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How To Determine Shingles Needed For Roof

Tips For Calculating Roof Area So Youll Know How Many Bundles Per Square Youll Need For Roof Area Coverage

How To Calculate Roofing Shingles including Hip Roofs by PawPaw

So you need a new roof, whether its to adorn your newly built home or to replace your existing roof. Like most North Americans, youve wisely decided to go with asphalt shingles due, in large part, to their vast range of styles and color blends. Like most of your neighbors, you plan to have the shingles installed by a professional roof contractor who will handle all the material calculations however, the information below will help you understand how to estimate the amount of shingles and accessory materials you need for your roof.

Calculating how many shingles you need for your roof is very similar to calculating how much carpet you need for your floors or how much wallpaper you need for your walls simply determine the area of the roof and divide by the area covered by each package of shingles.

Sounds simple, right? The only hard part is getting the actual measurements, and there are various ways to do this. Most likely, the roofer will physically get on the roof and, using a good old-fashioned tape measure, measure the areas of all the various roof sections and total them together. Of course, if the house is a new construction, these values will be readily available from the architectural drawings.

When Is The Worst Time For Roof Replacement

Many home improvement experts recommend that the overall best time to get a new roof is in the fall. If you poke around the internet for advice, the fall season is most likely going to be a highly popular suggestion.

However, as you will learn in this post, fall is actually one of the worst times to get the job done. Roofers recommend it, because this is the time they can charge premium for their services.

What is a better alternative?

The short answer is: get your roof installed during the SLOW season for contractors.

Recommended Reading: Cutting Roof Trusses

Calculating How Many Shingles You’ll Need

  • 1Convert the area into roofing squares, the measurement used for materials. In roofing terms, a “square” is 100 square feet . Therefore, divide your total area by 100 to get the number of squares.XResearch source
  • So, for instance, if your total is 2,381 square feet, that’s approximately 23.8 squares or 24 squares, rounded up.
  • You can also use an app or a roofing calculator to decide how many shingles you’ll need.
  • If you’re in a country other than the U.S., check the size of roofing bundles in your area before making this calculation, as they can vary from country to country.
  • 2Determine the number of shingle bundles you’ll need by multiplying by 3. Shingles typically come in a bundle that’s large enough to cover 1/3 of a square. To figure out how many bundles you’ll need, multiply the number of squares by 3.XResearch source
  • So if you have 24 squares, multiply that by 3 to get 72 bundles.
  • 3Figure out the amount of roofing felt you’ll need by dividing by 2 or 4. Felt is what goes under the shingles. If you’re buying 15-pound felt, 1 roll will be enough for 4 squares. If you’re buying 30-pound felt, 1 roll will be enough for 2 squares. Divide your squares by one of these numbers to get the number of rolls you’ll need, depending on the thickness of felt you want.XResearch source
  • If you’re trying to cover 24 squares, divide by 4 for a 15-pound roll to get 6 rolls.
  • If you’re trying to cover 24 squares with a 30-pound roll, divide by 2 to get 12 rolls.
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    Figure Out Your Homes Footprint

    If you use the square footage of your home, youll only get a vague idea of what the square footage of your roof is. Thats why you have to figure out your homes footprint.

    A person of average height will have a stride somewhere between 2 to 2.5 feet. To figure out your homes footprint, you can step off the dimensions of your roof by counting the steps you take to get the length of your home. You will then step off the width of your home.

    After stepping off the length and width of your home, youll multiply the two numbers to get your homes footprint.

    Length x width = your home’s footprint

    Your calculations are going to be off, but measuring this way can give you a basic idea of your homes footprint. Keep in mind, square footage of a house does not equal the square footage of a roof.

    The Shingles Are Curling

    Asphalt Shingles

    Shingles can curl in two ways: There’s cupping, which happens when the edges of the shingles turn upward and there’s clawing, which is when the edges stay flat and the middle starts to come up. “Both are signs of weathering and indicate that problems potentially leaks are relatively close to fruition,” says Mark Graham, vice president of the National Roofing Contractors Association.

