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Approving Hip Rafter Sizes

STB said:
Part of the language you have used is a typical everyday response, "YOU WANT ME TO PUT", no, the code requires it. My typical response would be "You couldn't build the house the way I want it"!If you tie the rafters to ceiling joists (both directions) and install a properly sized post/brace, 3 2x12's wouldn't be needed. And furthermore, if there is no thrust or downward weight, why would you need the post/brace that you originally suggested?

If the thrust in both directions is resisted by CJ and Rafter ties and the hip or valley is braced to bearing below, then the rafters are not treated as load carrying members. I have been around the block with this for many years and every organization that is affiliated with the codes has agreed with the above statement. I have recently contacted the AF&PA who is referenced in the roof code sections and that is their stand also. So understanding that you as well as I have a framing and a code official background, as a code Official, how can you allow non-prescriptive design and sign off on inspections and CO's which states that it is in conformance with the adopted codes?

There are things that I know as a framer that can be done that are not addressed by code, but without my 16+ years as a plan reviewer and inspector, but as a everyday framer, I cannot provide the proper paperwork for the file of a non-prescriptive design. I think the point of this post was to show that although we may think that something that is not prescriptive can or may work, without the required documentation, how are we as BCO's compliant with the codes.
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Bingo my friend, Bingo
 
I think Mjesse already touched on this, but let's look one more time.

This hip is 24 ft. long. How will you expect the splices to be handled, assuming they don't special order a 24' 2x12?

How would you handle the triple 2x12, if you were still to require it?

Great thread, Jeff!
 
Hip rafters would be just under 20'

A triple 2x12 is NOT required but it may look like it prescriptively if you don't read the entire code section in the IRC (hence my point in starting this)
 
STB said:
I think the point of this post was to show that although we may think that something that is not prescriptive can or may work, without the required documentation, how are we as BCO's compliant with the codes.
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Well, I took the long way there, but that was my point. I agree with you by the way.

It wasn't until the last couple years I was in the trades, that I even owned a Code book. It was a well versed and "picky" inspector that got me into the books. After some great discussions with him on the interpretation of the Codes, I realized I found my next career.

Whether we like it or not, we can only approve what's prescriptively written, or get an architect/engineers design. I have good success with contractors by explaining my past and the reasons for requesting additional information.

mj
 
jar546 said:
Hip rafters would be just under 20'
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If you're talking about a 2D flat roof it would be...

14 x sqrt of 2 (1.41) = 19.74' That is the diagonal FLAT distance of the hip. That is the "span"

Now raise that hip across that 20' distance to a height of 14' to find the "length"

sqrt [(19.74 x 19.74) + (14 x 14)] = 24' or so.

So back to the question...how do you handle splices?
 
Glenn said:
If you're talking about a 2D flat roof it would be...14 x sqrt of 2 (1.41) = 19.74' That is the diagonal FLAT distance of the hip. That is the "span"

Now raise that hip across that 20' distance to a height of 14' to find the "length"

sqrt [(19.74 x 19.74) + (14 x 14)] = 24' or so.

So back to the question...how do you handle splices?
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I was simply finding the hypotenuse of a right triangle. sq root of 14' run sq. plus 14' rise sq , just under 20'

Educate me.
 
span does not equal length. the span is.. well just that.. the horizontal distance.. the hypotenuse is the length of the member..

having said that.. that's a LONNNNNNNNNNNNNNNNNNNNNNG hip.. a hip truss set is a better way to go.
 
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peach said:
span does not equal length. the span is.. well just that.. the horizontal distance.. the hypotenuse is the length of the member..
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Oh great, now we have a PE in here slinging around all that technical jargon!! ;)
 
The top cut of the jack that goes against the hip rafter is 12/17 not 12/12. The cut is different for jacks. I agree that the load is self supporting (basically) as an old carpenter.
 
pyrguy said:
The top cut of the jack that goes against the hip rafter is 12/17 not 12/12. The cut is different for jacks. I agree that the load is self supporting (basically) as an old carpenter.
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The cut angle of a jack rafter is the same as the common, with the saw set at a 45 degree angle. That sets the side cut, which is on the scale on the framing square body. On a regular roof, the only thing that gets cut on the 17 is the hip or valley.

