You can do all the digging you’d like for the scientific answers to thesecontractor debates, but at the end of the daythe exact similarities and differences between all the measurements doesn't matter too much for the average homeowner.
Whether slope is different than roof pitch or the same doesn't help you determine how many roof square is on the home so you can order the correct amount of roofing materials. And if you're a home owner, it doesn't help you make sense of all the calculations that are jotted down on your roof estimate.
Some of you may want to know the exact scientific differences, however. So if that's you, keep reading below. But if you want to know the basic similarities and differences between slope and pitch, you can just click here.
Basic Incline Measurements
Let’s bring this thing back to 5th grade math class, shall we?
Completely flat surfaces have slopes of 0, while completely vertical surfaces have what's called an undefined slope. Everything in between has an inline, and thus, a slope and pitch. That's what we're here to calculate and understand, of course...
But before we're able to figure out the pitch of your roof, we need to get a handle on the definitions of rise, run, and span. These three measurements are the basic vertical and horizontal calculations needed to calculateboth slope and pitch.
For more of an in-depth, mathematical overview of slope you can check out thisresource from Columbia University.
What is rise?
Rise is the vertical change between two points. It's how much something goes up between point A and point B. And in the roofing industry, rise is a measurement you'll use regardless of whether you're calculating pitch or calculating slope. Rise is the first number in both pitch fraction and slope ratio, which are used to display any given roof's pitch or slope.
What is run?
Mathematically, run is the horizontal change between two points. It's how much distance changes between point A and point B. In roofing, run is the distance from the roof's ridge (or peak) and the edge of the roof right above your gutter line.
On aperfectgable roof, your roof's run will be exactly half its span (explained below). This is theperfect example,but unfortunately we don't live in a perfect world for measurements any longer...
The differences between span and run are important because they determine whether you're calculating the pitch or slope of your roof. In exact terms, run is used to calculate slope while span is used as the horizontal measurement in pitch calculations.
What is span?
Span is the end-to-end measurement of a roof.
It’s generally displayed in feet and can easily becalculated using a 100 foot tape measure. Span used to be a more important roof measurement than it is today because it gave you an overall measurement of the roof's length in feet. But as homes get more complex,roof stylesdo too...
For example, measuring a mansard roof isn't quite as simple as measuring agable roof.
Modern roofs aren't straight up and down any more and many times they're seperated into different sections, with dormers and house additions thrown in there to make everything extremely confusing.It's become much more difficult to calculate your roof's incline using just one measurement for length, which is what used to be a big benefit of span.
Advanced Measurements
Now that we understand rise, run, and span, we can dig into slope and pitch. After that, it'll be possible to determine whether or not the differences between the two even matter (and if so, which we should be using).
What is slope?
Slope Ratio
The exact slope of a roof is calculated by the difference between rise and run and expressed as a ratio.
For example: if the roof has 4 feet of rise for every 12 feet of run, the slope would be expressed as 4:12. This is the slope ratio.
What is pitch?
Mathematically, the pitch of a roof is different calculation than roof slope. Pitch compares the roof’s span to the rise while slope compares rise and run. To calculate pitch, you simply divide rise by span and display your result as a fraction. You'll often hear experts express pitch as X over Y.
Pitch Factor
A pitch factor (also known as a pitch multiplier) helps roofers calculate for waste, which is the extra materials they'll need because of the given roof pitch. For example, if a roof's slope is 8 over 12, then it's much steeper than 4 over 12. To help calculate the area for this part of the roof, an experienced roofer would first calculate pitch, then multiply the pitch by it's correspondingpitch multiplier.Doing so will account for extra material that's needed because of the steep pitch- and thus- the larger roof area!
Pitch Multiplier Chart
If you already know the pitch for a specific section of your roof, you can use the pitch multiplier chart below to help calculate waste so you (or your contractor) orders the right amount of materials for installation.
Pitch | Multiplier |
---|---|
1/2 | 1.01 |
2/12 | 1.03 |
3/12 | 1.05 |
4/12 | 1.08 |
5/12 | 1.12 |
6/12 | 1.16 |
7/12 | 1.20 |
8/12 | 1.25 |
9/12 | 1.3 |
10/12 | 1.35 |
11/12 | 1.41 |
12/12 | 1.54 |
Differences
Below is a comparison of the technical differences between pitch and slope.
