Replies

1. 
   Brian_Harding | Jun 11, 1999 02:23am | #19

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   Mr. Blue Eyed Devil my book deals mainly with figures "precalculated dimensions for rafter framed roofs". If you'd like a sample here's a gimme. How do most people figure their rafter lengths, from a rafter book, or Pythagorean theorem right? Well I use this try multiplying the base length or run which equals 1/2 the total span of the gable to be figured by a ratio to the pitch. The 10 pitch ratio is 1.301708279. So take a 42' wide gable 1/2 span being 21', 21'X 1.301708279= 27.33587387'. Breaking down this number we find that .33587387 X 12= 4.030486386".

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   Brian_Harding | Jun 11, 1999 02:34am | #20

   *continuing,breaking down one more step into sixteenths we find that .030486386 X 16= .487782176 sixteenths. .487782176 is basically 1/2, so 1/2 of 1/16 is 1/32 or a strong as we call it here. If you prefer to shorten this precedure, if you start by using inches as your unit of measure for your 1/2 span instead of feet you've shortened the precedure one step. find the same result using Pythagorean Theorem, first you find your rise using 21'run X 10" rise per foot=

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   Brian_Harding | Jun 11, 1999 02:46am | #21

   *continuing, 210"/12 to find feet in order to maintain the same unit of measure.This = 17.5'therefore 17.5 squared + 21 squared=747.25'taking the square root of this leaves us with 27.33587387'. Same answer that I have from using my ratio. Now if you were to use a standard roofframing book you might find that they don't provide spans for sixteenths of an inch, where some might say close enough I like proper numbers to match proper spans.

1. 
   Brian_Harding | Jun 11, 1999 02:48am | #22

   *These are for basic roof designs and pithes. So if I didn't bore you to hard E-mail me @ [email protected]. I've got plenty more boring crap like that.

1. 
   stevepsouth.net | Jun 11, 1999 03:48am | #23

   *I have used Brian Hardings Complete rafter book,and precut over 175 jack rafters and assembled them in less than 10 hours.

2. 
   Guest_ | Jun 11, 1999 04:03am | #25

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   Well we got the roof all put together and appears everything is planing out well for the decking and running properly. Brian i would be interested in your book for the bastard hips. When I get one of those bastards I will call you. Everything else I need is pretty well stamped on my framing square but I mostly use the Construction Master to calculate my span and rafter lengths. We did also snap some lines on the floor to establish the centerline of some floating ridges that intersected valleys and only had hips on them with no commons. We then used a plumbob to find the point of intersection. Blue I can appreciate your work with trusses. We avoid them on complicated roofs just for the facts you mentioned. Also get a high or low spot in the slab and its time to chisel plates. But this roof here, I beleive would have been impossible to truss or at least an engineers nightmare. Oh well its a done deal now and Im ready for another like it (in a couple years)

3. 
   Guest_ | Jun 11, 1999 04:03am | #24

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   I am framing a roof (8/12 with 12" overhang)and the plans show one hip on a 8' wall and one on an 11' wall. The span is 29'1". One wall is stepped in 4' from the other to complicate things. A ridge for a gable ties into the hip on the 8' wall. I have deduced that the actual working span will be 33' 7" ( 3 ft drop /8"=4 1/2 ft.) I am contemplating cutting the hips based on 33'7" span then backing up 4 1/2 steps on the framing square to cut the one on the 11' wall. The troubling thing to me is the off set is 4' but to drop 3' you must be 4 1/2' over.....any suggestions......

1. 
   Guest_ | Jun 03, 1999 07:21am | #1

   * Brain

   I'm not sure but, something tells me your missing a valley. Maybe Blue can chime in. . .

   Joseph Fusco View Image

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   Guest_ | Jun 03, 1999 07:41am | #2

   *yes two valleys here....one on the 11' wall and one on the 8'. The one on the 11' wall continues up past the ridge the 8' valley intersects and into a ridge on another 8' wall. To further complicate this the ridge on the two hips turns and has a short "dog leg" hip up to the main ridge. The 11' valley runs behind this dog leg hip up to another shorter ridge behind the main ridge....am i making sense or is this a chinese jigsaw puzzle

1. 
   Guest_ | Jun 03, 1999 07:51am | #3

   * Brian,

   How about you give the plan dimension length of all the exterior walls, so as to get a sence of it's shape. With all these changes in heights there must be some interesting ceilings in this house. A picture of the plan would help also.

