumb (their answer was 50 degrees....it's actually 45 degrees). Rules of thumb are great as long as they aren't posed as technically factual. No ones arguing that strings don't work. I know both ways and I happily take the shortcuts too. Bob's next test date: 12/10/07
Blue, the Hip/Valley rafter slope will always be less than the two common slopes.
To use 2/12 and 12/12 slopes intersecting at an eave corner angle of 90° as an example, the Hip rafter slope angle is 9.335859°, that's about 1.972788/12. Or 2.794783/17 for those who prefer an "over 17" value.
The formula is: Hip Rafter Slope = Common Rafter Slope × sin Plan Angle
Edit ... hope I wasn't out of line by responding. I'm not a Construction Master guru by any stretch of the imagination. LOL ... I can hardly use one.
Joe Bartok
Edited 2/29/2008 5:29 pm ET by JoeBartok
Edited 2/29/2008 5:31 pm ET by JoeBartok
View Image
The hip/valley for an 8:12 to 12:12 is 9 3/8 : 17. Found it in about 10 seconds with this handy little book.... and no calculators or math involved.
Okay...that basically answers the question.The rule of thumb is close enough to get the stock to land on the plates and there will be a little shaving to do LOL! As for the "handy little book". First, it would take me an hour to find it. Then, the writing would be so small, I wouldn't be able to read it. In any event, thanks for that fast answer. I don't doubt that if I'd apply myself to learn the book, or the CM, I would succeed but those days are over for me. When I did it, I first did it longhand. Then, I graduated to a calc using basic Geometry. I agree with Joe, the more important issue is to understand the rational behind the formulas and understand the basic geometry. I won't denigrate anyone who chooses a different path because we all have our different methods and needs. Obviously, the math gurus enjoy the challenge of the math and I commend them for that too. I also honor the string and line guys. Me? Even though I technically know how to do it, I rarely needed to cut an irregular roof from the sawhorses so I devised my own shortcuts. For the most part, I used overall height and overall run to get my numbers for my framing square, then measured the overall length of the hip with my tape. In my later years, I would consider myself more of a wood carver. Some would say "woodbutcher" but...wadda they know? Bob's next test date: 12/10/07
If this is a double bastard valley, with both different pitches and a different plan angle then 90*, you would have to take the lower pitch and use it's rise along with the lower pitch run x 1.0833 to determine diagonal and pitch, because of the 22.5 degree plan angle.So for this example you could use 10" rise 1.08333' run to come up with a diagonal of 16 3/8 which equates to a 9.23 pitch. I learned how to calc this on my CM with the string method. Most of the time the rise is known and using either the calculated run or the measured diagonal would give the pitch back pretty quick. Anyway, that rule of thumb posted earlier about a 10 and a 12 having an 11 valley only gets close is if the plan view is 90. If it's only close under only under one condition, then it's really only a rule of thumb. Which goes back to saying we all need to learn the math, or the geometry. Anyway, it's all in the way it all relates. The framing square formulas were cheats that the trig guys in history passed on to the others who needed the hints. These guys discovered these formulas by drawing and measuring. From Algebra up, math is just reproduced geometric formulas. That's why the framing square works so well. Use the plan view run with the associated rise and you have your pitch. Use your calculator and it's even easier. Edited 2/29/2008 11:00 pm ET by kpatrixEdited 2/29/2008 11:01 pm ET by kpatrix Thinking about it more, you can't just use the plan angle for a bastard pitch. It's going to be easier to string everything in and calc from there. A 22.5 plan view intersection and 22.5 bastard roof intersection require different calculations.
Edited 2/29/2008 11:38 pm ET by kpatrix
From: http://ca.geocities.com/web_sketches/framing_math/Framing_Angle_Formulas.html
For ridges/eaves at other than 90°:
W = Angle viewed in plan between Hip eaves or Valley ridges; any value greater than zero up to 180°.
Common Rafter Pitch Angle or Common Rafter Plumb Cut Angle
arctan (Pitch) or arctan (Rise ÷ Run)
The initial values of Pitch Angles are generally given as Over 12
Angle in Plan or Deck Angle measured between the Hip eave and the Hip run, or the ridge viewed in plan and the Valley run. Also the Cheek Cut Angle or Saw Blade Bevel Angle along the plumb lines of Jack Rafters, at the Hip peak or the Valley foot.
Major Side Plan Angle = arctan [sin W ÷ (Major Pitch / Minor Pitch + cos W)]
Major Side Plan Rise = 12 × [sin W ÷ (Major Pitch / Minor Pitch + cos W)]
Minor Side Plan Angle = arctan [sin W ÷ (Minor Pitch / Major Pitch + cos W)]
Minor Side Plan Rise = 12 × [sin W ÷ (Minor Pitch / Major Pitch + cos W)]
Hip-Valley Rafter Pitch Angle or Hip-Valley Rafter Plumb Cut Angle
Angle = arctan (tan Common Rafter Pitch Angle × sin Plan Angle)
Rise = 12 × (tan Common Rafter Pitch Angle × sin Plan Angle)
Jack Rafter Side Cut Angle on the face of the Jack Rafter set in the plane of the roof.
