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What Is the Minimum Slope Consideration for an Asphalt Shingle Roof?

Mar 14, 2019

Shingles Roofing

The asphalt shingle roof is the widely used roof covering in North America. This roof is resistant to extreme weather conditions and can add great value to your home. People choose this roof over other roofing options due to its easy installation and adaptability. Asphalt roofs are available in many colors and designs. Home designs not only include angled or steeper roofs but they may include a roof with a minimum slope.

What is the minimum slope requirement for an asphalt shingle roof?

Some manufacturers recommend 4:12, but the actual minimum is 2:12. The slope of the roof is measured in inches of vertical rise of the roof divided by the horizontal run of the roof. In 2:12 slope, the roof rises 2 inches for every 12 inches of horizontal run.

What is the “roof slope”?

The rise-over-run ratio is called the roof slope. If a roof slope rise is 4 inches when measured 12 inches along the bottom of the horizontal run, the roof slope is said to be 4:12. You can measure the roof slope either using tape or smartphone applications. The asphalt shingle roof contractors provide pitch estimator cards to measure the roof slope. A user-friendly roof slope estimator can help you measure the roof slope accurately for shingles.

What is the best slope for a roof?

For most home designs, the roof slope can be between 4:12 and 8:12. The best slope for a roof varies according to the type and purpose of the roof.

What is the minimum slope requirement where shingles can be installed?

The minimum slope for an asphalt shingle roof is 2:12. The roof pitch between 2:12 and 4:12 is considered as a low pitch roof, so shingles can be installed in the roof slope between 2:12 and 4:12.

Why is 2:12 the minimum?

Considering the roof slope requirement is important. For example, if it is a very low slope, water including snowmelt or rainwater drains slowly, and this increases the chances of lateral water movement around the shingles. Roof manufacturers recommend the roof slope between 2:12 and 4:12, as this is the lowest slope requirement for standard shingle installation. Shingle roofing is not watertight, and the minimum slope roof can work its way up between the laps. This is the reason why 2:12 is the minimum.

Asphalt shingles are the most-preferable roof covering option because of their:

  • Excellent weather resistance capacity
  • Affordability
  • Ease of installation
  • Adaptability
  • Wide range of designs and colors

Although asphalt shingles are widely accepted, your roof slope determines whether it is the best choice or not. Read on to learn more about the minimum slope for an asphalt shingle roof.

What Exactly Is “Roof Slope”?

The roof slope is the rise-over-run ratio. If a sloping rise is 4 inches when measured 12 inches along the horizontal roof truss’ bottom, the roof slope is said to be 4:12, meaning 4 inches of rising per 12 inches of run. You can measure the roof slope using tape or smartphone applications. Roofing contractors provide pitch estimator cards to measure the minimum slope for shingles accurately.

Types of Asphalt Shingles

Three-Tab Shingles – The most economical and popular option, distinguished by tabs and cutouts along their long lower edge. When installed, each shingle looks like three separate pieces. Architectural Shingles – The laminated additional asphalt layer on their lower portions create a contoured, dimensional look. Asphalt sealant bonds the layers, strengthening their waterproof capacity. Although long-lasting, these shingles are not recommended for low-sloped roofs that are prone to wind-driven rain.

Normal Roof Slope for Typical Installation

4/12 inches and above is the normal slope for all roofs, including asphalt shingle roofs.

Low Sloped Roof Shingle Installation

Shingles can be installed on low-sloped roofs with a pitch of 3/12 inches. However, it will require additional layers under the shingles, such as a double layer of asphalt-saturated felt paper or a single layer of ice and water shield.

Can a Roof Be Too Flat for Shingles?

Yes! The minimum pitch for asphalt shingles is 2/12 inches, and anything less than this is too flat for shingles.

Can Asphalt Shingles Be Used on a Flat Roof?

Asphalt shingles are not recommended for a flat roof, as shingles cannot be properly sealed if a roof has a pitch less than 2/12 inches, leading to water leaks. Therefore, low-pitched roofs should be covered with flat roof materials, and then shingles can be installed for aesthetic purposes.

What Is a 3/12-Inch Pitch?

A 3/12-inch pitch means a roof with 3 inches of rise, per 12 inches of horizontal run.

What Is the Difference Between Three-Tab Shingles and Architectural Shingles?

Characteristics Three-Tab Shingle Architectural Shingle
Physical Composition Thinner Thicker
Aesthetics Looks flat Looks dimensional
Wind Ratings Winds up to 60 mph Winds between 80 and 120 mph
Lifespan It lasts 7 to 10 years under severe weather or 12 to 15 years under mild climates Lasts 18 to 20 years on average, or up to 30 years under optimal conditions
Cost Inexpensive Slightly expensive, but the cost is worth its look and durability

How Long Do Asphalt Shingles Last?

Depending on the type, weather condition, and environmental factors, asphalt shingles can last up to 15 to 30 years.

Therefore, asphalt shingles can be installed on your roof if it has the required minimum slope of 2/12 inches.

Are you looking for the best commercial roofing company in California for roof replacement services? Contact Applied Roofing Services today at 714-632-8418, to get a quote online for our comprehensive commercial roofing solutions.

If you are considering asphalt shingle roofing or re-roofing, contact us!

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