How to Frame a Roof (Common Rafter Layout) скачать в хорошем качестве

How to Frame a Roof (Common Rafter Layout)

A quick framing roof tutorial showing how to effectively use the framing square with the rafter tables to layout and cut a common rafter. This is Kevin Morse again welcome back to York Construction Academy. We are going to do a quick session on rafter layout. This is a process that sometimes can be somewhat complicated, but there are certain aspects of the tools that we use now that make your life a little bit easier. So basically on a pitched roof you are dealing with a pitch that's based on 12 or 5. In this case we're going to use 5/12, it can be an 8/12 pitch which is steeper, it could be a 12/12 pitch which is very steep, but for today we're going to do a 5/12 pitch. So under normal circumstances most of your rafters would be larger than a 2x4 but if you're doing your own shed at home this would be a sufficient size to make a rafter. So the first thing I'd like to highlight on a common gable roof you're going to be using a series of common rafters. So on the blade of your rafter square your carpenter square there's a rafter table and on the first line common rafter length per foot run, that's the line that you want to look at. So it's as simple as going to the pitch that you would like to have the roof and in our case we're going to do a 5/12 and we're looking underneath the 5 to get that number. And the number in this case is 13. So what that represents is there's 13 inches on the hypotenuse the whole system is based on Pythagorean theorem of a right angle triangle, so you have a squared plus b squared equals c squared. So we know the two variables of 12 inches going in it's always based on a foot run going into your building. So we know that variable in 5/12 pitch we know the second variable which is 5 inches. And what we're trying to find out is the hypotenuse of the triangle which in this case 13. So all you simply have to do is take your rafters your tape carpenters square, and you put it on the 5 and the 12 and then you're going to lay the square right on your rafter and you're going to where the 5 and the 12 meet on the edge of the 2x4 you're just gonna scribe that line. And that will give you your first plumb cut. There are three plumb cuts, and one seat or level cut in any given rafter. The first thing we're going to do is we're going to take our skill saw and cut our first plumb cut. Part of the reason it's easiest to do that is now you have something to hook your tape measure on to get your measurement. So in a case where you have an 8 foot wide building. The building distance is called the span of the building. Half of the span is called the run. So if you have an 8-foot building then the total run of the building in that case would be 4 feet which gives you four units of run. Which is what is being referred to on the square here. So all you have to do is multiply 4 times 13 in this case and that gives you 52. And then that will give you what's called your point length. So I'm going to hook my tape on the end now and I'm going to measure but that 52 represents the edge of the building to the center of your ridge board, so you have to deduct three quarters of an inch from the 52 which gives you 51 and a quarter because your ridge is also inch and a half thick. So our actual rafter length is 51 and a quarter. So I'm simply hooking my tape on the end of the first plumb cut measuring 51 and a quarter and then I'm going to take my square and put it back on the 5/12 measurement or pitch that I've had before. If you have an overhang which most buildings do you can calculate that right away as well in this case I'm going to do a 12 inch overhang so because the fascia board is also inch and a half on the square I'm going to just lay out 10 and a half inches because once we put the rafter in we will have a fascia board that caps the end of the rafter. So I'm going to put that at 5/12 as well and all in one fell swoop I've got all three of my plum cuts. Now you just take your square and you flip it over and you square off the birds mouth this whole section of the rafter is called the birds mouth. In our case here in the building behind you behind me we have a 2x4 exterior wall so I'm going to make that measurement there three and a half inches because the 2x4 is actually three and a half inches in reality and now I'm going to cut my bird's mouth. Go back to my skill saw. And there you have a completed rafter with your bird's mouth, your final length is from here which runs up against the ridge, to here which is your building line the edge of your building, and then you're after gets seated on your exterior wall and that gives you your 5/12 pitch. And that's rafter layout 101. We hope to see here York Construction Academy. Thanks for watching. Follow YCA:   / yorkconstructionacademy     / york-construction-academy     / yorkacademy     / yorkacademyyca