*
I have two roofs to worry about on an L-shaped colonial. The L has a hip with 7/12 pitch on either side and the front being 12/12. The other roof is the main being 12/12 with the 7/12 L intersecting square to it.
My first problem, is the cheek cuts on the hip and jacks. Can the compound angle be determined from the scales on the 2-foot square? Or are these scales only good for equal pitch hips? Now that I think about it, I don’t even know how to figure the seat cut on this bastard hip. What marks would you hold on the framing square? And how much to drop the seat? (All lumber is 2x and CDX sheathing, so I’m not worrying about backing the hip.) I’d like to learn how to do this without lookup tables, because I know very well, the book will disappear when I need it most.
Second problem is the valley where the 7/12 L intersects the 12/12 main. Am I right in thinking the valley cheek cuts could be figured the same way as the bastard hip jacks? But the bigger problem is a complication I never had to frame for – the both intersecting ceilings under this valley will be cathedral, so the valley rafters can’t extend lower than the valley jacks of either the 7/12 or the 12/12. Is there a way to figure the width of the valley w/o putting it up and scribing along a few points of the valley jacks? And what about a bevel on the bottom of the valley, how would you figure these bevel angles? (It seems to me this is going to be a lot of trial and error, but structurally AND cosmetically it has to look right by the time I’m done. I don’t want to go into a job having to rely on rockers and tapers to cover my experiments)
I know I’m not the first to have to do this, so all advice and experience is welcome.
Tom
Replies
*
When I run into something like that I figure it mechanically, in other words I lay the squares aside, hold the board up there and eyeball the thing, not as impressive as knowing all the degrees and scales, but just as effective and much faster. Never been stumped this way, but made a lot of firewood cutting on the ground.
*First, your hip and valley is figured as such:1. 7x12 = 84.2. square root(7squared + 12squared) = square root(49 + 144) = square root(193) = 13.89243. 84/13.8924 = 6.046474. 6/12 pitch.We could give you all the formulas, but your best bet is just to frame the roof with your commons and ridge, then run a string exactly where your hips/valleys go. You can then use your speed square to find heel cut lengths and angles.If you're going to be doing any more of these, I'd recommend buying a Construction Master IV. If you need more info, contactme, I'll be glad to help. Billy
*Here's a good website to learn more about roofs, too. Forgot about it until after I posted.http://josephfusco.com/my_html/raftercutting.htm
*I am installing stairs in a well opening 8'10" and the floor height is 9' exactly.Stairs can project 8'10".What's the riser height?This is my first time attempting this.Thanks!
*Can you put a landing at the bottom and make a few steps turn an opposite direction off of this? Is the reason you can only have a total run of 8'10" because of 3' clearance at the bottom to a wall or something?I am having a hard time coming up with a good measurement because you will need 14 or 15 risers and your tread run would be too small. Please give me more info.Billy
*Remember if you think the stairs have to end at the same point as your stairwell opening, they don't. You just need 6'8" headroom. Also, if you have 14 steps, your rise would be 7.714". 15 steps would be 7.2". And also you have to minus the thickness of the finish tread from your bottom riser. Please send more info though and I will try to make the numbers work for your treads.Billy
*Or, just e-mail me with your plans if you prefer (pics or sketch or floorplan, something like that.)Billy
*I am working with limited projection space.There is a door at the right where the bottom step will be.The length of the projection will be 106".The finished floor to floor measurements is 108".Tread thickness is 1". Do the run determine the width of the tread?Thanks CD
*The problem is that you need to leave a 36" clearance between the door and the steps to meet code requirement. You could put in 13 risers (even though I don't like that for this total rise) but you will not have a 36" clearance for the door. I responded to your e-mail and will talk with our architect today. I'm busy right now but will get back with you later this evening.Billy
*It sounds like you have a nice project going Tomc.The bastard hip and valley system that you are describing can indeed be calculated. The tables that are supplied on the framing square will not do it however because they only concern themselves with equal pitched roofs.I'm going to pass on explaining the steps needed to figure your roof parts. It's not all that complicated if you are an experienced roof framer as I'm sure you are (I can tell you have significant experience because you are asking the right questions). I will however tell you that our resident roof expert is Ken. I'm amazed that he hasn't already swooped in here and did his usual great job of explaining the math and giving precise answers. He's probably too busy wrapped up in those circular stair threads on the main page that Stan has started.I would advise caution about only using the roof explantion reference website that Allyson suggested. I have extensive experience (including bastard hips) with roofs dating back to the 70's and I get very confused at the suggested site. It might be the perfect site for you however, so give it a look and form your own opinion. It might not provide the explanations that you seek however because the last time I perused the site, the author hadn't finished the section on unequal pitched roofs. I haven't been there in a while however and it might be done now.If I see Ken lurking or posting, I'll send him in here to educate you. I guarantee you will have good solid explanations with great easy to read graphics. Don't be afraid to seek him out and direct him in here. He loves these roofing challenges although this is just a walk in the park for him.blue.
*Hi devil,Thanks for the post (good name!),I hope Ken stops by soon. I'm anxious to hear from anybody on this roof problem. I've cut a few rafters in my time (~25 years) but I'm really stuck on this one. I know the language so Ken won't have to get too elementary.Tom
*Tom: Blue is correct about Ken. He is very unselfish with his knowledge and does his best to explain it. I e-mailed him telling of this interesting problem.
*Tom,After those flattering comments by blue eyed devil and Stan, I guess I better come up with some answers for you. Let's start with an easy one. 1) How do you determine the cheek cut bevels on the jack rafters?Draw a right triangle as shown in the diagram below. Since the unit rises are 7" and 12", make one leg of the triangle = 7", and the other = 12". Use your "speed square" to measure the angles of the triangle as shown to get the bevels for the jack rafters, as well as the hip and valley rafters.If you're at the job site, you can do this on a square corner of a sheet of plywood. If you draw the triangle accurately, you'll find that the cheek cut bevels are 30 1/4º and 59 3/4º, or about 30º and 60º.The smaller angle, 30º, will be the bevel on the 12/12 jack rafters, and the larger angle, 60º, will be the bevel on the 7/12 jack rafters.This method will work for ANY combination of intersecting roof pitches, provided you are working at a square corner of the building, or a 90º corner.Another easy way to figure out the bevels is to use a calculator that has trig functions.Arctan (7/12) = Arctan .5833 = 30 1/4º, andArctan ( 12/7) = Arctan 1.7143 = 59 3/4º.Here's yet another way, if you own a Construction Master IV calculator.Enter 7" as rise, and 12" as run. Then press pitch. Obviously, the calculator will display 7". Now press pitch again, and the calc will display 30 1/4º. This is the bevel for the 12/12 jacks, and if you subtract it from 90º, you'll get the bevel for the 7/12 jacks, or 59 3/4º. I have 2 questions for you Tom. Are the common and jack rafters for your roof 2 x 8 and the hips and valleys 2 x 10? If not, what are they? I'll need to know that information eventually.Also, when are you starting the roof cutting?
*Ken-Thanks for offering to help. The commons and jacks are 2x8 @ 16"O.C. The hips are 2x10. The plans don't call out a size on the valleys, but just a note showing "Double, Minimum". So I'm planning on 2x12's knowing I'll have to trim and bevel them. Woodwork won't start until mid April. VRTom
*Tom,Let me make sure I understand your last post.Are you planning on doubling the hips and the valleys, or just the valley that is vaulted?Ken
*Tom,Here's a sketch which indicates how the hips and valleys appear when the 2 roof pitches are 7/12 and 12/12. Notice that the angles that the irregular hips make with the plates, is the same as the jack rafter bevels that we have already found, 30 1/4º and 59 3/4º.Does your roof look anything like this sketch? Perhaps you could use the sketch to describe your roof in comparison.Here's another question. Do the blueprints show that the overhangs are equal or unequal for the 2 different pitches? If they are equal, the roof plan will show the hips and valleys offset from the corners. If the overhangs are unequal, they will pass directly over the corners of the house.Do you have a scanner?
