Cutting Common Rafters Ep.72

today we're going to cut and stack the common rafters that create the roof for the back porch of our spec house stack means install and a common rafter is a rafter that spans the entire distance from the exterior wall usually a wall to the ridge which is usually at the center of the span almost all of the wooden high beams you have seen us install as rafters are technically common rafters but they're after if you're making today are even more common because they're cut from real lumber and they have a seat cut which is part of a bird's mouth at the bottom you're getting a look at the patio here after it's completed because I want you to first get a look at a couple of specific parts these are the common rafters they're sitting on a ridge beam under the rafters are the ceiling joists we will also have our same overhang treatment with false rafter tails bird blocks and the barge rafter overhang at the gable end let's wind the video back go inside the house and show you how to cut these things with a framing square so the plans tell me and the decision has already been made that the pitch of this roof is 8 in 12 that means 8 inches of rise and 12 inches of run to mark that on to the board you find the 8 on the tongue or skinny side of the square and put it exactly on the edge of the board then you find the 12 on the blade or the wide side of the square and put the 12 on the same that is on the same side of the square in alignment with the same edge of the board 12 8 and mark it that's the pitch that is the cut at the top and at the bottom of the rafter you see the problem with marking this pitch cut it doesn't go all the way to the edge of the board that's a hassle here's how you deal with that an 8 and 12 is exactly the same thing as a 16 in 24 which by the way is about as big as a ordinary framing square will let you go but I take the 6 pain on the tongue and put it on the edge of the board and the 24 on the blade and put it on the edge of the board same edge of the square same edge of the board and draw all the way across a rafter for a complete pitch cut that's a way easier thing to draw and to cut in one move than the short distance and then extend it there is the end of my rafter that is going to coincide with the center of the top beam let's figure the length now let's calculate the length of the actual rafters from the back of the seat cut to the center of the top beam we know that the complete the overall span is 19 feet 7 inches you divide that by 2 because the span is the whole distance but each rafter only has to deal with half that amount so 19 7 divided by 2 is 9 feet 9 and a half inches that's the horizontal distance from the outside of the beam to the center of the top being that each rafter has to deal with now we convert the nine and a half inches to decimals of a foot you do that by dividing 9.5 inches inches divided by 12 inches per foot equals 0.79 so each rafter is dealing with nine point seven nine feet okay and now we get out this ancient and honorable tule framing square the top table on the rafter tables is length of common rafters per foot of run these numbers indicate those values at each pitch in other words if this was for 12 pitch the length of the common rafter per foot of run would be twelve point six five but we have an 8 12 pitch so the length of a common rafter on an 8 12 pitch is 14 point 4 2 inches per foot of run so nine point seven five feet times fourteen point four two inches of rafter length per foot of run equals 140 1.17 inches that's the length of the rafter 0.17 doesn't do us any good we're using a tape measure so let's convert 0.17 to fractions point 1 7 times 16 because they're 16 sixteenths per inch equals two point seven two sixteenths of an inch in other words just a little less than 3/16 so that our length of our rafter is a hundred and forty-one inches and three sixteenths 141 and three sixteenths week or conversely 141 and 1/8 strong either of those is going to work because I can set the height of my being wherever I want here's what this means we're gonna cut a rafter that is 141 and 3/16 from right here to a point that is exactly above the back of the seat cut or conversely it's 141 and 3/16 from the bottom of the pitch cut at the top to the back of the seat cut at the bottom 141 and 3/16 is the number from pitch cut to pitch cut we'll talk about what I'm doing with the tail and we'll talk about the depth of the seat cut later picture this as a plumb or vertical cut centered at the top at the very center of the beam at the top of this roof so if I come square off of a plumb cut it will be a level cut can you see that that that line right there will be level and will be sitting directly on one half of the five and a half inch wide beam that'll be located at the top the beams five and a half inches wide half of that is 2 and 3/4 so this vertical cut will be centered on the 5 and a half inch beam at the top of the world and this vertical cut will be up against the outside of it now for reasons that will become clear I'm putting the same length seat cut at the bottom two and three-quarter inches will mean that we have the same stand or distance from the seat cut to the top of the roof both at the bottom and at the top that makes makes the length of the rafter consistent when it comes to rest on the beams and doesn't change or tweak or mess up our calculation when we figured the length of this thing so I've got two rafters cut out either one of them I could use as a pattern and I could just jump right in and gang cut and then you know finish up the rest of the stack but I'm not feeling that gutsy I'm going to go out and I'm going to mock these up I'm going to put them up on the wall and I'm just going to make sure they fit sometimes you know if you're not doing this every day and you just are not entirely sure of your process there's nothing wrong with checking it before you commit yourself to really cutting up a bunch of wood so this is good it fits really nice we'll put our tails on the roof we'll stack out real nice it works great there's a lot of ways to to lay out and cut a rafter I mean there's books and there's tables and