Go Up To Your Roof And Physically Measure It
After you have gotten onto your roof, it is time to break out your diagram and measuring tape so you can get to work. Very carefully, measure the length and width of all the sections of your roof, paying particular attention to writing down the measurement on the corresponding sections of your diagram. If your roof has triangular sections, such as eaves, it is important that you measure these as well since they will also need to be shingled. As soon as youve completed measuring the entirety of your roof, it is time to descend your ladder and put your measurements to good use.
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How To Measure Your Roofs Square Footage
The square footage of your roof has a huge impact on the cost of your replacement. It affects a number of cost factors, including the amount of materials used, labor, and time.
Be aware, the only way to get a 100 percent accurate measurement is to have a local roofing contractor come out to professionally measure your roof and give you a quote. However, I can give you the calculations to get a rough measurement of your homes square footage.
What Is Slope Factor
Taking a 2D measurement of a roof either online via Google Earth or by measuring the exterior walls of the home doesnt account for the elevation of the roof, which adds square footage. Slope factor is a convenient way of using the pitch of your roof to convert a 2D measurement to an accurate measurement of the roofs square footage.
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How Shingle Quantities Are Measured
Roof shingles are sold by both the bundle and by the square. A square of shingles is the quantity needed to cover 100 sq. ft. of roof. Shingles are packaged in paper- or plastic-wrapped bundles designed to be light enough for a person to carry, so heavier shingles require more bundles per square. Three bundles to a square is most common, which applies to most three-tab strip shingles and some lightweight laminated shingles. Heavier three-tabbed shingles and laminated shingles require four, or sometimes five, bundles to cover a square. When shingles come three bundles to the square, there are 29 standard-sized shingles in each bundle.
Figuring out the roof area is the first step to determine how many bundles youll need to order. There are two ways to size up a new or freshly stripped roof: the measurement method and the sheet-count method. Theres a third method for calculating bundles when youll be laying new shingles over old or if the old roof is still in place.
Once you have a bundle or square count for the main roof area, youll add additional shingles to account for waste, starter shingles, and extra shingles for hip and ridge caps.
Determine The Roofs Pitch
You can determine the roofs pitch from the ground or attic. The latter will bear the most accurate results as theres no roofing material to block the way.
So, how do you measure a roofs pitch from the attic?
- Access one of the rafters in the attic space: Get to a rafter in the attic space to get the measurements. Alternatively, you can take measures from the overhang of one rafter at the roofs end or a barge rafter on the gables side.
- Place a level along the rafters underside: Use the carpenters level to find the rafters measurements by placing it on the rafters bottom. Adjust the level to center the bubble between the two lines.
- Locate the 12-inch calibration on the level: The standard measuring the length of the rafter for a pitch in the United States is 12 inches. If the level you are using lacks the 12-inch mark, use a tape measure to mark the 12-inch point.
- Measure the vertical distance between the level and rafter: By extending the tape measure perpendicularly to the level, find the distance between the 12-inch mark and the underside of the rafter to get the roofs pitch. For example, if the vertical distance is six inches at the 12-inch mark, the roofs pitch will be 6/12. That translates to a rise of six inches every one foot.
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Calculate The Roof Area
Now that you have all of your roof measurements, you can calculate its surface area. Simply multiply the length and width of each rectangular plane, and then add the combined area of the hips. Then multiply this number by the roofs slope factor, and then multiply this final result by 1.10 to allow for error.
In this example, our imaginary homes hip roof would cover a surface area of + , while the lean-to roof would be equal to . This gives you a total surface area of 935 square feet. Multiplying this by the slope factor of 1.03 equals 963.05 square feet. Multiply this by 1.10 to obtain 1059.4, which is a good estimate of your roofs surface area.
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Plan For Extra Valley Material
Valleys are either woven or cut both methods require about the same number of shingles. On a woven valley, each course of shingles is extended beyond the valley crease and at least 12 in. onto the adjacent roof plane. Youll use 2 ft. of extra shingle material for each pair of woven courses. In the case of cut valleys, the shingles from the first roof plane thats shingled also extend onto the adjacent roof plane at least 12 in. just like woven valleys. Shingles from the next roof plane are cut just up from the valley line, and the cutoff pieces usually arent big enough to use elsewhere on the roof. Order two extra shingles per linear foot of valley to account for the overlaps and cutoffs. On a 16-ft. valley, you would need 32 shingles or roughly one extra bundle.
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Calculate The Square Footage Of Your Roof
Now that you thought about the slope and complexity of your roof, youre ready to learn how to calculate the square footage of your roof.
To get a rough estimate for your roofs square footage, youll use this equation:
For example, if you have an easy up and over, walkable gable roof and a house that measures 56 feet lengthwise and 28 feet widthwise, your calculation will look like this:
2,038 = square feet of roof area
Using this equation wont be 100% accurate, but knowing your roofs square footage is a great jumping-off point to learn how much youll have to invest in your replacement.
How To Calculate A Roofing Square
Before beginning, make sure you can safely access your roofif you can’t, contact a roofing professional for help.
Grab your measuring tape, level, pen and paper, roof safety equipment, and your ladder. With these in hand, you can measure your roof in five simple steps.
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Draw Each Shape Individually Calculate Each Area And The Total Square Footage Of Your Roof
Now we have eight shapes to find the area of six triangles and two rectangles. Instead of breaking out the old textbooks to calculate triangle areas, we like to use a triangle calculator. It makes figuring out the area of triangles a lot simpler.
In the example above, we have two triangles with sides of 30, 20, and 20 feet. Pop those figures in the three-sides calculator and youll get an area of 198. Since we have two of those triangles, multiply by 2 for a running total of 396 square feet.