*Ken-Your picture is the right interpretation except reversed and the the main roof ends in a 7/12 hip. If you are interested, the lengthwise footprint of the main building is 45' long x 20' wide. The L is 14 wide x 16 long (the long side is square to the main). The soffit detail shows same height throughout, so I'll adjust the overhang width as needed to maintain the straight elevation. In other words, the hips and valley come to the corners. I think your other question was on the valley being doubled, but I'm seeing now that the hip roof which projects into the L may also have to have doubled up hip rafters in order to let me put on the correct bevel for the vaulted ceilings. Lastly, no scanner.Thanks again for helping,TomC
*Tom,Is this it? If so, which hips are do you think need to be doubled? Ken
*Ken-That is it exactly. The vaulted ceiling lies beneath the area of V1, H3 and H4. The V1 is definitely doubled because that is what the desiner wanted. H3 and H4 I am thinking should be doubled only to easily accomodate bevels on their underside to match the planes of the respective vaulted ceilings. I'm assuming you would extend H4 all the way to the plate (or would you run H4 to R2 and run R2 all the way through?) Maybe I'm assuming too much here, so I'll wait for your advice. By the way, I'm with you on the angle cuts for the jacks, I don't exactly see why your layout method works mathematically, but I got the same numbers as you on the Construction Master. What will be the settings on the square for the hips and valley? Thanks,TomC
*Tom,I like to use 22" on the body of the framing square when I cut irregular hips and valleys, such as in your roof. The setting on the tongue of the framing square would be 11 1/16" in this case. ( the pitch of the hip and valleys is just slightly larger than 6/12 )The number 17 has no particular significance when 2 different roof pitches intersect, but if you'd like to use 17 on the body of the square, the setting on the tongue would be 8 9/16".The reason that I like to use 22 rather than 17 or 12, is simply to get a longer plumb line on the tongue of the square.Tom, could you be a little more specific about the vaulted area? Where does it end? and at what level? ThanksKen
*Ken,The vaulted area is the 20x14 area directly below V1, H4 and H3. What you call vaulted - I really mean as cathedral. Plate height is 8 ft high. Ken I appreciate your help on this, and your spending a lot of time with me here, but don't go crazy on this (that is my job!) I'm just looking for general help and advice. But thanks for all you have to offer. For the rafter settings, on the bastard hip/valley, how are you figuring your 11 1/16 or the 8 9/16 ? TomC
*Tom,I've posted information showing how to determine the pitch of an irregular hip/valley several times in the past. As a matter of fact, if you scroll down towards the bottom of "Construction Techniques" topics, you'll find the thread, Maurice Doyle "Roof framing - HIP joining two different pitch roofs" 2/26/01 3:02amIn that thread, I showed how to find the rafter square settings for 17 on the body of the square, but as I've mentioned, I usually use 22 on the body to get a longer plumb cut line.Let me go over it once again for your situation where the 2 roof pitches are 7/12 and 12/12.The two unit rises involved are 7 and 12.Step 1) find the product of the unit rises...7x12=84Step 2) find the square root of the sum of the squares of the unit rises,square root(7²+12²)=square root(49+144)=square root(193)=13.8924 Step 3) divide the result of step 1 by step 284/13.8924=6.0465This is the unit rise of the hip/val. In other words, the pitch of the hip/valley = 6.0465/12 or about 6 1/16/ 12If you want to use 17 on the body instead of 12, just multiply 6.0465 by 17 then divide by 126.0465 x 17 = 102.7905102.7905/12 = 8.56, or about 8 9/16". This would be the setting on the tongue for 17 on the body.If you want to use 22 on the body, multiply 6.0465 by 22, then divide by 12.6.0465 x 22 = 133.023133.023/12 = 11.08 or about 11 1/16". This would be the setting on the tongue for 22" on the body of the framing square.This method will work for ANY 2 roof pitches at a 90º corner.I'm reposting the roof plan that I drew with the cathedral ceiling shown by the rectangle ABCD. Is this correct?Apparently, the bottoms of the rafters will form the ceiling in this entire area, which I find unusual. Usually a vaulted or cathedral ceiling is more symmetrical in appearance, as viewed from below. But so be it.Notice that a small part of ridge 2 (R2) extends into this area and will also have to be beveled to the plane of the ceiling.A quick comment about your concern regarding the time that I put into these posts. Nobody is twisting my arm Tom. I enjoy what I am doing here, as long as I have the free time, which I usually do.Ken
*Tom,I didn't get around to answering one of your questions from a previous post.As you suggested, you could either allow Hip 4 to run all the way to the plate, or, extend ridge 2 to butt to the king rafter as shown in the attached diagram.My choice would be to extend the ridge, but you could do it either way.Ken
*Ken-Your sketch is right on as always. I agree with you that it is an unusual structure, to the point that I don't think that I can't make a fair $ on it. It is being built as an "Outbuilding" on an estate to be used as a clubhouse/boathouse/workshop/"stable" for the porshe.Anyway, your post gives me a good formula for the hips/valleys that I was looking for. This looks just like what Allyson told me a few days ago but his base 12 was throwing me off. Your explanation brings it all together for me. So, now I'm smart on hip and valley cuts. I'm pretty good on the jack cheek cuts. I found your archive seminar on backing bevels. I quess the only thing I don't know now is how to figure how much to drop the hip, and maybe the common difference on these bastard jacks. Also Ken do you ever need to drop a valley rafter as we would do on a hip? If you get some time can you spare me a few words about these?Thanks againTomC
*Hey Joe,How is it you have the energy and mind matter to do these graphics after working all day? Your website is fantastic and a good service for any body coming along in our footsteps that wants to learn. If only I had access to this stuff years ago, and to guys like you and Ken. Anyway, this building is not much more than a clubhouse for a rich kid. My last posts to Ken basically describes all there is to know about it, except the area above the long part will have a loft.Thanks Joe,TomC
*Tom,I'll talk about dropping the hip in another post, if you don't mind. I don't have the time to go into it thoroughly tonight. But let me answer 2 of your other questions.There never is a need to drop a valley rafter. When the valley rafter passes over the corner at the building line, it should have the same HAP as the common rafters at that point. ( the HAP is the plumb measurement that remains above the heel cut of the birdsmouth ) The reason that you never have to drop the valley rafter is that the jack rafters can always plane into the center of the valley. This isn't possible with the hip rafters, as the edges get in the way. Here's how to find the common difference for the jack rafters. Let's do the 7/12 jacks first.Take your On Center rafter spacing, which I believe you mentioned was 16", multiply it by the larger unit rise, which is 12, and then divide it by the smaller unit rise, which is 7.16" x 12 = 192"192"/7 = 27.4286"Enter this as the RUN on your CM Calculator, then enter 7" as the pitch, and press diagonal to find the common difference for the 7/12 jacks. You should get 31 3/4"To find the common difference for the 12/12 jacks, multiply 16" by the smaller unit rise and then divided it by the larger unit rise.16" x 7= 112"112"/12 = 9.3333"Enter this as the RUN and then enter 12" as pitch and press diagonal. You should get 13.2", or about 13 3/16". That's the common difference for the 12/12 jacks.Talk to you tomorrowKen
*Tom,Arent these guys amazing ? Ken helped me sometime ago and these posts are just great for me to read as I wish to learn all I can about roof framing.....Thanks to all that are helping Tom, as many of us, as we peruse your posts, learn as well. Much appreciated. In Toronto, Ontario, Canada.