    How much time you’ve got left: “Depending on the extent of the curling, it could be anywhere from a year to five years before you need a new roof,” says Graham.

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    How To Measure A Roof Using Google Earth

    If youre looking for a free way to measure your roof using imagery you can find on a smartphone or computer, consider logging into Google Earth and searching for your home. If you live in a large enough metropolitan area, youll find both the 2D and 3D imagery needed to take roof measurements online.

    Begin by entering your address into Google Earths search function. Youll get a birds-eye 3D view of the property, which will allow you to get a good view of the roof pitch. Position the view, so youre looking down on the roof.

    Use Google Earths area measurement tool to outline the section of roof you want to measure, making sure to set the display to feet. Once you create a box, Google will tell you the length of each side and the total square footage.

    You can use that number with the slope factor of your roof to come up with a fairly accurate estimate.

    This method isnt as precise as the expensive apps, but it will give you a good enough estimate of the square footage of your roof to purchase shingles.

    Can You Install A New Roof On Top Of Old Shingles

    Many homeowners wonder whether or not its a good idea to install a roof on top of existing shingles .

    The biggest reason for keeping the existing layer of old roofing is obvious extra cost. As we just explained above many people would rather avoid spending an additional $1,000 on removing the old shingles.

    Despite the high cost, doing this is absolutely essential! Leaving the old material will greatly accelerate the disintegration of the new roof and shorten its life cycle.

    This is because ventilation is reduced, which in turn increases the average temperature of the shingles, causing the product to dry up quicker and the granules to start falling off faster.

    Another reason why you should NOT leave the old shingles is because a roofer will typically not install underlayment between old and new roofing. If there are pre-existing problems in the leak prone areas: such as skylights, chimneys, vents and valleys, installing new shingles will not solve them! This means that your new roof will continue to leak.

    Failing to tear off old roofing will also negatively impact your warranty. Most large shingle manufacturers explicitly state that your material and labor warranty automatically becomes void, if their product was installed on top of an old roof.

    In most states, the building codes require that you remove the old roofing materials, if there are more than two layers of it already there.

    Dont Miss: How Do I Know If My Roof Is Leaking

    Also Check: Large Overhang Roof

    How Many Nails Will You Need

    Nails will also be required for any roofing project. The average 3-tab shingle needs four nails per shingle. High wind areas and other types of shingles may need more. 320 nails will be needed to install a square of standard 3-tab shingles, assuming four nails per shingle and 80 shingles per square.

    How Many Roofing Shingles Do I Need

    Estimate the amount of Roofing Shingle Bundles Needed with Roach

    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.

    Also Check: How Do I Know If My Roof Is Leaking

    How Long Does A Roof Last

    by BarrettM | May 20, 2020 | Uncategorized |

    Are you aware of the condition of the roof over your family or employees?

    If you own a property, you should be.

    Most of the time, property owners dont realize that their roof is beyond repair until it is too late.

    Whats more, many property owners dont really know how long a roof lasts or when to replace a roof.

    In this guide, youll get answers to this question how long should a roof last?

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    Your Asphalt Roof Fails Prematurely

    Your roofing materials should live as long as the manufacturer specifies. However, there are cases when your roof fails prematurely and leads to a roof replacement well before you should need one.

    Two of the common causes of premature roof failure are improper roof installation andinadequate attic ventilation.

    When your roof wasnt installed using correct roofing techniques youre going to find shingles in your yard or even full sections sliding off your roof. If your attic wasnt properly ventilated then the damage from the trapped heat and cold will drastically shorten your roofs life.

    Be aware, when your roof isnt properly ventilated or properly installed the manufacturers warranty on your roofing materials will be voided. This leaves you with only your contractors workmanship warranty to fall back on to replace your prematurely failed roof.

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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.

