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How Do I Calculate Roof Pitch

Interesting Facts About Roof Pitches

How to Calculate Roof Pitch
  • There is no universal roof pitch. Factors like architecture, material, climate, and cultures affect how flat or steep a roof is.
  • The standard roof slope in the US is 4/12 to 9/12.
  • In the UK, the typical roof pitch is 40-50 degrees.
  • It would be best if you avoided 45-degree slopes for stability during storms.
  • Contemporary houses have near-flat roofs. They have slopes of 1/40.
  • Italian roofs have 16 to 25-degree roof pitches.
  • The minimum roof pitch suitable for snow-shedding is 6/12 or 7/12 .
  • A roof is walkable if its slope is less than 6/12 or 26.5 degrees. You can walk 7/12 roof pitch with caution. You can walk even 8/12 to 10/12, but it is not advisable and it calls for extreme caution. Roofs beyond this range are not walkable.

Some people apply the Pythagoras theorem, which makes it unnecessarily complex to understand. All you need is the slope, and the above four methods are sufficient to find it.

Please keep it simple and understand the logic behind it.

That is all about the roof pitch calculation. Remember, the basic idea is to standardize it into inches per foot.

The angle determines the pitch based on the rise and run sizes.

No matter what method you choose, measure the rise and run to get the slope, directly or indirectly.

How To Find The Pitch Of A Roof

There are two distinctly different methods one is more accurate, while the other is faster and easier.

The first involves climbing up on the roof, or at least the edge and actually measuring the pitch using a carpenters level and a tape measure.

The second is more of a guesstimating way to get the approximate pitch, while standing on the ground. Not as precise, the second method allows for a quick calculation when a ladder is not available, or when you need to get/provide a quick price quote, or quickly estimate roof size.

Method 1 how to figure roof pitch using level and measuring tape

For this most accurate calculation, you will need a ladder, long enough to reach the roof edge, a 2 feet level, and a measuring tape. Use caution when climbing up the ladder, and do not go onto a roof without adequate fall protection. We also recommend using a ladder stabilizer to prevent it from sliding to the sides.

Once you reach the top of the ladder, position your level so that one end touches the roof surface, while the other end is in the air, and it is leveled.

Now, measure the distance between the roof surface straight down from the levels opposite edge refer to the diagram below:

Method 2 Guesstimate roof pitch off the ground

This process is usually rather easy, fast and pretty accurate. However, if you need to order materials for a job, we still recommend getting a more accurate pitch measurement, such as in the first method.

Average Roof Replacement Cost in US:

Low End

What Is The Smallest Pitch Of A Roof

The smallest pitch of a roof is 0.5/12. A completely flat roof is a poor design, as water and snow will collect on it, eventually leading to your roof collapsing in from the weight of it all.

A common choice for flat roofing material is EPDM rubber, as it is highly durable, waterproof, and can be made from recycled materials. Flat roofs also tend to be cheaper and require less maintenance than traditional roofing, making them a perfect addition to your home.

Also Check: How To Extend A Metal Roof Overhang

What Is The Standard Pitch Of A Roof

Roof pitch refers to the measurement of the slope of a roof and you express this as a ratio. Although theres isnt any standard pitch of a roof used on all kinds of sloped roofs, you can determine the range of pitches by using a roof angle calculator and by considering factors like the local climate and roofing materials.

Express roof pitch as the ratio of the amount of the vertical rise of a roof or rise over the corresponding horizontal distance or run. You write the pitch assuming a run of 12-inches thus, the ratio would describe how much a roof rises for each foot of the run.

As aforementioned, there is no standard pitch of a roof. But the most commonly used pitches range between 4/12 and 9/12.

How To Measure Roof Pitch

3 Ways to Calculate Roof Pitch

Knowing the pitch of your roof is useful when designing an addition, installing skylights, or cutting new rake boards. Here’s an easy, safe way to determine the pitch from inside your attic.

  • To measure the roof pitch, you’ll need an 18- or 24-inch level, a tape measure, and a pencil.
  • First, measure 12 inches from one end of the level and make a mark.
  • Then, in the attic, place the end of the level against the bottom of a roof rafter and hold it perfectly level.
  • Now measure vertically from the 12-inch mark on the level straight up to the underside of the rafter, as illustrated. That measurement is the number of inches the roof rises in 12 inches.
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    S To Convert Roof Pitch From Degrees To Standard Fraction Form

    First, you have to convert the angle to slope in decimal and then convert it into a fraction by multiplying it by 12. Here, you will use the tan formula and then multiply by 12 to convert it into inches per foot.

    For Example, if the roof angle is 35 degrees, then tan = 0.70. Multiply by 12, and you get 8.4 inches per foot.

    Measure Slope By Climbing The Roof

    In this method, you need to climb the roof to measure the rise for any 12-inch run. We will need two instruments to mimic as a base and perpendicular of an imaginary triangle.

    We will fix the triangle base as 12 inches and then check what the rise is. You will require a tape measure and a level instrument of at least 12 inches.