*Joe and Ken-If I think about this stuff too much I get confused all over again. You are you saying that if we cut the valley seat to have the same HAP as the commons, that any additional "dropping" is not required. If so, when the valley jacks are cut (starting with a common difference from the last common), where will the jacks attach to the valley rafter ? by this I mean will the top edge of the valley jack cheek cut align with the top edge of the valley rafter, or will the valley jacks stick up from the top edge of the valley rafter a little bit ? Joe-Your attachment of the "Sunroom" is an interesting chronicle of all the calculations for a hip roof. However, your method of dropping the hip is a bit misleading and artificial, as it would only work if your hip was jacks were of the same 2x dimension. For a larger span roof you will likely have to work with 2x8 jacks and a 2x10 or larger hip. what would you really do in this case? TomC
*Tom,You have to hold the valley jacks up a little so that they can plane into the center of the valley rafter, unless you cut backing bevels on the top of the valley rafter, then they just plane right in with the edge of the bevels.You'll have to hold them up higher on the 12/12 side than on the 7/12 side, as you might expect. In addition, if you double the valley rafter, you'll have to hold them up twice as much to plane in, unless you cut the backing bevels ( 14 3/4º on the 7/12 side, and 37 3/4º on the 12/12 side)I'll explain how to handle the hip rafters over the weekend.Two questions. 1) are the outside walls 2x4 or 2x6?2) how much overhang, including the fascia, do the plans show?Ken
*Joe,In your last post, you mention that the amount to drop a hip is "((rise) * (1/2 thickness of the hip)) / 16.97)"That formula only works for regular hip rafters where a single pitch is involved. It wouldn't be of any use to Tom for his split pitch irregular roof.I'll go over how to handle the hip rafters tomorrow.Ken
*Joe,There's more than one way to cut the hips correctly. I'll go over it tomorrow, as I said.I've been very busy this week. I know that Tom is not in a big rush. He's not going to frame it for several weeks yet.Ken
*Ken, Joe-Sorry I have not been as frequent here as I should be lately, especially since this thread is all about my problem. Long days and very busy start ups, as I'm sure you're all aware. Plenty of time on this odd roof Joe, so 3 days or 5 days or whatever + weather delays, doesn't matter. The spirit of what we discuss does matter. The fact that this discussion exists at all is a credit to guys like you and Ken who are willing to help your lesser bretheren. Only a couple of years ago I would have thought all this communication and information exchange impossible.So Ken in answer to your questions, the outside plate will be 2x6 (why di you even ask this ? ) and the soffit calls for 6" fascia.VRTomC
*Joe,Once again, the information in your last post, (as you pointed out), only applies to regular hips in a single pitch roof, at 90º corners. I don't understand why you are bringing all of this information up when it has no bearing on Tom's irregular roof situation.The backing bevels for a 7/12 roof intersecting a 12/12 roof, where the plates are running perpendicular to each other, are 13 3/4º on the 7/12 side of the hip or valley, and 37 3/4º on the 12/12 side of the hip or valley.Ken
*Joe,Thanks for pointing that out. I see that I originally posted it correctly in my post number 36.Typing error.14 3/4º is correctTom,I made several drawings and scanned them this morning. I'll post them later on today.Ken
*Tom,I'm going to post about 10 skectches that should give anyone reading this material a good idea of how to cut the hip rafter birdsmouth as it crosses over the corner of the building line. Don't be insulted if I go into too much detail. There are many who read these threads that don't have the framing experience that you have, but are eager to learn.When I cut a split pitch irregular hip roof, one of the first things that I do is decide on a HAP ( Height Above Plate) for the rafters. For those of you that don't understand this term, look at the diagram below. The HAP is the plumb measurement that remains on a rafter after the birdsmouth is cut. It's important that the rafters for both pitches have the same HAP. This assures you that the roof surfaces will intersect at the center of the hip rafter.For your situation Tom, the 2 roof pitches are 7/12 and 12/12 and the common and jack rafters are 2x8. I chose 6 1/2" for the HAP which results in a 3 1/4" seat cut on the 7/12 rafters, and a 3 3/4" seat cut on the 12/12 rafters. You could choose some other HAP if you like, but that's what I'll use in these posts.It's generally a good idea to leave about 2/3rds of the width of the rafter after the birdsmouth is removed, but as you can see, I've gone slightly beyond that with the 12/12 rafters. No big deal. Those tails are plenty strong.
*Here's a diagram of the hip rafter as it passes over the corner of the building. The common and jack rafters must plane in with the outside edges of the hip rafter, so as the hip rafter passes over the plates, we want the plumb measuremens at those points to be 6 1/2" also.
*But look what happens if we make the HAP of the hip rafter = 6 1/2" at the center of the hip. On the 12/12 side of the hip rafter, the edge of the hip rafter is too high by 5/8". Now, if this were a single pitch roof, then the same situation would occur on the other side of the hip, and we could just remove 5/8" extra from the seat cut of the hip rafter to get the edges to plane in with the common and jack rafters. This is called "dropping the hip".But as you'll see in my next post, we have a different situation on the other side of the hip.
*Here's a look at what happens on the 7/12 side of the hip. Notice that the edge of the hip rafter is only 1/4" too high on this side.
*It's easy to determine how much each edge "sticks up" above the plane of the roof. Just place your speed square as shown on the center of the hip, after the two bevels have been cut on it, and draw a level line as shown in the diagram below.When this level line meets the side of the hip, just extend it up the length of the hip if you wish to cut the 37 3/4º backing bevel on it. Notice that when this line is drawn square to the top edge of the hip rafter, the measurement is 9/16", slightly less than the plumb measurement.If you repeat this on the 7/12 side, you are ready to cut the 14 3/4º backing bevel on that side also.
*This would be a look at bevels on the hip rafter if a square cut were made on the hip rafter at any point.
*Here's a look at the hip rafter sitting on the plate with the backing bevels cut on each side of the hip.
*You can use a combination of dropping the hip with cutting just one of the backing bevels as shown in the diagram below. Start by taking the plumb measurement on the 7/12 side of the hip and drop the seat cut by this amount. 1/4" in this case. Now this side of the hip rafter will plane in with the 7/12 common and jack rafters, but the edge of the 12/12 side of the hip will still be a little high. Using the square measurements, 9/16" - 3/16" = 3/8", scribe a line up the 12/12 side of the hip rafter and cut the same backing bevel as before, 37 3/4º.This is what a square cut through the hip rafter would look like using this method.
*This is what the hip rafter would look like sitting on the plate
*Here's a look at the hip rafter where it meets the ridge. The 37 3/4º bevel planes in with the 12/12 common rafter at the same time that the other edge planes in with the 7/12 common rafter
*Tom and others,In all of the above posts I showed the hip rafter without the tail as it crosses over the plate line at the corner. My purpose in doing so was to show why the backing bevels are used and to demonstrate how to determine the measurements.In practice of course, you cut the hip rafters with tails, as you do with the common and jack rafters, but the bevels and the backing measurements are the same on the hip rafter.