Pitch | Slope |
---|---|
Divide rise by span | Divide rise by run |
Displayed as a fraction | Displayed as a ratio |
More common roofing measurement | Less common roofing measurement |
Using Slope & Pitch Interchangably
Because home construction is now more complex, remodeling as a whole is too! And contractors have been forced to adapt. In doing so, most (if not all) contractors are now using slope and pitch interchangeably, especially when writing roofing estimates.
When reading about pitch and slope, the most common explanation you'll find is actually a hybrid of the two. You'll see a measurement referred to as pitch (and expressed as a fraction) but the real measurement is slope (rise over run). Historically, there's a few reasons for this...
A Hybrid Definition?
First, pitch is simply more accepted terminology.
Second, slope is easier to calculate for non-gable roofs.
The result?
A hybrid pitch-slope combo; a measurement that's technically slope but displayed as and called pitch.
Confused yet?
You don't need to be! You've got our permission (and thepermission of remodeling author Russell Burgess)to consider pitch and slope the same exact thing!
Though this simplificationmay make architects pull their hair out, slope and pitch are widely used as synonyms by both roofing manufacturers and roofing contractors alike. And if the differences don’t matter when we order your roofing materials, then there’s no use wasting time trying to be as specific as possible.
Now that we've got that out of the way, we can get to the important stuff. Roof angles! That's what roof pitch and slope are both out to determine anyway, isn't it?
Roof Angle Chart
Whether you call or slope or pitch, calculating the steepness of your roof is all about figuring out what angle it is.
Once you know your pitch, you can use the chart below to get a better visualization of your roof's incline:
Pitch | Angle |
---|---|
0/12 | 0* |
1/12 | 4.76* |
2/12 | 9.46* |
3/12 | 14.04* |
4/12 | 18.43* |
5/12 | 22.62* |
6/12 | 26.57* |
7/12 | 30.26* |
8/12 | 33.69* |
9/12 | 36.37* |
10/12 | 39.81* |
11/12 | 42.51* |
12/12 | 45.00* |
Common Examples
Flat Roof: 0/12
Flat roofs don't have a pitch, so if you needed to express the pitch of a flat roof you could simply use 0 or 0/12. Alternatively, you could use 0* or "zero degrees."
Low Slope: 1/12 and 2/12
Low slope roofs are often confused as flat roofs, but this isn't the case. They do have a slope, it's just not very pronounced. And because the slope is so gradual, you need specific low slope roofing materials.1 over 12 is the lowest of the low slopes.
You'll often find a 1/12 pitch on back patio porches or at the top of an older gambrel roof. 2 over 12 is a little steeper than a 1 over 12 pitch, but not by much. In degrees, low slopes are between 4.76 degrees and 9.46 degrees.
Standard Pitches: 3/12 through 9/12
Standard pitch roofs are the common roofing pitches you'll find on the main living areas of residential homes. Unlike low slope roofs, areas that have a standard slopecanuse regular roofing shingles without worry. Because there's enough of a slope, you don't have to worry about water drainage as much as you would with something like a 2 over 12 low slope roof.
In degrees, standard roof pitches are between 14.04 degrees and 36.37 degrees.
Minimum pitch for shingles
3 over 12 is the minimum slope a roof needs in order to qualify for roofing shingles.
Some roofers still opt for low slope materials with a 3 over 12 pitch, but this is not entirely necessary and just adds to the cost of your project.
Steepest standard pitch
A 9/12 roof pitch (36.37 degrees). is the steepest standard slope.
Anything above a 9 over 12 is consideredsteep slope.
Steep Slope: 10/12 and above
Any pitch that's at least 10/12 (39.81 degrees) is considered steep slope. This includes 10 over 12, 11 over 12, 12 over 12, and pitch where the rise is greater than the run.
An important note for roofing contractors: when replacing roofs with steeper pitches, it's important to consider the safety of your crew. All roofers should be harnessed and strapped in!
Exact Examples
If you're interested in seeing some real life examples of various roof pitches, we've created diagrams of some of our recent roofing installations for you.
To browse these examples, choose a roof pitch below that you'd like to check out:
FAQs
Is the pitch of a roof the same as slope? ›
Mathematically, the pitch of a roof is different calculation than roof slope. Pitch compares the roof's span to the rise while slope compares rise and run. To calculate pitch, you simply divide rise by span and display your result as a fraction.
