When I started framing in 1971, when cutting rafters we used to step off the rafter with a frame square. We had no nail guns.
I no longer frame, but build custom homes. Cutting rafters, my framer(s) use Framers Bible / Swanson Speed Square Blue Book / Construction Calculator / cccasionally the tried and true framing square step off…..
I had to teach one of the young framers the square step off method / he could not find his book, and was going to Home Depot to buy a Swanson Speed Square just for the book.
One of my Mexican framers uses a consturction calculator.
I am building a Church Parsonage, and I volunteered to frame and cornice the Well House with a carpenter friend, in gratis. Today, I was cuttng the hip roof for the Well HouseI was reminded of something we found when cutting rafters using the Blue Book as follows:
I always stepped off and later used the Blue Book. I used the Blue Book today and found it to be accurate on a total span of only 8′ and a total porch span of 4′. We subtracted the 3/4″ for 1/2 the ridge. Fit nicely.
I remember when we did larger roofs (SPANS 14′ +) using the Blue Book, we did not subtract the 3/4″ from the rafter length for 1/2 of the ridge. If and when we did the rafter needed it….a small gap would open at the bottom….if we did not subtract the 3/4″ …..it fit nicely.
Has any of the BT Crew framers out there experienced this with the Swanson Blue Book, or other methods? I never had problems with the old step off method. I meant to check the Blue Book against a frame square today, but did not / never have.
No big deal, just curious.
Birdsmouth / when used as a construction term, one word as spelled or two with an apostorphe after the “d” ?
If it is one word with no apostrophe, framers did it.
Replies
Step-off? Wow, haven't seen anyone use that method in ages. I used to use the trig calculator, lots of guys use the Construction Master. Plenty of threads here on hip-roof framing, check the search function.
here's a link to one
Let's keep it simple! Calculator and a rafter sq. to cut a hip valley cripple jack.
I use a Construction Master calculator to calculate roofs. The framer who taught me the basics, showed me how to do it with some simple multiplication and division. A scientific calculator works just fine also.
Check out Will Holladay's book at the JLC Library http://www.jlconline.com/cgi-bin/jlconline.filereader?436d8afe0023be2c27177f00000105d4+EN/products/RC102
My personal opinion is that while it's good to know how to use the rafter square, stepping off rafters is a slower and less accurate option nowadays.
"I no longer frame, but build custom homes. Cutting rafters, my framer(s) use Framers Bible / Swanson Speed Square Blue Book"
That's the problem with those books, they don't TEACH you anything by looking at a span and getting the rafter length. I saw Larry Haun in his video take out a book to get the rafter lengths and thought it was a joke. What would he do without the book to figure out a rafter?
The books might be good for and old timer but by the time Larry looked up the page and then went to the span and all that the rafter could've been mark already.
"I had to teach one of the young framers the square step off method / he could not find his book, and was going to Home Depot to buy a Swanson Speed Square just for the book."
See what I mean. If a Boss would take the time out to TEACH something about a simple Triangle, it would help a young guy starting out understand how to lay out a rafter. If you get a kid fresh out of high or college the math is still fresh in their mind.
If you just draw a picture of the two out side walls and a triangle representing a roof with the span and run and then draw little triangles of the run, rise and hypotenuse that will represent a rafter and the length and why those numbers work.
How I know this because in the course of all my years framing and actually drawing this on the deck by snapping lines as if it were a wall and rafter and writing those numbers down by drawing little triangles and then laying the Framing square on those triangles and numbers and stepping it off PLUMB seems to trigger off how the framing square and the triangles work.
Once you show them that then you draw the birdsmouth and the seatcut and what the seatcut represents.
I drew something with the step off using a 9/12 pitch roof with a 10' span and 5' run with no ridge deduction. Once you show someone this then you can teach them how to use the numbers on the framing square and why where it says 15 for "Common Rafter Length per Foot Run" line how you can multiply that by 5 and get your rafter length of 75".