*Good grief,What have I done to you guys, I wasted your whole day and weekend! Ken and Joe, this will take me 5-6 days to get through this marathon of information. I am humbled that you have spent this much time with me. I can't properly say thanks. But thanks for all, you guys are the best.Very, very Respectfully,TomC
*Ken, sorry for butting in here. I'd like to just let you continue on with your excellent seminar, but I feel compelled to question one of your remarks. In this paragraph:i "When I cut a split pitch irregular hip roof, one of the first things that I do is decide on a HAP ( Height Above Plate) for the rafters. For those of you that don't understand this term, look at the diagram below. The HAP is the plumb measurement that remains on a rafter after the birdsmouth is cut. It's important that the rafters for both pitches have the same HAP. This assures you that the roof surfaces will intersect at the center of the hip rafter. " you demand equaly HAPs (incidently, in these parts, we call them heels). I'd like to point out that this technique (equal heels) will produce unequal sized projections on the overhang. I've installed a large number of unequal pitched roofs and have never worked on one that had equal heels. I repeat....b NEVER!This results in the hip missing the outside corner of the building, but that really is never a concern, unless the underside will be vaulted. In that case however, there will usually be two seperate systems- one for the roof and one for the ceiling. It's impossible to satisfy both demands unless the architect designs the exterior with differently sized overhangs or different heights of the fascia. I've never seen it done like that however.In these parts, we are always concerned with ceiling insulation and we normally have larger heels. Our deilings almost always demand at least 9" or so of insulation and a simple 2x8 is never seen for vaulted applications.Interesting seminar however.blue
*blue,Thanks for posting your comments. I'm anxious to learn more about the system you use to frame an irregular hip/valley roof.QuestionsDo you put the hip and valley rafters directly over the corners of the building, or do you offset them from the corners?Do you raise the plate heights on the walls with the steeper pitch rafters, if necessary?Do you always attempt to get equal projections for both roof pitches?Ken
*Very astute questions Ken! I'm much more impressed with your response, than your counterpart, (or adversary) who could only call my post scary because he has such a closed mind about roofs.My answers:No, we do not locate the hips and valleys over the building corner. Since they start out at exactly the corner of our equally sized overhangs, they intersect the wall on the lower pitched roof. Yes we raise either the wall or the HAP (99.999% of the time we raise the HAP) on the steeper pitched slopes. Yes we ALWAYS have equal projections on each roof overhang. Occasionally some architects will specify different sized overhangs, but it isn't because they are concerned with HAPs. It usually is for some other reason that doesn't apply to this topic. In fact, even if some overhangs are different, the HAPs will usually be different. A typical house will have two HAPS minimum on the lower level and Two different ones on the upper level. Many years ago, I partnered up with a carpenter that had learned his trade in Texas. I discovered our roofline philosophies were quite different. Here, we calculate our HAPS by working from our window heights, frieze boards and given projections. His method was much simpler. He'd want to nail a fascia board on and change the projection as needed and set the window according to the roof. We went round and round as I tried to get him to understand that we weren't going to get payed unless we put the proper sized overhang on as well as getting the windows at the right height. Neither way is more right than the other, just regional expectations change. Like my mentor used to tell me, "When in Rome, do as the Romans".Heading for some fun in Jupiter, Fla.blue
*blue,Also reread my post #19 to Tom.In that early post, I asked him if the roof was to have equal overhangs (projections), in which case the hip and valley rafters would be offset from the corners, or if the hip and valley rafters passed over the corners, which would result in unequal overhangs (projections). He replied that the hip and valley rafters would pass over the corners. Apparently, you always offset the hip and valley rafters to make the projections equal, which is fine, but in many parts of the country, including here in San Antonio, the norm is to put the hips and valleys over the corners, resulting in unequal projections. I've done it both ways. It's pretty much up to what the architect draws in the prints. blue, I'm using the term overhang meaning the same thing as the projection, which is the level measurement. In other words, when I say 18" of overhang, I'm implying that means 18" of projection.I'm quite aware that others use the word overhang to mean the rafter length associated with the level projection, but I've found that this concept hasn't really "caught on" with other framers in the area.Technically, the way in which you use the word projection, is correct. I've got a good feeling about this exchange of ideas that we will have here in this thread. I believe that we'll both learn something, and others will also.Thanks again for posting your thoughts on this subject.Ken
*Joe, your posts always seem to entertain me. I find it ironic that you don't have any faith in my ability to figure these roofs, even though I learned how to calculate them, and actully built my first ones before you ever entered the trade. The irony is because you attempt to belittle me for making my statements even though i'm quite sure I've built and installed more roof systems already than you ever will intall in your entire lifetime. Remember, I specialize in rouugh residential framing and on every house, there are usually at least two seperate roof systems. Then, compare your attitude to Ken's. Even though he is a much more accomplished roof mechanic than I, he still takes the time to learn. Now, maybe it's just your insane hatred for me that makes you act as you do, but maybe it's time you let your head, not your heart, do some of your thinking. You might as well just accept that I know a little something about roof framing. You might not agree with my techniques, but only a fool would claim that a guy (me) that does them on a regular basis doesn't know anything about them. I mihght not know how to do them with trig, but I certainly know how to do them with geometry. If I even really needed trig, I'd be willing to ask anyone, even you, but certainly Ken would be my first choice, unless I put a call into anther local friend her that thrives on trig.How about just brying the hatchet and letting life go on Joe? Life is too short to carry such anger.blue
*Ken: You are right. Others are learning. I am not into roof framing, but I find the math interesting. I am lurking and learning on the side. Keep up the good posts.
*Blue and Joe,Can't we put our differences aside and stick to learning from each other and helping others?We've seen a lot of threads thrown off track in the past by these type of exchanges. Let's not let this happen here please, we're just getting to the interesting part.Ken
*Ken, I did not in fact remember that you had determined that the overhangs would be unequal. As such, I can easily see why your heels would need to be equal.When I am browsing through these type of threads, I don't actually do the math and double check your numbers unless something jumps out at me. In this case, the assertion that the heels must be equal jumped out at me. If the wording had the qualifiers, I wouldn't have butted in. The only reason that I butted in, was because a newbie might pick out these words of yours i "It's important that the rafters for both pitches have the same HAP. This assures you that the roof surfaces will intersect at the center of the hip rafter." The first sentence is true, only if the hip needs to cross directly over the corner and if unequal overhangs are used. The second sentence is the big problem however. It implies that equal HAPS are necessary to cause the roof surfaces to inter sect at the center of the hip rafter, when in fact we know that this is not true. Ken I don't have any doubt that you are the best at teaching roofs in this forum. I'm just doing my job acting as the devil's advocate and keeping you on your toes. And don't worry about Joe starting up his stuff with me. I've said enough to him about his problem. He can look objectively at the facts if he wants and I'll gladly discuss numbers and techniques with him if he chooses to do it in a neutral friendly spirit. If he wants to simply start a flaming thread, he can start a new one that focuses on me. I'll gladly go in there and easily hold my own.blue i
*blue,I am posting a diagram of Tom's roof showing equal overhangs(projections) as we would frame it if equal overhangs were called for by the plans.In the diagram I've shown that the hips and the valley rafters must be offset from the corners to achieve this result.Also, the wall plates between and including the points were the hip rafters cross the plates, must be raised. This is where you think that you and I DON'T agree, but I think we DO agree.When the overhang is small, and the roof pitches don't vary by too much, it's possible to make up the small difference that the walls must be raised, by simply making the HAP on the steeper pitched rafters larger. In reality, what you are really doing, is taking the measurement of the raised plate, and adding it to the HAP. So you really aren't changing the HAP blue, you're just adding the raised measurement to it.If the overhang were larger, say 24", and the roof pitches were for example 7/12 and 12/12, such as in the diagram, this wouldn't be possible. In this case, you would have to raise the plates12/12 x 24" - 7/12 x 24" = 24" - 14" = 10"There's no way you could make that up in the HAP of the 12/12 rafters. So in my opinion, assuming that I haven't made any math errors, the correct procedure would be to raise the plates 10" where I've shown in the diagram, but KEEP THE HAP THE SAME AS FOR THE 7/12 RAFTERS.How far do you offset the valley rafters from the corner?12/12 x 10" = 10"How far do you offset the hip rafters from the corner?12/7 x 10" = 17 1/8"This will be my last post for this evening. Need some sleep. Have a great time in Jupiter, and look forward to hearing more from you on this soon. Ken
*Ditto what Stan said (except I actually do frame roofs)....Good work guys...
