Is the Roof Pitch Affects Your Choice of Roofing Materials?
While you choosing roofing materials, it may seem that you have an endless choice of any materials on the market: metal, composite, asphalt, wood shake, and MSR rolled roofing. A lot of people thinking that the choice is mostly an economic or aesthetic one—that you choose a roofing material purely according to what you can afford or like more.
That’s not always true, let Veronica Contracting experts explain one of them in this article. Many different factors determine which roofing materials you can use, in your case. One of the main factors is the slope of the roof, known as the roof pitch. Like an example, you may think you want classic composite shingles on your roof, but if the pitch is below a certain ratio, you may be forced to install a different type of roofing—perhaps rolled roofing or standing seam metal roofing.
Roof Pitch what does it mean?
Pitch is the term used to describe the angle, slope, or slant of your roof. Roof pitch designations are comprised of two numbers indicating it’s ratio. This ratio can be indicated by a division slash separating the numbers, such as 3/12 or 5/12. sometimes, the colon can replace the slash, as in 3:12 or 5:12. Anyway, the notation designates a ratio between two measurements of the roof—a numerator and denominator.
The numerator, or first number, refers to the vertical (height) measurement of the roof.
The denominator, or second number, denotes the horizontal (length) measurement of the roof. To make things a little bit easier, for roofing purposes the denominator is always 12. Even though basic mathematics tells us that 12/12 can be reduced to 1/1, this is not done with a roof pitch. The denominator remains 12.
How to Calculate your Pitch?
The pitch of any roof is a ratio that indicates how much rise there is in the roof over a 12-unit horizontal distance.
Some of the Examples:
3/12: For every 12 horizontal feet, the roof changes 3 feet in vertical height.
7/12: For every 12 horizontal feet, the roof changes 7 feet in vertical height.
For most home styles, roof pitches fall in a range of 3/12 (a moderate) slope up to 8/12 (fairly steep). Also, some examples of extreme slopes range from 1/4/ 12 (almost flat) to 12/12 (sloping down at a perfect 45-degree angle).
Low-pitched: It was fashionable for modern-style homes built in the 1970s to have little pitch, just a barely negligible slope to help drain water. Visually, this roof appears flat. This pitch might be as low as 1/12 or 2/12.
High-pitched: Roofs presented the Victorian-era houses were often sharply angled with a steep pitch.
.25/12 to 3/12 Roof Pitches
Roof pitches with lower angles, such as 1/12 up to 3/12 are found in more urban, contemporary style houses and in industrial buildings and shacks. The flat roofing materials most appropriate to these shallow-sloped roofs include:
Built-up roofing: this kind of roof consists of alternating layers of bitumen and reinforcing fabrics.
“Torch-down” roofing: This is a single layer membrane-style roofing material that is heat-activated by a torch during its installation.
Rubber membrane: EPDM is a true rubber that can be applied to a roof with glue or mechanical anchors.
Standing seam metal: These roofs are made from panels of aluminum or steel joined together in raised seams. They can be used on roofs with pitches as low as .25 /12. They are also used on much steeper roofs.
2.5/12 to 19/12 Pitches
Clay or cement tiles can be used on a wide range of roof pitches. For pitches of 2.5/12 up to 4/12, the roof requires double underlayment. Slopes above 19/12 are not recommended since tiles on very steep roofs can rattle.
4/12 to 20/12 Pitches
Really a great variety of residential roofs goes into this category. The roofing materials most often used for these pitches include asphalt (composite) shingles. These shingles are appropriate for pitches as low as 4/12 pitch, all the way up to a 12/12 pitch. Think of them as taking the middle road in terms of roof pitch—not too flat, not too steep.
5/12 to 12/12 Pitch
Slate and wood shingles are used in many of the same types of roofs as asphalt composite shingles, but may not be appropriate for roofs near the lower end, since they are more susceptible to leaking. Wood and slate shingles do not lock together as tightly as other types of shingles.
Most roof materials have a recommended pitch range for which they are most appropriate. Sometimes the rules can occasionally be broken, but generally, you should not exceed the low range of the recommendation.
Standing-seam metal: 1/12 to 19/12
Clay or cement tiles: 2.5/12 to 19/12
Asphalt (composite) shingles: 4/12 to 20/12
Wood and slate shingles: 5/12 to 12/12
Built-Up (BUR): .25/12 to 3/12
Torch-down roofing: .25/12 to 3/12
Rubber membrane: .25/12 to 3/12