*
Just curious what the traditional method for joining the eight rafters at the peak has been in the past…
What is the concern, intent, or deep hidden meaning with the conncection at the peak? I mean, what could go wrong, and how to frame and fasten at the peak so it doesn’t…
2×12 rafters, octagon is 14′ or so in width, 6/17, and has a 16″ deep soffit, from bottom of 2×12 to bottom of 2×4, that will mimick the rafters above. I see a little room at the top here for some small collar-ties, maybe?
Any help or experience with octagon framing appreciated.
Replies
*
traditionaly the rafters frame into an 8- sided post...
this can be cut flush or extend up thru the roof into a decorative finial...
*Nathan,I don't know if FHB has covered this (but try the index) If you have access to back copies of "Old House Journal" (local lib?) they've covered this several times.
*Hi Nathan,You're getting off to a good start with your post by including some information about rafter sizes ( 2x12, seems like overkill, BTW ), octagon width = 14', which I assume means width from parallel wall to parallel wall, ( not diagonal measurement ), 16" deep soffit, which I assume means, that if the fascia board is 1 1/2" thick, that the total overhang = 17 1/2" to the outside of the fascia.The one thing that you mention, that you must clear up, before any of us can respond properly, is exactly what you mean by 6/17, in your original post.The roof slope, or roof pitch, of ANY polygon, i.e., rectangles, squares, hexagons, octagons, decagons, dodecagons, etc., always refers to the the pitch, or slope of a COMMON rafter, NOT the hips.In addition, Nathan, if the roof slope of the common rafters of the octagon is 6/12, then the slope of the hip rafters of the octagon, is 6/13, not 6/17.The number, 17, goes out the window, when 90 degree corners are not involved, and the roof has a SINGLE pitch. 17 no longer has any significance, other than being another "counting number".So take time to clear up the meaning of your post Nathan, and let's go from there, hopefully in a friendly, and helpful manner.Ken
*Ken, I'm sure that the attacks will not surface, at least for awhile anyways.I'm sure you're licking your chops for this one. I better go find my octogon pics. I'm sure they will come in handy...You are right, Nathan needs to provide a few more tidbits of info.Will there be a snow load?Overhang projection?Sounds like a nice nook.blue
*Mike, I kinda wish that I had some type of decorative finial, although I've never framed one that had one. I couldn't figure out how to finish the shingling on mine. I admit that I've never actually looked at how they are done. I'm still open to suggestions. A finial might be the answer.Although I've used a center post, I opted to simply lay each rafter against each other when I did my Huron house. I installed the hips first, without a ridge. This meant that the first two were longer than the subsequent two. The last four needed bevels. I actually liked the arrangement and will do it that way in the future.blue
*Hi blue,Okay, you're getting to know me much too well. ("I'm licking my chops") Sort of like me knowing where the slush fund went.Just trying to help out a fellow poster as best I can.Here's one of my crude hand drawings to help Nathan understand my request that he clarifies the 6/17 thing.
*Right on Ken. The unit run for an octogon hip is 13". I never use unit figures when I calculate hips. I always use total rise, total run, and total lengths. I ususlly divide the total rise and run figure by ten to find the numbers to use on the square for cutting.I learned how to cut roofs using the unit method, and stepping them off. I prefer the calculator and total lengths and heights for accuracy..and I don't have any clue about trig, although I could ask my kids about it if I needed to know. I just have never needed to know in my career ...yet.blue
*blue,Well, the ball is in Nathan's hands now. I want to see if he wants to run with it ( as many don't)I'll wait for a further clarification from him ( re: 6/17 ) before pushing on to the next level with this topic.Ken
*Neat. So, 17 applies to hips that are 90 in their relationship to one another, not in their relationship to the ridge( a common). For some reason, I think I knew that already. Then, there is a way to determine the 13" of linear travel to gain the 6", of hips that are 45 to one another. Please explain how the 13 is derived. When I spoke of soffit, I meant interior soffit. Perhaps a reflected ceiling would be a better explanation. The interior ceiling is dropped 12" from bottom of 2x12 to top of 2x4, which will hang on 2x4 gussetts face nailed to the rafter. There will be an interior octagon false ceiling, suspended from rafters. This 15 1/2" drop is for mechanical runs, to drop the ceiling a little from a 12' exterior wall height, and provide backing for box beams. This was the space is imagined collar ties laying in. Exterior overhang is 12", including fascia. Mike, I drew a scale detail of a 10"x10" post, cut to octagon, to receive each rafter, extended it down through the drop ceiling, and imagined it finished below. Are rafters simply toe-nailed into this post? I'm imagining an architect who thinks this needs to be a structural attachment, as if to help prevent the rafters from spreading, or coming apart in high winds. I'm curious what stresses are on this connection. From the sounds of a post being traditional, I would imagine the connection does little more than provide a secure resting place. So what prevents the octagon from coming apart at the corners, as eight rafters push out, as well as down? Does a finial provide ventilation as well? Continuous ridge elsewhere, cedar shake.all comments and teaching are gratefully received... nathan wegemer
*rafters are simply toe-nailed to the post..the spread is prevented by a double top-plate.. lapped and nailed round -robinanother way of preventing spread is to strap it with a steel band..but i'm sure these guys have some other tricks..also.. if you are in a high wind area... you're bldg.dept . may require engineering for the connections.....
*I hate to mention his name, but someone on "New Yankee Workshop" built a gazebo using the 8 sided kingpost like the guys abve mentioned.Don't know if this project is in one of his books or not.
*all right. I see the square of a and b equalling square of c. can you give any quick help on how to attach drawings to a post?sides of octagon are not all equal...4 @ 5' 6"2 @ 6' 8"last two scaled at 6' 6"at parallel walls, 14' 9" f.o. frame to f.o. frame
*Ken,Sorry to have not researched what I'm building before talking here.Octagon has:unit runs of 8' on all hipsalternating wall lengths of 5'6" and 6'8"width of 14'6" from 6-8 face to 6-8 facewidth of 15' from 5-6 face to 5-6 facesome of these numbers were scaled from a 1" drawing I did. The 5-6 and 6-8 numbers were called out.
