There’s a high probability you’ve never considered the pitch of any roof. Fair enough. But if you made your way to this post, there’s a high probability you need to.
Either it’s time for a new roof or you’re in the midst of new construction. In each case, roof pitch is important to understand.
What is roof pitch?
Pitch is just another term for slope. Rather than use a degree measurement, pitch is expressed as the vertical rise by the horizontal run in inches. For example, if a roof rises 3 inches every 12 inches, the pitch measurement is expressed as 3:12.
Any reputable roofing professional will and should discuss roof pitch when planning or installing a new roof and choosing roofing materials. You can measure your roof pitch from inside your attic if you’re curious.
Why does roof pitch matter?
Roof pitch is the primary factor that determines how effectively your roof sheds water and debris. In areas where rain and snowfall are more common, roof pitches tend to be steeper.
Roof pitch determines what materials and roof systems are suitable for your roof long-term. Roofing material manufacturers often include pitch requirements in their warranty agreements. If a material is installed on a roof with too much or too little pitch, it may void the warranty.
Though some may refer to low-pitch roofs as “flat,” it’s rare to find a roof with no pitch at all, although it may appear to. Low-pitch roofs are those with a pitch less than or equal to 3:12. These roofs are becoming more common as industrial design trend has taken the construction market by storm.
With a pitch as low as .25/12, low-pitch roofs require special materials. Some of these materials include:
- Built Up Roofing (BUR): Also known as tar-and-gravel, BUR roofing is alternating layers of asphalt and fabric.
- Rubber Roofing: Made of EPDM, an extremely durable synthetic rubber, this roofing is glued or anchored.
- Standing seam metal: Interlocking sheets of aluminum or steel are joined together to form a watertight seal.
Most common in residential construction, medium-pitch roofs are those with a pitch between 4:12 and 9:12. The common materials used to these roofs include:
- Asphalt Shingles: By far the most popular roofing material in North America for cost-effectiveness and ease of installation.
- Wood and Slate Shingles: Ideal for pitches 5:12 to 12:12
- Clay or Cement Tiles: Fairly versatile, but lower pitches may need a second underlayment
Common in climates prone to heavy rain and snowfall for a majority of the year, steep-pitch roofs are those with a pitch of 10:12 to 20:12.
The steep pitch leaves little opportunity for water or debris to stick around, reduces instances of mold caused by moisture, creates a large attic space for storage, and is more ornate than other roof pitches.
Materials fit for steep-pitch roofs include:
- Asphalt Shingles
- Clay or cement tiles
- Wood Shake
If you’re replacing your roof or constructing a new home, it’s important to understand roof pitch and how it affects the roofing materials you can safely use. If you roofing professional doesn’t bring up pitch in his pitch, find a new one.