there's calculators and there's framing squares and I like being able to use a framing square and if you're a carpenter you're dang sure ought to be able to do it with a framing square [Music] when I'm cutting rafters like this I'm trying to get within inside of a 16th of an inch of perfect now it's easy to be off by a sixteenth of an inch cutting these things which means at the end of the day when I've got this little roof system cut out I can expect the whole bundle of cut rafters to be within 1/8 of an inch of one another worst case scenario which is okay unless the bottom of the roof is going to be a sheetrock vaulted ceiling in that case perfect is the goal and any discrepancy must be in the top side of the rafter not the bottom [Music] now aside from cutting the rafters there's one other cut we need to make as well and that is for the beam pocket for the ridge beam this was measured carefully to be exactly halfway between the two exterior beams at the side wall where the tails of the rafters bear the height was indicated on our plans and we checked those calculations and then cut the pocket this is another case where a little too short is better than a little too high because you can always shim it up [Music] you're seeing now that I cut all of the rafters before I installed the ridge beam that was intentional it's much easier to raise or lower the ridge beam just a little bit in order to get a nice snug fit with the rafters you cut then it is to match the rafters perfectly to an already installed Ridge now that's not always possible to do it like this but when I can the common rafters are cut first and the ridge is installed to fit boy it'd be nice if we could get our lift back here to help hold this beam up but there's no access at all in the backside of the house so we're doing it the old-fashioned way [Music] a lot of the fastening that happens when you're stacking a roof our toe nails at the wall line at the beams at the edge that means shooting a nail at an angle to secure two pieces together now toe nails are not near as strong when they're not placed properly so pay attention place your shot and typically two from one side and one from the other as a general rule the toe nails should go in at about a 45 degree angle with half of the length of the nail through the rafter and half of the length of the nail into the beam or the wall now toe nailing can be effective with a shorter nail than standard through nailing but in general a 16 penny nail is the right thing to use in framing a roof it's ideal in almost every situation and in addition to the nails there are special hangers and clips that will fasten rafters to beams and walls in a hurricane proof way and your plans may call for something like that it's certainly never a bad idea to make something strong now I'm putting these ridge blocks up here two reasons to keep the rafters from rolling over and to make sure they're right on layout I probably made this plenty clear earlier but I'm going to mention it again here it's really important to be careful about hitting your layout with your rafters it's easy for beginners to think what's the big deal nobody's gonna see this anyway and it's not like the roof is gonna fall down if this thing is a half an inch off layout and you're right but when you come back to sheet this when you're throwing the plywood or the OSB down if one of these rafters is off by a significant amount it really complicates your life now you got to cut the sheets on the roof and get sawdust where you're walking or on the ground and pass it up there's a it's a special cut so there's more waste it's just a headache when the rafters are right on layout you can just slam the sheets down the edges line up the nailing is good and you get through the job much quicker but if you do mess up the layout and get several rafters in the wrong spot before you realize it sometimes it's a lot less work to just fight the roof sheathing a little bit through that one segment that one area than it is to stop tear out and relocate several rafters this porch is gonna get a ceiling I'm not exactly sure what the finished surface is going to be I'm not even quite sure what the elevation of the ceiling is going to be but it's going to make everything on the bottom side of this roof diaphragm invisible it's going to go away but what is not invisible is the overhangs just like the rest of this house we're going to have the false tales on the O on the eave that has to have to be put on you've seen that happen and we have the overhang on the gable end the barge rafters with everything that is implied about getting that car decking in there at the right elevation and matching you've seen all that so these last rafters have been lowered the seat cut has been deepened so the top of the rafter comes down it's a similar problem to the ones that we've solved on these other gable ends just a slightly different solution so I believe that any pretty much any homeowner anybody with an interest in building something anybody that has worked with their hands even a little bit could do a project like this and about nine times out of 10 if the do-it-yourselfer is careful and will take in as patient and we'll take the time to do some rework if he has to he can get a product that in many cases is nicer than the product that a professional may get the big difference is that the pros gonna get it done a lot faster and he won't waste the material and he'll be I mean it happens it appears to happen more effortlessly as a function of how many times you've done something like that before now it's not necessarily effortless but that's the way it looks from the outside I mean everything's easy once you know how right there's another variability though that has to be mentioned and that is that a pro many times is comfortable taking risks and being up off the ground perhaps in ways that are not all that smart right or perhaps there's a type of a numbness that gets built in over time and it's easy to overestimate your own capabilities I get that and so if you are thinking of doing something like this don't back off just be careful and be patient and set aside I don't know maybe four times