Angle = arctan (cos Common Rafter Pitch Angle ÷ tan Plan Angle)
Rise = 12 × (cos Common Rafter Pitch Angle ÷ tan Plan Angle)
Sheathing Angle, also the angle on a Jack Purlin on the face of the Purlin set in the plane of the roof.
The Sheathing Angle is complementary to the Jack Rafter Side Cut Angle.
Angle = arctan (tan Plan Angle ÷ cos Common Rafter Pitch Angle)
Rise = 12 × (tan Plan Angle ÷ cos Common Rafter Pitch Angle)
Solar & Super-Insulated Healthy Homes
Do you work in the field ? Im guessing not . Im willing to bet you are one of those guys that call themselves an architect that draw things on a computer that look good in 2d but will not work in the 3d world. Ive been in the trade for over 15 years. Ive been a lead carpenter for 10 of those years and have been building high end custom homes all the while. When I say high end Im talking 10,000 or better on the sqft . Framers in the field dont use over exaturated formulas to build a roof . Not practical and not accurate. Nothing in the field is as perfect as a numerical formula therefore rendering it useless. A framing square and experience have no rival!
Edited 2/27/2008 9:21 pm ET by seek1970
I think this is what you're describing
CaliforniaRemodelingContractor.com
But this is what needs to happen
CaliforniaRemodelingContractor.com
It would appear that your if your 24' wide house has a 12:12 roof pitch, then the garage, being 28' wide, would likely have a 10.29:12 roof pitch, so that the ridge would be at the same height. The valley pitch, as drawn, would be 10.13:12. You must continue the garage top plate until it hits the top plate of the house - the valley would proceed from that point of intersection.
CaliforniaRemodelingContractor.com
Oops - my bad. I had the garage angled off 22 1/2 degrees to the one side, not the other. Here's the corrected version. But the math remains the same.
CaliforniaRemodelingContractor.com
Thanks for the drawing, it is a help. I am looking through my pictures to see if I can show you exactly what I am looking @. The framing is with conventional lumber not log. I am attaching a picture to show you the angle, however it is not that good. I will take some new pictures tomorrow and post. The weather has us shut down right now.
jake
Huck
Your second drawing is close although it appears to be 24' wide on the garage. It is actually 28' @ the angle where the garage attaches to the house.
Jake
OK, I'll try again. This is the same roof, but shown from a slightly different perspective. You say the garage "is actually 28' @ the angle where (it) attaches to the house". I drew it 28' wide. Are you saying it is NOT 28' wide when measured straight across? Trying to visualize is difficult from your verbiage.
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View ImageView Image “Good work costs much more than poor imitation or factory product” – Charles GreeneCaliforniaRemodelingContractor.com
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View ImageView Image “Good work costs much more than poor imitation or factory product” – Charles GreeneCaliforniaRemodelingContractor.com
I don't think anyone was trying to "bust ballz" or be snide. It's a pretty good group of guys here.
"Old school methods" is exactly right! And a calculator certainly isn't necessary to understanding complex roof math. In fact it's best to begin without the so-called "higher math" and start with the geometry ... that's where the formulas come from in the first place.
For anyone interested, here are a couple of links to a couple of Hip-Valley roof geometry threads. Although formulas are a part of the discussion all of the angles and proportions can be solved with nothing more than a geometry set, or a framing square.
Hip and Valley Roof Compound Angle Formulas and Geometry
Roof Math
LOL ... now the only problem at the moment is that all the geometry and trig in the world is no good whatsover. Despite reading this thread over three times yesterday, and studying the drawings posted, I still cannot seem to wrap my brain around exactly what the original question is. :)
Joe Bartok
Edited 2/29/2008 10:32 am ET by JoeBartok
Edited 2/29/2008 10:33 am ET by JoeBartok
When I used to cut roofs frequently, I started with a CM. Eventually I got to the point where I preferred a trig calculator over the CM, but I haven't used any serious trig in years. And really all that occured in a short span of time where I was doing nothing but roofs.
One of the reasons I like working out construction details with google sketchup is that its kind of a CGI stringline/geometry visualization in 3D, and I tend to be visually oriented when it comes to working out roof-cutting details.
My frustration with this particular query is that the OP is not providing the necessary information to fully work the problem out. Hopefully he'll show up soon and give us the rest of the story.