*Nathan,Thanks for the reply.I took a few minutes to work out the math for you. Open the Attachment below to see.You must have made a very good scale drawing, as your results were very close.Notice that the run ( 7' 5 9/16" ) of a common rafter to the shorter side, is slightly longer than the run of a common rafter to the longer sides ( 7' 2 11/16" ) So if the roof pitch in the 4 sections with the 6' 8" sides were 6/12, then the roof pitch in the 4 sections with the 5' 6" sides would be a little less, ( 5 13/16" /12 ) This won't be noticeable and shouldn't present any problems during the framing, just something to be aware of.The run of the hips is just under 8', and the length and width of the irregular octagon are 14' 11 1/8" and 14' 5 5/16"Hope this gets you off to a good accurate start with your frame.Ken
*Ken....If I ever have to build that roof, I'm just gonna fly you up here and be done with it!near the stream using my noodle effectively,aj
*Ken thanks for the time taken to generate the numbers. I am sure I could learn the path taken to get the results, however I am wondering if you have the time to post the proof. Something as simple as a progression of the calculations required would help me greatly I think, to understand how you arrived at the results. The actual computations themselves may not be needed, just your starting point, relative relationships and some theory. While your'e at it, could you also pick up my car from the mechanic, make sure the drywaller isn't getting sloppy at 5847 McKinley, and then call me for what's next.Thanks. ps I'm going to prefab this whole thing, fascia, sheathing, etc., on a slab. Den boom'er onto my walls.
*Nathan,I'll be more than happy to demonstrate the mathmetics behind the information that I posted, as you requested.Since I have no idea of how strong your background in math is, let me start with the basics. If you open the attachment below, you'll see a sketch of a rectangle ( square ), and a regular octagon. BTW, the word "regular" simply means that all 8 sides of the octagon are equal. The octagon you are framing is an irregular octagon.I conveniently choose 24" as the overall width of the square, as well as the octagon, to make the run of a common rafter = 12" ( BC in the square, EF in the octagon )To find the run of the hip rafter, AB, in the square, we could use the Pathagorean theorem, or we could use some simple trig. I chose to use trig, since it works with all polygons, without having to find the length of the third side, such as DF in the octagon.The cosecant of an angle, such as 67 1/2 degrees in the octagon, is the ratio of the hypotenuse of the triangle to the length of the side that is opposite the angle, or 12. To find the value of the cosecant of 67 1/2 degrees, first find the sine of 67 1/2 degrees, then divide the result into one.sine 67 1/2 degrees = .92391 divided by .9239 = 1.0824finally, 1.0824 x 12 = 12.99 ( rounded ), which is very, very, close to 13. So if the common rafter has a roof pitch of 6/12, as in the drawing, then the hip rafter has a pitch, or slope, of 6/13.You can use this method to find the run of the hip rafter that corresponds to 12" of run for a common rafter, for any polygon, regardless of the number of sides. In a regular dodecagon ( 12 sides ) the run would be 12 x cosecant 75 degrees = 12.4233 or about 12 7/16"So when you cut the hip rafters for the dodecagon, use the unit rise, say 6", on the tongue of the framing square, and 12 7/16" on the body.Before we go any further, take time to study the drawings and let's clear up any questions you may have. Then we can take a closer look at the math for your irregular octagon, if you wish.Ken
*Nathan,There are a few things that I neglected to mention in my last post, as well as a few additional comments about my post.First, after rereading it, I'm concerned that the math that I presented might be a little intimidating, as I should have made it clear, as how someone would find the sine of 67 1/2 degrees, etc. In general, in trying to not get too "wordy", I may have gone a little fast for some readers.Second. How committed are you to using a center post? I never use one, unless the plans show it as a decorative feature, and the rafters are exposed to view from below. It isn't necessary to use a center post, and the framing is much easier without it, in my opinion, altho I'm sure there are some that would disagree. If you'd like, I'll sketch out how I would frame your octagon without using one. Let me know.Third. I like your adventurous spirit. Prefabbing the whole thing, sheathing and all, then "boom'ering" it up onto the walls shows you really like a challenge. Almost wants me to be there with you., but there is one problem that prevents me from doing so. When I picked up your car ( nice Mercedes BTW ) and drove to 5847 Mckinley to check on the drywall situation, the guys convinced me that we should take it to Las Vegas for a quick weekend. You really shouldn't leave your VisaCard laying on the dash anymore.Talk to you after the slots. Did I spell that right?Ken
*I'm not too sure about that framing it on the ground thing. I used to do a lot of pre-framing but have now graduated to doing pre-framing when it makes sense. I nail four studs across opposite sides (on the inside) and drop a few planks. In very short order, I have a comfortable working height (I install the overhang from the inside, leaning over) and ready made saw horses (the top plates.) I've done quite a few of these things and know many slow ways.blue
*blue,Quite frankly, I would go your route with this if I were Nathan. I really DO LIKE his spirit, but it's difficult, especially with an irregular octagon, to build on ground, then lift all into place, and expect it to fit without beating it to death to make it fit.If you know how to make the cuts, all hips, commons, jacks, plywood, etc., can be cut by one person working alone, ahead of time, and then, when ready to rock and roll, can be framed in about 2 hours or so, from scaffolding, as you suggest.I'm looking forward to Nathan's responses to your comments and some of the ones I have made, also.Talk to you later, I'm sure.Ken
*Ken, the actual framing and cutting is the same on the ground and on a scaffold. The erection of the scaffold takes a few minutes and the setup on the ground takes a few minutes. The only real difference I can see is the crane fee and time.The other appreciable difference is the risk. The risk of it not fitting like you thought it would. I've done it several ways and like my final version. Off the scaffold, I install the second top plates, cutting them tight an nailing them securely. After all they are an intregal part of the frame that will keep the thing together. I work my way around fitting the Frieze first, then the soffits and finally the sub fascia and fascia. I don't see how it would be faster working on the ground. Besides, I'd have to bend over more and I hate bending more than I hate recounts.blue
*Blue,I think we're coming from the same place. It only takes a few minutes to set up the scaffolding. Why not just build it in place the first time, and watch it fit, and not have to worry about beating it to death to make it fit? Building on ground and then lifting may sound appealing, but as you say, why "bend and pray for fit"?
