Cutting Common AND Hip Rafters: Simple Solutions for Roof Framing

hi I'm Rick Arnold and I'm going to show you a really easy way to cut and install a hip roof hip roof only consists of three components for the most part the hip rafter jack rafters and the king rafter which is actually a common rafter from the rest of the room I'm gonna take you through four easy steps calculating the rafters marking the rafters cutting the rafters and then stalling the rafters very very simple so let's have some fun okay so we're gonna start with common rafters there's four simple steps to cutting and installing the rafters first step is calculating the rafter lengths using a construction master or even a regular calculator the second step is transferring those calculations to our rafter stock once they're transferred to the rafter stock we cut the rafters once the rafters are cut we take them and install them up on the roof four simple steps no matter what type of rafter you're cutting so let's start with the common rafter so to calculate the common rafter we only need to know two things one is the run of the rafter the other is the pitch of the rafter the run of the rafter is the distance of the building that is covered by the rafter itself so this rafter comes up right up to the peak drop a perpendicular line down from here over that measurement is our rung we have to adjust the run a little bit because our rafters do not come up and meet in the middle like that if they did then exactly half of the building would be the run but because we put a ridge in between the rafters at the top our rafter stops exactly three quarters of an inch back on both sides because we're using a 2 by Ridge here so we draw a plumb line down from that rafter and from that point over that is our run so in other words if I'm measuring over our building is 8 feet and 1 inch I measure over here to 4 feet 1/2 inch that's our exact center but because we have a ridge here we have to subtract 3/4 of an inch back so 4 feet 1/2 inch minus 3/4 of an inch this plumb line comes down that gives us 47 and 3/4 of an inch that's our run all we're doing is forming a triangle with our roof rafter in our building so our adjusted run is 47 and 3/4 of an inch from the end of the building to this edge right here that's the bottom of our triangle so I'm going to write it right on here 47 and 3/4 of an inch that's our rug now the second thing we need to determine is the pitch of the roof for every foot of run of a roof rafter the pitch is the distance that it goes up in this particular instance we're going to do a six-inch pitch roof so that means 12 inch run we have the roof going up 6 inches I know it some of you are thinking right now this isn't the pitch this is a rise because we're going up so that's a rise and the pitch is some degree measurement here but the common language and calculating our rafters this is the pitch this is a pitch in an inch measurement six inch pitch it's on the calculator that's how we enter it so what we have is the Run which is 47 and 3/4 of an inch and the pitch is six inches those are the only two things we need to calculate everything we have the run we have the pitch so I get the calculator out and I'm going to enter 47 and 3/4 and that's my run comes right from here and then I'm going to enter 6-inch and push the pitch button now I can calculate all of the rafters to get the rafter length which is a diagonal measurement we push the diagonal button and our common rafter length is 53 and 3/8 of an inch so let's write that here common is 53 and 3/8 we're doing a hip roof and the hip and the valley or same calculation so whether you're doing a hip or a valley same thing we're doing a hip all I have to do to find the length of the hip rafter let's push the hip valley button 71 and 5/8 is the length of our hip rafter so the hip is 71 and 5/8 that's the length now the jacks are the intermittent small rafters that come off the hips to find those we just push the jack button we have to push it a few times because it runs us through the on Center spacing giving us options whether to increase it or decrease it but a set of 16 inches on center and I push the jack button Jack number one is 35 and a half we're going to write that here jack thirty five and a half push the jack button again jack number two is seventeen and five-eighths push it again and Jack number three is zero because we've gotten to the end of the hip roof and there are no more jacks now to transfer our calculations our rafter length onto the rafter I'm using a framing square there are a number of different ways to transfer it on there but this is the best way that I found this is the most accurate and we want the first rafter to be the most accurate because again we're cutting all the other rafters off this one rafter so to set the framing square we need to set it at a six-inch pitch and to do that I'm using a straight edge and a couple of spring clamps and I'm going 12 inches over that's where the straightedge meets the 12 inch mark right here and being very careful with this I'm really dialing it in and over here I'm going six inches up that's our pitch 12 inches over six inches up I'm going to mark this top cut so that's the plumb cut of the rafter now rather than measuring the length of the rafter from this line I'm first going to cut this then I can hook the tape on to the long point measure the rafter and I know it's going to be right on the money [Music] so now we're ready to mark the common rafter calculations the common rafter length is fifty three and three eighths so now that I've cut the plumcot looking the tape on the long point measuring down fifty three and three eighths of an inch right there keeping that oriented in the same direction I'm going to slide this down until we hit fifty three and three eighths of an inch [Laughter] here's our rafter end of the building to the ridge but this isn't going to work I did this to illustrate a point what we need to do is mark the rafter properly so we have a tail we need the tail to have the hole all the components of the roof we have to make a seat cut and a heel cut