   Joseph Fusco View Image

1. 
   Guest_ | Jun 03, 1999 08:15am | #4

   *Joe,There are some interesting ceilings. The draftsman did not do a real wall section and we found out today all our jack rafters and one valley on the back run through the middle of the 11' wall on the master bedroom. LOL we will work this out because it has a vaulted ceiling. The ceiling over the hips I am speaking of is vaulted into the gable that ties into the hip with a large circle top window. I have made a thumbnail sketch......sorry bout my drafting...its after my bedtime...most dimensions are not plate to plate as the house has brick veneer with a 5 1/2" brick ledge. This has got to be one of the most cut up roofs ive done yet.

2. 
   Guest_ | Jun 03, 1999 08:31am | #5

   *Brian:The house that I am doing right now has a rather complicated hip roof: 3 slopes, 2 different ceiling/wall heights, and some walls have brick veneer, some don't, and for some added spice, all the overhangs are not the same width.Although I am not framing it myself, I wanted to fully understand the process, and the people here at Breaktime were good enough to get me through the basics - Ken, Joe & Blue to name a few. To read that thread, search for "multi slope" (no quotes).The icing was that they recommended a book: The Roof Framer's Bible, which I bought, and it covered all my questions. It's a small book of rafter tables with a section for bastard hips, etc. About $19.00. I'm sure Mr. Smith wouldn't waste his money on such…Anyway, the framers have just completed framing it - I've got a lot of respect for those guys. 2 of 'em did all the figuring, one of which did all the cuts, the other did all the measurements, and then the other 6 guys did, well you know… It took 'em a couple of more days than they planned, but it was interesting to observe their methods - the cut man (the brain), rather than using rafter tables to calculate length, stepped off the rafters using his framing square. He made patterns for each type of rafter - ie: "8/12 - brick" or "10/12 - no brick". All the jacks, etc, they measured off the house.

3. 
   Guest_ | Jun 03, 1999 05:56pm | #6

   *Brian,No offense but...better you than me. I'd have to be there to solve this mystery. Where you at?While we're talking roofs, what do you all think about using straps/ties where the rafters meet ext wall as opposed to cutting a "bird's mouth"?Pete

4. 
   Guest_ | Jun 03, 1999 10:03pm | #7

   *Brian,I tried to draw your plan with AutoCAD as shown but it doesn't produce a closed polygon. Do you have different eave heights? Are all slopes 8/12? How does the porch roof meet the main roof? Is its slope the same or shallower? Perhaps with a bit more info we could figger this one out. I'm no roof building expert but am always up for a geometry challenge.Pete, Since rafters are in compression, I like to see a birdsmouth on the top plate, if for nothing more than peace of mind. If you're using an engineered truss I'd be comfortable with just the metal ties.

5. 
   Guest_ | Jun 03, 1999 10:18pm | #8

   *The reason I asked is that I was reading about using those types of ties in stick building and how it supposedly saves time and money but I really am not too comfrtable with the idea either...just wanted some second opinions. Maybe some of you have used them and they work as well.Pete

6. 
   Guest_ | Jun 04, 1999 02:20am | #9

   *As to the birdsmouth, in my opinion, theres nothing more satisfying than lifting a rafter to the ridge and feeling the back of the birdsmouth hit the plate as the top of the rafter hits the ridge. I would miss this with metal ties. As to the house in question, yes Gerry all slopes are on 8/12 and wall heights are different. The beam on the porch is where the span of the two main ridges are based. The main roof in the back is one plane down to the porch beam. We set the two hips in question today and it appears to be working using the 4 1/2 step back on the framing square. Actually the hip on the left side does not intersect the 8' wall but does the ridge for the front left gable. Oh well its confusing enough looking at it what more trying to explain it. Pete I am in Louisiana, if you want to come help us your more than welcome, LOL. We are slowly but surely getting this thing together. Next time i am going to add another dollar a square foot to frame a roof like this.

7. 
   Guest_ | Jun 04, 1999 05:38am | #10

   *Brian Whenever I build a very complicated roof I first snap lines for the ridges, valleys and hips on the floor. It helps me understand the roof much better.PeterI have framed many roofs made up of TJIs. Usually no birdsmouth is used. The wall is built and a cant strip is attcahed to the top. The bottom flange of the TJI sits flat on the cant strip. Hurricane clips are then attched to the outside of the wall. This enables the nail for the clips to attach to the top plate and not the cant strip. If the ridge is steel or a wood beam I place a cant strip on top and the rafters go over the ridge- no top birdsmouth.