*Ken,I just came across this post and it seems it is very similar to my recent problem.The only difference is that Nathan is going for a full octogon and I was using 1/4 of a deod..... He was also looking to use what I was trying to avoid, irregular hips. The help you gave me allowed me to fully understand your solution to his problem. Nathan, as Ken stated to you , I think it is important that one have a fundamental understanding of trig to take full advantage of his method. As he also stated, there are many different methods to solve your question. I have a prety good background in Trig and love to use it although I an not a framer per say.I have made two templates, one to use on the rafters and one fullsize rafter template to test the fit before I start chopping up my 4x8 rafters that I had to go to the Adirondacks to obtain. It cost me 600 bucks to have them shipped and I cant afford to loose one because of a miscut or a misplaced ridge set. [see my earlier post "HIP RAFTRES}.It is also very important that the walls and posts be right on the money. I am a trim person by nature and am used to working with next to zero tolerance in my joints. I just installed a 6 piece buildup of crown in a 30 ft kitchen and not more than once or twice did I have adjust my miters.The reason for this was that I measured every angle with a Bosch angle finder and used trig when applicable to find the cut. There is nothing worse than trying to correct a buildup of crown when it starts to go awry.This is the principle I am using on my porch roof. It may be a little time consuming but my house is one time deal for me. I supose If I were a framer I would have to become a lot more efficient unless I had Ken there at my side chopping out the pieces for me. I have taken a great deal of time to make sure my walls are plumb, lengths exactly 34x64x8 and the diagonals equal.What I have stated is by no means a roof framers bible but if you choose to use the math method,understand it and apply it correctly, it is infallable.Why not use an equal pitch roof system. I would think it would be easier, especially when you get to the soffit.Mike
*Ken,I see enough to be dangerous.# of sides of polygon / run of hip per unit rise 3 - 24 4 - 175 - 14 13/16 6 - 13 7/87 - 13 5/168 - 139 - 12 3/410 - 12 5/811 - 12 1/212 - 12 7/1613 - 12 3/8tell me if I at least have the fishing line in my hands...cosecant of an angle describes the relationship of length of hypotenuse to length of leg of side directly opposite the angle being figured. Once we know the relationship expressed as a fraction, we can multiply this by the unit run of the common to receive the unit run of the hip/valley.So, you could play with the new guy's head by figuring the rise of a 6/12 common in 15 inches run, solve for cosecant of 67.5, multiply this by 15 and come up with a hip of 7 1/2 inches rise in 16 1/4inches run. This could be too much fun...if everything is good, please do carry on. I'm going to try to follow, and probably end up refreshing some very stagnant high school math.
*Hi Mike,I agree fully that understanding is different than knowledge. I'll just dive in here, and see what skills I have left from the math I took 18 years ago. "Understand why your'e firing each nail", is a phrase my new guys come to dread. With Kens help here, I'll have a much better understanding of roofs, particularly the one I'll be framing in a few weeks.I too agree that the walls should be the same on top as they are on the bottom. As for the irregular roof, it is so because the sides of the octagon have different functions. Two exit to hallway, four have windows, and two, double patio doors. I appreciate your sharing that the trig applies to the finish...principles apply themselves everywhere, huh?Nathan
*Nathan,Nice work. Your calculations are on the money. You now have a nice little chart for the settings on the body of a framing square, to go with the unit rise setting on the tongue, for any polygon, up to 13 sides.Now, let's take the next step.Look at the attachment below. It's exactly the same octagon that I posted earlier, but I went one step further. Once again, using 6/12 as the roof pitch, I used the pathagorean theorem to find the length of the hip, for 12 inches of run. It turned out to be 14.3076 inches.Next, I divided the hip length by 12, to get the ratio of the length of the hip for 12 inches of run of the common rafter, = 1.1923.Now, any time we're working with a regular octagon, and the roof pitch is 6/12, to find the length of the hip rafters, all we need to do is find half the width of the octagon, which would be the run of a common rafter to the center of the octagon. and multiply it by 1.1923For example, let's say that the width of the regular octagon is 15 feet. Then the run of a common rafter is 1/2 x 15' = 7' 6" = 90"The length of the hip = 1.1923 x 90" = 107 5/16"Piece of cake.I call these ratios LINE LENGTH RATIOS, in this case, for regular octagon hips. You could make a similar chart for other polygons ( I have ) if you wished.In your next post, please answer two of my questions.Is the roof pitch in your project 6/12? Are you committed to using a center post?Ken
*Hi nathan... Isnt this a lot of fun worrking with ken? And he makes it so easy to understand.Ken,While we are on this math thing I have a side question that often confuses me.Is there any rule of thumb on how to measure an angle? I noticed that on my project you determined the 30 deg turn angle from a horizontal line outside the porch.I know sometimes I am tempted to to put that angle, whatever it may be, on the inside,ie, if the vertex angle were 15 the other two angkes would be 75 and 90. I am sure there are others who have this same problem. Thanks,Mike
*Mike,I think I understand your question. If you extend one of the sides of any polygon, you form an "exterior angle" of that polygon. (See attachment below). Since Nathan's framing project involves an octagon, I'll use it for an example.To find the number of degrees in an exterior angle of any REGULAR polygon, divide 360 degrees by the number of sides. For a regular octagon, which has 8 equal sides, 360/8 = 45 degrees (step 1)To find an "interior angle" of any polygon, subtract the the number of degrees in the exterior angle from 180 degrees, so for an octagon,180 - 45 = 135 degrees ( step 2)To find the angle that the hip makes with the wall plate, just divide the interior angle by 2,135/2 = 67 1/2 degrees ( step 3 )The "speed squares" that we carry in our nail bags, don't measure the "true" angle that is formed on a piece of wood. They measure the "complement" of the angle. So to cut the wall plates equally, subtract the hip angle in step 3, from 90 degrees,90 - 67 1/2 = 22 1/2 degrees ( step 4 )Mike,In your dodecagon ( 12 equal sides )step 1, each exterior angle = 360/12 = 30 degreesstep 2, each interior angle = 180 - 30 = 150 degreesstep 3, angle that hip makes with plate, = 150/2 = 75 degreesstep 4, "speed square" angle to cut equal angles on the wall plates = 90 - 75 = 15 degrees.Ken
*Ken,For now, lets assume that the pitch of the octagon is 6/12. Lets also assume that we will use a king-post. In reality, those are both up in the air. I think the g.c. was interested both in the finial, and in the possibility of finishing the post below, as it drops through the reflected ceiling.Side question. How are octagons of this size usually vented? This is right out in the open, patio and garden on two sides, upstairs bedroom windows on another look down on the roof as well... cedar shake with continuous ridge vent elsewhere.So you let them boys use that silverset stuff, huh. I'll let you sand it when your'e back from vegas. Pretty nice second coat, though. Almost looks like I did it myself...( on a Sunday, too :)
*Nathan,Mathematics and roof framing are my trip. I'm not much of an authority on venting ( don't have enough asbestous underware to participate ). Others who read this thread will have more to offer than I will, but it would help them if you would post a plan view of the octagon, showing its relationship to the other walls in that part of the structure.I'd be interested to see the plan view also, in the vicinity of the octagon, to be of more help in the roof framing.Ken
*prints are with my lead. Sorry. I could post something from memory, but I'm in the process of re-installing my scanning software. reviewing your last post of math.when's my vacation?
