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Pete- Ususally, hip roofs have an opposite side that mirrors the first. So, if you combine the two roofs together to make a square, then all you really need is length x width, or in the case of roofs, rafter run x length of facia. Often, triangles combined become squares, and squares are simple to “figger”. Good luck!
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MATT G.Bastard hips have to be the biggest pain and I dont think any designers ever draw the corner of the hip ,not a true 45
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Pete,I figure hip roofs the same as gable roofs...that is width of longest side times height(by height I mean what you would call lenght of rafter)x 2.Then I add 5% for scrap,starter and cap.So it comes out to WxHx2 sides plus 5%.This will give you plenty of extra for hip and ridge cap.
You may have a few bundles to return but better to many than to few.
If the roof is presently shingled,and non metric,you can measure from the ground by counting tabs(5" high,and 12" wide)
Good Luck,Stephen
*Pete,I figure hip roofs the same as gable roofs...that is width of longest side times height(by height I mean what you would call lenght of rafter)x 2.Then I add 5% for scrap,starter and cap.So it comes out to WxHx2 sides plus 5%.This will give you plenty of extra for hip and ridge cap.(hip roofs take about a mile of cap)You may have a few bundles to return but better to many than to few.If the roof is presently shingled,and non metric,you can measure from the ground by counting tabs(5" high,and 12" wide)In the real world this method and formula works suprisingly accurate for me.Good Luck,Stephen
*Ok guys,I did the math and made a spreadsheet of sorts for quick reference. It took more work converting the spreadsheet, from MS Pub, to a readable jpg file than it did to make the damned spreadsheet.PeteView Image
*Dsob, thats how I do it! There ain't nothing like a few simple calcs!If you have to punch in a four digit number, you might as well punch in the exact.Example:a 5 pitch = 13" So: 42 (assumed span) x 13 divided by 12= answer x 91= total footage.Notice I added the two feet for starters and caps, and built in a foot on the gables for waste.Count the punches on the calculator: 12 punches!What could be easier?Oh yeah, it assumes you know the unit lenght for each pitch. Hmm?Do like I do. Learn the C squared amount.example: 5x5 + 12 x12= 169 sq rt8pitch = 208 sqrt12 pitch = 288sqrt etc.Its actually less punches to use the calculator that way, and more accurate.blue
*Hello Pete,Couple of years ago picked up a freebie at Menards. Its a clear plastic chart with actual roof pitches 2/12 to 18/12 drawn on it. You can stand out on the curb, look through it and match up the roof pitch of an existing building. It alsohas the slope factor for all those pitches.Don't use it very much but could be a very handyitem for a roofer.Mike
*Blue Hey, that's quicker than finding my square. ThanksScott
*PeteThanks for the tableScott
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Hey guys,
Does anyone have a relatively reliable method for figuring how much roofing is needed for hip roofs. I know the obvious but am looking for something like width x height x X% (depending on the pitch) that would give a good idea of coverage requirements. I would like to be able to use this for measuring from the ground while maintaining a reliable estimate of area.
Just wondering,
Pete Draganic
*Morning Pete,The way I do it is to think of it as 2 separate roofs. The run (hypotenuse) is calculated by finding the square root of the (sum of the width squared of each section by the height squared) Then you multiply the run by the width of the entire roof. Do the same for the upper section as well,Add them both up and multiply by 2 to give you both sides.Offhand, I don't know of any formula that does it in one shot.Sorry I can't be more helpful,Gabe
*I find the most reliable way is to get the rep out on site and he can get up there and figure it!!!
*Pete- Ususally, hip roofs have an opposite side that mirrors the first. So, if you combine the two roofs together to make a square, then all you really need is length x width, or in the case of roofs, rafter run x length of facia. Often, triangles combined become squares, and squares are simple to "figger". Good luck!
*Slope Factor:Assuming that all slopes are the same (not a bastard hip) find the slope factor and use it as follows. The following uses an example roof that is 30 x 40' with a 6:12 slope.1) find the hypotenuse for the standard rise & run. i.e.: for a 6:12 slope roof the square root of (6 squared + 12 squared) = 13.412) the slope factor = hypotenuse / run (usually 12) i.e.: 13.41 / 12 = 1.1175 3) using the slope factor: multiply the roof width x the roof length x the slope factor i.e.: 40' length x 30' length x 1.1175 = roof surface square footage 40 x 30 = 1200 1200 x 1.1175 = 1341 sq. feet or 13.41 squares This works on gable roofs, and hip roofs, provided that slopes are uniform.
*Pete Aaron is absolutely right, I was talking hip but thinking gambrel. The area of a common hip roof is exactly the same as a gable end roof. Only the waste is greater on a hip roof.Sorry, Gabe
*Matt,Thanks, you gave me exactly what I was looking for. I checked your figuring method against a longer method of mine and it works out beautifully. Iworked out the measurements as if I measured form the roof and the figures came out the same as in your equation. The only drawback is I will be guessing the pitch but it shouldn't bring about too large of a variation. Now I can just make a reference table per the differing pitches and keep it as a ready reference. Perhaps I will post it here as well if I can find a good way to do so.As for you others, I appreciate the effort but I was looking for a fairly reliable way to guesstimate without climbing up on the roof.I am looking at roofing 10 buildings at 3 stories high and each is nearly 40 x 90. A decent guess at the pitch would be 5/12.Mark, I truly like your idea best but my rep got tired of it. (Just kidding). I really hate to publicize much on what I bid.Thanks a million,Pete Draganic
*Pete:I probably didn't catch something earlier, so forgive this if it is a dumb question on my part but,wouldn't the "common rafter length per foot of run" table on a framing square be your reference table? It would give you the hypotenuse for your slope factor calculation, or just use a rafter table for the one side?>(30*lgth per ft run)/12 * width = sq ft.>(30*13.41)/12 * 40 = 1341 sq ft.>or (40*13.41)/12 * 30 = 1341 sq ft.Scott
*DSOB,I am sure that your framing square has the right info. I don't have that framing square. That must be one of those triangle squares. However, I now have all the numbers I need to figure what I need to. For instance on my project, the 40 x 90 & 5/12 pitch buildings I now simply multiply 40 x 90 x 1.0833 which equals 38.99 square. I originally wanted to know if there was a simple percentage rate to multiply WxH by depending on the pitch. I now konw what it is without having to do so much math each time i look a job over. I hate trying to find the square root of numbers without a calculator. I now have 3 simple numbers to deal with. Matter of fact, I no longer know the equation to get the square root of a number without a calculatorIncidentally the rest of the math on this project is:I am looking at roofing 10 buildings at 3 stories high and each is nearly 40 x 90. A decent guess at the pitch would be 5/12. Therefore, there should be 39 square of actual area before accounting for waste. Plus 168 lf of ridge capping and 260 lf of starter shingle (or 87 shingles). I think fair waste can be accounted for by multiplying the ridge length by 3, giving me 5 sq in waste. I now have a material count of just under 47 sq. Sound right? Of course it does.Pete
*Pete, save some Lira for a Construction Master IV, hell, I'm dyslexic enough without all those formulae.
*PeteCool deal on the mathBTW I had 3 hours of windshield time to get to a job last week. I spent most of it trying to remember how to do square roots without a calculator (interstates are boring!) NO WAY could I remeber. I remember it being taught, I even remember the teacher, but I'll never rememberhow to do square roots by hand!Scott