Roof pitch is the measure of the slant of your roof. It is one of the many important elements of your roof, and there’s good reason to understand its purpose and what it means for the health and safety of the roof over your head.
Not long ago, the local news in Ellisburg, NY reported that a barn roof collapsed and killed some cows during a winter storm. A day later, an elementary school roof collapsed in Montana, but thankfully no injuries were reported. Roof collapse is such a problem in snowy climates that the Massachusetts state government even publishes guidelines on clearing snow in ways that avoid roof collapse. The guidelines mention that “flat and low-pitched roofs — mostly found on industrial buildings but also used in certain home designs — are at the greatest risk of buckling under heavy snow and ice accumulations.” So clearly, roof pitch matters in terms of the integrity of a building and safety. But what is roof pitch, exactly?
Roof Pitch Defined
Roof pitch is one of the most visible aspects of a roof. It’s the measure of the steepness of a roof, or its slope. Roof pitch is expressed as a ratio of the roof’s vertical rise to its horizontal span, or “run.” In the United States, roof pitch is typically measured in inches and expressed as a ratio. The higher the first number (rise) in the ratio, the steeper the roof. The second number is the horizontal area measured, usually measured as a standard 12 inches (one foot of roof). So a roof pitch of 10:12, as seen below, means for every 12 horizontal inches of roof, the roof rises 10 inches. This is a steep slope roof.
For the curious or do-it-yourselfers, Wikihow has a good explanation on how to measure the pitch of your roof in easy to follow steps. Just use common ladder and roof safety rules, or, if you have one, you can take the measurements from inside your attic.
Why is Roof Pitch Important?
Roof pitch is mainly intended to allow run-off of rain and snow. Most of the time, areas where higher levels of snow or rainfall are common prefer to build roofs with steeper pitch. Well-built roofs are designed to prevent pooling of water or accumulation of snow, as over time, these can cause roof damage, from mold and leaks to cracks, or even collapse. Many states, particularly northern states where snowfall is a normal occurrence, include minimum pitch levels in their building codes. This insurance carrier gives some general guidelines on calculating safe snow load for homeowners dealing with a surprise heavy snowfall that some areas have experienced in the last few years.
Common Types of Roof Pitch
While categories of roof pitch are not strictly defined, typically they may be grouped as follows:
- Flat – No roof is truly flat, since they are at least slightly angled in order to allow for drainage of water, and thus flat roofs are those that have a pitch (in inches) of only ½ :12 to 1:12.
- Low-slope – 1:12 to 4:12. Low-slope roofs require special techniques and materials to prevent leaks. Flat and low-slope roofs are easily to walk on, but are much less efficient at allowing the run-off of rain and snow.
- Medium-slope – 4:12 to 9:12, which are often mathematically reduced and expressed as 1:3 and 3:4. Roofs with pitches of 6:12 are the most common. A nice balance between water and snow run-off and ease of access.
- Steep-slope – Any pitch above 9:12. These roofs may require extra fasteners, and these steeper roofs are very challenging to walk on.
Many homes are built with a steep pitch because the angled shapes are attractive to the eye. Building a high pitched roof costs a little more as the vertical angle means the roof span is longer and more materials are required to build it. A high pitch roof may also require more skilled labor to build and maintain. Decorative additions like gables or eaves will add more cost, but these also add to the interest and charm of the roof.
Generally, though, in areas with no more than light snows, a fairly low pitched roof does the job and fits well with popular styles like ranch homes and most homes in the Southwest. Some materials are more appropriate for a low pitch, such as metal or concrete roofing, while tile and shingles, which are layered to shed precipitation, work best on moderate to high pitch roofing.
Of course, climate is a key factor in selecting the roof pitch for your home. If you live in a heavy snow zone, you’ll want a higher pitch roof to protect from snow loads being trapped on your roof. Here in Southern Nevada, while our homes don’t require high slopes, our seasonal and intense monsoon rains justify having enough roof pitch to make sure that water can be shed quickly from your roof. Your roofer can go over all your options if you are re-roofing or designing a new home.
Prestige Roofing Can Answer Your Roofing Questions
Customers in Southern Nevada, Utah and Arizona can rely on Prestige Roofing in North Las Vegas for professional advice and installation of quality roofs. We are not only licensed roofers but TRI (Tile Roofing Institute) Certified Installers as well. Whatever your roofing needs, don’t hesitate to call the professionals at Prestige Roofing.