*I see enough to be dangerous. # of sides of polygon / run of hip per unit rise / line length ratio for 6/12 common pitch.3 - 24 -2.0614 - 17 -1.5035 - 14 13/16 -1.3326 - 13 7/8 -1.2567 - 13 5/16 -1.2178 - 13 -1.1939 - 12 3/4 -1.17410 - 12 5/8 -1.16511 - 12 1/2 -1.15512 - 12 7/16 -1.15113 - 12 3/8 -1.146for example: 12 1/2 run, 6 rise, diag,divide by 12= LL for 11 sided polygon. The cmaster probably dropped a thousandth in some fraction conversions.hope you can continue with the irregular theory without the prints. What concerns you?
*Nathan,Geez Nathan, you are getting dangerous! But your math appears to be accurate and reflects a good understanding of what we're talking about here.I really don't need to see the blueprints. I just thought it might give us all a better "feel" for your project if you could scan the area where this roof occurs in the structure, and post it as an attachment. It was a reaction to your question on how to vent the structure, more than anything else.Now that we've discussed regular polygons, I think we're ready to return to your irregular octagon, and look at the lengths of the common, hip, and jack rafters for it, as well as how to make all of these rafters fit with each other at the peak of the roof.Is your Construction Master Calculator a III or a IV?The CM4 can do trig and give us the angles that we'll want to know. The CM3 doesn't have this capability.I'll demonstrate how to get the angles using a CM4, as well as with an inexpensive scientific type calculator, such as Texas Instruments TI 30, that has trig functions ( sine, cosine, tangent), About $13.OPEN ATTACHMENT
*cm IVnathan
*Nathan,Since the GC is not really sure at this point if a center post is necessary, or, exactly what the roof pitch will be, the approach that I'd like to take would be to work out the hip rafter lengths, the hip rafter pitch, the common rafter lengths, the common rafter pitches, assuming that they will all run to the center point of the peak. Then, when a decision is made, you can shorten the rafters appropriately, according to the dimensions of the post, if one is to be used. How does that idea appeal to you?I must say, that with the roof frame only about 2 weeks away, I find it unusual that these decisions haven't been made at this point. Glad you have the CM4. That will make things easier.
*makes sense to me. figure as if no post, easily adjusted after I know what the k-post will be.seems kind of unusual too, but then.. whadda I know? just beginning to see how this gc works, along with the architect, designer, client, project manager, PE...lots and lots of design in the casework in the new library. I can see how a some roof details got put on the back-burner. I take heart in that I have observed quick decision making so far...i'm gone for a few hours...
*Nathan,Okay, we'll give it a go in the morning.I have tomorrow free, and will post some numbers.
*Ken....Nice calcs....but i tried all the buttons and none of them worked!near the stream,aj
*Nathan,Okay, it's time to get back to the irregular octagon that your need to frame and put a roof on. (See diagram below)Think of the octagon fitting inside of a square. If we can determine the length of the sides of the square, then snapping the sides of the octagon will be a breeze.In the diagram below at the bottom left, you see a right triangle with two equal "legs" = 1 unit. By applying the Pathagorean theorem, we find that the hypotenuse of the triangle = 1.4142 units. In other words, the hypotenuse of a right triangle that has two equal legs, is always 1.4142 times the length of a leg.A good example is if the legs are both 12", then the hypotenuse = 1.4142 X 12" = 16.97". So if we were framing a hip roof at a square corner and the roof pitch were 6/12, the the slope of the hip would be 6/16.97, or 6/17 for practical purposes.Of course, the process works in reverse just as well. If we knew the length of the hypotenuse, we could find the length of the legs, by DIVIDING the hypotenuse by 1.4142.In your octagon, the shorter sides are 66", so the legs are 66"/1.4142 = 46.67", or 46 11/16". Now, that's just the info we need to find the sides of the square. Double 46.67" and add 6'8" and we get the side of the square = 14' 5 5/16".An even easier method to find the legs is to use your CM4 calculator. Think of the triangle as a 12/12 roof. Enter the pitch as 12 inches, enter the diagonal as 66" and press either the rise key or the run key to find the legs.Now it's time to snap out the square. I think it's clear from the diagram how easy it is to snap the octagon. You can measure out 3'4" from the centers of the sides to get the 6'8" sides, or you could measure in from the corners 3' 10 11/16" to find where the sides begin, and then mark them off. I'm not sure if you'll be able to snap all sides of the square ( another reason I wanted to see the floor plan), but snap as many as possible.
*Nathan,Now that we know the size of the square that the octagon fits into, 14'5 5/16", if we take one half of the side of the square, we get the run of a common rafter to the 6'8" side. See diagram below.In the diagram, AD represents the run of the common rafter to the 6'8" side, AB represents the run of the common rafter to the 5'6" side, and AC represents the run of a hip rafter.Follow along with me using your Construction Master IV.1) enter the width of the octagon, 14' 5 5/16"2) divide by 2, to get 7' 2 11/16", the run of the common rafter.3) enter this as "rise" in triangle CAD4) enter 3'4" as "run"5) press the diag key. this will give you the run of the hip, or 7' 11 7/16"6)press the pitch key repeatedly. It will change back and forth between 26 inches, (which simply means that if the triangle CAD represented a "roof", it's pitch would be 26/12 ), and 65.22224 degrees, which means that angle ACD, the "roof angle" for a 26/12 pitch roof is 65.22224 degrees. That's the angle the hip rafter will cross the 6'8" plate. I guess you realize that I'm "tricking" my CM4 into doing some trig for me without mentioning the words sine, cosine, tangent, etc7) Since the total number of degrees in angle BCD is 135, subtract 65.22 degrees from 135 degrees to find the number of degrees in angle ACB, or 69.78 degrees, the angle the hip rafter will cross the 5' 6" plate at.Clear the calculator by pressing On/C twice.Now look at triangle ABC. Think of it as representing another steep roof. 8) Enter 7' 11 7/16" as the diag. Enter 2' 9" as the run, and press the rise key. What is displayed will be the run of the common rafter, 7' 5 9/16", to the 5'6" side of the octagon.Nathan, in an earlier post, I incorrectly showed the hip run as 7' 11 11/16". This was my brain mixing up too many 11's and 7's. Sorry about that. Please don't shoot me. Any Questions?
*Finding the rafter lengths is easy, especially with your CM4. Let's start with the common rafter that runs to the 6'8" plate and find its length, assuming the roof pitch to be 6/12.1) enter the run = 7'2 11/16", then press 6 inch pitch, then diag to find the rafter length = 8' 0 15/16". While were here, hit the rise key to find out how much rise this rafter has. Rise turns out to be 3'7 3/8" (See Diagram below)To find the length and the pitch of the common rafter to the 5'6" plate,2) enter the SAME Rise, since all of these rafters are being considered to run to the same point at the peak, and then enter the run, 7' 5 9/16". Press diag to find the length of the rafter, then press pitch to find the pitch for this roof section = 5 13/16" /123) follow the same procedure to find the length and the pitch of the hip rafter.Of course, all of these rafters have to be shortened appropriately to fit with the King post, if one is to be used.Nathan, what size rafter stock are you going to use, and what's the O.C. measurement?
