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How To Measure A Gable Roof For Shingles

Laying Out Successive Courses

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Starting from the top of the first course, make a series of marks equal to the exposure of the shingle, or 5 inches for standard Heritage shingles, from the eave to the ridge on both sides, accounting for any variances found previously. Snap a line across the roof at each pair of marks and use the resulting lines as a guide for installing the shingles.

How Many Roofing Shingles Do I Need

To estimate how much roofing material you need, such as bundles of architectural shingles or rolls of synthetic roofing underlayment, you need to know the total square footage of your roofs surface.

How to Calculate Total Square Footage of Your Roof

To find your roofs total square footage:

  • Measure the length and width of each plane on the roof then multiply length times width.
  • Add the square footage of each of the planes together.
  • Example #1: Shed Roof with One Roof Plane

    For example, this shed roof has one roof plane.

    Multiply length times width :

    A x B = 40 x 30 = 1200 sq. ft. for the total square footage of the roof.

    Example #2: Gable Roof with Two Roof Planes

    This gable roof has two planes.

    So to derive the total square footage of the roof, you would:

  • Multiply length times width and length times width to get the square footage for each plane.
  • Add the two planes together.
  • For example:

    • Plane 1 : 40 x 30 = 1200 sq. ft.
    • Plane 2 : 40 x 30 = 1200 sq. ft.
    • Plane 1 + Plane 2 = 2400 sq. ft. for the total square footage of the roof.

    How Many Bundles Of Shingles Per Square

    A package of roofing shingles is called a bundle. Laminate or architectural shingles, one of the most common types of roofing shingles, are generally packaged in three bundles per square.

    So in the 2400 square foot gable roof example, you would need 72 bundles of shingles .

    Here are a couple more examples:

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    What Is A Roofing Square

    In roofing, one square equals 10 X 10 ft., or 100 sq. ft. This unit of measurement determines how many shingles you’ll need for every 100 sq. ft. of rooftop. As you prepare for your roofing project, you’ll use squares to determine the amount of roofing materials you need, from asphalt shingles down to the underlayment.

    Roof Size And Roofing Materials

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    Of course, the real reason why you are calculating the roof area is because you need roofing materials. In most cases, this is shingles. But it could also be slate tiles or a metal material. All roofing materials are calculated in terms of squares, and not square feet.

    The roofing and construction industry has determined that one roof square = 100 square feet.

    Thus, if you measure the roof at 500 square feet, that translates into 5 roofing squares. When you go to your local home improvement store, that is the number that you need to focus on, not the actual dimensions of your roof.

    This should make intuitive sense, especially if you have a complex roof with many different slopes, angles, hips and valleys.

    Just one important point to keep in mind here you will want to build in a small amount of overage when you measure and purchase roofing supplies.

    As a general rule of thumb, that amount is 10% for a traditional gable roof and 15-20% for a more complex roof shape . You dont want to over-estimate too much, though, otherwise your bill is going to be entirely too high!

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    Measuring The Length And Width Of Each Plane By Hand

  • 1Draw an overhead view of your roof. Each area on the roof is a single plane, which just means it’s a surface with a 2D shape, like a rectangle or square. Add lines where the different planes come together. Make sure to include all the planes, as well as any shingled sides of dormers your roof may have.
  • You don’t have to draw this to scale. You just need a basic drawing of what your roof looks like.
  • Draw the roof like flat planes. Don’t try to add perspective for the pitch. So if you have 2 rectangles meeting together at an angle, just draw 2 rectangles with a line in between.
  • 2Climb a ladder with a notepad, a pencil, and a measuring tape. Stow these items in a shoulder or hip pack while climbing for easy access. Wear closed-toe shoes with good grip and avoid working on wet or windy days.XResearch source
  • Use a sturdy extension ladder and prop it against the side of the roof. Make sure the ground is level underneath if it’s not, use plywood to even it out by placing pieces under one side. Tie the ladder to stakes to steady it on the ground, and then tie it with wire to a 20d nail driven into the roof.
  • To step onto the roof, hold on to the ladder extending above the base of the roof with 2 hands. It should extend at least 3 feet from the base of the roof.
  • Read the measurement and write it down on the small map you made of the roof, putting the measurements on the correct sides as you do.
  • Always be careful to balance yourself while you’re making measurements.
  • 5
  • Calculating The Area Of A Complex Roof

    Areas of complex roofs with multiple hips and valleys take the most time to calculate. Start by making a rough sketch of the roof. To simplify the calculation, break down the sketch into rectangles and right triangles , then take as many measurements of the roof as you can to match the sides of the rectangles and triangles on the sketch.