which will enable to wrap the top of the rafter to come up off the plate and this is what's known as the height above plate no matter how high above plate you raise the rafter the rafter length remains the same all we're going to do is add a tail to it the rafter length is 53 and 3/8 of an inch I put the rafter square back up in the proper orientation slide it down and draw a plumb line this is represents the outside of the building it's also the start of our bird's mouth cut this part is called the heel cut to determine that seat cut I'm going to use the width of the top plate plus the half inch sheathing the top plate is three and a half inches the sheathing is a half inch so my seat cut is going to be four inches from that plumb line so there's my seat cut here's my heel cut there's the bird's mouth I simply notch that out but before I do that I want to determine the edge of my overhang for this I'm going to slide the square back up along the plumb line along the inside and for this roof I'm going to have a eight inch overhang so for an eight inch overhang I'm going to use an inch and a half sub fascia which comes to six and a half inches so I'm going one two three four five six and a half there's the outside edge of my tail cut and that's the outside edge of the rafter bottom of the sub fascia is five and a quarter inches down from the top of the rafter so I'm going to go five and a quarter inches go Mart slide the square back up market horizontally now there's our soffit cut also known as the plants our cotton [Applause] [Music] [Applause] [Music] [Applause] [Music] [Applause] okay here's my pattern fits on top this flush it fits perfectly now that we're done with the common roof let's move on to the hip roof now that the common rafter is cut we have to know the exact measurement of the height above plate to do that I put the square on the outside edge against the heel cut draw straight up and then measure that distance and this is exactly four and a quarter inches so our height above plate is four and one quarter inches this is a critical measurement we're going to need it when we lay out the hip rafter but how do we know where the common roof stops and the hip roof starts very very easy all we need to know is the run of the common rafter in this case our run was forty seven and three-quarters of an inch so all we do is measure from the front of the building forty seven and three quarters of an inch that's where the common roof stops and the hip roof starts the first part of the hip roof system is actually a common rafter from the same roof now this is no longer a common rafter is called the king rafter all that's left are the remaining rafters the hips and the jacks this is the stock for our hip rafter you'll notice it's larger than the common rafters typically a hip rafter is one size larger than the common rafters here we use two by six common rafters so the hip rafter is going to be a two by eight but before I mark it out I have to do one major important thing and that's a justice square to mark the hip rafter do that I'm simply going to move my stick from 12 inches to 17 inches and it's going to take a while because I go from one end and that adjust it a little bit back up here this stays at six is still a six inch pitch but because it's a hip rafter we're moving the gauge to 17 inches this is the only time we change the run on the rafter square now I know some of you out there asking why 17 inches I'll tell you why because I said so I'm going to March the top of the hip an inch and a half wide because at the top of the hip rafter I need a point in the center which means a double bevel cut or a double cheek cut so when I cut this with a saw I'm setting it at a 45 degree angle I'm going to go along this side and then go along this side and that'll give me a nice point at the top of the hip rafter which fits into the intersection of the common roof so I'm setting a saw 45 degrees and how do I know which line to cut first well after I cut the first one and I look for the second line and it's on the ground with the cut off I know I have to start over again [Applause] [Music] [Applause] so there's a double 45 bevel or a double cheek cut now that the top bevel is cut I can hook my tape measure on the long point and Mark the length of the rafter which is 71 and 5/8 then I take the framing square which again was adjusted to seventeen six slide it down draw a plumb line now this is where we have to vary a little bit from the common rafter with the common rafter we determine the seat cut of the bird's mouth by the top plate which was four inches if I did that here the height above plate would be much taller than the height above plate for the common rafter so what I have to do is measure from the top of the rafter down the height above plate of the common rafter which is four and a quarter inches raise this up and now that is the seat cut for the hip rafter it's going to be much longer but that's that's the way it works because we have a larger dimension board here the important thing is to make sure that the height above plate is four and a quarter inches down from the top so that it matches the common rafter so here's my seat cut but I have to adjust the seat cut for what's called a hip drop if I don't do that the top of the rafter won't plane out with the rest of the roof now here's a trick to find out the hip drop very easily rather than pulling the calculator out it's based off the thickness of the hip rafter here I have an inch and a half hip rafter half of that is 3/4 so I'm always using half the thickness of the hip rafter all I do is hold this along the seat cup and then along the plumb cut I'm going to move this square up 3/4 of an inch off the plumb line and then draw a new seat cut there's my new cut line and that's the thickness of the hip drop now I know there are a few of you out there that are wondering how does this guy know that the hip drop is based on half the thickness of the rafter because I said so the last thing we have to layout is the tail it's a little different than the common a little bit more complicated to layout we have