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Installing Asphalt Shingle Roof

Understanding the Minimum Asphalt Roof Slope

Asphalt shingles are an effective roof material for sloped roofs that can be used on slopes as low as 2:12. Concerning shingle application, roof slopes from 2:12 to 6:12 are called low slope roofs, while roof slopes of 6:12 or greater are considered to be standard slopes. Asphalt shingles should never be applied to roof slopes below 2:12, this is lower than the minimum slope of a metal roof so ensure to check the different minimums for each roofing material.

When installing asphalt shingles on a low slope roof, after the manufacturer’s application instruction has been completed, an extra underlayment with a specific method for application is required. As it is a lower slope, these styled roofs tend to allow more water to enter, primarily because of severe ice dams and harsh rain. The need for underlayment help to enhance the water-shedding element of the roof system. More about asphalt shingles 101 here.

Minimum Slope of an Asphalt Roof  

What is a Roof Slope?

A roof slope is defined by the rise-over-run ratio. For example, if a roof rises 4 inches over a horizontal distance of 12 inches, it's defined as having a 4:12 slope, (which means 4 inches of rise for every 12 inches of run). While "roof pitch" is a related term, it's technically different and won't be covered here.

You can measure your roof slope from the underside of the roof deck at an accessible point, like the rake, using a tape measure and basic geometry. There are also smartphone apps for this purpose, and shingle manufacturers often provide pitch estimator cards for a quick roof estimate.

A handy roof slope estimator is useful in determining if your roof's slope is too low for shingles. In North America, most residential roofs are built with slopes ranging from 4:12 to 9:12. Roofs on the lower end (about 4:12 to 6:12) are easier to walk and work on, but always use proper safety gear and precautions.

Steeper roofs display shingles more prominently, making them more suitable for premium designer styles. Shingles on steeper roofs also weather more slowly due to their angle to the sun's rays.

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Related: What Are The Different Types of Shingles: How To Choose The Best Shingles for Your Home

Asphalt Roof Slope FAQs

Here are a handful of commonly asked questions about the minimum slope of an asphalt roof:

What is the minimum slope for an asphalt roof?

Since asphalt shingles aren't designed for holding water, the manufacturer's instructions and building codes require a minimum of a roof slope of 2:12.

Can you shingle a 1 pitch?

No, never install asphalt shingles to a roof slope that's less than 2:12. This will cause long-term problems with your roof in the future, such as pooling and premature breakdown of your asphalt shingles.

What can I put on a 1/12 pitch roof?

While you can't install apshalt roofing on a 1/12 pitch roof, we recommend using Built-Up roofing (or tar-and-gravel or BUR roofing) instead.

If at any point you have a question about your roof's slope, be sure to reach out to the experts at LOA Construction today! Here are some reasons to choose a professional for your residential or commercial roof.

Measuring Asphalt Roofing  

Questions on Understanding Asphalt Roof Slopes? Contact Us!

If you have inquiries on asphalt roof slopes, roof repair, maintenance, what's the best time of year to install a roof, the longest lasting roofs for inclement weather, and more, our professional roofers are here to assist! Our friendly team has decades of combined experienced in the roofing industry and can provide a prompt roofing inspection. Besides asphalt shingle roof types, we are also skilled in metal, tile, TPO, EPDM, and more.

We are the asphalt shingle experts in Austin, Houston, San Antonio, and Belton, Templete, and Killeen! With years of experience, we are a trusted source in the community for the best asphalt shingle replacements, repairs, hail damage repair, roof coatings, emergency services, and more for homes and businesses.

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