    Use visual cues from the existing roof shingles or roof sheathing to determine square lines off eaves edges or ridges. These cues will help you measure the lengths of the sides of the rectangles and triangles. For instance, the cutout slots on shingled roofs run perpendicular to the eaves, and nail rows in sheathing are pretty close to square also. It is difficult sometimes to get accurate measurements. Dont get too concerned though just round lengths to the nearest 6 in.

    With the sketch filled in with measurements, you can determine the size of the roof area. The area of a rectangle is length multiplied by width, whereas the area of a right triangle is the length of the two sides that meet at the 90-degree corner multiplied together and divided by two .

    Tally the square footages of all the rectangles and triangles, which will give you the total square footage for the roof. The example here shows the calculation for a roof with two hips.

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    Whats Your Roof Slope

    You will also need to know the slope of your deck.

    To determine this, measure the vertical rise of your deck in inches over a 12 horizontal distance.

    If this rise is 4, then your roof slope is 4 in 12.

    Roof slopes are always expressed with the vertical rise mentioned first and the horizontal run mentioned second.

    How To Measure A Roof From The Ground

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    If you’re planning work on a roof and don’t have the building plans, taking preliminary measurements from the ground allows you to approximate the roof area and estimate some costs. Measuring hip roofs, dormer roofs or roofs on hillside homes from the ground requires experience and special equipment. But, you can measure a gable or flat roof from the ground with the help of an assistant.

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    Hip And Ridge Cap Shingles

    Hips and ridges are covered with cap shingles, which are 1-ft. shingle squares that wrap over the hip or ridge. Like regular shingles, they overlap for a 5-in. exposure.On roofs shingled with three-tab or no-cutout shingles, you simply cut standard shingles into caps. You can cap about 35 lin. ft. of ridge or hips with each bundle of three-tab shingles that come three bundles to the square. You can also salvage waste shingle pieces and portions of damaged shingles for use as caps.

    For roofs shingled with laminated shingles, multi-cutout shingles, and other patterned shingles, youll have to order hip-and-ridge shingles that are manufactured as companions to the specific shingle product you are using. Theyre sold by the bundle and usually cap 35 lin. ft., but check with your supplier because some products vary. Just measure the length of the ridges and hips and divide by 35 to determine how many bundles of regular or hip-and-ridge shingles youll need.

    Measuring A Roof Area

    For many people the idea would never cross their mind, that they may ever have the need to measure their roof for roof shingles.

    Invariably for most homeowners, the time will come when somebody will have to measure their roof either when a replacement roof is needed, or when some structural change involving a permit, may become a requirement.

    Due to the height and steepness of many roof configurations it is typically not advised that people attempt to measure their own roofs. But it can be very important to those who are purchasing a replacement roof, to understand how a roof should be measured properly, and why.

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    • Cindy on Jun 02, 2018Hi Butch, All you need to know is the square footage of the roof. Add 10% extra for do overs or mistakes.
    • Jewellmartin on Jun 02, 2018The width of the house times the pitch , for each section of the roof and gables, Then add all the areas together and convert to square yards. Shingles are usually sold in bundles that cover a certain number of square yards. Divide the area of the roof in square yards, by the square yards for a bundle, and you will know how many bundles you need, at a minimum. Buy 5-10% more bundles than the minimum, with a buy-back guarantee for unopened bundles. You will need roofing nails or staples, waterproof caulk for around every vent, pipe, gable, apex of roof sections, chimneys, and even more, plus metal flashing at each crease and around all the chimneys, etc., You will need at least one good ladder that is taller than the roof edge, and a retractable measuring tape, hammer, nail gun, caulk gun. Budget at least 10% over your projected costs for contingencies, like rotting roof boards. Best wishes to you

    Next Divide Your Total Area By 100 To Calculate The Number Of Roofing Squares You’ll Need To Buy

    Roof Pitch Calculator

    How to measure a roof for shingles. This can make it even safer to do your measuring and it also removes a level of guessing. Then each measurement is recorded on the diagram, applicable to that roof surface. How to manually measure a roof.

    Record these values as roof rise over run, with the vertical measurement listed first and the horizontal second. Measure the width and length of each plane of the roof , and then multiply those numbers to get the correct figure for the square footage of that area. Conversely, you could measure the roof from the ground using a very rough approximation.

