What is a 8 on 12 roof pitch – 8/12 roof pitch (with Calculator)

The 8 on 12 roof pitch or 8/12 roof pitch is a pretty common residential roof pitch that corresponds to an angle of 33.690 degrees. It depicts the steepness of a roof such that for every 12 inches or horizontal run there’s a rise of 8 inches in height of roof.

We express roof pitch, inclination, or slope of roof in fraction that relates horizontal measurement or run corresponding to the height or rise. So 8/12 roof pitch is Vertical rise (8 inches)/ Horizontal run (12 inches).

Roof pitch is a pretty common concept on sloping roofs like gable, mansard, hip roof, or gambrel roof. We also refer sloping roof as the pitched roof. While you’re looking to have a new roof for your house, a common question is how much should be the pitch of the roof.

At that stage, the most obvious choice is 8/12 roof pitch. But a lot of homeowners don’t know what is 8/12 roof pitch or how to express 8 on 12 roof pitch in degrees.

So, in our today’s read, we’re going to elaborate a method to express the roof pitch properly so there’re no surprises while having a new roof.

What is roof pitch?

Roof pitch in general, is the slope of a roof that helps shed rain water quickly on sloping roofs. We, in general, can express roof pitch in ratio, percentage, fraction, and in degrees. The extent or amount of pitch depends on factors like:

  • Roofing material
  • Local climate condition
  • Use of the building – Purpose

But because most of the residential buildings in prevailing weather condition doesn’t require some unorthodox slope, so 8/12 roof pitch is pretty obvious choice.

The extent of slope or inclination in 8/12 roof pitch not only allow quick shedding of rain water but is also comfortable for human to walk. The spruce has given some ranges of roof pitch as a guide:

  • Very low roof pitch – 25/12 to 3/12
  • Low roof pitch – 2.5/12 to 19/12
  • Moderate roof pitch – 4/12 to 20/12
  • High roof pitch – 5/12 to 12/12
  • Very high roof pitch – 18/12

So, in above scale, 8 on 12 roof pitch correspond to moderate roof pitch.

If you’d like to compare the roof pitch with roofing materials; it’s worth mentioning that roof pitch between 4/12 to 20/12 is recommended with Asphalt (composite) shingles. Whereas for wood and slate shingle roof, it is not recommended to install it below 4/12 range.

What is a 8 on 12 roof pitch - 8/12 roof pitch
What is a 8 on 12 roof pitch – 8/12 roof pitch

8 on 12 roof pitch

It is the pitch of a roof such that the roof rafter has vertical rise of 8 inches after every 1 foot or 12 inches of horizontal distance (aka run). It also means a slope of “8 on 12”. Some manufacturers also express 8 on 12 roof pitch is 8/12 with Vertical rise / Horizontal Run. In angle, 8 on 12 roof pitch corresponds to a sloping angle of 33.690 degrees (more precisely as 33° 41′ 24″).

Let’s discuss the info in a bit detail:

If you see the above scale of roof pitch, you’d notice that denominator of all roof pitch is 12. Even for a roof 12/12 – we can’t express it as 1/1 – obviously in Mathematics we can do that – but in roofing terms – 12 / 12 or 12 on 12 remains 12 on 12 slopes.

Anyhow, please note down that while expressing pitch as fraction, here’s what numerator and denominators tell us:

  • Numerator = The first is always numerator indicating the vertical rise or height of the roofing measure.
  • Denominator = The second number is always the denominator and it indicates the horizontal length or run of the roof.

In such terms we can express that roof pitch shows the vertical run a roof has per feet of horizontal run.

Can you help me in understanding why the roof pitch of 8/12 has a slope of 2/3? That’s a simple mathematics question.

Anyhow, just remember my above description of roof pitch and you’ll be at ease. That’s how you can easily remember the definition of the roof pitch.

8/12 roof pitch angle

The 8/12 roof pitch corresponds to the angle of 33.690 degrees. So, let’s now see how we can calculate or convert the pitch and express it as an angle.

  • Just simplify the roof pitch by cutting so, 8/12 = rise / run = 2/3 = 0.66
  • Now find the inverse tangent of the above figure to get the angle in degrees. So, tan-1(0.66) = 33.690.
  • So, the roof pitch in fraction 8/12, 8 over 1w or 8 in 12 slope is equal to 33.69 degrees in angle.

Now you might be asking why we need to convert or inter-relate these terms.

Well, in many roofing literature, the pitch or slope of the roof doesn’t go along one way. Some roofers refer slope instead of fraction while the other use angle as a reference. So, it is pretty important that you know what the roof pitch means, and how you can convert that fraction into degrees to avoid confusion.

Why 8 on 12 roof pitch is ideal?

Well, the purpose of pitch in roof is to allow rainwater to quickly shed off the roofing material and prevent any trouble like roof leaks and drips. But having too steep roof is also a trouble. Apart from difficult walkability, the roofers will charge you more in case of maintenance or inspection. Similarly having more roof pitch will need more shingles to cover that’s an unnecessary expense at your end.

On the other hand, a low pitch roof can easily catch tree limbs and debris. The gutters can easily get clogged after a heavy rain. Moreover, you’d be troubled by a premium attic space.

So, having a moderate pitch roof or 8 on 12 roof pitch is ideal that not only sheds water easily but also allows easy inspection or maintenance.

I hope it helps. If you’ve loved the article – don’t forget to share it with your friends and subscribe to our newsletter for relevant and interesting information.

  • The Spruce has a very good guide about basics of roof pitch, the materials, and even some examples of roof pitch calculations.
  • If you’d like to know about the pros and cons of having high pitch or low pitch roof, head on to this guide by DeLaurier Roofing
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Saad Iqbal

Here I’m, Saad Iqbal – a civil engineering geek and a passionate blogger – with handy graphics designing skills. I’m in the online civil engineering community from over a decade now and have many fans, followers and friends throughout the world.

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