Calculate Roof Pitch From The Ground In Three Quick Steps
Roof pitch is one of those things that middle school math and geometry instructors can easily point to, and say, See? Learning how to work with rise over run is fun and useful, right? If at any moment you start having PTSD flashbacks to algebra or geometry class, take a deep breath. Well walk you through this slowly in three simple steps. All you need is a tape measure, and possibly a helper to hold it.
Step One: Grab that tape measure, notepad, and pencil and head outside. Find the slope of your roof youd like to measure, and start measuring the distance from the outer edge of the eave to the point at which the plane of the roof slope is barely visible to your eye. Write that number down in both inches. This figure is the horizontal run.
Step Two: Stand directly underneath the gutter or edge of the roof plane you want to calculate the slope for. Measure the distance from your eye to the top of the drip edge of your roof overhang. Write that number down in inches, too. This figure is the roof rise.
Step Three: Take the roof rise figure in Step Two and divide it by the horizontal run from Step One. In the example above, the rise is 60 inches and the run is 120 inches. This reduces down to a roof pitch of 6/12. Well use this figure in just a bit, so keep it handy.
Roof Calculations Of Slope Rise Run Areahow Are Roof Rise Run Area Or Slope Calculated
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Roof slope, pitch, rise, run, area calculation methods:
Examples of simple calculations of stair or roof slope by several methods.
This article series gives clear examples just about every possible way to figure out any or all roof dimensions and measurements expressing the roof area, width, length, slope, rise, run, and unit rise in inches per foot.
Page top sketch of various roof slopes is provided courtesy of Carson Dunlop Associates, Toronto.
Introduction: Gauging Roof Pitch From The Ground
Knowing the slope of your roof is good for all kinds of things! From knowing if you have to worry about ice dams to wondering if you should really send you kids up to take down the Christmas lights because you dont want to, or any reason in-betweenits good to know the pitch of your roof. Although we could break out the ladder, a level, a tape measure, and get ourselves to get on the roofits a lot easier to gather this info from the safety and convenience of the ground. Heres how! BTWthe tape measure will still be required.
Step 1: Walk away from your house, perpendicular to the wall that is under the roof pitch youd like to measure. Walking backwards, and watching where youre going, walk out to the distance where your eye aligns with the plane on the roof pitch. So you should essentially see the top edge of the eve or gutter line up with the peak of the roof pitch. Assuming the ground is relatively flat, measure the height of your eye from the ground. Record this measurement.
Step 2: Measure the distance from where youre standing to the face of the wall you walked away from. As a tip, if you had hooked the tape measure to the house when you backed away from the wall, youll be able to do this without help from someone else! Youll also need to know the distance of your homes overhang. By subtracting the overhang distance from your standing distance, we will have identified the Run value of your roof pitch! Record that value in both inch & foot values!
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Take And Save A Measurement
Add more details when you save a measurement
In the “New Path” or “Edit Path” window, change fields like altitude, color, or style.
Roof Slope Multiplier Chart
We also have a much more complete roof slope multiplier chart that includes slopes by the half inch and slopes up to 30.5-in-12.
If youre using the table below, you should consider getting yourself a construction calculator. That way you can instantly calculate the factor for any slope, among many other useful things. This one is very good.*
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Measure Roof Slope From The Ground Using A Folding Carpenter’s Rule
As you’ve see from out other roof measurement examples beginningat ROOF MEASUREMENTS, knowing the roof slope is really handy as something we can measure up close but also from a distance, obtaining a number that plugs into simple formulas for roof area too.
What if the roof is inaccessible from outdoors, and there is no access to the building interior so we cannot make direct roof slope measurements, but we still need to know its slope?
You need a simple folding carpenter’s rule. It helps to have a steady hand and to read the instructions on exactly where to read the inches on the bottom scale in the folding rule triangle that we show at left.
Details of how to use a folding carpenter’s rule to obtain roof slope, area, and other measurements along with a table that translates inches along the bottom scale of the folded rule into roof slopes areat ROOF MEASURE by FOLDING RULE
How To Measure The Slope Of A Roof
To measure the slope of a roof you will need a level and a measuring tape. You will mark your level 12 inches from one of the ends. Hold that end on the roof and bring your level up until the level bubble is centered. Now measure the distance between the roof and the 12 inch mark on your level. This measurement is the rise over 12 inches. If the distance between the 12 inch mark on your level and the roof is 5 inches then the roof is a 5 in 12 roof if the distance is 4 inches then it is a 4 in 12 roof and if the distance is 3 inches, then the roof is a 3 in 12 roof.
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Final Thoughts On Measuring Your Roof
If youre looking for a simple ballpark estimate of your roofing materials needs, Google Earth really does a great job of quickly allowing you to measure the square footage youll need to cover. While its technology sure is surreal, it has drawbacks in its ability to precisely measure distances represented in 3D. Therefore, it can be helpful to gauge estimates of your materials costs by measuring from the ground and on top of your structure. As always, if youre feeling confused, dont hesitate to get in touch with a local roofing contractor to help you out. Many will provide estimates for free. Simply ask how many squares of material they estimate youll need, and compare that to the results you got from using any of the methods we outlined above.
How To Measure Roof Slope Or Angle Or Rise & Run & Roof Area
Measuring the roof slope, pitch, or rise and run is easy if you’ve got a tape measure and more accurate still if you’ve also got a level on hand.
