Roof angles

Are roof angles necessarily standard? I ask because I'm going to be working on the rafters and need to cut an angle piece to fit in beside the 2x8 holding up the roof.
I measured it out and came out with 9 inches over, 2.5 inches up which should equal ~15.5 degrees for the roof angle. I'm not interested in perfection, it just has to fit reasonably, but if I can get it exact it sure would be nice. However 15.5 deg doesn't match a 3 in 12 or 4 in 12 pitch more like 3.5 in 12. That's why I'm asking if roof angles are standard, or at least WERE standard in the 1960's.
Just for clarification, my attic is ridgepole construction, 2x8 supports for the roof, every other truss has a 1/2 x 10 board connecting the 2x8 supports. Weird construction, doesn't look sturdy at all in my eyes.
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No, there is no standard for the angle but all houses built to the same plan will have the same rise (angle).
Stop by any store selling hardware and pick up a "Bevel Gauge", set it by holding it against the rafter/ridge, lock it down and use it to layout the cut. Only costs a minimum amount and should be a part of any tool kit.
Harry K
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My house built in 1930 the roof is bascially 8 in 12 but the different areas of the roof based on an electroinc level vary from 7.8 to 8.2 in 12
which is 33.0 to 34.3 degrees pretty good for 1930
btw according my clac 2.5 in 9 is 3.333 in 12 which seems like a reasonable number
Maybe that 1x10 was a construction aid
cheers Bob
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wrote:

Nah, those 1x10s every other rafter are part of the roof structure- they keep it from pancaking. Commonly known as collar ties, IIRC.
aem sends....
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Actually, is sucks for any time in serious engineering. Yes, it is well within limits of tolerances for a house being built today, but the reality is, ancient civilization was able to work to finer tolerances than that. Aqueducts built 2000 years ago used angles to plot a course through mountains and they came out in the right spot on the other side.
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Correct. Even a beginning carpenter knows to cut one pattern rafter and use it to lay out all lthe others. That was known since ancient times. Shouldn't be any measureable (using a tape and such like instruments) from one rafter to the next.
A house built back then has probably settled some which would cause some variation.
Harry K
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There's no standard. Consider them the MSRP of construction.

Construction drawings usually show a pitch, such as 7/12 (read 7 in 12 - rise to run, or 7 pitch), and the drawings are _usually_ followed with some degree of accuracy. The pitch can be changed for a number of reasons, such as the framer realizing that a slightly lower pitch means he can buy 2' shorter rafters - that can add up to a fair savings and the architect should have picked up on that.
I think you should lose the torpedo level and buy an electronic level (yes, I am superb at spending other people's money) or put the torpedo on a framing square and measure the rise

Those 2x8s are your rafters. If the 1/2(?) x 10s are about a third of the way down from the ridge they're collar ties. That's fairly standard construction, though the 1/2" is odd and the 10" is too. Collar ties are not infrequently made out of whatever is left over, but those are some odd leftovers.
R
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wrote:

Well that's two suggestions for a new level - guess I didn't need to save money this month after all.
Those collar ties, are probably left over tongue and groove, some of them have an obvious tongue on them although they aren't plywood. Probably are 1x10's, in the same way 2x4's are about 1 3/4 x 3 1/2 or so. Just look skinnier to me given the width.
Didn't realize they weren't structural or at least not in the same way the rafters are. Makes me worry about walking around up there on the roof and in the attic. I now understand why that punching bag I've been trying to stabilize is so problematic - my attic simply isn't intended to support a load.
I've never actually seen a ridgepole roofline before, I always figured those went out of favor a long time ago - but I guess the roof truss is only 60 years old or so.
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wrote:

But dramatically change the look and the value of the house. More expensive homes are tending to have very steep roof pitches, 7, 8, 9 or even more! If the framer does not follow the contractor's spec's he will not only not get paid, but will get sued for what it cost to redo the roof and will never work for that contractor again. NOT good for the workers. We did and REdid some work when some arches were not done correctly. Guess who pays for that? Do you really think the contractor is going ot pay him to redo what teh framer messed up on? NONE of the expensive homes I have worked on had prebuilt rafters. They were all custom built.

From what you are describing I have been hanging drywall in $200,000+ homes with this type of construction. These are extremely steep roofs.
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The "bevel gauge" that I suggested is not a level. Will only cost a few bucks. You don't need any kind of level to find rise/run. A simple tape measure does the job. Of course a lazer level or even a quality bubble level 4 ft long is nice to have, I would even say mandatory for a DIY kit.
Those "collar ties" are most assuredly structural. Pull them and watch the walls of your house begin to spread out with eventual total collapse of the roof.
Harry K
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I would use a 4 foot level and divide the resultant total rise by 4. This method gives an average rather than concentrating on very small section. Cut a few scrap blocks at 3:12, 3.5:12, 4:12 and test fit.
You describe a typical cut roof with collar ties. Very normal, very strong, and still built every day. Trusses are just an alternate system. There are times when one is more appropriate than the other. They each have their strengths and weaknesses.
The rafters have nothing to do with the ceiling structure as far as hanging a punching bag. The ceiling joists form the bottom structural chord of the rafter triangle and function in tension to keep the outside bearing walls from spreading. If you are having some kind of problem hanging the punching bag, then ask about that, not about the roof rafters. The roof rafters should not be involved in a ceiling hung load.
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The simple, fast, and very cheap, method is to use a friggin bevel guage. It will let you lay out the exact angle in a few seconds and there is no figuring or measuring (other than for length) involved. You don't even need to know what the rise/run, or angle, is.
I am surprised at all the people who think you need to do all that leveling, measureing, figuring. A bevel gauge should be one of the added to a DIY kit at a very early stage.
Harry K
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Bevel gauges (aka sliding T-bevels) are useful, no doubt, but they're not commonly the tool of choice for roof framing. A framing square with stair gauges is the traditional layout tool. http://www.tpub.com/content/construction/14044/css/14044_65.htm And speed squares are a more recent development. (Amazon.com product link shortened) Both have advantages over a bevel gauge.
R
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Yes, for the _original work_. This guy is trying to match an existing rafter. That is a job for a bevel gauge.
Of course a framing square (and knowledge of how to use one) should also be a part of a DIY kit if anyone is going to be building a roof or stairs.
Harry K
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Well at any rate I have a 12/4 pitch roof, pretty shallow really.
Now all I gots to do is make the cuts and put the support struts in.
I'm pretty close to stabilizing that punching bag. Putting down plywood duckboards along the ceiling joists stabilized the ceiling side to side - good suggestion, now adding vertical stringers to the rafters will prevent it from jumping up and down

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4/12
R
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wrote:

No way man, my roof angle is 82 1/2 deg , 12/4, I'm living in the TransAmerica tower
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