*Ken, I'm excited. I learned something today.I learned that i In other words, the hypotenuse of a right triangle that has two equal legs, is always 1.4142 times the length of a leg!I think I'll try to remember that one and see how many ways I can use it. I'm not so sure about making and using the charts for the hip runs.blue
*
View Image © 1999-2000"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich W. Nietzsche
*blue,I glad to see that you took the time to follow this thread. Sometimes, when I bring out the math, which I try to keep under control, and in moderation, I wonder if anyone is really reading any of the stuff that I write. I have a feeling that there are a lot of people just reading and not posting responses, but I'm not really sure. If it weren't for people like yourself, that provide some feedback, I'd feel like I might just as well e-mail my thoughts directly to Nathan, in this case. But I post it here, hoping that others can learn from it also. I know that your math background isn't as strong as mine, but it's encouraging to find people like you, that I admire, responding in a positive manner, and getting excited about "learning something today"Now I feel encouraged to go on to the next step, cutting the rafter tails properly, dropping the irregular octagon hips so they plane in, etc.The charts for hip runs are useful when all sides of an octagon, or any polygon, have all sides equal. In Nathan's case, where the sides are not all equal, you could use 6/13 to make the plumb cut on the hips, it would just be off by a "leetle beet"Zoe
*Ken, oops! I just figured out that pushing the 1.4142 button times the run is more pushes than my current method.Oh well, it's still nice to know these things, even though I'm not going to use them.blue
*Ken, I'm following the thread...somewhat. If you are doing a poor job with the math, I'd never know, because I don't have a calculator at my desk. It's in my pouch.And don't go answering all these questions directly via email. Just trust that someone somewhere is learning, or simply enjoying it. I kinda got a kick out of Nathan figuring out how to do the calculations, especially since I still don't have a clue how to do the sine and consine thing. And I ain't about to spend the 13 bucks on the sci calc. My kids learned on those and my daugther taught me how to do it once. I made here give me a chart on the exact angle for each pitch. I still have that tidbit in my purse (wallet, or organizer or whatever you call it) but I've never looked at it again. I can't even see the numbers on my saw, so why would I care if I'm off a degree or not.Anyways, after she showed my how to figure the roofs with trig, I decided that I could live with Geometry. Happily ever after...bluePs. if I ever get involved in a circular project that will require trig, I'll simply include enough in the estimate to get my trig loving buddie to do it. I hate round walls and round things and don't like doing them.
*blue,Good point.Actually I very rarely do it that way either.For example, suppose I need to snap out a square, each side of the square = 14' 5 5/16", and after I finished, I wanted to measure the diagonals to see if it were truly square. I would just enter 12 inch as pitch, and 14' 5 5/16" as EITHER the run or the rise, and press diag on my CM4. Answer? 20' 5 1/8", with no decimals to convert.Using a "regular calculator", you would get the same answer, by multiplying 14' 5 5/16" X 1.4142, but it would be a much more tedious process. Decimals SUCK. My tape measure has 16ths, 8ths, quarters, and halves, and that's what I want to see coming out on the display of my calculator, not some funky decimals.BTW, how do you do it on your Soar calculator?Zoe
*blue,Interesting comments. I actually enjoy doing circular work, elliptical work, circular stairs, etc. It definitely takes a little more time, but if you understand the math, it's a big help.
*Ken, it would be a bit more tedious to find the diagonal on the cheapie.5/16+5/12+14x M+ M+ MRC sqrt That's 16 pushes. Then I'd have to convert the number which is a foot-decimal of a foot answer. The answerwould be 20.xxx so I'd. -20/12 the anwer would be 5.1xxxthat would take an additional 6 pushes for a grand total of 22 pushes. I can actually whip that out very fast. Much faster than my calculator can keep up. On some calculators, I have to be careful not to go faster than it can comprehend. That is the limiting factor.I've squared many a' foundation like that.blue
*Ken, I understand the basic principle of circular math. I've skipped the learning of ellipses because I've never had a need. I know where I need to go to learn, if the need arises.I've done my share of circular stairs. I'd just as soon have a simple straight set nowadays. I'll soon be looking at some plans for a 17000 sq ft home. I'm sure there will be a circular set in there somewhere...blue
*blue,I know you have a Construction Master 3 Calc., that you claim is buried under the beer cans and the pizza boxes in the back of your truck.Find it.1) enter 14' 5 5/16" as either run or rise2) enter 12, inch, pitch3) press diag to see 20' 5 1/8"If your trying to square a foundation that is 52' 4 1/4" by 63' 5 1/2".1) enter 52' 4 1/4" as rise2) enter 63' 5 1/2" as run3) press diag to see 82' 3 3/16"Think it over. What's easier?
*KenJust got in and printed out whats new. I'll review it over the holiday, snapping tomorrow, I'll give you a shout Saturday.Thanks, in advance.Happy Thanksgiving, everyone.
*Ken, that would be easier. But then how do you add 4.375 + 9 1/4 -mrc (whick is the number that the top of the fascia is down)...I had too much trouble making the const calc into a regular calculator. I'm hopelessly caught in my old ways....blue
*KenI'm with you. 2x12 rafters, 16 oc. Print showed purlins, but with no details. I'm having a ball watching you build this, continue on with purlins, please. If I remember there was one run, at what looked like 4ft from f.o. frame. I know you called 2x12 overkill, I agree. Gotta go with what this guy draws, otherwise I have to spend time RFI. The extra hap gives me some room to play the bottom of the fascia versus the ridge venting below, which is coming in one two of the 6-8 sides. It is tight there, could simply raise the walls of the octagon a little to gain some clearance. 2x6 tails, as well.Is r-value a consideration in rafter size?