Here are examples of every method we can think of for measuring the pitch or slope of a roof from various positions on the roof, near the roof, and from ground level.
Article Series Contents
- ROOF SLOPE TABLE, TYPES, WALKABILITY – separate article
There are several neat tricks that allow you to just a carpenter’s rule to get a close approximation of the roof slope or pitch. We describe all of them here. All of these examples work best for a simple gable end roof. Additional measures may be needed for hip roofs, mansards, and intersecting gables.
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How Various Roof Measurements Are Calculated
Details for calculating roof area are at ROOF AREA CALCULATIONS
RA = Roof Area = RW x RL
If you have safe access to the roof surface you can quickly make the needed area measurements: just measure from the ridge to the lower edge or eaves, keeping your tape straight. With a decent 3/4″ or 1″ wide 30 ft. tape measure you can extend the tape out to catch the roof eaves without having to walk dangerously close to the roof edge. Also measure the roof edge or length.
- RW = Roof Width – dimension a in my sketch at left. Remember to include in the amount by which the roof extends out over the building walls – its eaves.
- RL = Roof Length = dimension of the roof from one gable end of the building to the other. RL is simply the building width plus the amount of overhang at the two gable ends of the building.
Details for calculating the slope, pitch or grade of a roof or any other surface are
Slope is simply the relationship between increase in height and horizontal distance traveled. In my sketch above if we travel up my triangle along from left to right, we will cross a horizontal distance and we will ascend in height an amount .
Slope or pitch or grade has several means of expression: Rise/Run, Angle in degrees, Tangent, Pitch, or Percent Grade – all compared in our little table below.
Tangent = Rise / Run
E.g. Tan = 1.00 – that is, we will travel 12″ up for 12″ of run
Below is a tiny summary that shows the range of these values.
Measuring Roof Peak Height From The Ground
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The Positive Roof Measuring Method
The positive roof measuring method requires you to break the roof up into measurable sections. For image 1.2 find the area of all sections of the roof, and then add them together to find the total area of the roof.
Area of section A = 20 x 60 = 1200 sqft
Area of section B = 20 x 40 = 800 sqft
Area of section C = 20 x 20 = 400 sqft
Therefore, the total area of the roof plan above is 1200 sqft + 800 sqft + 400 sgft = 2400 sqft
How To Determine Roof Pitch
Heres how to measure and calculate roof pitch from inside your attic.
The angle, or pitch, of a roof is calculated by the number of inches it rises vertically for every 12 inches it extends horizontally. For example, a roof that rises 6 inches for every 12 inches of horizontal run has a 6-in-12 pitch.
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Measure A Roof From The Ground
Take the following steps to measure your roof from the ground:
Determine your roof pitch if you need help. Make a outline of your roof on paper. Go all the way around your house and fill in your outline with your measurements making sure to account for overhang. Section off your roof and write your calculations down as shown below . Hips and top ridge: Visually count how many ridge pieces are on your roof. Multiply the pieces by inches based on exposure, then divide by feet. eg: Exposure comp shingles 5.5, shake 10, tile 13.5-14. You may want to measure a couple to be sure.
Binoculars can be helpful on high roofs.
Rakes and Valleys: Visually count how many rows of existing roofing, multiply by inches base on exposure, then divide by feet. Open the Roof Calculator Writer program, select the appropriate roof pitch or use our Roof Pitch Calculator Enter your measurements for roof area, hip etc.
If you are totaling these numbers by hand dont forget to add for pitch to the roof area, hips, valleys and gables . See below for the amount to add for pitch.
Open the Roof Calculator , Click the add pitch box, select your pitch and the correct amount will be added automatically to your totals.
Definition Of Roof Dimensions
Roof rise : first we will obtain the total roof rise by counting siding courses. We measure siding width & then we count courses at the building gable end. If we start counting siding at a horizontal lilne even with the lower roof edge or eaves and count up to the ridge, we’ve got a close guess at the total roof rise.
The number of siding courses from the roof triangle base to the roof peak x siding course width = total roof rise =
Roof length : Measure or step off building gable end width.
Roof width : This data allows us to calculate the roof triangle as we know two sides and of the three sides of a right triangle . Let = the vertical rise in the roof and = the roof length . The third side of the triangle, its hypotenuse or the sloping surface of the roof, or side is which is calculated as follows:
a2 = b2 + c2 – the square of the length of the hypotenuse equals the squares of the lengths of the opposite sides of a right triangle and .
Given a2 we use our calculator to take the square root and bingo, we have the length of the sloping side of the roof.
Given that we now know all of the lengths of our triangle we can easily obtain roof slope too if we need it.
Now finally to get the roof area, we just need one more figure, the length of the roof along the building eaves or ridge. From the ground we measure or step off building length .
The roof area is calculated easily:
RA = x
The Tangent of any angle expressed in degrees is nothing more than a ratio:
Tangent = Rise / Run
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What Is The Standard Pitch For A Roof
There is no standard, universal roof pitch. Roof pitch varies depending on culture, climate, style, and available materials. In the USA, the range of standard pitches is anywhere between 4/12 and 9/12. In the UK, the typical house has a pitch between 40°-50° although 45° should be avoided.
Contemporary houses often have flat roofs which shouldn’t be completely flat but should be around 1:40. In Italy, with its more temperate climate, the range of angles is 16-25.
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.
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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.