to go back to the calculator just like the common rafters the only thing we need to know the only two things is the run and the pitch we already know what the pitch is it's a six-inch pitch but what's the run the run is based off the length of the projection of the common rafter if you remember our common rafter tail was projected out six and a half inches away from the building that's our run first I enter six and a half inch rung then I enter our six inch pitch and because it's the hip rafter I push hip Valley rap button and the length of our tail there is nine and three quarters of an inch measure down nine and three quarters slide the square down in order to mark the soffit cut I first need to extend the plate line out past the birds mouth now I need to determine how far down the soffit cut is from the plate it's kind of like the height above plate only in Reverse this is the measurement that I need to determine here's my soffit carrying it straight over and I'm measuring the distance from the soffit to the plate and in this case it's exactly four inches so here's the plate line I want to go four inches below the plate line so I slide the square down along the plate line until it reads four inches that four inches is my soffit cut now I cut the bird's mouth I cut the soffit cut I cut the tail cut and I'm all set here's a little trick to make it easier to cut the double bevel cut or the double cheek cut on the tail of the rafter slide this down and I'll bet you didn't know what this little hole was here for on the tongue of the framing square since this is an inch and a half thick I'm putting the cut line right in the center of that hole and then I simply mark both sides all the way down and these are my two cut lines just like the top I'm going to cut a 45-degree angle going this way reverse the saw cut a 45-degree angle that way and I have the opposite point down at the tail of the rafter right where I need it [Applause] [Applause] 45 degree bevel [Music] [Applause] I know what you're waiting for and it's not gonna happen perfect fit [Applause] now let's go cut the jack rafters before I mark out the jack rafter I have to readjust the framing square remember I said the only time we changed a framing square from 12 to 17 inches was on the hip rafter well we're marking the jack rafters which are really common rafters that are interrupted by the hip coming down so I have to put this back to a common rafter measurement which is 12 inches over and 6 inches up you might have to go back and forth a couple of times to dial it in and make sure again it's very precise right on the marks run my tape that's a top long point measure down the length of my first jack rafter which is 35 and a half but I'm going to extend that just 7/16 of an inch simply because I want my jack rafters to fall exactly 16 inches on center from my last common rafter so all I do is add seven sixteenths of an inch onto that measurement on all of the jack rafters and I'll draw the plumb line why is it seven sixteenths of an inch because I told you so now the last part of marking this out is very simple what I did was cut the tail off a common rafter I simply use this to trace out the tail of the jack rafter I line it up to the plumb cut and I trace the tail and then the seat cut I use the same piece to mark out the next jack rafter which is a little bit shorter here's a plumb cut the measurement is 17 and 5/8 of an inch plus again the 7/16 of an inch extra to make sure it lands 16 on center with the last common rafter here's the heel cup line up the pattern mark the seat cut the tail and the soffit cover now I'm ready to cut the jack rafters I'm going to adjust the saw at a 45 degree bevel for the plumb cut of the jack rafter because it seats right up against the diagonal hip rafter [Applause] [Music] [Applause] [Music] [Applause] the jacks on the opposite side of the hip rafter are mirror images of this so we have to make sure those jacks have the opposite bevel cut to do that is very simple neat little trick I'm going to use these jacks to trace out the next Jack's and as long as I put the long point on to the stock and cut with the stock facing up I'll get the exact mirror image whenever I'm tracing these any rafters and using one is a template or a pattern the key thing is to make sure that top is perfectly flush I don't care if the bomb is flush at all but the top of the roof has to be flush after all I'm a framer I want the top to be flush who cares about the finish guy that has to deal with the underside of the roof [Laughter] [Applause] [Music] [Music] [Applause] [Music] now we have mirror image jack rafters marking the jack rafters 16 inches on center off the face of the King rafter when I mark the other side I'm going to mark them 16 inches on Center off the face of the last common rafter the reason I can mark right off the king rafter and the last common rafter is because I added that seven sixteenth of an inch onto the jack rafter measurement if I didn't I wouldn't be able to lay them precisely where they belong and there you have it but several times during this video I told you to do something because I said so but if you're going to make this part of your profession you really need to understand all the details and all the elements of a roof but that's another video so I know somebody's out there saying how do I know this is really gonna work because I said so trust me it works now I know somebody out there saying how does he know that the hip drop is based on half the thickness of the rafter because I said so but trust me I've done this many times and it works all right you're rolling okay I know some of you out there are questioning how did this guy know that the tip drop is based on half the thickness of the rafter trust me I've done this before and because I said so I know there's somebody out there that's saying how did this guy know that the hip drop is based on half the thickness of the rafter because I said so

Channel: THISisCarpentry

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Id: B3wbHFeUrFs

Length: 31min 16sec (1876 seconds)

Published: Tue Dec 24 2019