*Ken, I'm sure we agree on most of this stuff. Probably all of it.Again, I assumed that the plates are equal. Most of the roof systems that I have to install are hybrid truss systems (as much as possible is done by the truss manufacturer). They simply adjust their heels by adding a heel block. When we cut our own roofs we often add that same type of heel block, but I can remember an occasional adjustment to a wall height if it can be easily done. It usually can't though because the heel already starts out quite large and it simply easier to add a leg under the conventionally framed members. Besides, since almost all of our studs come precut, we normally don't have longer studs available to raise a wall. I think the last roof I conventionally cut, I had to triple the end wall plates to make the HAP adjustment. But that still left me with two different heels, no matter how you cut the mustard.Sleep tight.blue
*blue,Sometimes you might do a combination of both. Suppose you had to raise the plates 1 3/4". Let's say the HAP on the lower pitched rafters is 6"You could add a plate ( 1 1/2"), but you're not going to run around the plates again and add 1/4" plywood to make up the other 1/4", so you just adjust the HAP to 6 1/4" on the steeper rafters.It might seem that you are using 2 different HAP's now, but all you have really done is take part of the raised plate measurement ( 1/4"), and added it to the HAP, giving you the illusion that you have 2 different HAPs.Reread my last post with the diagram. I edited it and made some changes that you might be interested in at the bottom regarding hip and valley offsets.Ken
*Ken, go to bed!Thanks for the formula for calculating the offset. I've never really calculated it mainly because I've never needed to. I can easily see the relation ship however...I think. (I really didn't think too hard about it.)A very typical roof system here would be an 8:12 main with 12:12 ends. A 12" overhang would be quite common. The upstairs walls would be all built with 92.625" precuts. The truss heels would be figured this way:(2x10 header) would start the calculations. The architectual details would eventually create a heel of about 6" on the main. That would place the top of the roofline, at the eave @ 2" below the wall. On the end, the roof starts at 2" below the wall and rises 12". That puts the heel at 10" above the plate. So the main has a 6" heel, and the end has a 10" heel. The main trusses will easily make the 6" heel using the top and bottom chords. The end trusses will need a heel block. Any conventional framing that we do will be with 2x6 material. Since there is no way to cut a birdsmouth, we simply duplicate the heel blocking that the end trusses use. It's simply a matter of different regional techniques. That's what makes this forum fun to read. I guess the entire point of this conversation is to prove that the heels do not need to be level to make the roofs plane into the center of the hip. They do need to be equal to make the roofs plane into the center of the hip, i exactly at the outside corner line.That qualifier is not important to me. I already know how to cut and frame these things. It's the novices that I'm worried about.Nighty night.blue
*Boo!
*blue,Regarding you post#83. You have roof pitches of 8/12 and 12/12 and the overhang(level), or projection, is 12". The heel, or HAP, on the 8/12 rafters or trusses is 6".To find the raised plate, or block measurement, I would calculate(12/12 x 12") - (8/12 x 12") = 12" - 8" = 4", so on the 12/12 end you still have a heel or HAP of 6", with a 4" block under it, for a total of 10".You're calling the sum of the block measurement, 4", plus the 6" heel measurement, or 10", the heel measurement on the end walls, which is fine, if that's the way you like to think of it.I'm saying that the heel, or Hap measurement, is 6" for both pitches, but needs a 4" block, or raised plate, on the 12/12 end walls, for a total of 10"We both get the same end result however. Your hips should be offset from the corners12/8 x 4" = 6", andthe valleys should be offset from the corners12/12 x 4" = 4" Ken
*Hi all I am new to this forum, but have been reading through some of the post and find it very interesting. My question is with styraphome crown molding, I am use to wood crown and only used the other a couple of times. Both times I used it I had problems, first one, its to big for a most miter saws. So I make my own plywood box to cut the angles, but the angles are never close enough for me. I have to block plane them to get close enough for caulking. Which I don't like using.Dose any one have any experience with this type of product? And is it made to be caulked? I am not use to using caulking and it makes me think I am doing something wrong.Gray
*Gary,The subject of this thread is irregular roof framing.You should start another thread with your question.Just go back and click on "add a discussion". You'll get more responses to your question in this way.Ken
*Thanks,I realized it went to wrong place as soon as I hit the enter key.
*Ken and devil-A couple of questions occur to me right away on the equal overhang, unequal pitch situation-1. when raising the plate on the steep side, does Kens discussion of dropping the hip still apply?2. On the offset calculation for locating the hip and valley rafters- I presume these measurements (post #79) are with respect to the rafter centerline, along the outside of the plate?3. How would you go about accurately locating the birds mouth in the hip or valley? It seems when raising the plate you would lose a baseline to calculate or step off from?4. For Ken - all of your diagrams showing the interference which would occur between the two roof planes at the hip rafter, seems like it should also be true for the valley, yet you have indicated that you would not drop a valley rafter.5. For devil - do you make any attempt to match the birdsmouth plumb cut of the hip/valley with the angle it will cross the plate, or do you just square cut the plumb cut and nail 'er up?Regards,TomC
*Tom,Regarding your last post:"Ken and devil- A couple of questions occur to me right away on the equal overhang, unequal pitch situation- 1. when raising the plate on the steep side, does Kens discussion of dropping the hip still apply? 2. On the offset calculation for locating the hip and valley rafters- I presume these measurements (post #79) are with respect to the rafter centerline, along the outside of the plate? 3. How would you go about accurately locating the birds mouth in the hip or valley? It seems when raising the plate you would lose a baseline to calculate or step off from? 4. For Ken - all of your diagrams showing the interference which would occur between the two roof planes at the hip rafter, seems like it should also be true for the valley, yet you have indicated that you would not drop a valley rafter. "Question 1: Yes, you drop/bevel the hips in the same way as you would if they occured at the corners.Question 2: CorrectQuestion 3: Mark the center of the hip rafter on the raised plate at the proper offset. Mark the center of the valley rafter on the normal plate (not raised). Those are the locations of the birdsmouths. I'm not sure I understand what your problem is there.Question 4: Tom, once again, regardless of whether you are framing a single pitch regular hip/valley roof, or a "split pitch" irregular hip/valley roof, you always hold the jack rafters above the outside edges of the valley rafter (unless you cut bevels on the top of the valley rafter) so that they plane into the center line of the valley rafter. That is precisely why you do NOT drop the valley rafters. There is no need to.Just the opposite occurs with the hip rafters. If you use the same HAP as the common rafters at the point where the center of the birdsmouth crosses the plate line, it would be impossible to get the jack rafters to plane into the center of the hip rafter (unless you cut backing bevels on the top of the hip rafter). The edges of the hip rafter would get in the way. So you must "drop" the edges down to plane in with the jacks and commons, or in the case of an irregular hip/val roof, either bevel both sides of the hip rafter, or use a combination of dropping and beveling as I prefer to do. It cuts the time in half. I call the method the "drop and chop".By the way Tom, don't forget to bevel the flying hip (broken hip) also. That would be Hip#4 in your roof plan.Ken
*Joe,That's incorrect.You DON'T shorten the Hap on the valley rafter. That would not make any sense at all. You offset the valleys onto the regular plates so that the rafters on the raised plate can plane into it. Once again, the HAP on the valley rafter is the same as for the common and jack rafters.Look back at the roof framing plan that I drew for equal overhangs. The areas where the plates are to be raised are clearly indicated. It doesn't show the plates being raised at the valley rafter location. Ken
*Another very interesting treatis on mathematical solutions to intersecting roof framing details and such.Imagine the force of all three of you working together even! Is it time for blue and joe to kiss cheek to cheek?...Yes yes cries the audiance!...Imagination running overtime...near the stream,ajKen, This session looks damn near publishable big guy...Great work.
*Wow what a headache. I think if I had to frame a roof with this crew I would just go buy a trailer.
*Gunner...Are you saying that you just show up with a framing square and knock it all out as you cut or what? Please share with us your knowledge.near the stream,aj
*Nope don't know a thing about it.... And that's a good thing around here. ;)
*Joe: I don't see why moving the valley off the corner changes the HAP. We call it "lift" in Illinois. It still has to plane into the exact same HAP as the common rafters. What I think is getting confused is, you are correct in it is going out further on the valley rafter, but this makes the valley at a lower pitch in the same proportion as it moves away from the corner. It still has to end up as Ken says at the same HAP, lift or whatever one call it. Am I missing something?
*Joe,Later this evening I'll post some information that should clear this up for both you and Tom, as well as for others who are following this thread.It's never necessary to shorten the HAP on a valley rafter. At the center of the valley rafter, where it crosses the top plate on the building line ( normally at a corner of the building), it should have the same HAP as the common and jack rafters as they cross the plate.Hip rafters have to be dropped or backed, because the outside edges of of the hip rafters stick up above the plane of the roof.This is never a problem with valley rafters. Common and jack rafters can always plane into the centerline of the valley rafter. The outside edges are LOWER than the plane of the roof, by exactly the same amount that the hip rafter edges are too high.Ken
*Ken: What you just said is pretty boiled down. The HAP has to be the same as the common rafters at the plates edge, or it would not be in the same plane.
