What is the Difference Between a Pitched & a Sloped Roof?

This article has been update August 2020.

Asking the difference between a pitched and gently sloped roof is a bit like asking about the difference between modern and traditional architectural design. As a rule, traditional architectural design features reflect influences from Neoclassical, Colonial, Victorian, and Craftsman architecture.

Common traits include big porches and pitched roofs. Modern architectural design includes features like large, expansive windows and flat (low-sloped) roofs. Both styles can be found in the hills and lowlands of the Bay Area.

In terms of how roofing materials differ and which type of roof is easier to repair, there are a number of things to consider. Roof pitch can determine whether one type of roof covering, say composite shingles, will work. If the pitch or angle of the roof is below a certain amount, you might have to use a single ply membrane system, like Duro-Last.

But What is Roof Pitch Anyway?

Here is where your math comes in. When someone remarks on the pitch of a roof, they are referring to the angle, slant or slope of your roof. A roof with the least pitch would be a flat roof.

The pitch is measured by a simple formula. Wikihow.com gives a detailed explanation of the formula for roof pitch.  Simply put, the pitch is determined by taking a level (18” to 20”) and a measuring tape into your attic (if you have one) and placing it against the bottom of a roof rafter, holding it so it is absolutely level. Make sure you can see the 12” mark on your level. Take your measuring tape at that 12” mark and measure up vertically, to the underside of the rafter. That number, whatever it is, will determine the rise of your roof. If your tape measures 4” the pitch formula is 4:12, which makes it a low-slope.

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Categories describing roof pitch are loosely defined by the slope:

  1. Flat– That may actually be a misnomer, because no roof is completely flat, since they need to have a slight angle to enable rainwater to drain off the roof. Still, they can get away with a minimum pitch of only ½:12 inches to 1:12 inches, with proper drainage techniques.
    • In in Marin’s Terra Linda and the Lucas Valley areas, you’ll find entire neighborhoods filled with Joseph Eichler homes, known as the California Modern style, built between the late 1940s and early 1970s. Signature features of these homes were large ceiling to floor windows and flat or low-slope roofs.
    • Eichler homes and those of similar design and very minimal pitch often suffer from leaks due to standing water, so the proper roofing material is crucial.
  1. Low-slope–As with a “flat” roof, low-slope roofs also may require special attention to techniques and materials to promote proper drainage and prevent leaks. You have ease of access with flat and low-slope roofs. They are easy to walk on, but most of them shouldn’t be walked on by people who don’t know what they are doing, as the roofing materials themselves can be damaged by too much foot traffic. Low slopes are much less efficient at allowing the run-off of rain and snow. Low slopes have a pitch of between 1:12 to 4:12 inches.
    • Modern architectural design embraces low-slope roofs to dramatic effect. When paired with open beam ceilings, large windows that diminish the border between indoor and outdoor living and clean, unencumbered lines, the appeal often outweighs any concerns about extra maintenance or leaks.
    • On the topic of extra maintenance, flat and low-slope roofs do require that plant debris, from leaves, small branches or pine needles be removed on a regular schedule. Otherwise, the debris can cause standing pools of water, mold and damage to the roofing material resulting in leaks. The trick is to remember that the less you walk on your roof, the better. So using techniques, like gently blowing the debris off from a ladder, rather than standing and sweeping will extend the life of your roof.
  1. Medium-slope– This slope is the most common. You’ll see them in the flatlands and on the hillsides. They provide both ease of access, stability and enough of a downslope for runoff. Their pitch is between 4:12 to 9:12 but the most familiar have a slope of 6:12.
    • Different geographic regions may fair better with one roof slope than another, but this is the one that works best in most geographic areas. Even with the varied microclimates you find in Marin and Sonoma counties, the medium-sloped roof is an enduring feature on most homes. It can withstand the vagaries of hot dry summers, rainy, windy winters and the wind and fog of the coastal areas.
  1. Steep-slope– Roofs with steeper slopes often require extra fasteners and can be very challenging or even impossible to walk on. We don’t see many buildings with severely steep sloped roofs in the San Francisco Bay area. They can add a decorative charm to a home but cost more to install and maintain. A steep slope is any pitch above 9:12.
      • Steep-slope roofs are more common in certain climates in Europe and occasionally in the mountainous areas of the Sierras. Extremely sloped roofs, with a pitch of 12.12 or 45 degrees, are rare but not unheard of in both the mountains and the flatlands.
      • Aside from the decorative appeal, they serve a purpose which is why steep-sloped roofs are more common in the mountains. In geographic areas that receive heavy snowfall, the extreme angle provides little purchase for the snow to cling to and can’t build up to dangerous levels. Wet snow can add so much weight to a roof, causing less sloped roofs to collapse under the added pressure.

Roof pitch can be a health and safety issue on homes in geographic areas that experience heavy snow and rain. A steep slope to a roof makes it more difficult for wet snow to accumulate and put undue stress on your roof. That isn’t an issue in the Mediterranean micro-climates of the San Francisco Bay Area.

However, heavy rains, like those we experienced in Marin County in late 2018, pooled and accumulated on a flat commercial roof on the Home Goods store in San Rafael causing it to collapse. The store remained closed for almost a full year.

Knowing something about roof pitch will come in handy when envisioning that addition, or remodeling job for your home or even something as simple as choosing the right skylight for installation.

Conferring with an architect or contractor is always a wise option before making major decisions about moving forward with a project:

  • Knowing the difference between a sloped and pitched roof, you’ll be better prepared to discuss with your architect or contractor, why you might prefer one over the other. That will help to guide the process.
  • If the way a new addition looks is more important than the added expense or maintenance, you won’t be deterred.
  • However, if budget restrictions impact the initial outlay of a project, and the ongoing yearly maintenance, you’ll be making a wise investment by choosing a design that meets your needs and is affordable.

The Professional Roofers at Booth And Little are Here To Answer Your Questions

If you are designing a home improvement project that involves roofing or planning a rainy-day fund for a reroofing project, the team at Booth and Little Roofing are happy to discuss your roofing questions. Contact us today for all your roofing needs.

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