8. 
   Guest_ | Jun 04, 1999 04:22pm | #11

   *BrianGood luck and let us know how it works out. A photo of such a complex roof would be interesting to see. DavedThe way I understand it, by using TJI's for roof joists you are fully supporting both ends(beam at top), therefore the load is in bending only. Since there is no compressive load as part of a rafter/collar tie system, there is no benefit from using a birdsmouth anyway. Maybe someone with a thorough understanding of truss dynamics can chime in here.

9. 
   Guest_ | Jun 05, 1999 12:30pm | #12

   *Brian, I coudn't access the picture but I'll give this thread a try anyways.It sounds like the stepped up wall is purposely raised 4 units of 8", so the planing of the roof is constant. There is a slight diffference in the math, but that might be explained by different overhang projections, different wall thickness's (brick veneer w/frame vs. frame only), or different heel requirements to accomodate inside ceiling details (sometimes vaulted ceilings will necessitate a higher than normal heel).I noticed on your later posts, that you were successful at stepping up 4 1/2 steps. That confuses me, because you already stated that there was a 4' offset. A 4' offset would indicate the need to step up 4 units, and then adjust the heel to accomodate the wall height at that point.One of the things that I often do, when working with multiple wall heights, heel heights. slopes, and overhangs, is to assign each point a number based on Overall Height, or OH. This helps to keep things clear, especially during an inevitable double-checking process. For instance: If you calculated the OH for your 8' wall and found that 96" (wall height) + 10" heel height = 106", then I would assign that point a value of 106".Then by adding the 32" rise that the offset generates, you would find that your OH at the stepped up wall would require an OH of 138". Since the wall is already 132" high, you will need only 6" more heel to achieve the desired OH.I jot these numbers down at the variuos points on the plan, and it speeds up the process greatly.blue

10. 
    Brian_Harding | Jun 08, 1999 08:06pm | #13

    *Hello my name is Brian I've been framing custom houses for several years now and would be glad to help with any problems concerning any style of roof you may have. But a better description of the jogs in walls in your drawing are needed to come to proper results. I've written my own rafter book which covers hip roofs to a great extent as well as common roofs and offset, "bastard" hip roofs. So if you'd like to provide a more detailed drawing covering all the wall dimensions with the shape as well I'm sure I could help with your problem. You can E-mail me a [email protected]

11. 
    Guest_ | Jun 09, 1999 05:52am | #14

    *Thanks for the help everyone. I think we have this roof licked. We are tying in the last two little dog leg hips in the morning and a few jacks. So far everything is fitting good. Blue...as to the reason we stepped back 4 1/2 steps....There is a 3' height difference between the two hips (8' and 11' wall). In order to get this difference we had to use 3 steps(8"x4.5 for the commons). The wall offset, in my opinion, was a drafting error and should have actually been 4'6" instead of 4'(The 11' high wall was stepped in 4' from the 8' wall). Luckily the hip on the 8' wall did not go all the way to the plate but intersected a ridge from another gable. We were able to accomodate this difference at this point. I will let yall know how this thing turns out

12. 
    Guest_ | Jun 09, 1999 06:56am | #15

    *Brian. It sounds like you got the hang of it. Most of my work requires me to figure and re-figure the roof trusses, and the plans. There are discrepencies like that of which you mentioned quite often.I have to laugh at those who thnk working with trusses diminishes the carpenter's skill. Let them try to decrypt a roof package with 150 trusses, and 35 different types!Then, because of the way we pre-build, you better have the entire roof figured out BEFORE you install your first header!It's actually easier to cut your own, because then you are ultimatley the designer, and will have known what/how you created it.I've had several jobs where it took me up to 12 hours to figure the package, and the wall heights, and heel heights, and the projections out! And they are given on the specs! But you have to verify everything.And I can usually figure most out in five minutes or less!blue

13. 
    Guest_ | Jun 09, 1999 06:59am | #16

    *Daved, I have never snapped the lines for the hips, and valleys on the deck. It might be a very useful idea, to teach the recruits.I might give it a try.Thanks for the tip! I'll let you know if I do.blue

14. 
    Guest_ | Jun 09, 1999 07:04am | #17

    *Brian, I'm kinda interested in your book. I managed to teach my very bright protege all he needed to know in a few moments, with additional moments added as the questions arised.Total amount so far: 15 minutes max.I'm interested in how an entire book can be wrote without boring me to tears.Would you please toss me a bone. Type the first paragraph of the 31st page as a sample for me. And give me the title. If that paragraph is good, I'm a buyer.blue

15. 
    Guest_ | Jun 09, 1999 07:07am | #18

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    Old dog are you barking at the nice man? ;-} I was just waiting. . . .

    Joseph Fusco View Image