It sounds like part of the problem is that the plans he's working from have given him a complex roof connection (two differing pitches meeting in a valley where the walls intersect at other than a right angle), without giving a good clarification of the construction details.
Incomplete or poorly drawn plans, in other words. Possibly exacerbated by the fact that he has limited practical experience in roof cutting, on a roof where even experienced roof cutters could get tangled up.View Image “Good work costs much more than poor imitation or factory product” – Charles GreeneCaliforniaRemodelingContractor.com
It seems more info from the OP isn't forthcoming and all we really know is that we have unequal slopes at an irregular corner or eave angle plan view ... might as well consider how to deal with real bastard roof in general.
The first move is to split the corner angle correctly into the Major and Minor Plan Angles (a.k.a. Deck Angles). General Deck Angle Equations shows how this may be accomplished and the solution of two different formulas.
Irregular Plan Angle Formula ... an html rehash of the last formula in the pdf document. This page includes some example solutions.
We already know the two component common slopes which meet at the same height or rise. Now we have a plan angle for the major and minor side of the roof and can find the Hip/Valley slope to whatever degree of accuracy we desire. In fact we can continue on and find every nitpicking angle in a complex roof, right down to the chamfers or square cuts for the mortises and tenons.
Joe Bartok
Edited 3/1/2008 9:34 am ET by JoeBartok
Just for the sake of argument, let's say this drawing by Huck is the correct interpretation. (IMO this is likely what the OP is describing ... but who knows for sure???)View Image
Main Slope = 12/14
Adjoining Slope = 12/12
Corner Angle = 180° – 22.5° = 157.5°
Main Plan Angle = 99.89240°
Adjoining Plan Angle = 57.60760°
Hip Slope Angle = 40.17771°
An interesting roof. If the Hip rafter were to be backed the main side is beveled at 6.41938° ... but troughed, like a Valley. The adjoining side is cut at 22.25984° with the bevel oriented to produce a ridge, the way we would normally cut a Hip.
Joe Bartok
Edited 3/1/2008 2:43 pm ET by JoeBartok
Edited 3/1/2008 2:43 pm ET by JoeBartok
An interesting roof. If the Hip rafter were to be backed the main side is beveled at 6.41938° ... but troughed, like a Valley.
That's because it IS a valley on the near side.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
OK For all concerned I figured it out, Huck thanks for the drawing it was a big help. Sorry for the lack of info on the discussion, but we had good weather the past few days and I had to be working. I brought the 10/12 pitch across as in hucks drawing and things fell right into place.
THANKS EVERYONE....
Jake
I do understand the math and I do understand the geometry. I was not saying that I use the string method for every roof either . I was merely
trying to point the man in a direction that would be more of a visual aide to him. He said he had tried everything and couldnt figure it out.
I just wanted to get the point across that when all else fails there are other avenues to explore that would be in what I perceived to be his scope of experience. In a perfect world math would always be the solution, but framing material is not always exactly what it is supposed to be and top plates are not always perfectly straight after being in the weather. long headers in walls make it harder to tweak a top plate too. Typically what my boss likes us to do is set the ridge and measure each rafter individually to ensure a tight fit. takes a little longer but no gaps on the top cuts
Edited 3/4/2008 12:22 pm ET by seek1970
BTW, my drawing is essentially the same thing Blue drew for you in plan form several posts back.
CaliforniaRemodelingContractor.com
“I dont know if this helps or not but typically, if you are planing two different pitches together, the hip or valley pitch will be the difference between the two. You are going from a 10 to a 12 so the valley pitch will be an 11. also the seat cut of your valley will not sit at the intersection of the two walls, it should be thrown to the side of the steeper plane.”
<!----><!----><!---->
<!---->Sorry ... this isn't so. <!---->
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“BS it aint right Ive been doing it like that for 10 years and my roofs ALWAYS plain out ! you can plugit into all your formulas and cad programs all you want . Do you guys even cut rafters or just tell other people to do it ? Back when I came up in the trades we all used carpenters squares . Im guessing you dont know what that looks like.”
<!----> <!---->
The formulas in the link below are correct. There is no such thing as a “stand alone” formula. Formulas arise from studying the roof geometry. This is the first step … understanding the formulas.
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http://ca.geocities.com/web_sketches/framing_math/Framing_Angle_Formulas.html
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Drawings … nah. A Valley rafter is worth about 5K and it’s best to minimize the chances of an error. Any proposed joints are modeled in 3D.
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3D Models of Joinery
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And then the roof components are cut.
Hip Valley Roof Images ... 1
Hip Valley Roof Images ... 2
Hip Valley Roof Images ... 3
Joe Bartok
Edited 2/28/2008 10:24 am ET by JoeBartok
Yours is so much more elegant and precise. Thank you! Bob's next test date: 12/10/07