    Hold the level and check if it indicates a flat reading. Now measure the height or rise from a 12-inch point to the point that touches the roof below. The value you see on your tape is the rise or perpendicular.

    For Example, if the value is 5 inches, then the top has a slope of 5/12 or 5:!2.

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    What Is Roof Pitch

    Roof pitch is represented in inches rise of 12 inches run. For example a 3 pitch or 3 in 12 pitch or 3/12 pitch, all mean that the roof rises 3 inches, for every 12 inches of its horizontal run.

    Using pitch, its footprint, and basic geometry, you can quickly and with a high degree of accuracy calculate the length of the gable sides. This will allow you to get very precise area measurements.

    A roof may have many other attributes, but its pitch is often important in determining the cost of replacement, as well as in choosing the correct materials.

    It is also a useful measurement to have if you are designing an addition for your home, cutting new rake boards, or installing skylights.

    A roof can also be measured in degrees. However, it is often a difficult and an unnecessary way to estimate slope. On the other hand using pitch is simpler, faster, and often more accurate. Nevertheless, our Roof Pitch Calculator provides instant conversion from pitch to degrees and backwards. You can also use it to instantly estimate the pitch, as well as the area, and rafter length.

    However, if you want to go the long, manual route, keep reading to find out how to do this calculation yourself.

    Key Terms In Measuring Your Roof Pitch

    How to Determine the Pitch of a Roof

    Before we proceed, there are key terms that you must understand and some measurements you must learn.

    1. The Rise and Run The vertical distance from one point to the highest point of the roofing is known as rise.

    When you examine a right angle, youll see the vertical component as the rise and then the horizontal component as the run.

    The length of your roof, commonly known as the height, is measured in feet.

    The distance between your roofs peak and the exterior wall is referred to as run.

    2. Roof Angles Roofs come in many different varieties, and depending on your type of roof youll have a slope ratio or pitch fraction thats unique to the condition.

    3. Roof Slope Roof slope is often mistaken for pitch and it is critical to distinguish the significant distinction.

    Slope is the slope of the roof itself and is measured in inches of vertical rise per foot of horizontal length.

    A roof then with a 3-inch rise for every 18 inches of run would appear like: 3:18. The measurement will always be represented in terms of inches per foot.

    4. The Roof Pitch The slope of a roof is referred to as pitch, and it is measured in a fractional ratio of the rise divided by the span, that identifies the distance between exterior walls.

    A roof with a 3-foot rise and a 24-foot span would be a 1/8 pitch of the roof.

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    One: Measure From The Roof

    One method to find the pitch is to climb on the roof and measure the rise for a 12 run. Youll need a level that is 12 or longer and a tape measure.

    On the roof, hold the level perfectly level, and measure the height from the roof to the level 12 inches away from where the level touches the surface this will be the rise.

    For example, if the end of a level is 4 above the roof at a point 12 away from where it meets the surface, then the pitch is 4:12.

    What Is The Average Quote For Getting A Roof Pitched

    There are a lot of factors that will affect how much getting your roof pitched will cost design, style, accessibility, cost of labor etc. In the USA, you can expect to pay between $3.19-$4.43 per sq.ft. for asphalt shingles. If you choose another material, such as metal or wood, the range is $7.35-$10.73 per sq.ft.

    In the UK, the price of getting a roof fitting is £72-£75 per square meter. These are only estimates though, talk to your neighbors to see what roofing costs in your area.

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    How To Calculate Your Roof Pitch From Inside

    An easier way to calculate your roof pitch without going on the roof is to measure the rafter length ortruss system in your attic. Place your level under the bottom of the rafter, and after the bubble is in the center, mark it at 12 inches. Then measure vertically from the level to the roof rafter. This measurement will tell you the number of inches your roof rises in 12 inches of run.

    Roof Pitch To Angle In Degrees

    Roof Pitch Angle Chart

    Roof pitch formula help you to convert roof of pitch ratio or fraction of slope in angle in degrees in following two steps:- 1) divide the first part of the ratio by 12 to figure out the pitch and 2) find the inverse tangent of pitch to find the angle in degrees.

    For 2/12 roof pitch into angle in degrees:- 1) pitch = rise/run such as 2/12 = 0.1666, 2) tan inverse of pitch = tan-1 = 9.46°, thus a roof pitch of fraction 2/12, or 2 in 12 slope, or in ratio 2:12 is equivalent to 9.46 degrees.

    For 4/12 roof pitch into degrees:- 1) pitch = rise/run such as 4/12 = 0.33, 2) tan inverse of pitch = tan-1 = 18.43°, thus a roof pitch of fraction 4/12, or 4 in 12 slope, or in ratio 4:12 is equivalent to 18.43 degrees.

    For 7/12 roof pitch into degrees:- 1) pitch = rise/run such as 7/12 = 0.583, 2) tan inverse of pitch = tan-1 = 30.26°, thus a roof pitch of fraction 7/12, or 7 in 12 slope, or in ratio 7:12 is equivalent to 30.26 degrees.