*Quietly learning.Thanks,Jerry
*Nathan,I cut roofs in south central texas ( San Antonio ), and really don't know a whole lot about R-values, just the basics. That's someone elses job. There are many others here that can help you with that aspect of the framing, perhaps they will respond. BTW, What part of the world are you building this in? Just curious. We'll get to the purlin thing soon, but first I wanted to take a close look at the rafter tails.(See Diagram below)We've already seen in previous posts, that if we let the common and jack rafters that go to the 6'8" walls have a 6/12 pitch, the common and jack rafters that go to the 5'6" walls will have less pitch, 5 13/16" /12. As a result, they will have slightly more overhang so that the fascia can remain at the same level.Here's how to go about determining the correct overhangs. You mentioned earlier that the total overhang ( the LEVEL measurement, as seen in the plan view below) was to be 12". Look at the triangle ACD.AD represents the 12" overhang, and AC represents the overhang ( the run) of the hip rafter on its centerline, from where it crosses the plate at point A, to the outside corner of the fascia at point C.Now, imagine the triangle ACD to be a steep little roof. The pitch of this imaginary little roof is the angle that it crosses the wall plate, which we have already seen to be 65.22 degrees.Using your construction Master IV, 1) enter 65.22, then press pitch. Since you didn't enter it as "inches", the calculator knows that it's an angle and will display it that way.2) enter the rise as 12"3) press the diag, to find the length of AC, 13 13/16". That's the overall run of the hip rafter.Now, let's see how to find the run for the tails of the 5 13/16" /12 rafters.Look at triangle ACD this time. Once again, imagine it to represent a steep little roof.1) enter 69.78, then press pitch2) enter 13 3/16 inches, then press diag3) press "rise" to find the total overhang. The CM4 should display 12 3/8". If you subtract 1 1/2 inches from this measurement, for the fascia thickness, the result is 10 7/8", the run of the overhang for the tails.Final step. Lets find the actual lengths of the rafter tails using CM4 once againFor the 6/12 rafters1) enter 10 1/2" for run2) enter 6 inch for pitch3) press diag to see the answer = 11 3/4"For the 5 13/16" /12 rater tails1) enter 10 7/8" for run2) enter 5 13/16 inch for pitch3) press diag to see answer = 12 1/16"I'll post later on how to cut the hip tails, this enough for right now.Happy Thanksgiving to ALLKen
*Nathan,Here's a much easier way to find the overhangs for the 5 13/16" /12 rafter tails. ( Diagram below )In the top part of the diagram, a 6/12 rafter is shown that has a total (level) overhang of 12", including the fascia. Therefore, as it passes over the plate line, it will lose 6" of rise to the outside edge of the fascia, as shown.We want the 5 13/16" /12 rafter to also lose 6" in rise, so the fascia remains at the same level for both rafter pitches. So all we need to do is find the amount of run for the lower pitch that results in 6" of rise. Using your CM4 once again,1) enter 5 13/16 inch pitch2) enter 6 inch rise3) press run to find answer = 12 3/8"Therefore, the run for the rafter tail = 12 3/8" minus 1 1/2" = 10 7/8", as we found using the first method.
*Nathan,This post concentrates on the tail of the hip rafter. Most framers would just let the tails "run wild", snap a line across the common and jack rafters, and cut plumb at 22 1/2 degrees on each side. The cuts would be off a little bit as you can see from the diagram below, but you could "make it work". It all gets covered up anyway. This is the most common approach used in these situations, I believe. Another approach would be to cut the tails "short", nail up the fascia, and then later scab on some 2x4's to the sides of the hip rafter for better support for the decking. A better approach would be to snap the lines as mentioned in the first paragraph above, and then make the cut at 25 degrees on the 6'8" plate side, and 20 degrees on the 5'6" plate side. Then the cheeks cuts would fit the inside of the fascia as shown in the diagram.I like to cut all of the rafters in the roof ahead of time, so over the years, I've learned how to deal with these irregular hip problems. It's not necessary that you, or anyone else know how to do this, but I thought I'd include it as you, and others, might be interested in how to cut them. You might just as well go ahead and cut the tails now that I've done the math, so let me comment on the drawing.At the top of the drawing, you see the corner of the octagon walls meeting. Using a "speed square", we all make these cuts at 22 1/2 degrees on each plate as shown, and then overlap with a 45 degree cut on the top plate ( not shown). The fascia is cut the same way, 22 1/2 degree bevel on each piece.Notice that the centerline of the irregular hip rafter passes over the outside corner of the wall framing, and also goes to the outside corner of the fascia.In an earlier post we calculated that the run of the hip tail from point A to point C in the drawing was 13 3/16". We also have worked out the pitch of the hip to be 5 7/16" /12, so using your CM4, you will find that the length of the tail for this much run is 14 1/2" (see bottom diagram)The only problem of course, is that it must be shortened for the fascia, and be beveled properly. Since the hip crosses the 6'8" plate at about 65 degrees ( accurate enough for me) the saw bevel on this side is 25 degrees, and using the same reasoning, 20 degrees on the other side of the hip rafter.Notice that you must move ahead 2" before making the cut on the 6'8" side, and 1 7/8" on the 5' 6" plate side, before cutting.Start by marking a plumb line on the hip as shown at 14 1/2 inches. Immediately square this line across the top of the rafter, then set the line ahead 2" as shown. Set the saw bevel at 25 degrees, and cut. On the other side, set ahead 1 7/8" and cut at 20 degrees.As you might guess, the math for working out the "set aheads" ( 1 7/8" and 2" ) is a little involved. I'm not going to go thru it at this point, in this already long post.Happy Turkey again to ALLKen
*blue,First, Happy Thanksgiving Day to you and your family and friends. May this post find all of you happy and in good health.Second, I've been thinking a little about a post you made recently in this thread, "Ken, that would be easier. But then how do you add 4.375 + 9 1/4 -mrc (whick is the number that the top of the fascia is down)..."I'm thinking that the 4.375 is the HAP, or the "Heel", as I believe the locals in your area refer to it as , on a 2 X 6 rafter, the 9 1/4" is the rise for the rafter overhang, and "mrc" is memory recall, which you say is the number that the top of the fascia is down.Could you explain this in a little more in detail? I'd be glad to show you how I would do this, to answer your question.Ken
*I'm almost lost myself with that calculation Ken.Happy Turkey day to you too. The equation is my method of figuring the bottom of the pine line. Remember, we install all of our overhangs before the roof, so this calculation is most important.The 4.375 represents the sub fascia (2x4) and the soffit thickness of 7/8". The 9.25 represents the 1x10 frieze. Actually, my reply was intended to question the ability of the const calculator's ability to switch modes easily without losing data. One of the most important features that I need is a seperate memory recall and memory clear. I calculate the drop and immediately add all the pines, which gives me my header height. The problem I had with the const calc was switching from one mode to the next and inputting data that I had already calculated. Often, I'd lose the number or have to write it down, then re-enter. Maybe this has been improved in the latest versions.Maybe I'll ask Santa for a new one for being such a good Boogerer.How much are they nowadays (I'm pinching pennies due to the slowdown in the field)?blue
*blue,Maybe Santa will give you a discount for being such a good Boogerer. I don't think price has changed much over the years, about $75I'd really recommend getting a CM4 blue. It's a big improvement over CM3, in my opinion.To clear memory, without changing current display,Press Conv, then press RclTry it on your CM3Yeah, it's 2 presses instead of one, but on the other hand, there's one less key on the calculator.near the turkey.........Ken
*Nathan,I'm thinking that you're going to cut the 2 X 12 rafters something like I show in the attachment below. Whether you do or not isn't important, but I wanted to mention something about "dropping the octagon hips" In the diagram below, if the 2 X 12 is 11 1/4" wide, and 1 1/2" thick, as we normally expect, then after you cut out the birdsmouth, the HAP that remains will be close to 10 13/16", providing you use a 3 1/2" seat cut at the birdsmouth.Whatever it turns out to be, make it 1/8" less on the hip rafters, where they cross the outside plate line. In other words, "drop the hips" 1/8". This will allow the outside edges of the hip rafters to plane in with the jacks and common rafters.
