Upgrading your roof isn’t something you do every day. Depending on the roof materials you select, you might only invest in a new roof once in a lifetime.
That makes your roof selection an important process.
For many homeowners, the process starts by looking at materials or color. And while both of those are important to create curb appeal, the final selection also depends on your home’s style.
You have many choices when it comes to roofing material selection: asphalt, composite, wood shake, rubber, tile, metal, and more. But it’s more than an economic or color decision; it also depends on roof pitch styles or the slope of the roof of your home.
What Is Pitch?
Pitch is the term used in the roofing industry to describe the angle or slope of your roof. Roof pitch is comprised of two numbers in the form of a ratio. You’ll see it expressed either with a slash – 5/12 or 8/12 – or with a colon – 5:12 or 8:12. Either way, the numerator and denominator work together to tell you the pitch of the roof.
The numerator refers to the height of the roof.
The denominator refers to the length measurement of the roof.
To keep everything relatable, the industry will always rank with a denominator of 12. Therefore a roof pitch will always be referred to as how much rise there is in the roof over a 12-unit horizontal distance.
For the roof pitch styles from above, for example, the 5/12 means that for every 12 horizontal feet of change, the roof rises 5 feet vertically. For the 8/12, it moves 8 feet in vertical rise for every 12 feet of horizontal space.
With most homes, roof pitch styles range from 4/12 to 8/12, with the lower being a moderate rise and 8/12 being a fairly steep ratio. But roof pitch can have a lot more variation.
A 1/2/12 roof would be almost flat. You might find a low-pitched roof on a modern home where the slope is barely there; just enough to allow water to flow. A 12/12 roof would slope at a 45-degree angle. Old Victorian homes often have sharply angled roofs with a steep pitch and, in some cases, they can even move beyond the 12/12 ratio.
Why Roof Pitch Is Important
The roof pitch is important for two reasons.
One, in order to estimate correctly for the amount of material needed for the job, you must have an accurate measurement of the pitch of the roof.
Two, not all materials are suited for the roof. By knowing the pitch, you’ll have a better understanding of the roofing materials that will work best on your home over time.
When a roof is perfectly flat, the calculation for materials is simple: width times length.
As a roof rises, the different pitches require more material to compensate for the slope. The industry has tables for slope factor based on the angles of your home to help determine the extra materials needed. In our examples above, a 5/12 pitch would have a slope factor of 1.085. Use this to multiply with your answer from width times length and you’ll have an accurate measurement of how much material you’ll need.
Roof shapes have evolved over time. Head back hundreds or even thousands of years and you’ll find roofs were made from very simple materials. Straw, mud, grass, wood – only gradually did they start learning the benefits of using different materials and to gently slope the roof for protection.
Flat roofs make sense on some structures. But if you make it perfectly flat, water has nowhere to go. Even a gentle slope is needed for proper drainage. Angles help control the elements and give a building style. But no matter how much you like a particular material, some homes simply aren’t meant for some types of roofs.
Roof Pitch Styles
These are the safest roofs. They are easy to walk around on and easy to perform maintenance. But they are also more prone to leaks and require more frequent inspections. That’s why you won’t find a lot of low-pitched roofs where weather is extreme – both water and snow buildup can be detrimental and put a building at risk. Low pitch is usually the design of choice on modern, sleek, contemporary homes.
Flat roofs cannot be covered with traditional materials such as shakes or asphalt shingles since there isn’t enough pitch to combat damage from wind. Flat roofs are limited to more commercial-grade roofing applications, such as tar and gravel, rubber, or roll roofing.
This is where most home roofing systems lie. A medium-pitch gives you ample choices in materials while providing enough slope to keep rain and snow from accumulating on the roof. While it still needs periodic inspections, this is where most roofing choices exist.
If you prefer clay or cement tiles, they can be installed on roof pitches from 2.5/12 up to 20/12. However, for flatter roofs 2.5/12 to 4/12, it is recommended that they are installed with an underlayment to handle the extra weight.
A vast amount of the choices fall into the 4/12 to 20/12 range. This is where asphalt or composite shingles are, which are the most popular types of roofing options on the market today.
If you like the look of wood or slate shingles, they need a more gentle sloping roof, with roof pitches in the 5/12 to 12/12 angles working best.
These are the most expensive roofs to install, but also give dramatic architectural elements. A contractor cannot work on a high pitch slope without safety gear, so more cost will go into it for both repairs and renovation.
Your final selection will also determine which warranties are in place and how long your roofing materials will last. Be sure to ask about both material and workmanship warranties as the two are often separate.
If green building is important, roof pitch can impact your final selection. Consider both the shingle material and any underlayment necessary to complete the job.
Also investigate fire ratings for the different types of roof pitch styles, especially if you are in an at-risk area.
So what type of house do you currently own? What type of roofing are you interested in? Knowing the roof pitch plays an important part in the selection process; what questions can we answer to help you make your final selection?