What is the meaning of roof slope? ›Slope is the incline of the roof expressed as a ratio of the vertical rise of the horizontal run, where the run is some portion of the span. This ratio is always expressed as inches per foot. Slope Ratio. A roof that rises 4 inches for every 1 foot or 12 inches of run is said to have a "4 in 12" slope.
What is another name for the slope of the roof? ›The pitch of a roof is its vertical 'rise' over its horizontal 'run' (i.e. its span), also known as its 'slope'. In the imperial measurement systems, "pitch" is usually expressed with the rise first and run second (in the US, run is held to number 12; e.g., 3:12, 4:12, 5:12).
How do you find the pitch of a roof is its slope? ›- First, you need to measure the run of your roof. ...
- Next, you need to figure out the rise. ...
- Now, divide the rise by the run. ...
- Then, divide 1 by your tangent.
- Finally, multiply this result by 180/π and you've calculated your roof pitch!
Remember, slope is expressed as a ratio and in inches per foot. And pitch is a fraction derived by dividing the rise by the entire span.
What should be the slope of roof? ›For metal panel roof systems, NRCA recommends slopes of 1/2:12 or more for structural panel systems and 3:12 or more for architectural panel systems. For asphalt shingle, clay and concrete tile, metal shingle, slate and wood shake and shingle roof systems, NRCA recommends slopes of 4:12 or more.
What are the 4 types of slope? ›Slopes come in 4 different types: negative, positive, zero, and undefined. as x increases. The slope of a line can also be interpreted as the “average rate of change”.
What is a 25% roof slope? ›A 3-in-12 roof rises 3" for every 12" of run. That's the same as a 14 degree slope, or a 25 % slope.
What is a 12% slope? ›Slope is often described in terms of percent. For example, an area that rises 12 feet over a distance of 100 feet has a 12% slope.
What are 3 other names for slope? ›- incline.
- inclination.
- gradient.
- diagonal.
- climb.
- pitch.
- lean.
- ascent.
Which terms refers to slope? ›
Slope is the 'steepness' of the line, also commonly known as rise over run.
How do you determine the slope? ›Using the Slope Equation
Pick two points on the line and determine their coordinates. Determine the difference in y-coordinates of these two points (rise). Determine the difference in x-coordinates for these two points (run). Divide the difference in y-coordinates by the difference in x-coordinates (rise/run or slope).
Convert Roof Slope from Degrees to Standard Roof Pitch | |
---|---|
29° | 6.652 in 12 |
30° | 6.928 in 12 |
31° | 7.210 in 12 |
32° | 7.498 in 12 |
The slope of a line is a measure of its steepness. Mathematically, slope is calculated as "rise over run" (change in y divided by change in x).
What is pitch in simple words? ›pitch, in music, position of a single sound in the complete range of sound. Sounds are higher or lower in pitch according to the frequency of vibration of the sound waves producing them.
What pitch Should a roof be UK? ›In the UK, traditional roof pitches measure between 30° and 50°, while low-pitch roofs are defined as less than 30°. Traditionally, a minimum pitch of 20° was recommended, modern roofing products have made it possible to create equally performing roofs with angles as low as 12.5°.
What are the 3 formulas for slope? ›...
Fact | You can use this fact when you know: |
---|---|
Slope formula: | two points on a line |
Slope-intercept formula: y = mx + b | the slope and y-intercept of a line |
Point-slope formula: y - y_{1} = m(x - x_{1}) | the slope of a line and a point on the line |
Parallel lines have equal slopes | the slope of a line |
Whenever the equation of a line is written in the form y = mx + b, it is called the slope-intercept form of the equation. The m is the slope of the line. And b is the b in the point that is the y-intercept (0, b). For example, for the equation y = 3x – 7, the slope is 3, and the y-intercept is (0, −7).
What is a 4 and 12 slope on a roof? ›Another way to express a 4/12 pitch is "4 and 12." In this pitch, the four is your roof's rise and the twelve is the roof's run. The roof's incline increases four feet for every 12 feet of horizontal measurement.
What does 7/12 roof slope mean? ›For example a 7:12 roof pitch means that for ever 12″ of horizontal distance the roof will increase in height by 7″. The following diagram will let you easily convert roof pitch to degrees; a 7:12 pitch equals 30.26 degrees.
What is a 100% slope? ›
o Degree of slope is measured in degrees from horizontal (0 – 90) ▪ A 45-degree slope is a 100 percent grade.