*Ken,I see the principles that keep applying themselves during this buildup of information. The octagon is different by a couple inches in the field. Funny, huh? I'll need to apply what you've shared to a complete octagon. I'm confident that using your posts as a reference, I can achieve the correct numbers for what I'll be building to. I'm looking forward to becoming more of a geometrically friendly framer. i Everyone!.... Free the math!!!!Still thinking about what you and Mike shared on the pre-fab. I'll post a few pics soon. Many thanks (from Seattle).
*Nathan,Looking forward to the pics, especially a good shot of how you handle the connection at the peak. Let me clear up one thing from my most recent post about "dropping the hips"When I said to make the HAP 1/8" less on the hip rafters "where they cross the outside plate line", I intended to mean where the hip crosses the outside corner ( where the outside plate lines intersect). Then, at the point on the seat cut where it crosses over the plate, it will have the same HAP as the common and jack rafters.What it all boils down to is this. Take an extra 1/8" out from the level cut (seat cut) on the hip rafters.
*Nathan,I framed an octagon roof about 3 years ago. It was the top of a round stair enclosure that housed spiral stairs. The top 3' of the tower was made up of 8 windows with post in between. The roof was 8 -6x12's. The radius of the tower was 8' or 9'. I first framed the roof on the ground. The ridge connection was fairly simple. The first two rafters went in directly across from each other. There was nothing at the ridge the plumb cuts of the rafters were square and the rested against eachother.The next two rafters were perpendiculer to the first two. I took 2 3/4"(the thickness of a 6x12) off the run of these rafters. These two rafters rest against the first two. The final 4 rafters had plumb cuts that were beveled both ways. I think the bevels were 45s.The rafters were lagged together from the top. We may also have put some Simpson straps or steel plates across the top. I can't remember which it was.
*Thanks davedI had to look twice to make sure you said 6x12. Someday I'll work my way into some large member framing projects. Sounds neat. Our connection will be a 12x12 ripped to receive each rafter, and connected with a hanger. I don't recall the numbers, but using the dimensions of the octagon, I divided each face by an equal number, to give me a scale replica of the octagon framing on the post. This will drop down below the reflected ceiling and be finished with something pretty. You say you framed the roof on the ground. Care to share how that process went?nw
*Nathan,We framed the roof on the ground but then took it apart to bring the rafters up. We built a top plate octagon on saw horses. Then we cut all the rafters and assembled it on the ground. The rafters were numbered then taken apart. It was finally reassembled in place.
*davedSounds similar to our plan. Blue thinks he's as fast off scaffold, and I say no way. I'll cut all the material off piles, and pass off to framers who are standing next to me on concrete, and able to walk around the frame, into the frame, over the frame.. Continuous strapping around the perimeter, with a gun, walking without interruption as you go. Fascia and ply stocks right next to the frame (think of the time saved in sheathing while standing off the roof). I'll even black-paper the roof for them, as I'm standing there without my safety gear, smiling because my tools are laid out conveniently around the work. Wow. I probably won't spill my quad-tall americano, either. The crane will already be there to set ridge beams.I will definitely be holding my breath slightly. But if the rafters go together like a puzzle, and no warning lights go off, then it should be a piece of pie.looking for third gearnw
*Nathan, keep track of your accumulated time. I'll be doing one in the future and will keep track of mine. YOur time needs to include all the cornice work too because I put my cornice on first before I install the rafters. Blue
*blue,It doesn't look like I'll prefab this one. My lead broke his fibia while skiing last Saturday, and things have been restructured to suit the crew changes. After seeing the size of this thing, partly framed, I would be a little leery of committing all that time to something I can't really check along the way. I promise, someday I'll prefab something really significant. We were able to prefab some trusses and skylights, complete with chases, so I don't feel too bad. I will keep track of hours, we should start with the roof on this on tuesday or wednesday.Stay warm. Nathan
*Interesting pics Nathan. Keep 'em coming...I think I'm seeing the skylights being preframed. It appears that these are common rafters with a false ceiling attached. Basically, you are installing two roof systems parallel with each other..in a "A-frame" house with a partial second floor. Your efforts are admirable, but I'm not convinced that they are time saving. In the "old" days, a considerable amount of time was saved by prebuilding because of handnailing drawbacks. In today's era of guns, a lot of prebuilding is needlessly done, simply because it can be. For instance, you probably still will need to set up a scaffold system to install your prebuilt components. So, there is no time saving there. During the prebuild phase, you need to set up paralell lines to represent the parallel walls which neutralizes some of the perceived prebuld savings. The awkwardness of heavier prebuilt units also eats time.One safty note...Please cover your stair well unless it is absolutly necessary to leave it open. The fellow working is one step backwards from a life of drooling in a wheelchair...Keep the pics coming..blue
*attempt at editing in Corel Photo Paint
*attempt at editing in Corel Photo Paint
*Sorry ,everyone, about the unedited pics. So, this saves to my desktop. When I try to open by double clicking, it says it can't find the application program. But when I drag the icon into the active window, it opens as I edited. How to get it to open from the link, without it saving to the desktop? What is anyone else seeing?
