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Understanding the Minimum Slope Required for Asphalt Shingle Roofs

Posted on March 15, 2024

minimum slope for asphalt shingles

There are varying slope requirements for different roofing materials and designs. Some roofing materials require a steeper slope for better functionality, while others can be installed at low slopes. The same principle applies to asphalt shingle roofs. Asphalt shingles are installed on pitched roofs, and have a minimum to maximum slope. But below and above that acceptable range, asphalt shingles don’t function properly. 

In this blog post, we will explain the minimum slope for asphalt shingles as well as the ideal slope for certain roof designs so you can ensure proper installation. Continue reading through the end to make an informed decision for your shingle roof. 

What Is The Minimum Slope For Asphalt Shingles?

Asphalt shingles are the most popular roofing material in the U.S. They have earned an immense reputation throughout North America for their ease of installation, affordability, and availability. However, like any other roofing material, asphalt shingles have slope requirements that allow them to function properly without damaging the structure below. 

In general, the recommended roof slope for shingles is 4:12. However, the acceptable minimum slope for asphalt shingles is 2:12. Below this slope, installing asphalt shingles isn’t recommended. This is because shingles are meant to be installed on sloped roofs, generally above 4:12, as this provides greater support and enhanced water flow. 

You can install shingles on low slope roofs with a slope of as low as 2:12, but you may have trouble with effective water drainage or water pooling on the roof. This is because gravity is the main driving force of water runoff and on low slope roofs the horizontal effect of gravity is reduced, resulting in slower drainage. This can result in water pooling or seeping under the shingles and major damage to the roof. 

Therefore, when installing a new roof or replacing the existing shingles, you need to ensure that your roof meets and is above the minimum slope for asphalt shingles. 

minimum slope for asphalt shingles

The Most Common Roof Slopes For Asphalt Shingles

The best roof slope for your home is determined by considering many factors. Climate conditions, building codes and regulations, and the architectural design of your roof are a few major factors to keep in mind. 

In this section, we have explained the best roof slope for shingles for different architectural designs. 

1. 6:12 to 8:12

This roof slope range is common for residential buildings in the U.S. A roof design that features a steeper slope is the mansard roof. Mansard roofs present a distinctive appearance, as they feature two slopes on all four sides with a lower slope that is steeper than the upper slope. Because of this design, a steeper slope of at least 6:12 is needed. 

2. 4:12 to 6:12

A slope of 4:12 to 6:12 is ideal for asphalt shingles on hip roofs, striking a balance between efficient water runoff and architectural harmony. Hip roofs feature slopes on all sides, with each slope meeting at the top to form a ridge. They offer a more complex and visually appealing alternative to gable roofs, with all sides sloping downward to prevent water accumulation. 

3. 2:12 to 4:12 

This slope range is common for shed roofs, which feature a single surface sloping in one direction. A slope of 3:12 to 4:12 is suitable for asphalt shingles on shed roofs, balancing water drainage with the architectural intricacies of this design. 

Another suitable roof design for this slope range is a gable roof. A gable roof, characterized by its triangular shape, is one of the most common architectural designs. It features two sloping sides that meet at a ridge. This range provides sufficient water drainage while minimizing the risk of water infiltration and structural damage.

Also Read: 10 Best Asphalt Shingles Of 2024 According To Roofers

Best Roofing Materials For Low Slope Roofs 

But, if you have a low slope roof  (flat roof), there are better performing roofing materials on the market. Here is a quick overview of some of the options:   

1. Modified Bitumen 

Modified Bitumen

Modified bitumen is a popular choice for low slope roofs because of its flexibility, durability, and ease of installation. This type of roofing material is made up of asphalt-based sheets that are strengthened with fiberglass or polyester and modified with rubber for better performance. Modified bitumen roofs can withstand harsh weather conditions, UV rays, and punctures, making them ideal for low slope roofs. 

2. EPDM (Ethylene Propylene Diene Monomer)

EPDM Roof

EPDM, a type of synthetic rubber membrane, is commonly used on low slope roofs. Its exceptional resistance to UV rays, ozone, and weathering makes it an ideal choice for property owners. The installation of the EPDM process involves using large, seamless sheets of the roofing material that are mechanically fastened to the roof substrate. 

3. TPO or PVC

TPO Roof

Single-ply membrane roofing systems, such as thermoplastic polyolefin (TPO) and polyvinyl chloride (PVC), are becoming increasingly popular due to their exceptional waterproofing and durability properties. These roofing systems consist of a single layer of synthetic polymer material designed to withstand harsh environmental elements. 

TPO roofing systems, for instance, are made of a blend of thermoplastic and ethylene-propylene rubber that offers exceptional resistance to UV radiation, chemicals, and punctures. This roofing material is typically installed using one of three methods: fully adhered, mechanically fastened, or ballasted. 

Final Thoughts

Understanding the minimum slope for asphalt shingle roofs is important to ensure the long-term performance and durability of your roof. By maintaining an adequate slope, you can prevent water damage, preserve structural integrity, and enhance energy efficiency. 

Contact B&A Roofing In Mississippi For Your Roof Installation

If you want to install a roof but aren’t sure about the right slope, contact our professional team of roofers at B&A Roofing. The contractors at the company are proficient at handling any roofing project. Whether you want to install a new roof or replace the existing shingles, our skilled roofers have got you covered. Contact us today at (601) 520-3183 to consult our roofing professionals.

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