Stepping off rafters is way to slow and not as accurate as using a calculator but knowing all this will help you punch in the numbers on whatever calculator you use.
The books are a waste of time to give to a new kid just starting and for anyone else. You can punch in a rafter length in seconds. Like I said above,by the time you go through looking in a book and flipping through the pages to get a rafter length the rafter could be marked already.
My first boss showed me how to lay out a rafter by stepping it off first and what all the numbers meant on the tables of the framing square and then he showed me what to do using math and multiplying the run in feet times the Common Rafter Length Per Foot Run number.
Great post by all, in particular Framer's, he see the value in mixing and teaching the general princliples with the old step off, yet encouraging the use of a Construction Calculator for speed. Yeah, what if some steals your calculator or you lose or forget your book?
NOTE: Accumlative errors in step off can be almost omitted by numbering the steps. Measure twice cut once, or measure three times before cutting the two trial rafters using 26' doug fir material.
I have never used a calculator, but probably would learn if I still framed.
I need to go teach our adult Sunday School class...later.
Nice post Joe, I agree with you 100%. I find that most of the time when my guys make a mistake its because I left them in the dark. I have to constantly remind myself as their foreman to not piece meal the task, but help them to see the outcome, the final product. This teaches them to think and when they understand the concept and are thinking and solving problems they are more valuable. The approach you suggest is of value to everyone. I still haven't bought a construction master yet but when I do it was you who sold me.
You know what else I've also done is to actually lay out the step off on a rafter like a stair stringer with no ridge deduction and then cut the rafter and scribe it on another one and then cut the birdsmouths and overhang and nail them right on the shoe on the deck with all the marks facing us.Then they can see exactly what the run, rise and hypotenuse is and why those numbers are on the framing square and why they work for a level run and a plumb rise. After they see that I will measure back plumb 1/2 the ridge thickness on both rafter patterns and actually draw the ridge. Once the ridge is draw it show them how half the thickness of the ridge creates a small triangle which gives you a run, rise and hypotenuse and which that little rise lowers the ridge if you wanted to figure out an exact ridge height that would be the measurement that you would deduct from your overall ridge rise if you figured to the center plus adding your HAP cut.Teaching is a great thing and I enjoy every minute of it and then to see it click in or here someone tell you that now they understand and then actually lay out a rafter, cut it and then try ity out and see it work is a great feeling for me.Joe Carola
I learned to cut basic gable rafters by using the rafter tables on a framing square. Today I use the Construction Master for pretty much all rafters in all roofs I frame. The thing I like about the CM is that it lowers the human error factor big time.
Just out of curiousity, I've stepped rafters off with a square to see how accurate it is. My opinion is that it's slow and very prone to accumulative error.
I've never used the Blue Book, but I have read through it out of curiousity a few times. Doesn't seem to be anything in there that isn't in Roof Framer's Bible which sits in the door pocket of my truck at all times. The thing I seem to use RFB for the most is for looking up hip drops.
I like the calculators because they are relatively cheap, very fast, and very accurate. But I do think that you need a decent mathematical foundation to do much roof cutting beyond the basics. I'm not saying that you need to be a calculus major to cut roofs, I just mean that it's important that you learn some of the "whys" insteads of just the "hows".
I love roofcutting because it seems that there is a never ending learning curve. (at least from my current position on the curve). I know that I understand a heck of al ot more about roofcutting than I did a few years ago, but I also still have dozens of unanswered questions too. I'd like to think that there will always be a set of plans out there that will make me scratch my head. Of course I say that on a Sunday morning...... ask me mid week when I'm pulling my hair out 40' from the ground if I'd like to have it mastered!
"The thing I like about the CM is that it lowers the human error factor big time."as long as you are not weaaring gloves, LOL
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dieslpig,<!----><!----><!---->
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“I've never used the Blue Book, but I have read through it out of curiousity a few times. Doesn't seem to be anything in there that isn't in Roof Framer's Bible which sits in the door pocket of my truck at all times. The thing I seem to use RFB for the most is for looking up hip drops.”