as much time as you think it's going to take and be be able to kind of get into enjoying the process instead of being in a hurry to enjoy the outcome so if you have just stumbled into this little video of me sitting up here talking about this roof system maybe you haven't recognized yet that we have a whole series associated with this this is one episode in a series of building an entire house there's a house sitting right over there that you probably can't see on the screen and we've built every square inch of it and we prepared the grade and we've made we've made a series out of it because here's the reason is because it has become apparent to me after 40 years in this business that not a lot of people get to see this process from the beginning to the end even some tradesmen I mean think of an electrician or a plumber they show up when it's time for their craft and they leave when they're when they're rough and work is done and then they come back to put the top out you know to put the fixtures and the switch plates in and they see that little window of time and then they're gone and so in many cases even a construction specialist hasn't seen the whole process and we thought that perhaps there would be some value in bringing that to YouTube and maybe there is you see this post right here I had to cut it twice and I flatter myself that I'm a pro that happens to everybody even the people that put a set of bags on every single day in fact dare I admit it this is a fourth time in this project that I've put a structural member in or in the first case a pony wall and forgot to subtract the thickness or the height or the depth of what was going to sit on top of it I guess this may be early onset something but I forget what you call that so anyway don't be afraid to try it don't be afraid to do some rework and don't be afraid to enjoy the process and for those of you who are regular viewers of this series it seems clear to us that the reason people are finding this is because you're telling them thank you for your interest and thank you for sharing it with your friends [Music] you're going to be seeing these aluminum bridges or bridge planks as they're called around here a lot as we work around the exterior of this house they are so handy one is 20 feet long and 12 inches wide the other is 24 feet long and 16 inches wide they're kind of heavy they're unwieldy to move around but boy once they're in place they allow us to create a very stable and a long work platform in a short amount of time you don't always need a full scaffolding setup in order to get the work done a lot of times you just need a place to stand trying to do this job on a ladder would be slow and risky since there's no good stable level ground to set it on and since I need to move back and forth a lot so although it takes some time to build shoring and platforms like this it's almost always worth the time and effort plus it is safer by a wide margin ladders are very dangerous tools and honestly I try and avoid using them as much as I can now for one or two items a ladder will make you money but after that after just one or two repeat performances you ought to build a platform and regarding platforms there's a common saying on framing job sites never walk on anything that you did not build yourself this is good advice don't make assumptions about things that could have a real negative impact on your own safety and well-being if your assumption doesn't quite pan out even though these are the same sort of false tales that we've put in other places on the house these are installed a little differently on these I cut a bird's mouth right into the 3 by 8 so that the top of the rafter is an inch and a half above the top of the tail that way the top plane of the tongue-and-groove decking at the overhang and the top plane of the rafters the common rafters are flush there's the same height and the sheeting can cover it all up uniformly putting these vents in here was a little bit optional since the air temperatures on this porch above and below the roof will always be pretty much the same so condensation will be at an absolute minimum in the attic and ventilation is not as important but vented eave blocks on this house are a big design element and I figured it would look silly not to have them and if anybody ever does decide to enclose and heat this porch turn it into living space it would be miserable to put these vent blocks in later besides anything worth doing is worth overdoing [Music] part of the engineering that Dave Thomas provided is to install drag struts that is Simpson straps that tie from the roof diaphragm back into and tying to the floor diaphragm the second-floor diaphragm what that does is tie that two edges of this roof to the house in a really really bulletproof way and man I got to tell you it really stiffened this whole thing up [Music] the rest of this patio is fairly routine carpenter work which you have seen a lot of so we won't do a whole lot of extra explanation as you can see there's a little bit of space inside this roof that will be accessible for storage we'll probably put an attic access panel in there this would be a good place for Christmas lights and outdoor decorations maybe complete with a pulldown stairway haven't decided on that yet and in case you haven't stumbled into it I hope you check out our podcast we cover all sorts of topics there including topics related to the spec house it's a fact of my life that I forget a lot of the questions in the comments and we found that the podcast is a good place to go back look them over remember the ones that recur and discuss and answer some of those in detail thank you for watching essential craftsmen and keep up the good work [Music]

Channel: Essential Craftsman

Views: 738,785

Keywords: anvil, forge, blacksmith, forging, craftsman, mentor, trades, tradesman, career, smith, carpetner, builder, wisdom, workbench, fabricate, tools, tool, tips, trick, hacks, protip, common rafters, cut and stack, seat cut, birds mouth, ridgebeam, ceiling joists, framing square, beam pocket, gable ends, roof ventilation

Id: leTqgJFZ-Z8

Length: 24min 15sec (1455 seconds)

Published: Mon Mar 23 2020