Roof Framing Math Made SIMPLE!

What's going on everybody? Welcome back to the channel. In this video, we're going to be talking all about roof framing, taking you from the initial planning to the build. We've done a lot of videos about roof framing, but in this video, we're going to compile all of that information so you have everything you need to know to design, plan, and execute your own A-frame roof build. Let's get into it. [Music] The most complicated thing about doing any roof structure is figuring out your measurements, your rise, your run, and your pitch. That's something that we're going to get into in a little bit, but we're going to start with our foundation, which is our post. Now, the project that we're talking about, we're building the roof over top of the deck structure. The deck has been designed to handle this load. If you were building this as a standalone structure, you would put each one of those posts onto a dedicated footing. So, we've got a 20 by 20 roof structure that we're building on top of this deck. We're going to have four posts. We're gonna have two at the house and two on the outside. Getting the post installed is very simple. We're going to use a 6x6 base connector on top of our beam on the deck. And then we're going to install that 6x6. And the most important thing here is they're just going to be by themselves at this point. So, we need to brace them. We'll put a brace both ways on these posts to make sure that they don't move and they stay plum as we take our measurements and we install our beams. In this application, we're doing two posts at the house wall as well instead of pocketing them into the wall. This eliminates a little bit of uncertainty knowing what's behind that wall and just knowing that we can put a post there and have the beam fully supported. On an A-frame roof like this, most of the load is going to be on those outer walls. So, we're installing a 5 1/2x 12 LVL for all three of our beams here. We've got two on both eaves and then we've got one across the gable side. Getting those installed, especially if you have larger beams like that, you're going to want to use a lift of some sort to make it easier to get them on top of the post. Once the beam is on top of the post, we connect it with a metal strap. This is going to ensure that the connection is solid. And then we can proceed to the next step, which is the most important, figuring out all of our numbers and all the math behind rafter layout and roof construction. So, for this part, I'm going to bring in our trusted expert, Anthony Lombardo. All right, we got Mr. Anthony Lombardo here to tell us all about everything that you need to figure out before you start cutting in your roof. These measurements, your rise, your run, your pitch, height above plate. We're going to break down all of that stuff and he's going to show us how he figures it out for a roof like this. So, >> so >> teach it to us. >> All right. I'm going to do my best here. So, we're dealing with a >> Hey, explain it like I don't know what I'm doing, even though I definitely do. >> Okay. So, we're dealing with a basic gable roof here, which is just an a A-frame. And uh we're trying to find that diagonal measurement of the roof rafter. So, we're dealing with a roof. There's going to be two pieces of information, two numbers that are already going to be dedicated, and that's going to be the overall width of my building and my pitch. So, I know my overall width of my building is 20 ft. And I know I'm dealing with a three pitch, which is the angle of that triangle. So, I like to use a calculator. Makes it a little bit easier. So, the first thing I'll do is I'll put in 20 feet because that's my overall width. I'm going to subtract the thickness of my ridge, which is two by material, which is inch and a half. That gives me 19 foot 10 and a half. And now I need to divide that by two because we're only dealing with half of the roof. And that gives me 9 foot 11 and a quarter. And that's considered my adjusted run. Now, once you have that number, all you have to do is hit the run button and it's stored. Then the other information that I have, I know I'm dealing with a three pitch. So I'll just hit three inch pitch. And now that's stored. And once you have those two numbers stored, just have to hit diagonal. And then that'll give me my top of my rafter plum cut to the outside of my wall plum cut. And it also will give you your rise, which is two foot five and 1316. Now, that'll give me the height from the top of my beam to the top of not necessarily the top of my rafter. This is where it starts to get a little tricky. And by tricky, I mean there's one piece of information left out, which is height above plate, also known as HAP. And you necessarily can't get that until you start laying out your rafter. So, what I'm going to do now with the information that I have, I can start laying out my rafter. So, the first thing I need to do is I'm going to lay out my plum cut, which is at the top of my ridge. And with doing so, you just need a simple speed square. In this case, I have a 12in square. So, I'm going to line it up at the edge. And if you notice, there's a word called common. And we're dealing with a common rafter. And all these numbers that are on there signify that that's what