Rafter Step Off Method - Made Simple

today i'm going to show you a really clever little tip and it's using this roofing square you can pick these roofing squares up for as little as a fiver just bear in mind if you do buy one of those they're not built to last these numbers will rub off so this is a nice new one although it's cheap it's new it's nice clear numbers on it so i can show you what we're going to be doing today the first thing i'm going to show you is a quick tip on how to work out the pitch of a roof so that you don't need to go through all of these numbers on the square so we're going to go for as the americans would say a 5 over 12. we're going to work on this inside scale but it's important to remember that if you're working on the inside scale here you need to work on the inside scale here you can't work on the inside of this and the outside of that or vice versa it just won't work so this one we're going inside so we've got the square sitting nicely all over the timber so firstly we're going to go for five this is our rise going up the roof and then we're going to go 12 which is our run along the roof that's 5 over 12. the great thing about using tape like this is that especially on this square we have inches on this side and millimeters on this side but because we've taped it all the way around we can flip it over and we just use our tape marks we don't need to worry about the numbers on this side it's all been worked out there first so when we lay our roof and square out onto our rafter in this case it's a six by two we use our marks on what is going to be the top edge of our rafter we always mark from the top everything's done from the top down we set up our tape against the edge of the timber there and we roll this one around until that lines up the edge of the timber it's slightly awkward working on modern timbers which have got these rounded edges on them all you need to do is make sure that where your tape lines up on there if it's slightly over like halfway into the round that one also needs to be halfway into the round or you can get your eye right over the top make sure you're flush with that edge there and there but with experience you get used to these things and it's quite easy to pick it up as you go along so we've lined up our two points here along the top of the rafter and then along this edge which is our rise we're going to go like that and that is our plum cup which will fit against our ridge board which would be in effect something like that so we've got our plum cut so what we need to know is this distance from here to here i'm going to say it's eight feet across so the first thing we need to do is cut that in half so that is now four feet so i know that from this corner to the center is four feet that is the distance that our rafter is going to cover because we've got one rafter here one rafter here but how do we know that's four feet how do we know how long that is that is going to be longer because if we laid that obviously you can see that if you laid that flat down there it's going to end up somewhere like that and if you stand up from the center up there we're going to be over here so how do we work that out but i must emphasize that we are working from the outside of the building to the outside of the building there so we're going to the right to the extremities of the building so we can uh work out the length of the rafter using this table which is supplied and printed out onto the side of this roofing square so you find the pitch that you want but it and it gives you a multiplier but you've still got some sums today you've got to work out some maps to find out your length and quite often like i said before these numbers do get rubbed off then you've lost it then you've got to start searching on the internet for the multiplier but there's a far easier way of doing it you can also get an app to do this daniel cox has got an app for his roofing square and you can input the information and it works all out for free but i'm going to show you a way that we can do it on this square with no calculator no app take your tape measure and you hold it between that point there and that point there that we marked earlier so our 5 over 12 and you measure that distance that is 13 inches so 13 inches is from that corner there 13 inches up that's running up that angle which is that that's our right angle and that is our 13 inches up there so that is two that's two foot halfway across here is two feet so if i draw that line up there that distance between there and there is 26 inches if i have that again and put a line there that's one foot draw that up that's 13 which is our 13 on our square so 13 26 we can do it again up here so that's now three feet across 13 26 39 all right perfect yeah yeah 39 and then up the center that's our fourth one which is then 52. we're ignoring the ridge ball at the moment we can talk about that later it's not important in fact it's a good thing to leave that on because we can cut it off to to adjust later if we need to in carpentry just remember you can't add a bit on but you can always take it off right so we worked that out using a little bit of my limited mental power am i adding up skills which is not great i'm going to show you how to do it you haven't even got to add anything up we're going to use a bit of our old mate pythagoras this is our plum cut this point here we'll put our inside tape measurement there our tape there and then we're going to put a little mark there and then what we do is using this point from the five we slide it up and line it up with that mark that we just made there then we make another mark there can you see what's happening already i'm going to say this is number two that was number one then we're going to slide it up again line that mark up there get that flush on there another little mark this is number three once more that mark on there i want to tape up with the edge that mark there that's number four so that is now our rafter length for the final one i'm going to line up the tape on there now this is the mark that we want to mark for so don't get confused and then mark it on that side of the blade we need to be here so you can do it here like this or you can slide that pass but as long as you're on that mark and at least two are lined up we're good we can go straight along there like that so now a moment of truth i said 4 times 13 is 52 that is true that's not the truth bit let's hit let's see if the the trick worked so we'll put it on there that's our top of our plumb cut and i'll measure down to our new cut 50 let me put a mark there and i can pull it away 52 look at that bang on so hang on james i sense a little trick here mate because yeah that's very nice you've got an eight foot building i've got an eight foot six building okay it doesn't quite work out for you does it it work i'll promise you i'll show you it's it's just as simple it still works eight foot six is your building so now we're talking four foot three for our center line so let's so we're eight foot six so now we are four foot three inches i'm not going to even going to attempt to add up whatever that's going to be because it's too easy to do it this way why would i so i'm going to show you how it's done four foot free so we'll do exactly what we've just done we'll start there we've got i'll use the marks we've already got so we've got number one and we've got number two number three number four that's our four feet and then to get the three inches we go along one more time up to here okay so number four is there we slide it one more time okay so five times 13 is too much we want four foot three so this is how we work that last three inches out we've got we're lined up there on our tape on our tape this is our run so we've gone four times twelve and then the three comes from here that's zero one two three that's four foot three put a little mark there and then we slide it up again up to that mark there line our tape up here line our tape up there on that mark now that is our new plum cart for a four foot three roof just because you're awkward okay mate all right i'm persuaded that's lovely all right so we'll get that fully across the timber there let's move over to that side now that is going to be the outside so that's the plumb cut that goes down onto the wall plate that's correct and now i need a seat cut what are you going to do for me so a seat cut you the rule of thumb is don't go any more than one third through the thickness of the timber our timber is around about 150 mil or six inches so i've gone to the the closest whole number and then i'll take a third of that so that will be two inches or 50 millimeters so we're going to mark two inches up hang on a minute isn't that the wrong side no we're working from this is the top of our timber oh yeah so we want to take two inches at the bottom which is going to sit over our wall plate that way see i would have made that mistake i would have cut the plum cut on the seat cut on the wrong side well you could have stuck it back in no you can't so i'm now going to mark out our bird's mouth and we still keep the square with these tape lines on the top of our rafter and then what we need to do is slide it up to that new mark that we've made the intersection there which is our bird's mouth and what you need to remember is that this is the outside of the wall place the outside of the building so we're cutting back this way so from that point there we got that line there and that is what we cut out for our bird's mouth you're a genius pythagoras is a genius so there's a quick tip for you there and if you don't want to miss any more installments of our complete carpentry guide subscribe to skill builder and click on the bell for notifications [Music]

Channel: Skill Builder

Views: 79,352

Keywords: common rafter, uk site carpentry, framing square, framing square basics, roof rafters installation, common rafters, stepping off method, rafter step off

Id: YwE3MrmLahc

Length: 10min 40sec (640 seconds)

Published: Wed Apr 28 2021