While there is most of the “Blue Book” in the “RFB” there is no “Hip Drop” in the “Blue Book” I only bring this up because “Hip drops” are not a necessary part of cutting regular or irregular hips. I understand the concept of them but I have never had to calculate them or apply them to my hip/val rafters. I let my saw do it for me. Read the blue book again (pg 19 in mine) and compare it to the RFB’s pages 20 & 21. Try the Blue Book’s hip drop-less method if you can understand it. I will have to agree with most “Blue Book” reviews that it is a poorly explained and overly concise explanation of roof cutting but I have used their method to cut Hips/Vals most of my life and they fit perfect without the added mathematical computation.<!----><!---->
Mr. Jalapeno<!----><!---->
I don't think I even have a blue book around anymore, so humour me...
How do your rafters plane in to your hip if you don't drop the heel stand some? The way I understand it is that if you don't make the deduction, the roof will plane in to the center of the hip, so the 'edges' of the hip are up out of the roof plane. Lowering the hip the appropriate amount sets the edges of the hip rafter into the correct plane rather than the center.
Only other way I know is to bevel the hip.
Is it that you do actually drop the hip, but the math is buried somewhere else in how you calculate your hip rafter?
Here we go again.
???
Brian,
He doesn't drop the hip at the birdsmouth, the method he cuts the double cheek at the ridge takes into account the hip rafter thickness. It saves a layout step and makes the hip plane with the roof
Edit,
I believe this was hit on a thread this year. Sometime last winter or last spring.
Edited 11/7/2005 11:26 pm ET by Timuhler
Hmmmmm, I still don't get it. Guess I'll run a search and see if I can dig it up. Thanks.
I'm not saying that you need to be a calculus major to cut roofs
lol. I'd agree that Isaac Newton had some other things in mind when he developed the theorems.
Tx, I was taught to step off rafters the same way. We used the framing square exclusively. No one had calculators and I never heard of anyone going to a book to look at a table.
The "art" of stepping off squares isn't that difficult. More importantly though, is that it is a basic skill that becomes the foundation of many more layout processes.
For many years, I've bemoaned the fact that speed squares have become the tool of choice for laying out lines. Most of the youngsters nowadays have never developed basic layout skills with a framing square. Since they don't know the basics, they certainly can't/won't know the advanced uses.
I don't know how to use a speed square, I've never been able to do anything other than make a simple basic square line, or a plumb cut, so I probably am not as good as an advocate for the framing square as someone who knows both. But, I know for sure that the framing square can do ten times as many things as a speed square, and if the kids really want to develop some quick layout habits, they would be wise to leave the speed square in the tool box and start learning things like "stepping off rafters".
blue
blue,
I hesitate to chime in here---
But---you would have enjoyed meeting my father-in - law.
Old school carpenter, child of the great depression----came up though the CCC.
anyhow-----he used to tell me 2 framing square stories REPEATEDLY
1)--- he claimed you could use a framing square to do anything to a house worth doing, except paint it.
2) worked as a construction superintendent for about 40 years. his company used to do a lot of contracts for ---what was then-- Goodyear Areospace ( now sold), and Sohio ( now BP)
One day he arrives at work and 3 Sohio engineers are arguing about how they are gonna layout this gastation on the lot----got a transit on site---arguing about where to set up---where the appropriate benchmark is to start from etc.
Old nick gets out a framing square and a piece of string and goes to work.
couple hours later the engineers finally get their act together---locate the benchmark---shoot the site---and proclaim old nicks layout good enough for Sohio( done with a piece of string and a framing square)
BTW---he used to tell me that in his youth he would have thought nothing of being assigned to take 1/2" of the length of a oak door with a hand saw.
Stephen
BTW---he used to tell me that in his youth he would have thought nothing of being assigned to take 1/2" of the length of a oak door with a hand saw.
That's a good, typical sting and square story Stephen.
I had to laugh when I read that last sentence though! It's funny to me because the first exterior door I hung, I used a handsaw, plane and chisels too! I had to make a cross cut on the bottom and bevel the edges. I don't remember ripping it full length though I'm sure I would have without thinking twice!