*Joe,I believe that I have already explained how to do that in my earlier posts.You must offset both the hip rafters and the valley rafters from the corners as I demonstrated in Tom's roof plan. The wall plates must be raised in the areas from hip to hip on the steeper plates, once again, as I've already demonstrated, along with the math for finding the raised plate measurement, the hip offset, and the valley offset.I'm going off line for awhile to make a few diagrams, scan them, resize them, and post them, on the subject currently under discussion here. If I don't have enough time to finish tonight, I'll continue after work tomorrow evening.Ken
*Joe,I'll post later today, after work.Ken
*TomC, the question of fitting the angled birdsmouth cut in one of aethetics. If it is exposed, and therefore important in any way, I fit it. If it is buried in the closed soffit system (it's always buried here in michigan), then I just square cut it. 99% of the time however, we don't have enough stock to cut a birdsmouth. Since the jacks are normally 2x4 trusses, the hips are only 2x6. A 2x6 does not have enough material to cut a birdsmouth and we normally install a heel block.blue
*Gary don't fret. We all had our learning pains as we starting posting to this forum. I had multiple posts to delete the first time I posted here myself. Keep in mind that you can edit or delete your topic in the first 30 minutes after you post it. That's one of the nice features about this forum.blueps Welcome aboard!
*Ken-Before you get to far ahead of us mere mortals, back in your posts #50 and #51 you show the edge heights of the hip corners above the roof planes to be ¼" and 5/8". How do you get these numbers? I can obtain the 3/16" dimension and the 9/16" dimension that you show in post #54. I know 1/16 inch doesn't matter too much in this type of work but I want to be up with your thinking because you again talk about the ¼" dimension in your "drop and chop" method in post #56. TomC
*TomC, I wouldn't recommend dropping the valley, unless there was some special circumstance that dictated it. The centerlines of the jack rafters automatically will plane into the centerline of the valley without any special dropping or raising. blue
*Stan, it is not correct to say that " still has to end up as Ken says at the same HAP, lift or whatever".That statement is misleading. A rookie might assume that all haps, lifts, or whatever need to be the same when that is only true if the hip passes directly over the outside building line. I will certainly agree that some of this discussion/confusion is caused by regional vernacular differences. The term HAP is being touted as height above plate. I suppose that it is assumptive on my part to assume that the intersectingplates on a corner of a building are level, but since 99% of the hips that I build are on level plates, I simply make that assumption. That would dictate that if unequal pitches are employed, and equal projections are also dictated that the HAPS need to be unequal.I don't have any useless graphics that are unsupported by data to prove this, but simple math will. I've already posted that and have not seen anyone correcting my supposed mathematical data. I have had an irrational response from Joe, but what would I, or anyone expect?blue
*AJ, I've extended the olive branch so many times and had it stomped into the earth that it's grown roots.Good idea however.blue
*Stan, I forgot to mention the obvious about why the HAP changes when you move it off the corner on unequal pitched roofs, with equal projections. You are missingsomething. The HAP of the hip lies in the plane of the steeper pitched roof as shown in Kens hand drawn plan layout of the roof. The hap of the hip matches only the steeper roof at the point that it crosses the wall line. Since the hip doesn't actually cross over the corner of the wall line, it can't be calculated. To attempt to do so would be an oxymoron. If it was possible to measure it, and the projections were equal, and the haps were equal, then the roof planes would be equal pitched and this discussion would be moot.blue
*Joe, after reading all of your responses, it's apparent to all that you are incapable of discussing anything in a relevent, polite manner. Of course, there is no great suprprise there.I see you have not attempted at all to show me why the different heel heights are incorrect. Instead you use innuendo to "challenge" my calculations but the facts bear me out. If you would like to see the different heel heights on any equal picthed roof, with equal projections, and equal plate heights just drive over to mighigan and check out one of the million or so that are now standing. Bring a tape measure and ladder and scurry up and measure. If anyone asks what you are doing, don't actually explain because if they sense that you don't know this most basic fact, they will immediatly mistake you for a first yeaar apprentice that hasn't had any roof experience.Just tell them your looking for dropped "toe nails" in the overhangs.blue
*Blue: I don't think I am saying it right. I am calling the HAP for the valley measured at where it cuts the plane of the wall, and at the point that it intersects the plane of the common rafters. Does it not have to be the same at this point? If you say no, then I think I am still not saying my point right. Hey, I am not a roof framer anyway, I will boot myself off this roof and hope I land in a bush. Ha.Thanks anyway, I think I will stay with curved stairways. They don't have all this math.
*Tom, POST 1I'd like to take the time to clear up the matter of the HAP of the valley rafter. I've consistently maintained, and have explained my position, as to why the HAP of the valley rafter as it crosses the outside of the plate, must be kept equal to the HAP of the common and jack rafters. There is no need to shorten or drop the valley rafter.Here is the area of the roof that is under discussion, if the overhangs were to be made equal. The center of the valley rafter is offset from the corner 10", as we talked about before.
*Tom,POST 2Here, once agin, are the HAPS for both the 7/12 and 12/12 comoon and jack rafters, that I used in this example.
*Tom,POST 3Here's a close up plan view of the area near the valley rafter, showing the valley offset from the corner, the raised plate, which I've shown extended all the way to the corner, and two 7/12 common rafters near the valley.Notice also, that I've added a 12/12 valley jack at the corner which would run from the flying (broken) hip, down to the valley rafter. That 12/12 valley jack would have to plane into the center of the valley rafter on its center line.Also, the rafter tails have been eliminated so that I can focus on what's happening at the plate line.
*Tom,POST 4Here's is an elevation view of the plan view in POST 3. Notice that the HAP of the 12/12 valley jack, the 7/12 common rafters, AND the valley rafter at its centerline as it crosses the plate, are all equal to 6 1/2".The 12/12 valley jack planes into the center of the valley rafter. To do so, notice that the valley jack must be held above the outside edge of the valley rafter by 5/8" (plumb measurement), the same amount that the hip rafter sticks up above the plane of the roof, before it is beveled, and/or beveled and dropped, as I suggested earlier.( "drop and chop" )I've shown a birdsmouth on the valley jack just to demonstrate why the raised plate works as it does. In practice, you wouldn't actually cut a birdsmouth on it. Instead, just stop the raised plate before it gets to the valley jack.The 7/12 common rafters also plane into the centerline of the valley rafter. Notice that the jack rafters on this side ( not shown ) must be held up above the edge of the valley rafter by 1/4", the same plumb measurement that the hip rafter sticks up above the plane of the roof before it is dropped or beveled on the 7/12 side of the valley.If you add the raised plate measurement to the HAP of the 12/12 rafter, 10" + 6 1/2", you would get the total measurement that the top of the HAP is above the "regular" plate, or 16 1/2". I believe that this is the measurement that blue eyed devil is referring to as the "heel" on the 12/12 rafters, and explains why he insists that the heel of the 12/12 rafters is different than the 7/12 rafters.If you look at it in this way, you can understand his point. However, I prefer to think of ALL of the rafters in the roof system as having the SAME HAP, and referring to any adjustments to them, such as "dropping the hip", raising the plate, etc., as just that, adjustments.In this way, you can work out the math for any measurement in the roof that you wished.I'm not sure where Joe stands on the issue of the HAP of the valley rafter at this point. He's gone to great lengths in his posts #100 and #106, explaining how to "drop" a valley rafter. In my opinion, the information in those 2 posts is incorrect.Ken
*Ken: That last post is exactly how I picture whats going on. The HAP, is the same, or there would be a discrepency. Keep up the good work
*Stan, you are probably understanding the dymnamics of the situation. If you look back to the original point of contention, you will simply see that there were some statements made without qualifiers that appeared to be misleading, to a novice. Now, when you look at some of the graphics posted, the qualifiers (raised walls, unequal projections, or whatever) are being inserted. And that was my entire point. I was just trying to put the qualifiers into the lesson, so that the novices don't learn a lesson that needs to be unlearned. I've met way, way too many carpenters in my days that have taken simple, unqulified statements at face value, without learning the real reasons about them. There is a tendency for information to be passed on (like "all studs are to be 16" oc" or "cantilevers need to have a 2:1 ratio" etc) and accepted at face value without the indepth explanation that makes the knowledge flexible. The lesson in this discussion (if there is one) is that some adjustment in height, or projection, or fascia level must occur for unequal pitched hip roofs. It's a simple basic concept, one that seems to be getting blown way out of proportion given the factual basis for it. I find it rather amusing especially since I've done probably a hundred unequal pitched roofs with different Haps, on the adjacent walls, of them.Maybe Joe can't figure out what I'm talking about, but I'm sure any roof framer can.blue
*Hmm...Anyone seen Tom???