We have four remaining triangles, all with dimensions of 15, 20, and 25 feet. That same calculator reveals a result of 150 square feet. Since there are four of those triangles, multiply by 4 to get 600 square feet.
Lastly, we have two rectangles of 15 by 30 feet. This one is easy, just width times height for a total of 450 square feet for each one. Multiply by 2 and their total square footage is 900.
Adding all the areas up yields a total of 1896 square feet . Since roofing material comes in 100 square foot squares, youll need at least 19 of them for your roofing project. Itd be wise to get at least 20 to account for mistakes and waste.
How To Accurately Measure A Roof From The Ground
What Im about to share with you is one of the best kept secrets for measuring residential roofing jobs without your feet leaving the ground. If you are not the owner of a residential roofing company then you most likely havent heard of this before. This was taught to me, several years ago, by one of my roofing subcontractors. It is a super-simple way to quickly and safely measure the size of just about any style of asphalt shingle roof. Did I mention that it is highly accurate, as well?
The first technique is referred to as the Shingle Count Method, which is used for estimating the measurements of all rectangular-shaped sections of a roof.
To sum it up, each individual tab on a 3-tab shingle measures approximately 12 wide by 6 high. I typically begin by counting the # of shingles from left to right, which gives me the total width of the section . And then I will count the # of rows of shingles between the gutter and the peak of the roof and then divide the number by 2, which gives me the height measurement. Then I simply multiply the two numbers together and the result is the total square feet of this particular section. I would then, of course, proceed to do the same thing for each of the remaining sections.
For Hip Roofs, I measure the length of the house and then I measure the width. I then multiply these 2 numbers together and I take that number and multiply it by 1.35.
I hope you find this info to be as time-saving and helpful as I have.
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Do I Need Underlayment Under The Shingles
Underlayment is an important part of a roofing project. Some people will try to skip the underlayment to save money, but this can be very costly in the long run. Unless you want to get on the roof every time a few hailstones fall or a branch hits your roof, you probably will have a cracked shingle or two on your roof from time to time.
If you dont have underlayment, moisture will seep into the crack, seep into your roof decking and eventually cause mold, mildew and rot. It also is a way for insects to get in.
If moisture gets in because of an undiscovered cracked or broken shingle, youll eventually have a more expensive roofing project to replace the damaged decking that will end up costing more in materials and labor than the underlayment would have cost. Since a roof is something that you want to last a long time, why skimp on it?
Your roof measurements not only apply to the shingles but also to figure the number of rolls of underlayment youll need. Typically, a 15-pound roll of underlayment will cover about four squares. Again, youll want to allow about fifteen percent more to cover accidental tears or cover odd shapes.
Find The Area Of The Footprint Of The Roof
To calculate a roofs dimensions, you need to measure the roof as if it were flat, then account for roof pitch, calculate square footage, and finally determine how many squares of material are required for the roof.
The calculator above can handle all of this, simply enter the length, width, and pitch, and it will determine the size of the roof in squares.
Start by measuring the roofs length and width in feet as youre standing on the ground. Remember that the length and width need to be found for the roof, not the house, so take into account that the roof overhangs the building.
Then determine the area of the roof as if it were flat. Multiply the length by the width in feet to get the area measurement.
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Finding The Size Of The Roof In Squares
Roofing contractors estimate projects and materials by the square, so it is crucial to find this measurement to estimate the amount of material needed accurately. A square simply refers to a 10 x 10 square of roofing. This is simply 100 square feet of roof.
To find the squares, divide the overall roof area by 100 and then round up. For instance, if the roof is 1550 square feet, then it is 16 squares.
How To Calculate Square Footage Of Roof For Shingles
The most precise way to calculate the square footage of the roof for shingles is by taking exact measurements. This is also one of the riskier methods, as it involves you climbing up on the roof with a tape measure and physically measuring each plane of the roof. If the roof is 8/12 or steeper, do not attempt this method!
Once on the roof, use a tape measure to take measurements of the length and width of each plane of the roof. Multiply the length and width of the roof to get a measurement of each planes total area. For example, a roof with a single plane that is 50 feet long by 30 feet wide has a total square footage of 1,500 square feet.
For roofs with two roof planes, such as a gable roof, add up the areas of each plane to get the total square footage of the roof. For example, a roof with two sides that are each 30 by 50 square feet would have the total square footage of 3,000 square feet.
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How To Measure A Roofing Square
Starting a new roofing project can introduce homeowners to many roofing-specific terms, and one of the first you’re likely to come up against is “roofing square.” Measuring in squares is unique to the roofing industryfor homeowners, understanding how these measurements work can be an unfamiliar but vital part of planning for your roof repair or replacement.
How To Measure Your Roof With Google Earth
Using your computer to get a ballpark estimate of your roof area is easy and fast. However, using satellite imagery may not be an ideal solution if your structure is in a very remote location that hasnt been 3D scanned. Thats because well need to grab an accurate representation of your roofs pitch for measuring purposes. From above with a 2D image, everything looks flat. If you were to just measure your roof area from directly above, you wouldnt be accounting for its pitch, or slope.
Consider two homes with the same base area square footage, but one of them has a much steeper roof pitch than the other. That structure would need to be taller, and there would be a lot more roofing material to account for. If youre just measuring from above in 2D, both of these structures might look identical. If you dont account for roof pitch, youre going to underestimate your materials requirements, which could be a costly mistake.
Satellite technology has progressed a lot in the past few years. With , you can easily find your address and a 3D replica of your structure, including your roofs pitch. Lets get to it. Once you load the site, youll be presented with our beautiful planet:
While you can switch to 2D mode by clicking the button in the lower right, youll want to stay in this 3D view so you can get a good view of your roofs pitch.
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Next Divide Your Total Area By 100 To Calculate The Number Of Roofing Squares Youll Need To Buy
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.
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