Brent.
 
pyrguy said:
Been too long since I had a saw in my hands. You're right I guess i had a case of CRS,
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Ha! You have an excuse.

Back in the 90's the sacramento valley was awash in these giant ranch house hip roofs. Hips and valleys everywhere.

I was the cutter on a roof crew and had done maybe 20 of these monstrosities, so I could do them in my sleep. But for whatever reason I decided one day that all the jacks had to be cut on the hip scale. Imagine my surprise when the stackers swore nothing was working. Total mental fart.

Then the time on the fine home using forum, or Badger Pond, when I offered up the lamest stupidest way to find the sides of an octagon. 100 percent wrong. Got maybe 20 pm's telling me what a retard I was.

Ego shattered again.

Brent.
 
jar546 said:
I was simply finding the hypotenuse of a right triangle. sq root of 14' run sq. plus 14' rise sq , just under 20' Educate me.
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That is the first part and it is 20'. But then you need to find it on a right triangle formed between the 14' height of the roof assembly and the 20' distance. For that, use the old "A squared + B squared = C squared" That becomes "20 squared + 14 squared = X squared" Then take the square roof of "X squared". This becomes 24'. Considering room for bearing and a tail, you'd need about 26 ft.
 
Glenn said:
That is the first part and it is 20'. But then you need to find it on a right triangle formed between the 14' height of the roof assembly and the 20' distance. For that, use the old "A squared + B squared = C squared" That becomes "20 squared + 14 squared = X squared" Then take the square roof of "X squared". This becomes 24'. Considering room for bearing and a tail, you'd need about 26 ft.
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Thanks, I forgot about the distance to the corner for the hip vs distance to the sides.
 
jar546 said:
Wait a minute. If you use 2x10 jack rafters to be compliant with the tables at 10# dead and 30# snow, then I agree that the jack rafters must be a minimum of 2x10. But, if they are cut at a 45 degree angle for the 12/12 pitch, the cut ends are now almost 13.5" so the use of a 2x12 cannot be compliant with R802.3So per the IRC this cannot be prescriptively done unless we use the WFCM?
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The hip is angled too so the jack will fit. The plumb line depth increases at the same rate for the jacks as well as the hip.

Brent.
 
MASSDRIVER said:
The hip is angled too so the jack will fit. The plumb line depth increases at the same rate for the jacks as well as the hip.Brent.
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May fit. Excellent point. Looks like this thread is really turning into something. I appreciate all the input.
 
jar546 said:
May fit.
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May fit? Au contraire.

You're framer is not amused



Buts that's totally cool, cause I have this 2 X 12 here in the garage to play with.

So in the interest of accuracy:



You get about 16" out of this one as it's shrunk to 11 1/8", but it should be 16.97 on the diagonal. But hey...who's counting.

Brent.
 
Damn you! I was too lazy to do the math not knowing you had the lumber and framing square right in your possession the entire time and you are 3 hours behind me in time with daylight.

I am wrong, humbled and ashamed at my laziness.

Nice to see someone use a real framing square for a change btw.
 
Holy Crap! you ARE a Marine!

The furrowed brow, the withering stare, the hair that won't grow more than 1 1/2" lest it be smoked by pushups.

You ever just hit someone with a roll of plans?

And yes...my methods are sneaky and underhanded.

:devil

Brent
 
Not to veer off center of topic, but, is there any objection to substituting engineered lumber for solid lumber for hip or valley rafters, or ridge boards . . . to increase dimension or avoid spilces? Also, what are acceptable methods to splice a hip or valley rafter?
 
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