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How do you figure out how long a rafter is? You take the height from the ridge board to the top plate and half the width of the house and then what?
Does anybody know a good site to look at concerning rafters and how to figure for them?
Thank you in advance for advice
Prescriptive codes don't address the connection at less common angles, so base the connection off more typical ones using bolts, structural screws, blocking, and steel tension ties.
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Couple of suggestions:
1. Buy a speed square and read then book that comes with it.
2. Buy a construction calculator
3. Buy a book about framing and read it.
*buy the full lengthroof framer from A.Reichers,it will tell you all you need to know. e-mail afreichers@aol .com
*Pantango,Do a search for "Joe Fusco", click on his link and check out his site. He has all the info you need to know.Jon
*pantango, I think you are looking for the Pathagorean Theorem: A squared plus B sqaured=C squared, where C is the hypotenuse. There are other ways to figure it too, but that's the simplest with the info you seem to have. If you are cutting to fit, and not just estimating lumber, ya gotta allow for the thickness of the ridge beam too, and don't forget rafter tails, and the width of the plate. Joe Fusco's posts on this are very useful, as well as the resources stated in the above posts.
*Got a regular ole framing square ? Flip to the side that has the table that starts off "Length of common rafter per foot of run"Out from it, reading left to right horizontally,you will see a bunch of numbers under each inch number, for example under the 5" mark, the first # in that column is 13. That means for every foot of run ( the horizontal measurement or "base" of the right triangle) your rafter is 13"....the hypotneuse of the triangle. The 5" is your rise.Example:Your house is 20' wide. The ridge is dead center.The "run" of the roof in this case is 10' ( half the width). We'll make it a 5/12 pitch roof....5" of rise for every 12" of run.Since we have 10 total feet of run, and from the table, we know there is 13" of rafter per foot of run, 10x13=130" rafter...from the outside edge of the wall to dead center of the ridge....you have to subtract 1/2 the ridge thickness from the calculation, and also add any for overhang from the wall outward.You notice the numbers go down as the roof slope goes down....under 4" is the numbers 12 65, which means 12.65 inches of rafter for each foot of run, and conversely, the numbers go up for steeper slopes, under 12", you see 17 for 17" of rafter per foot of run on that pitch.If you buy a good framing square, there usually is a neat little booklet that comes with them that explains the different tables.Handy, dandy calculator...no batteries required !!
*http://www.josephfusco.com/
*pantango,
*since you're new to this, appreciate thomas' input (seemed to be what you were looking for) and andy's input (all that you need), then do this (strictly to get beginner's on their way). it's not rafter "length" you're actually after but length of rafter between the ridge cut and birdsmouth cut.just take a tape measure or use the pythagorean theorem to determine a rough length and cut your birdsmouth a couple of inches short of this length. nail a scrap piece of lumber on top of the rafter, set the mouth on your top plate and the scrap on the ridge, mark off the ridge location on the scrap. you now have the location of your ridge beam cut. call this border-brother method (not exactly "fine homebuilding").follow directions that come with your framing square to use it for mouth and ridge cuts. it's simple. you'll get it. once you get going, try following andy's instructions to appreciate that square in your hand and the money you paid for it.brian