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    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 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 but the real measurement is slope . Historically, there’s a few reasons for this…

    How To Calculate Length Of Rafter

    take the measurement of horizontal run length:- it is horizontal distance out side of walls top plate to a point directly below the centre of the Ridge or hip of roof, assuming it is 10 meters

    measure the vertical height of rise of your roof, assuming it is 2.5 meters.

    to determine the rafter length by using this formula, as Rafter^2 = rise^2 + run^2, Rafter^2 = 2.5^2 + 10^2, Rafter^2 = 6.25+100, rafter = 106.25, Rafter = 10.31 meters, hence rafter for pitched roof will be 10.31 meters.

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    Three: Measure The Total Rise And Run

    If you know the total height of the peak and the roofs width, you can also find the pitch with a little math. For example, if the peak is 4 feet and the total roof width is 20 feet, then the total rise is 4 feet, or 48 inches.

    The total run is the distance from the peak to the edge of the roof, which in this case is the total width divided in half, which is equal to 10 feet or 120 inches.

    Since the pitch is the rise over a 12-inch run, you can divide the run by 12 to get the multiplier, in this case, 120 ÷ 12 = 10.

    Then, divide the rise by the multiplier to get the pitch, e.g. 48 ÷ 10 = 4.8. The pitch of this roof is 4.8:12. The calculator above can handle much of this math.

    The Importance Of A Pitched Roof

    How to Find Roof Pitch in Less than a Minute

    If a home orbuilding’s roof didn’t have any pitch at all, it would be at a high risk ofcollecting standing water that ends up deteriorating the roof itself,presenting a serious and inevitable risk of leaking through the roof and intothe building. Even on roofs that may appear flat to the naked eye, a slightpitch has probably been built into the roof to facilitate water run-off fromrain and snow.

    Pitched roofsare even more important in regions where snow can accumulate on a roof. Thelower the pitch, the greater the amount of snow that can accumulate on theroof’s surfaceand the weight of this accumulation could potentially break theinterior structure of the roof itself. With a higher roof pitch, snow and heavyrainfall can be sloughed off before structural integrity becomes a concern.

    Roof pitch canalso have the following implications on a home:

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    Calculate The Surface Area Of The Roof

    Youll notice as an area is drawn the area and perimeter results are displayed in the bottom right corner. With a single pitch roof youll have only one area result that relates to the entire footprint or perimeter of the roof. Both metric and imperial measurement systems are displayed in a popup menu over the results area.

    Take your area result and multiply it by the pitch multiplier found in the table above to arrive at the roofs surface area. Now youre ready to price out the materials.

    For multi-pitched roofs simply add the areas of all common pitches together by toggling layer visibility from the summed layer at the left of the layers control.

    Use the appropriate pitch multiplier for each totaled area calculated, then sum all the areas together.

    Gable Roof Sheathing Calculator

    Estimate the amount of plywood or OSB needed for sheathing a roof.The calculation is based on that the Plywood or OSB sheets are of a 4′ x 8′ size. One sheet = 32 ft²

    This basically calculates the number of sheets needed for a Gable roof.The square footage of a Hip roof area is identical to the square footage of a Gable roof of the same measurements. If you are calculating the number of sheets needed for a Hip roof then for the value of the gable overhang use the eaves overhang dimension, assuming it is the same all around.The amount of waste on a Hip roof will be higher than for sheathing a Gable roof and even more so if you are using OSB sheathing. OSB sheathing has a rough side and a smooth side. You always want to make sure the rough side is up with OSB sheathing. Never install the OSB sheathing with the smooth slippery side up!

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    Calculating Pitch From Slope

  • 1Define roof slope. Most people interested in roof “pitch” are actually measuring the slope, which is the most useful measurement when considering roofing material and rainwater. Slope is the correct term for the ratio of vertical to horizontal distance on a particular plane of the roof. Even carpenters often use the terms slope and pitch interchangeably.
  • For example, if one side of the roof rises by 8 inches for every 12 inches of horizontal distance, it has a slope of “8 in 12” or “8:12.”
  • 2Understand roof pitch. Technically, roof pitch is the ratio of total vertical roof height to total horizontal distance from wall to wall .XResearch source Although most homeowners do not need to measure pitch, it still pays to understand this term. When you’re arranging for repairs or roofing material, your calculations will be way off if you misinterpret “pitch” to mean “slope.”
  • Again, some carpenters and manufacturers use both terms to mean “slope.” Just ask if there’s any confusion about which measurement they’re referring to.
  • For example, if a roof is 32 feet from wall to wall and the ridge is 8 feet above the walls, the pitch has an 8 to 32 pitch, simplifying to “1 to 4” or “1/4”.
  • 3Find the pitch. If you do need to calculate the pitch, an estimate or shortcut is usually more practical than measuring the roof’s overall dimensions. Here are a couple examples:
  • For a simple gable roof, the span will be twice the size of the run . Divide the slope by two to get the pitch.

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