Oh yeah, I think I finished that door up at about 11pm on a worknight, after work of course! I had to get it closed in, the elderly people that I was working for would have been scared if they couldn't lock their door! Lol!
blue
I cut my first roof in 1973. It was just a single ridge gable. I used a slide rule to calculate the length. I have tried just about everything to cut a roof and still fall back on any technique I feel is fastest for the time (except the slide rule). Stepping the rafters is OK for simple and small gable roofs where all the rafters are the same length. "Cumulative Errors” will become evident if stepping is used for big multi-spanned complicated roofs.
I used the Swanson’s “Blue Book” for at least 10 years of my framing career. It was equally as accurate for single rafter length calculations as any other mathematical method. I would step the jacks and did find “Cumulative Errors” with them. The CM Calculators helped to refine my jack’s lengths accuracy.
I have not found any rafter book table errors. (not in the “Blue Book, or A.F. Riechers, or The Roof Cutters Bible by Barry D.Mussell, or any of many others I did not list. Rafter Tables are just lists of Hypotenuses for given right triangles.) For single Rafter Length (Hypotenuse) calculations the books are all close enough to the calculators for framing accuracy. Definitely no problems with removing 1/2 the ridge dimension and having the rafters fit poorly. That is, as Blue Eyed Devil stated, probably just a marking error. I use the 7” speed squares for occasional “Out of my Tool Pouch” cuts/work. I use the framing square, or the 12” speed squares for accurate roof cuts.
My father told the simplest statement that explained the concept of roof cutting to me the day before I cut my first roof. “A rafter length is just the Hypotenuse of a right triangle.”
These days I use a spreadsheet calculator to create a list of rafter lengths at home and give it to my carpenters/helpers to cut while we build the walls.
We're in agreement Mr Jalapeno!
If I was doing simple ranches like my mentors used to do, the framing square was as good as anything. They only had perhaps two rafter lengths to make a pattern for: the main roof and the attached "L" shaped garage that intersected it. They all used the tables on square to get their differences in lengths of jacks, and they simply took their measurments off of the commons. Unequal pitched roofs were a rarity.
By the time I got heavily involved in framing, things were changing. "McMansions starte popping up all over the wealthier areas and roofs suddenly became complicated. Cumulative error had some significant implications. I learned to double check my stepped off rafters with hard math. Often I would find a 1/4" error at the minimum. So, I decided to stop using the step off method.
It's important to note that I still use all the other framing square skills that I acquired in youth. Sadly, I've noted that even Frank, whom I mentored, has not developed some significant square usage techniques because he never developed the basic stepping off fundamental techniques. He always used a calculator from day #1 and therefore doesn't think to employ the simple techniques that often make the framing square so unique and so fast for many differnent tasks. Alas, I think that the framing square is rapidly losing it's appeal on may levels and skills will be lost, perhaps forever.
Sigh!
blue
Blue,<!----><!----><!---->
I'll have too Agree, We Agree. <!----><!---->
I owned a framing square first. The guys I worked with in my youth were sold on the speed square so I joined in too. The use of the speed square has brought me full circle back to understanding the framing square in a complimentary fashion to the speed square. I use both daily but I rarely crawl through the rafters with a framing square in my hand.<!----><!---->
I don’t believe the framing square will ever completely fall from grace unless it just quits selling. That is a possibility though. Money caters to the ignorant you know.
Mr Jalapeno<!----><!---->
I'm with Joe Carola, Mr. J, et al ... learn the math. Understand why things work the way they do in terms of the geometry, ratio and proportion and trigonometry and in time you won't need a book and it won't matter if you lose your calculator. The folks I usually help with joinery are log builders and the sessions often feel more like tutorials than work. I've always enjoyed helping with the layout and calculations, explaining why the math works and often learn something new or find a better way to do things.
Joe Bartok
Edited 11/7/2005 12:23 pm ET by JoeBartok