*BT Readers,In recent posts, I've shown in detail how the 7/12 rafters sitting on the "regular" top plate, can plane into the center of the valley rafter, while the 12/12 rafters, sitting on the 10" raised plate, can also plane in to the valley center.The next 2 posts show the same type of detail where the hip rafters cross the plates. In the diagram below, the circled area is where HIP#1 crosses over the wall, sitting on the raised plate. In the next post, I'll show a detail of this area.
*This sketch shows both the plan view of the corner detail, as well an an elevation view directly above it.I've shown the hip rafter with backing bevels on both sides. In practice, I very rarely do this myself. I use a method I call the "drop and chop", where I first drop the hip the necessary amount for the 7/12 side, ( the lower pitched side) to plane in, 1/4", then bevel off the necessary amount from the 12/12 side, so that it will also plane in. I've discussed this along with diagrams in earlier posts, for anyone who would like to see how this works.Notice that in the elevation view here, that the HAP is 6 1/2" for both the 7/12 rafters, the 12/12 rafters, as well as the hip rafter at its center line.I've shown a 7/12 jack rafter at the very end of the wall planing in with the top of the hip rafter, while a 12/12 jack rafter, sitting on the 10" raised plate, planes in with the hip rafter also.The hip rafter in the sketch appears to be wider than 1 1/2", because you are looking at what a cheek cut on it would look like, beveled at 59 3/4º, as it crosses over the outside edge of the wall. The width of this cut would be about 3".Notice also in the plan view, that the seat cut of the birdsmouth on the hip rafter has plenty of bearing on the raised plate, so you can just cut the raised plate square at the 17 1/8" offset mark.
*Yeah Mike,Tom is still back at post #50 and 51. I understand Ken's discussion on the HAP for equal overhang and the raised plates, I can layout on a sheet of plywood and see exactly what he and the devil are talking about, so no need for me to get involved with all the crossfire lately. But I am still hung up on some of the geometry.TomC
*Joe-Regarding your post #122 to my questions in #112, I can see mathematically where the 1/4" and the 5/8" comes from. And based on what I think Ken has showed us, these are the heights of the corners of the hip rafter above the planes of the adjacent roofs. But I am still not seeing what the relationship is between these two dimensions and the 3/16" and 9/16" dimensions that Ken talks about in post #54. Why is there a difference between these two sets of numbers? Any chance of you showing where these two sets of numbers fit into the scheme of things with your super duper graphics? I don't mean to get hung up on a stupid 1/16" difference, but it must be important to the theory or Ken would not have brought them out.Quick note to the devil - Thanks for turning the discussion into a problem of equal overhangs. Ever since Ken asked me about my soffit detail back around post # 19, I started to wonder what would happen if I was constrained by equal soffits, how would things be different? Well now we know! thanks to you and all the fun that has gone on since.TomC
*Tom,
View Image © 1999-2001"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Tom,You're question is easy to answer. Look back at my sketches in post# 50 and 51. Notice that the measurements that the edges of the hip rafters stick up above the plane of the roof are 5/8" and 1/4".These are PLUMB measurements, and are indicated as so in the diagrams.In my post #54, notice that the skectch shows the cut through the hip rafter as a square cut, not a plumb cut. Therefore, the measurement will be smaller, in this case, 9/16" as shown below in the diagram.The same situation occurs on the 7/12 side. The plumb measurement is 1/4", and the square measurement is 3/16"So, once you know one, you can use a little trig to find the other. cosine 26 3/4º = square measurement/plumb measurementsquare meas. = plumb meas. x cos 26 3/4ºsquare meas. = 5/8" x .8930 = .56 = 9/16"Same sort of deal on the other side.Ken
*Ken and Joe-I’m clearly seeing where the 3/16” and ¼ “ measurements are coming from now. I understand just about everything now. Joe your last graphic must have anticipated my next question which is about the hip rafter length. Since you are developing the “unit length” of the hip based on the 7/12 common, I presume you multiply the unit length times the ½ span of the 7/12 roof. But will this work if we have the equal overhang situation? I think not because of the raised plate. Let me try my hand at it for the case of the equal 12” overhang and 14’ span under the 7/12 roof. Tell me what you think of stepping off the hip based on total rise instead of run: 1. starting from the 7/12 common, we can get a ridge height of 7/12x7’x12”= 49”+ 6½” HAP = 55 ½ ” . 2. The centerline of the last 7/12 common will be measured back from the bldg corner by 44”. I get this by 7/12x(8’x12)x12/12 – 12”overhang = 44”.3. For the 12/12 common, the total rise is 55 ½” minus 6 ½”HAP minus 10”plate difference = 39” so I would step down this 39” to locate the level cut of the birdsmouth and draw the plumb cut of the birdsmouth where a 6 ½”HAP meets the level cut line. Ridge cut gets a ¾” ridge deduction for 2x lumber. 4. The hip rafter square settings will be close to 6 1/16” rise to 12” run or better would be 11 1/16” rise to 22” run (based on Ken’s explanation in post 25 or Joe's explanation in post 31). With this setting I can step down the hip for a total rise of 39” to locate the level cut of the hip birdmouth. Locate the plumb cut where the 6 ½” HAP meets the level cut line then adjust the level cut for appropriate drop (unless beveling both sides). The birdsmouth plumb cut line gets adjusted out from the centerline of the rafter by the angle that the hip meets the plate (30.26 degrees) and I would mark this with a bevel gauge or speed square. Ridge cuts gets a ¾” ridge deduction for 2x lumber. Double check with a direct plate to ridge measurement. Will this work properly? Comments welcome. Faster/more accurate method? Also, who has the best way to cut the sharp bevel angles (59 ¾ degrees) for the 7/12 jacks accurately?VR again and again,TomC
*I know this probably won't help you out now, but there is a great book named (Roof Framing by Marshal Gross) that explains how to cut just about any roof that you might encounter. Alot of what Joe Fusco explained, is in this book. There are two other books that may be of interest to you, both by the same author. The Steel Square and Roof Framing, by H.H. Siegele. I have all three of these books and highly recommend them. I think you can get all three books threw Craftsman books. Hope this helpsBill
*Tom,In your last post, you wrote,"Let me try my hand at it for the case of the equal 12” overhang and 14’ span under the 7/12 roof. Tell me what you think of stepping off the hip based on total rise instead of run:"If the overhang ( projection ) is 12", the raised plate measurement would be 5", not 10", correct?If so, you'll have to rework your figures in step 3 of your post.Is there a better method? I think there is, but I don't have the time today to go through the steps. Perhaps this weekend.And regarding your last comment,"Also, who has the best way to cut the sharp bevel angles (59 ¾ degrees) for the 7/12 jacks accurately? "I specialize in roof cutting Tom, so naturally I need the proper tools to do the job. Currently I own three circular saws. 2 of the saws are made by SKIL, model 5860, which is an 8 1/4" worm drive (left swing) capable of beveling up to 60º, and a Skil 8 1/4" "sidewinder", model 5660 (right swing), also capable of beveling up to 60º. My third saw is a 7 1/4" Dewalt (right swing) with electric brake and depth set.When cutting a single pitch roof, I use the 7 1/4" Dewalt on my left side at the saw horses, and the 8 1/4" worm on my right side. ( this allows me to crown all of the rafters away from me as I cut)When cutting an irregular ( split pitch ) roof such as yours, I use the 8 1/4" worm on my right side and the 8 1/4" sidewinder on my left side. This allows me to make the sharp 59 3/4º cuts necessary on the 7/12 jack rafters in your roof. That, to answer your question, is the "easiest way", in my opinion.If you only have a 7 1/4" circular saw, here's how I would reccommend making the 59 3/4º degree bevel.1) Draw a 7/12 plumb line on the jack rafter on the OPPOSITE side of the rafter that you want the 59 3/4º bevel on. Set your saw a 30 1/4º and cut through the plumb line as if you were cutting the bevel on the 12/12 jack rafters.2) Lay the rafter down flat on the saw horses with the bevel facing UP, and hanging slightly off the end of the saw horses.3) Set your saw tilt back to ZERO degrees and cut through the short point of the 30 1/4º bevel, allowing the shoe of the saw to ride on the bevel as you make the pass.4) Finish up the cut with either a handsaw or a sawzall if necessary.Ken
