Easy Common Rafter Layout Step Off Method

i'm eddie ferrari carpenters local 255 in new jersey this is work force education 105 lesson number five okay the program is carpentry the course title is rough framing and we were talking about the common rafter and we're going to demonstrate the step off method so in my opinion as a carpenter we're the most rewarding tasks is framing a roof however sometimes it can be the most frustrating if calculations and formulas aren't made exactly right today we're going to discuss the step off method the step off method is a technique that allows a carpenter to effectively lay out a common rafter without using any mathematical formulas only the framing square we're going to learn parts of the framing square the making the markings on the framing square and how the framing square it does to wrap their calculations for us once we have learned the framing square and how can work for us I'm going to demonstrate the step off method and how you can make it work for you without doing no mathematical formulas so it was my hope that the step off method will help you gain confidence and understanding of roof framing you'll be able to tackle the process on your own alright so our objectives for today are to define the parts of the common rafter identify layout tools describe rise and run and demonstrate the step off method alright so this is a typical common rafter the common rafter is the basis of any roof humor that you're going to make everything comes off of the comic record commodore after all the calculations everything is based off the common rafter so we're going to start with this one first so this is a common rafter okay the part up here this is our reach cut the part that's at the top of the roof Arizona for his mouth this is our keel and this is our seat Cup we're a minimum of an inch and a half here so it grabs the top plate a minimum of a three and a half inch seat so it sits completely on the top plate here is our a rafter towel our plumb cut and our soft cut the dimension from the ridge to the the building line also called the hat is what we call our called our line length of over after this is our half hour half stands for height above plate that is the distance from the sea cut to the top of the rafter so now we're going to talk about rise and run rise is the vertical distance run is the horizontal distance anytime we do common rafter if we base everything on 12 for 12 inches so the roof that we're going to do we're going to start out with is a 5 12 it's a 5 12 pitch meaning that this group's rises 5 inches for every foot of run so what's the rung well first we have to start with this dimension here outside a building 2 outside a building is we're going to call it for room purposes here 8-foot so that's our span so our span is 8 foot run is half of that distance so your run only travels to the center because he draught there only travels halfway across the roof so our run is 4 so that's telling us that we have four units of run to make it to the center part of the rich so if I draw it out for each one one two three four each one is 12 inches now when this rafter is rising up its going to travel 12 inches on the level but because it's rising that distance is going to be greater from unit of runs unit or um there's one two three and four it so an easy way to find out what the run of a 5/12 roof is is to go to your framing square the framing square has a blade and a tongue the blade is 24 inches long and it has a scale on it so the scale says linked per foot of a common rafter so you find your number and I'm gonna come to five so I'm at five okay and the number is 13 so right there it gives us the map that every distance here is going to be 13 inches so every unit that rafter to travel 12 inches the travel of a foot of run it has to be 13 inches long because it's because it's on that angle so there's a there's a mathematical formula for it but because we have the framing square which is 16 by 24 if we measure 12 being our unit rung and 5 being our rise by measure from 5 and 12 so you can get that in there right here the dimension is 13 if you know if you wanted to change it up you just measure from your rise to your grunt oh that's going to be 12 and then it'll it'll tell you the distance okay so now we're back to the rise and run we know that we have a 512 roof and we know the distance over 512 when our rafters traveling 13 inches so if we were to do the mathematical formula all we do is we take our run at four times it by 13 and it equals 52 okay so that's telling us the line length of a rafter when we go over the counter after our line length from the top of the plumb cut this is before deductions the plumb cut all the way to our building line where our heel cut is at the top here is 52 inches from Ridge cut to the path however we don't even need that mathematical formula because we have our frame and square and we're going to take this frame and Square and step off the units of run four times one two three four to lay out the rafter so if I was going to step off this rafter I don't need any math all I need to know is how wide the building is which is 8-foot divide it in half to get my run as soon as I have that four so I have that four and