    Potential Signs That Your Roof May Need To Be Replaced:

    You Can Calculate The Shingles Needed For Your Roof Repair Easily, But ...
  • Shingle edges are curled or shingle tabs are cupped.
  • Bald spots where granules are missing.
  • Cracked shingles.
  • Your roof is at least 20 years old while many shingles today are produced for durability, many factors can accelerate the aging of shingles. For example, if your roof is not properly ventilated, it can negatively impact your shingles.
  • The roof just looks old and worn.
  • Neighbors are getting new roofs. Homes built around the same time period can be experiencing the same types of weather conditions can mean that your roof is nearing its useful life.
  • Dark streaks. Airborne algae cause dark streaks on roof decks. While this may not necessarily harm the roof shingles, it may not look good.
  • Moss can grow on roof surfaces that dont get much sunlight, especially in cool, moist climates. Moss growth can be more than a cosmetic issue. Moss holds moisture against the roof surface and over time in freezing climates can cause damage to the granules on the top of the shingles. Moss can be brushed off but it wont prevent it from growing again take care not to damage the shingle surface. You may need to contact a professional roofing contractor.
  • Read Also: New Roof Cost California

    How To Measure A Roof For Shingles

    August 28, 2019 By Taylor-Made Roofing

    Whether youre re-roofing your home or purchasing shingles for a brand-new house, its important to understand that a successful roofing project often requires a significant investment of both time and money. As you begin shopping for materials, you might wonder how to measure a roof for shingles. After all, roofing materials vary greatly in cost and are priced per square foot. To determine the size of your roof, contact a professional roofer who can measure your roof and provide an estimate for the roofing project.

    How Do I Measure A Steep Roof

    Most roofers wont go on a roof with an 8/12 roof pitch or greater with special equipment such as scaffolding and roof jacks and neither should you. Instead, use one of the four methods described above that allow you to measure the roof while standing safely on the ground or from the comfort of your computer.

    While these methods may not be quite as accurate as taking actual measurements from the rooftop, theyre close enough for calculating how many shingles youll need to purchase for a new roof.

    Read Also: How Much Does A Roof Cost In California

    You Can See Sunlight From Your Attic

    You don’t need us to tell you that this isn’t a good sign because it’s not! If light can get in, so can rain, cold air, and snow. Check for light and also look for water stains. “If you find any, watch them over a few rainfalls and if they change shape or size, that means you’ve got an active leak,” says McGavic.

    How much time you’ve got left: It depends on the extent of the damage, so call a pro. Small leaks can be patched, but larger ones, structural damage, and the age factor might make it wise to replace your roof sooner rather than later

    Calculating The Area From The Building’s Square Footage

    How to Measure the Roofing Materials Needed – Blueprint for Roofing
  • 1Find the square footage or square meterage of your home. You’ll need this information to estimate the area of your roof. You can find this information online on real estate websites or on your house or building title.XResearch source
  • Keep in mind that this estimation won’t include any areas like garages or enclosed patios that the roof covers. You may need to measure these rooms by hand to figure out the area.
  • To figure out the area of a square or rectangular room, measure length and width and multiply them together to get the area. Add that to your square footage total.
  • 2Measure the pitch of your roof in the attic. Mark a length of 1 foot on a long level, starting from one end. Hold the end you measured from against the bottom of a rafter so it’s sticking straight out horizontally and is level. From the 1 ft spot you marked on the level, measure upward to the rafter. The number is the first part of the pitch, while “12 inches” is the second part of the pitch. So if you measured a “5” going up, the pitch is 5/12, or 5 inches every 1 foot.XResearch source
  • You’re basically making a triangle. The level and measuring tape will make a right angle, while the rafter will be the hypotenuse of the triangle.
  • Most roofing calculators will accept this measurement as is, such as 5/12.
  • The pitch is important because it increases the area of the roof by stretching out the height.
  • For example, the slope factor for 5/12 is 1.08.
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    What About The Waste Factor Should I Order Extra Roofing Materials

    You want to order extra material to account for waste. Waste factors vary.

    10%-15% is a good rule of thumb, but your results may be different. More complicated roofs will have a higher waste factor because there are usually more cut shingles around corners, walls, and edges.

    It is okay to have a few shingles left over. They can be saved in case there is roof damage later or if repairs need to be done in the future.

    So for the 24 square roof example, you would want to add 2.4 squares which equal about 7 or 8 more bundles.

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