What is a 1 in 100 slope? ›A 1:100 slope means that for every 100 metres along the ground, the slope height increases or decreases by 1 metre.
What is a 35% slope? ›Slope | ||
---|---|---|
Angle (degrees) | Gradient | |
35 | 1 | 1.428 |
36 | 1 | 1.376 |
37 | 1 | 1.327 |
There are two common formulas for slope: Slope =riserun Slope = rise run and m=y2−y1x2−x1 m = y 2 − y 1 x 2 − x 1 where m=slope and (x1,y1) ( x 1 , y 1 ) and (x2,y2) ( x 2 , y 2 ) are two points on the line. The images below summarize the slopes of different types of lines.
What are the types of slope? ›- postive slope (when lines go uphill from left to right)
- negative slope (when lines go downhill from left to right)
- zero slope (when lines are horizontal)
- undefined slope (when lines are vertical)
If you look at the line from left to right, a line that is moving up will have a positive slope and a line that is moving down will have a negative slope.
What is the most common roof pitch angle? ›Conventional slope roofs are most common with residential roofs. This means the slope has a pitch between 4/12 and 9/12 on most homes. Roofs with a pitch exceeding 9/12 are called steep slope roofs. Steep slope roofs are used for their beauty but they also have other benefits.
What pitch is 45 degrees? ›Roofs with a pitch of 12/12 are approximately 45 degrees, depending on how exact you'd like to be in your measurement. Check out our roof angle chart for more examples of the exact angles (expressed in degrees) of common roof pitches.
What does a roof pitch of 8 mean? ›The first number represents the vertical rise in inches and the second refers to horizontal progression in inches. As an example, 8/12 means that for every foot, the rooftop rises 8 inches. Slopes around 6/12 are the most common, while anything below 4/12 is typically considered a low pitch.
How steep is a 12 pitch roof? ›Roofs with a pitch of 12/12 are approximately 45 degrees, depending on how exact you'd like to be in your measurement. Check out our roof angle chart for more examples of the exact angles (expressed in degrees) of common roof pitches.
Is a 12 12 pitch roof steep? ›
Architecturally described as a "dramatic pitch," the extremely steep roof (ESR) is considered to have a pitch in excess of 12:12, up to a plumb vertical plane. OSHA defines a "steep roof" as any roof with a rise/run ratio over 4:12 (18.43 degrees).
What roof pitch is 30 degrees? ›What roof pitch is 30 degrees? A 30° roof pitch is roughly the same as a 7/12 roof pitch.
How do I calculate my slope? ›Using the Slope Equation
Pick two points on the line and determine their coordinates. Determine the difference in y-coordinates of these two points (rise). Determine the difference in x-coordinates for these two points (run). Divide the difference in y-coordinates by the difference in x-coordinates (rise/run or slope).
Steep slopes: 16 - 30 % gradient. E. Extremely steep. Extremely steep slopes: 31 - 60% gradient.
What is the steepest roof pitch you can walk on? ›The roof's pitch is the angle of the roof, usually presented as the inches of vertical “rise” over 12 inches of horizontal “run.” Generally anything above a 7/12 is considered a non-walkable roof and requires some extra equipment and usually some extra cost to the customer.
What does a roof pitch of 8/12 mean? ›The first number represents the vertical rise in inches and the second refers to horizontal progression in inches. As an example, 8/12 means that for every foot, the rooftop rises 8 inches. Slopes around 6/12 are the most common, while anything below 4/12 is typically considered a low pitch.
Can a roof be too steep? ›In terms of angles, a roof would be considered steep-sloped if it rises at an angle of 18o or more — that would be equivalent to about a 4/12 roof pitch. Of course, many roofs are much steeper than 4/12, and the steeper a roof is, the more problematic it can be to measure, fix, or replace it.
What pitch is considered a low slope roof? ›Low- slope roofs typically have a minimum slope of one-fourth inch vertical to twelve inch horizontal (¼:12 or 2 percent) depending on the roofing material. Roofs are considered low-slope roofs up to 3:12 pitch. Low-slope roofs traditionally have been constructed with an asphalt built-up roof covering.
What is a 45 degree roof pitch? ›By this method a 12 pitch roof would be a 45 degree angle. Roof pitch is calculated by measuring the distance that the roof raises over a distance of 12” so a roof that increases 5” in height over the length of 12” would be called a 5 pitch. By this method a 12 pitch roof would be a 45 degree angle.