measruing roof for shingles


Old 11-19-04, 07:40 PM
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measruing roof for shingles

is there a way l can measure a roof for shingles without actually climbing up on the roof.
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Old 11-19-04, 08:40 PM
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Sure, if you have the perimeter demensions of the roof and know the pitch. But I'm a bit confused. If you don't want to climb on the roof to measure it, what will you do when it comes time to actually INSTALL it??? (You can't do THAT from the ground!!) And if you are planning on having a contractor install it, so you don't have to climb up there to do it, why not have the contractor MEASURE it as well?

What is it that you're not telling us??
Old 11-19-04, 08:55 PM
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IMO, the best, quickest and most accurate is by getting on the roof and making a sketch of each "plane" of the roof. Get the area of each and add them together.

If you can't or won't get on the roof you're not likely to be doing the work yourself so you could just call a roofer for an estimate. But if you want to measure from the ground and you don't know the area of the house, and the pitch of the roof, it's still doable.

If your roof is pretty straightforward gable roof, without too many hips and valleys, then you can assume that the area of the will pretty closely match the perimeter of the house. So measure the perimeter of the house to get its area and then you can use a formula to calculate the area of the roof based on the pitch of the roof. To do this from the ground you will need a FOLDING RULE, which you will use kind of like a SEXTANT. Most folding rules fold in 6 inch increments. Stand a good distance away, like across the street and hold the rule out at arms length.

Fold the rule into a triangle with the 1"-6" section and the 6"-12" sections forming the SLOPES, that is lining up like the roof lines. Then use the next two 6" sections to line up a horizontal line to complete the triangle, and align it with a horizontal line of your house. Then keeping the horizontal steady and adjust the slope parts of the rule so that they EXACTLY FOLLOW the line of the roof slopes.

If you've done the right (it's easier with a picture but I don't know how to do that on line) the BEGINNING SECTION OF THE RULER, will cross the horizontal section somewhere between the 20" and 24" mark. The point at which the CENTER OF THE END OF THE RULER, THE END THAT WOULD BE 0 INCHES, crosses the middle of a measurement mark, is the point that you want. So if it crosses at 21 1/4" your RISE is 10" per foot. If it's that high you DON'T WANT TO CONSIDER DOING IT YOURSELF. AT 22" mark your rise is 8" per foot, at 22 3/4" it's 6" per foot, at 23 1/8" it's 4" per foot.

To confirm this estimation you could put the ladder up to an accessible part of the roof and measure the inches of RISE along a HORIZONTAL RUN. This is like eighth grade geometry is you paid more attention than I did when you were 14, I had to wait until I was in college to learn this kind of stuff. The ratio of run to rise is the pitch. So if you measure 3 feet horizontally and there was a rise of 18" that would be 6" per foot, or a slope of 6. So a slope of 6 (inches per foot) equal a pitch of 1/4.

Once you know the rise and pitch and the horizontal area you multiply the HORIZONTAL AREA times the following to guesstimate the area of the roof.

Rise 3" (pitch 1/8) multiplier of 1.031
Rise 4" (pitch 1/6) multiplier of 1.054
Rise 5" (pitch 5/24) multiipler of 1.083
Rise 6" (pitch 1/4) multiplier of 1.118
Rise 8" (pitch 1/3) multiplier of 1.202
Rise 10" (pitch 5/12) multipier of 1.302

Once you have that add 10% for errors, waste and scrap. Spend a month looking at all kinds of roof to get an idea of color, grade and shading. Get a good framer's square, lots of razor blades, including the hook kind, lots of band aids, roof nails, tar paper (if stripping to deck), lots of friends who'll never talk to you again, find a place that will do roof top delivery. Then take a couple of weeks delivery.

Also read up on roofing. I've got a reference called "Modern Roofing" by Donald Meyers and a booklet published by (IIRC) the roofing manufacturers trade association, read up the back of a bundle of shingles. NO JOKE, I'VE NEVER SEEN A "PROFESSIONAL" ROOFING CREW DO INSTALL A ROOF CORRECTLY. I'm speaking particularly about the starter course.

