When constructing the roof of your house, you might have heard the term “slope.” If it’s your first time hearing the word, the slope of a roof refers to its incline, which is a ratio of its vertical rise to the horizontal run. Basically, the slope determines how steep the roof is. Knowing your roof slope would help you choose an option and design for your home. 

If you’re considering having a metal roof system, perhaps you’ve wondered what the standard or minimum slope requirements for metal roofing are. This mainly depends on the characteristics of the metal surfaces you use for your roof. To get into the specifics, read on to understand the recommended minimum slope for metal roofing. 

Why it’s important

Before getting to the details, it’s best to first fully understand why it’s vital for you to know about the minimum slope for your roof structure. For other types of roofing materials, the slope would depend on the design or aesthetic that you’re going for. For example, some people prefer having steep-slope roof systems, while others have existing low-slope roof systems. It’s the same for metal roof systems. Besides this, though, having the proper slope for your metal roof helps you avoid certain factors that can ruin the roofing panels. 

Weather factors

You need to be careful of certain weather conditions that can damage your roof. Specifically, you should look out for heavy snowfall and rainfall. Following the minimum requirements for metal roofs helps prevent roof system failures by removing excessive water and heavy snow. 

While some types of metal roofing have more resistance to water damage, you still need to know the minimum slope that’s suitable for the roofing material. Having the right slope prevents ponding water and helps the removal of water by letting it run down from the metal roof surface and toward the gutter. 

Similarly, having the proper slope for your roof helps snow run off the surface instead of building up on your house. If your roof is way beyond the minimum slope, heavy snowfall might cause snow to build up. This buildup of snow can strain the roof panels, damaging these and your house. 

Dirt collection

Since your roof is exposed to different environments, dirt and other rubble can gather, leading to molds or rotting. A suitable roof slope ensures that the surface does not collect these pieces of dirt as easily as they could slide off. This allows you to minimize roof repairs and cleaning. 

Ventilation

Finally, having the right roof slope also means proper ventilation for your house. Especially if you have an attic, a sufficient roof slope ensures enough air circulates in your home, making the space feel less humid. 

Minimum Slope for Metal Roofing

Now that it’s clear why knowing the appropriate roof slope is important, you should then know what the minimum slope for your metal roof is. This value depends on the roofing project or roofing system for your house. 

The National Roofing Contractors Association (NRCA) and International Residential Code (IRC) lay out some guidelines and recommendations for the minimum slope for different kinds of metal roofing. 

  • Metal roof panels with non soldered seams, without lap sealant – 3:12
  • Metal roof panels with non soldered seams with applied lap sealant – ½:12
  • Standing-seam metal roof panels – ¼:12
  • Metal roof shingles – 3:12

As the minimum slope varies, it’s important to know about the various kinds of metal roofs and materials you can use when constructing your home’s roof. You have a wide range of options available now, especially with metal roofs since this has become a more popular and common type of roofing over recent years. 

Read more: A List of Roofing Materials to Consider for Roofing a House

Measuring the Slope

The slope of your roof should ideally follow the minimum requirement before it’s even constructed, but there are cases where measuring the slope to ensure it’s correct might be needed. It’s recommended that you hire a roofing contractor as they have the experience level and equipment to make this process easier, especially if you’re dealing with a complex roof design. However, it is still possible to do this yourself to get a pretty accurate measurement. 

You’d need a level, tape measure, and a pencil for this. First, from one end of the level, measure 12 inches and make a mark using your pencil. Next, go to your house’s attic and place the end of the level against the lowest edge of a roof rafter. 

Holding your level horizontal, use your tape and place it at the 12-inch mark. Next, measure the distance vertically between the level and the rafter – this measurement is the number of inches the roof rises in 12 inches. For example, if the distance between the level and the roof is 5 inches, then the slope is 5:12. 

Minimum Slope for Metal Roofing FAQs

Can you put metal roofing on a 1/12 pitch?

Yes. Very low roof pitches with low angles, like 1/12 to 3/12, do exist. This makes your house roofing appear flat. If you plan on using metal roofing for a house with a 1/12 pitch, it’s recommended to use standing-seam metal roofs. 

What is the minimum pitch for a corrugated iron roof?

The minimum correct roof pitch for a corrugated roof is 5° or 1.05/12. This relatively higher pitch is required to avoid the pooling of water on one area of the roof. 

What type of roofing is best for a low-pitch roof?

As mentioned previously, you can use standing-seam systems for low-pitched roofs (2.5/12 to 19/12) if you want to use metal. For other materials, you can also consider going for clay or cement tiles, single-ply roofing, or roll roofing, depending on how low the roof pitch is. 

What is the minimum slope for a shed roof?

For sheds, you’d usually expect to have low-slope roofs. If you’re going for metal roof systems, which can handle low pitches that may be suitable for your shed, the recommended minimum pitch is ¼/12. 

For other measurements, this would depend on the material you’re going to use for your shed roof, which can then be affected by different factors, including the purpose of your shed, climate, and your wanted design. 

Knowing the correct roof pitch and slope for your roofing system is crucial to ensure that your roof is ideal for your house and its location. Whether you want to have a lapped, non-soldered seam metal roof or standing seam metal roofing, you now know the best slope to look out for to have successful metal roofing systems. There are many reasons why people want to use metal roofs, and understanding these details about metal roofing can get you one step closer to finishing your dream house.