I have my pitch so I need to know if it's a 512 pitch but four units are wrong so we talked briefly about the framing square for this purposes all we need to know is the tongue and the blade so this is your unit rise and this is your unit run if you have any trouble forgetting which goes where the roof pitch is always the smaller number 5 12 6 12 10 12 and this is always going to be 12 on a common rafter so big number big side little number little side so we're going to hold 5 on the little side and 12 on the big seven the biggest thing is to hold when on the markings is when you're going to lay it out that if I'm holding five here on the outside I have to hold 12 on the outside you can't put one on the inside and one on the outside it throws it off so if I'm holding 512 I have to be both inside are both outside so we're gonna to lay this out the only tools we need is a framing square I call these acorns people call them stare gauges but I just always call damn acorns and this is going to let us know we can do a repetitive motion of our layout with our Raptor square they're made out of brass okay pencil and all we need to tape measure for is our deductions okay so I have my framing square I have my tongue I have my blade I have my black magic marker that you should always use a pencil time just for demonstration purposes I'm going to show you with the marker so I like to do it by hand I'm going to hold the 5 on the little side of the square the tongue and 12 on the big side of the square so we start off and the first mark I'm going to make is my Ridge cut 5 and 12 so we have four units of run so I make a little mark here I'm sorry and I rate a 1 that's my first unit of run and we have four of those so I slide on down okay so I'm at 5 and 12 5 on a little side 12 on the big side make a little mark I rate it to slide down again 5 and 12 then mark again and I rate a 3 remember we said the rafter travels 13 inches so every single time we move this square down we're traveling 13 inches on our board going down again so this is our last unit of rum some 5 and 12 so I mark it okay I come down here and hold 5 and 12 I square that down the mark that I just squared down that's our building line as the outside of our building so if you come back here we have one two three four units of run to give us 52 inches bigger okay so the first thing I do once I have this I check out online my Ridge cut make sure everything's good and I come down and I'll mark out my rafter town you can do the calculation for the red cell as well but I just like to bring the square straight up put a level on the line and I want a six-inch rafter towel so I leveled with the line on a 512 pitch and then I just measure out six inches mark it and I bring my square in five and twelve and slide it into position okay that's my rafter towel so now we're talking about the birds mouth right here you can measure up an inch and a half and then slide your square in to get that minimum inch and a half but you may not always end up with the seat cut so what I like to do is take the 512 and we'll just slide it in until them three and a half inches away so right around 15 and a half so I hold 512 and then when 15 and a half hits the line that's when I Square crossed my birds mouth so I'm gonna get three and a half on the seat and an inch and a half up so it can grab you know grabs a full bearing on the top plate and the heel grabs against you know the side of the to buy material so the only other thing you have to do left that is your deductions you have to deduct half the thickness of your Ridge generally when your stick framing that everything is won by material so it's three quarters of an inch so I'm gonna mark 3/4 got 5 12 I always exit out so I don't cut the wrong line so there's my deduction there and I have a 2 by 6 going for my fascia board so this I deduct it as well but I deduct a full inch and a half your framing square measures an inch and a half so you're going up the measure on this one either I hold 512 slide it in just square down my square X that out give myself a cut line ok so there we have it we have a 512 common rafter that we stepped off with no math today we learned how to make the framing square work for us we had the framing square do all the calculations of the common rafter and my hope is that it gave you a little bit of confidence more understanding of the process of the roof theory and so you can kind of tackle it on your own if you have a framing square scrap piece of wood at home or on the jobsite you can practice it takes a few few minutes to to really get it down you kind of fumble with the square first but you'll be just fine so next class we're going to go over the 1 number method using a speed square all you guys carry a speed square every single day not many people even look at the markings on it the speed square is even way easier to layout a comment or after so next next week we're gonna go over the 1 number method of using a speed square to lay out a common rafter so have a good evening do your homework and I'll see you next week

Channel: Mrs Ferrari

Views: 184,871

Keywords: Common Rafter, Roof Framing, Carpentry

Id: OAMdAAWDDpA

Length: 15min 35sec (935 seconds)

Published: Mon Jun 20 2016