Once you're ready get to work. Console yourself that you've spent 2 years and $25,000 to get an MBA and that you're taking vacation from your $75,000/year job to do a job that you probably could have hired done a lot cheaper. Particularly if you live in a part of the country where "casual" laborers, generally recent immigrants, can be found hanging around "shape-up" areas in many cities. Then if you feel confidant in your supervisory skills, and at least a couple of them seem to know what they're doing load about 3 of them into your car and take them home. They'll work hard and in many cases do as good a job as a "professional" might have done. IN FACT, IN MANY INSTANCES THE PROFESSIONAL WOULD HAVE QUOTED YOU THE JOB THEN GONE AND GOTTEN THESE SAME GUYS TO DO THE JOB, THE DIFFERENCE IS HE MIGHT NOT HAVE HUNG AROUND TO SUPERVISE THEM, SO BY SUPERVISING THEM YOURSELF, AFTER STUDYING UP YOU MIGHT GET A BETTER JOB IN ADDITION TO SAVING MONEY.

Some of the above is tongue in cheek. Roofing isn't difficult, BUT IT IS HARD. Like most things the study and prep go a long ways toward getting a good result. Like lots of other things the DEVIL IS IN THE DETAILS. The details on a roof being, STARTER COURSE, GABLE ENDS, VALLEYS, VENTS AND RIDGES. If trouble comes that's the most likely place, the vast majority of the shingles, nails AND LABOR, will be in the FIELD. If your dog had a wrist and thumb you could train him to do the field installation. But no matter how much time you took, and no matter how close they may be to us DNA-wise, you probably could NEVER train your chimpanzee to do the 5 key areas I listed in this paragraph.

Good luck, keep us posted and post your follow-on questions here.

Old 11-20-04, 01:20 PM
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Call around and get 3 bids for the roof job. they will tell you how many sq you need .

Old 06-03-05, 04:14 PM
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Lets say your house is 24'-00" x 55'-00" with 2'-00" overhang.

So half the width is the 'Run' plus 2'-00" of overhang is 12' + 2'= 14' as the base of a triangle. The 'Rise' is measured, from under the roof peak to the top edge of the siding or sighted along the top of the wall. Which we will say is 4'-00" of Rise. and is the height of the triangle.

The actual length of the roof, is the Hypotenuse of a triangle. To find the hypotenuse, you must find the square of the root. For the Run and Rise.

which is Run=14 x 14 = 196 is the sq. of 14 (root) and Rise= 4 x 4 = 16, By adding the two together 196 + 16 = 212 being the sq. of the hypotenuse of the roof area we want the length of.
Use trial and error, 15 x 15 = 225, try 14.7 x 14.7 = 216.09, try 14.5 x 14.5 = 210.25, try 14.56 x 14.56 = 211.9936 or use your trusty calculator.

212 x 2ndF sq. root, which is 14.56022, which can be rounded off to 14'-8" for the length we need. Being one half of the roof, now to the length of the house being 55' add both overhang at the gable ends, is 2' + 2' = 4' plus 55' =

59' overall, times that by 14'-8" and since we have feet and inches, do it this way 13 x 59 = 767 sq. ft. and inches would be 12" x 8" = 96" x 59 = 5,664 sq.inches divide this by 144, gives sq. feet, being 39.3333
39.3333 + 767 = 806.333 sq. ft. for half the roof, 806.3 times 2 = 1612.66 sq. ft. and divide this by 100 to find how many Squares of roofing is required, which is 16.12 squares, 3-Tab roofing is three bundles of shingles per square, some newer shingles are four bundles per 100 square feet.

So 16.12 squares would require 48.38 bundles to do the roof, 10% more would be 52 bundles, plus roofing felt rolls, nails, tubes of sealer/patch, razor blades, rolls of metal flashing, drip edge, and enough roof cap for 59 ft., knee pads, a few helpers, a sunny day, and beer on ice, when the job is done. Call me only if you need a cook for the Bar-BQ!

Last edited by T-Square; 06-03-05 at 04:33 PM.
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