*Tom, I can tell from your approach that you normally step off most of your rafters. That is the method that I learned many years ago. I now use the calculator and simple Geometry rather than the step off method because it's faster. However, I still use the same principles that I learned and sometimes employ a hybrid method. On almost every roof that I frame, I work with the total heights and runs rather than converting them to units. The need for unit calcultions has diminished with the proliferation of calculators and speed squares. To calculate the unequal pitch roof members, I use the total rise method that you are describing. Since all of our overhangs are already installed, and they are almost always equal, I calculate most of my lengths from the fascia to the ridge. Incidently, your mthod of stepping down the rise to the level cut works fine but I normally work it from the other direction. I calculate the overall length (the rafter = the projectin) and then find the wall line by making one step from the fascia line. In your example of the 12" overhangs, I simply measure 12" on the level with my framing square to locate the building line on the commons and jacks. I calculate the hip length by using total rise and total run. The total run of the hip is the hypotenuse created by the total run of the two different dimesions of the commons. In your example, you started with a 7' run (144") on the major roof. That resulted in a 44" total rise. Of course the total rise is the same on the 12/12 (minor) roof and that dictates a total run of 44". The hypotenuse of the two runs is a simple calculation : (144 x 144) + (44 x 44)x sq rt = 150.57"I then use the same simple principle to calculate the length of the hip. I use the total rise and total run and calculate the total length. That equation would look like this. (44 x 44) + ( 150.57 x 150.57) x sq rt = 156.86. I also use the total rise and and total run to find the numbers to use on my framing square. In this case I have the numbers 44 and 150.86. Since my square isn't that large I divide the two numbers equally. I'd probably just move the decimal (divide by ten) for this one. I'd then be holding 4.4" and 15.8" on the framing square. If I was using the stepoff method I would have to make ten steps using the two numbers.blue
*Tom,You haven't mentioned anything about the cathedral ceiling lately.Have you thought about what the ceiling would look like from the inside of the house if you offset the hip and valley rafters from the corners, as well as raising the 12/12 plates?If your total overhang = 12" ( level projection ), the 12/12 plates will be raised 5", which would offset the valleys from the corners by 5" also. The hips would be offset from the corners by 8 9/16".This makes for a rather peculiar looking "cathedral ceiling" from the inside, if you can imagine it.I think a more sensible, as well as eye-pleasing approach, would be to frame the ceiling somewhat independently of the roof, ALL on a 7/12 pitch. You could use the 7/12 jack rafters that run from HIPS 3 and 4 down to the plate in my diagram as part of the ceiling however. There's are a number of possiblities what this ceiling could look like. Ken
*Ken...Your bringing back memories of an inside framed 4-way intersecting cathedral ceiling with upside down birthday cake and more....Parkers....just down from me and the stream,aj
*Ken-Let me catch up on these last several posts. From your post 147; I see you are right about the 5" raised plate, in my haste I pulled the 10" raised plate from post #179, forgetting at that time we were looking at 24" overhangs.Your description of cutting 59 degree bevels with a 7 1/4 " saw has me scrathing my head. I'm going to ask you some more about this on another day.From your last post - I am not worrying about the cathedral at this moment, the foundation for that job has not even began. I think I'm OK with everthing for that job for now... won't know for sure until I start cutting wood though.That job will not have equal overhangs, the only reason I started asking you guys about unequal roofs with equal overhangs is because the devil brought it up and I wanted to know more...just in case. But I think you are right, that would present one peculiar set of cathedral ceiling lines! I can't imagine that anyone would find that look appealing (except maybe a carpenter). But fortunately that is not the problem at hand. I guess the only thing left that I'm hoping to reinforce myself from you guys is as I asked in #144, the best layout method for the unequal hip when it sits on a raised plate. I'd be glad for your methods on this Ken. The devil gave me some good information in his last post about stepping back from the soffit and fascia cuts. Super trick on the square settings too!VR,TomC
*Tom,
View Image © 1999-2001"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Joe, I'm surprised that you finally directed a conversation at me that includes facts. Is this to be considered a breakthrough?I would not be surprised if my math is wrong. Forgive me if it is. I'll only offer this as an excuse. I'm working at a relatives computer in Florida. I don't have my trusty pad of paper and faithful $6.00 calculator with me. I was forced to do the math on the computer calculator and I hate that thing so much that I never double check the results. I did look at the length of the hip and thought it strange that it was so close to the total run of the hip. I'll be glad to redo the math and thank you for finding and correcting the error. blue
*Okay fellas, I blew it. The numbers don't make any sense even though the method does.Too much jumping back and forth between screens.7' run = 84" run 7' run on a 7/12 = 49 rise.49 rise on a 12/12 = 49 run.(84 x 84) + (49 x 49) x sq rt = 97.247 (the total run of the hip)(97.247 x 97.247) = (49 x 49) x sq rt =108.89"I'd use 4.9" and 9.7" on my square to get the cuts. Since they are small numbers, I'd probably double them to 9.8" and 19.4". I prefer to use my framing square with the larger numbers, especially when working on larger stock.Garbage in: garbage out. The hip length is 108.89". I stand corrected.Thanks Joe for keeping me on my toes,blue
*Magnanimus of ya blue...near the stream,aj
*Mr. Devil,
View Image © 1999-2001"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Joe, if the rise is 44" then some other value changed which would require an entire new set of calculations.Where/why/how are you coming up with a 44" rise?blue
*Joe. I already posted that those were faulty numbers. I have no idea where that 44" came from other than I had a brain fart. Remember, I'm on vacation and I don't let my mind think too hard.bluePs I must admit that I've been on permament vacation for more than a decade.
*
I have two roofs to worry about on an L-shaped colonial. The L has a hip with 7/12 pitch on either side and the front being 12/12. The other roof is the main being 12/12 with the 7/12 L intersecting square to it.
My first problem, is the cheek cuts on the hip and jacks. Can the compound angle be determined from the scales on the 2-foot square? Or are these scales only good for equal pitch hips? Now that I think about it, I don't even know how to figure the seat cut on this bastard hip. What marks would you hold on the framing square? And how much to drop the seat? (All lumber is 2x and CDX sheathing, so I'm not worrying about backing the hip.) I'd like to learn how to do this without lookup tables, because I know very well, the book will disappear when I need it most.
Second problem is the valley where the 7/12 L intersects the 12/12 main. Am I right in thinking the valley cheek cuts could be figured the same way as the bastard hip jacks? But the bigger problem is a complication I never had to frame for - the both intersecting ceilings under this valley will be cathedral, so the valley rafters can't extend lower than the valley jacks of either the 7/12 or the 12/12. Is there a way to figure the width of the valley w/o putting it up and scribing along a few points of the valley jacks? And what about a bevel on the bottom of the valley, how would you figure these bevel angles? (It seems to me this is going to be a lot of trial and error, but structurally AND cosmetically it has to look right by the time I'm done. I don't want to go into a job having to rely on rockers and tapers to cover my experiments)
I know I'm not the first to have to do this, so all advice and experience is welcome.
Tom