the pitch is. And we're dealing with a three pitch. So hold it. You have your pivot point, which is tight. You line up the top of your rafter with the three because it's a three pitch. And then that's your plum cut. Now I know my run is 10 foot two and 516. Again, you're going to put your speed square on there. Pivot. Move it to three to where it's lined up. Draw a line. Now, those two plum cuts are the inside of my ridge and the outside of my wall. The next step is the bird's mouth cut, which has a seat cut and a plum cut. But this is where the hat comes along, the height above plate. I know mine's 6 and a/4. So I'll measure down 6 and 1/4 and square that across. And what this does is this is what's going to sit on top of our 5 and 1/2 inch beam. And this is the outside of my wall. All right. Now, that is the end of my wall. Now, we have to make our sophet, which we're going to go with a 12 in overhang. So, all you have to do is measure over 12 in. You want to subtract an inch and a half because you're going to be putting a subfacial on. And again, set your speed square to three. Hit your mark. We're going to use a 2 by six fascia. So, what I'll do is I'll measure down 5 and 1/2, but I'll come up maybe five and a quarter so it doesn't come into play. Heat. [Applause] right, we've got all our measurements. We got our rafter cut. And what was that? Hap height above plate. So the hat height above plate is a very important part of your math when you're building a rafter. And that's that's over here. It's your hat. Height above plate. We know it's six and a quarter. So now if you come to this end, I like to measure down six and a quarter. Now that mark is technically my rise from the top of my beam to that mark is the 2T 5 and 1316. Now, to get to the top of my ridge, if I was going to set it, I would need to add six and a quarter to 2 foot five and 316. And that'll be the top of your ridge. All right. So, we've got really the rise here, the 2T 5, 1316 is from top of our beam to whatever that pitch is, how much that rise is. So the rise um is that number, but that's not going to be the height of our ridge because we need to add that height above plate because the rafter is actually sitting above the beam and that obviously needs to be taken into account. So we can add 2'5 13/16 plus 6 and 1/4. >> Mhm. >> That is going to give us the true number of what our full rise is from top of beam to top of ridge. Correct. >> Correct. I'm learning. It's like I already knew all that stuff, obviously. All right. So, now we've got all the important math figured out. We've got our first uh pattern rafter cut out. So, the next step would be we're going to take all those measurements. We're going to come up off of our beam. We're going to do a level line all the way across the house beam to beam. And then we measure up from there 3T 1/16th. That's going to be the top of our ridge. We can install the ridge. And then we'll take this first rafter. We'll install it. We'll test fit it. We'll maybe cut four of them, two at both ends, make sure that everything is lining up. And then once it is, we take this, rinse and repeat, cut all of our rafters, install them. As long as all the math worked out and everything was built square, everything should work out. All the rafters should be the same. Should be square, nice, tight, good fit. All right. Well, that's it for this portion of it. So, let's talk about what's next. Thank you, Anthony. Hey, we need that. So, now that we've got all of our math figured out, we're going to set the ridge beam or rafter. In this scenario, we're using 2 by material. It's a ridge rafter. What we need to do is brace it up temporarily on both ends. So, we'll put a piece of 2 by on the house to support that end. And then we'll build a temporary brace for the outside so that it can sit right in there and it's going to stay nice and plum and centered exactly where we need it. So once we get that up in the air, then we can take those rafters that we just cut, install them, make sure that they're a good fit, rinse and repeat, install the rest of them, and that is pretty much your roof. From there, you're just going to want to install some sheathing. For sheathing, there's a couple options. You can use OSB oriented strand board, or traditional plywood. We like to use plywood around here because it's a lot more sturdy. Uh it's just, I think, a better product and it's not that much more expensive. So here we build it with 1/2-in plywood. We have 16 on center rafter. So that is plenty of strength for that. And that's really the final stage for us. After we get our faces on, we sheath it and then it's ready for the roofers. They take it from there. But that is pretty much everything you need to know to design and build your own roof. Once you master those numbers, everything else will become unlocked for you and you will be a roof building master just like Anthony Lombardo. So, let us know if you have any questions in the comments down below. We'll try to answer them. If you want a followup with some more highlevel roofing stuff, let us know. We can do some of those videos as well. But that's it for this one. So, make sure you hit subscribe if you got any value out of this or learn something. And until next time, this has been Premier Outdoor Living.