*Blue,Here's how it went:-snap the rafter, with all cuts, on the floor. -snap the ceiling joist parallel to and the proper distance from the beam and exterior wall -snap of gussets, skylights-take dimensions of all pieces, take count for 4 skylights, cut man has at it.-nailed down 2x4 falloff at key "stops" for a jig-build skylight units, build truss units.total prefab time: 10 man hours.I would agree some extra time was spent with the weight of these things. I also had a "curb", that was pre-nailed on the top plate, and sheathed, that caused some problems. The curb sat flush with the exterior of frame, and ate up 1 1/2 inches of the seat cut on the rafter. I wanted this thing there to form a stop, to keep these skylight units from sliding, at all, during the set. The problem was, these things were heavy, and the curb had nails protruding through from the sheath nailing, which meant prying them with the cats-paw some inches. I didn't get final numbers for placement until after they had been set down. They were close, though.I have a very nice lid, exactly placed skylight openings for box beams that will carry up the walls, run next to the skylight casements, and down the other wall to the casework below. The only scaffold so far has been a catwalk down each wall. I will need to erect a center walk to do the ceiling to beam framing. I think I will end up with far fewer hours spent erecting and moving scaffold this way, as 90% of the work is done. There is blocking at two feet in between joist for the seven box beams. So, the scaffold will be moving across the entire ceiling area like you mentioned. But, look at the amount of wood that would have been nailed in, overhead, and to string lines to boot. This way is much more consistent, I think, and in the end, how fast isn't so important here. The finish on this is cream, and I was going for the route with the least possibility of error. So I built every one exactly the same, and the jig keeps it that way. I'd do it again, for sure.Start the octagon tomorrow. It has expanded to include a shed on the existing, and a half-octagon at the corner of the existing. Kens lessons gave me the reasoning to solve for the new frame. Let me know if you're able to open these attachments.Built hand-rail, first thing this morning. You're absolutely right.
*Nathan, I can't open the pics. They are saved as a b EEDC2E6 File.What in the heck is a EEDC2E6 File?Save them as a Jpg.blue
*the pics want to download....I want not for that to happen....please repost pics.
*canNOT figure out why my jpegs are downloading after editing in Corel Photopaint. Am saving as jpeg "bitmaps", only jpeg option I have under format type. The jpeg straight out of the camera posted fine.
*These might be large, but I can't seem to edit their size without formatting in such a way that won't download. Sorry.Ken, I pre-cut the tails of the hips according to the calcs on the adjusted dimensions. The angles were very close to what you had figured, and I defaulted to 20º and 25º. I have to say that it is going to take some getting used to trusting the math, but I don't see how I would have arrived at the correct numbers with a string line. After setting the hips, blocking and purlins today, we taped long-point to long-point of each beveled and plumb-cut tail, for the fascia. Each of the two sets of dimensions were within 1/4" of each other. At some point today I forgot about trying to understand why it wasn't perfect, and resorted to just putting it together. One question. Is there a way to determine the two angles (plumb and bevel) of the vent block, that goes from the last common into the hip? We ended up with four sets of numbers, depending on which side of the hip, and which side of the octagon (long or short) we were on.
*did have to knock this thing into place a little. glad I didn't try to prefab it.
*Nathan,Thanks for posting the pics. It looks like things are going well on the project.I'm not sure exactly what you mean by the words "purlins" and "vent blocks". Could you clarify? I've heard the word "purlin" used to describe about everything but the kitchen sink.If the vent blocks are the blocks that you have shown already installed (plumb at the outside plate line) in the first photo, then the cut should have been 0º angle, and either 20º or 25º bevel, depending on which side of the hip.I want one of those Jose Cuervo Gold headbands. Where did he get that?
*purlins (?)
*vented blocking ("bird blocks", here)the solid corner backing is yet to be screwed tight. notice the slightly larger reveal on the v-groove from one side to the other 0:)thanks again. what is your fav resturaunt in your area? I'll buy you dinner
*Nathan,Don't have time to give a full answer tonight, but perhaps tomorrow.As far as my favorite restaurant in San Antonio, (as you'd like to buy me dinner), forget it. I've spent too much time with blue-eyed-devil, and only eat Original Milkbones these days.
*Nathan, what is the purpose of the blocking that is installed in the DSCN0005.jpg?They aren't purlins.blue
*Nathan,Blue is correct about the blocks. If anything, I would call them "header blocks" not purlins.In general, purlins are what you use to brace UNDER the rafters when the rafters are over spanned. The purlins should be the same size as the rafters, in most cases. The purlin is then braced down to existing walls or beams, about every 4 feet, to support the load of the roof.As I mentioned earlier, I've heard the word purlin used to describe just about everything but the kitchen sink.A quick question about the vent pieces you were asking about. Wouldn't the cut on them ( the angle ) be the same as the plywood cut on the roof decking, directly above? In other words, if you knew the plywood cut, you would know the vent cut, true?
*blue,here is a photo of the original detail. I leave it to you to interpret the intent. As there were no common rafters detailed, I did a no-no here and put them in any way, without consulting anyone. I was short on 2x12, so I made them die into double head-outs, and then continued the original detail of 2x8's on 2' centers, which just happened to be one. I could be in trouble...but then, running the v-groove for 8' unsupported isn't going to work, either. Right, gotta have commons, with tails. Right? Right? please tell me I'm right. Ken. The plywood cut would be the same angle as the angle as the header blocks, as you call them, yes? These blocks are parallel with the face of frame, and plumb. But these bird blocks are not plumb, rather, they are pitched so the top faceof the block is parallel with the top of the hip. What was the term to describe the top of a rafter?...I think that since the block is not plumb, this is adding another dimension to the bevel angle, and plumb angle. I cannot and have not seen any rythm to figuring this out. Trial and error every time. Anyone who has installed these bird blocks into hips has probably wondered the same thing. Blue?wasn't suggesting we dine together. besides, I don't swing that way, bub.would be happy to send you a box of Milkbones. You one sick puppy.
*Nathan,Perhaps you're taking some of my comments a little too seriously, but I can understand that. I have to admit that my humor is a bit offbeat at times. Breaktime made me that way. If you hang out here long enough, you'll understand.In the meantime Nathan, I've enjoyed working with you and wish you, and your family, and friends, a very merry X-mas, and a Happy New year.Ken
*I think that I should leave wit and humour to those who have practiced the art. Thanks for all the help, and making me look better than I am. At the job, I have tried to not take credit for anything concerning this octagon, besides maybe pursuing understanding through your help. I'll pass on the merry christmas, but if you hold it special, then I hope it is what it is what you are expecting.many thanks to you, and to Blue, for reigning a cowboy framer in.Happy New Year, everyone, at Breaktime
*
Just curious what the traditional method for joining the eight rafters at the peak has been in the past...
What is the concern, intent, or deep hidden meaning with the conncection at the peak? I mean, what could go wrong, and how to frame and fasten at the peak so it doesn't...
2x12 rafters, octagon is 14' or so in width, 6/17, and has a 16" deep soffit, from bottom of 2x12 to bottom of 2x4, that will mimick the rafters above. I see a little room at the top here for some small collar-ties, maybe?
Any help or experience with octagon framing appreciated.