    Record the measurements on your sketch of the roof. In such a case, you need to take measurement of. How to measure a roof for shingles.

    In the united states, a run of 12 inches is used, and pitch is measured as the rise of the roof over 12 inches. Place the end hook of the tape on the corner and run it all the way to the opposite corner of the house. On this page, we provide you with three different ways to measure roof area for shingles or a new metal roof.

    This was before i started using these two calculations. So if your roof is 20,000 square feet, that means youll need 200 squares to coat it. The next step is to measure the pitch of the roof deck.

    To use this method, you will need to measure the length of the eaves on each of the roof planes. How to measure a roof for shingles steps. How to measure your roof for shingles.

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    Here’s How To Check For Squareand How To Compensate For A Roof That’s Out Of Square

    During the initial evaluation of a roofing job, you checked the roof at a few points to determine how many shingles to order, but you may not have checked whether the roof is square. Roofs that are out of square can make the slots between shingle tabs look cockeyed.

    To determine if a roof is square, measure from the eaves to the ridge at several points along the roof to see how parallel they run. Do the same from one gable end to the other to determine parallel and also measure the roof diagonally.

    Use your eye or a taut string to check how straight the roof edges aresome adjustments can be made with the shingles to overcome crooked edges so the roof looks even.

    If the roof isnt square, you can give the illusion that it is by tweaking how you position the shingles. Make a sketch of the roof and note your findings. This will help you decide how to correct the errors when you lay out for the roof shingles.

    Laying Out The Starter And First Course

    Moving from the eave to the ridge of the roof, measure at several locations across the width of the roof to see if there are major variations. To account for small variations, an overhang of 3/8 inch is typically used for the starter course and the first course, though if you measure larger variations along the roof line, up to an inch, adjust the overhang accordingly while avoiding shingles hanging beyond, or down into the gutters. Variations larger than an inch may require some extra work on the roof structure to straighten the edge of the eave. Measure the height of the starter shingle and subtract 3/8 inch from the height to allow for the overhang. Snap a line across the roof at that distance and, starting from the left side, install the starter course with the top edge even with that line and overhanging the rake by 3/8 inch. The rake is the edge of the roof running from the eave to the ridge. Install the first course of shingles with the bottom edges even to the bottom edge of the starter course.

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    How To Lay Out A Roof For Shingling With Heritage Shingles

    A properly-installed roof has evenly-spaced, straight courses that parallel the ridge-line of the roof. With Heritage shingles, like any others, a good layout can compensate for irregularities in the roof’s construction, making the finished job look perfect. Creating the layout takes only a few extra minutes of time and if you are not using standard-sized Heritage shingles, you can customize the layout according to the shingle’s specifications.

    What Are Some Common Mistakes Of Measuring A Roof Size

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    In my thirty plus years of experience as a roofing contractor, I can tell you that some people who are in the business of measuring and calculating roofs dont do it properly. Many of course do. The problem for a homeowner comparing estimates is that they may not know which type of person they have had evaluated their roof.

    As an example, I have witnessed people get out of their truck, and literally guess from the sidewalk. looks like about this size.. I have also witnessed people read a measurement of 84 on a tape measure, and record the number as 48. A simple error, but a significant error nonetheless. I have further witnessed people who could not do the mathematical calculations required to determine the area of a triangle or an obtuse shape.

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    Plan For Waste Factor

    The only roof that will generate no waste from cutting is that rare simple gable whose roof length is divisible by the 3-ft. length of a shingle. Other simple gable roofs will require cut shingles at the rakes. From there, the waste factor increases with every obstruction, such as a chimney, and with every hip or valley.

    Laminated shingles typically generate less waste than three-tab shingles do because you dont have to maintain a cutout pattern, but its tricky to determine exactly how many square feet of shingles you will be able to salvage. Its best to plan your order using the same waste factor that you would use for three-tab shinglesat worst youll just have a couple of bundles to return.For a simple roof, I generally figure 1 percent as a waste factor. On a complex roof with open valleys, I add 5 percent and sometimes more. Theres no calculation you can use to determine the extra shingles youll need for waste. With experience estimating jobs, youll get a feel for how many extra shingles to order.

    Waste is also generated when shingles are damaged, which is inevitable when youre moving shingles around a steep roof slope and some will slide off. You may be able to salvage part of the damaged shingle, but dont count on it. You can also waste shingles when you nail them improperly and have to remove them. You may drive nails too low in the exposure or fasten one off a control line.


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