The FMP Blog

Understanding Metal Roof Pitch Requirements

  • June 15, 2024

Metal roofing is gaining popularity, and for good reason. It’s durable, affordable, and environmentally friendly. It’s also visually appealing — polished, sleek, and modern. 

Like any construction project, there are a variety of important factors that must be considered when deciding on the minimum pitch of your metal roof.

We cover all of that – and more – here.

Table of Contents

1. What Is The Minimum Pitch For A Metal Roof?
2. What Is Roof Pitch, And Why Does It Matter?
3. What Are The Different Types And Styles Of Metal Roofs?
4. What Types Of Metal Are Used For Metal Roofing?
5. What Factors Should You Consider When Determining The Pitch Of Your Metal Roof?
6. How Do You Choose The Right Roof For A Metal Building?
7. How Do You Replace A Traditional Roof With A Metal Roof?


What Is The Minimum Pitch For A Metal Roof?

To truly capitalize on the benefits of metal roofing and preserve it for years to come, it must be laid at the appropriate pitch. Depending on the type of metal roof used, the pitch requirements differ

  • The minimum pitch for interlocking metal roofs is a 3-inch rise for every 12 inches (1 foot) of run, represented in a ratio of 3:12. 
  • Corrugated metal roofs can have a lower pitch of 1 ⁄2:12, especially when large single sheets are used, rather than smaller sheets adhered together.  
  • For roofs made from metal shingles, the recommended pitch is at least 4:12.

What Is Roof Pitch, And Why Does It Matter?

Roof pitch refers to how a roof rises or how gradual or steep the angle of a roof is. If you think about traditional adobe buildings, there’s no pitch. The roof is just a flat surface.

Compare that with a steep-slope roof such as an A-frame. The pitch is so abrupt that it resembles its namesake, the capital letter A.

Pitch is measured by vertical rise (the angle that it’s set) over horizontal run (the length of the roof) and the ratio is represented as rise:run

Determining the appropriate pitch for your metal roof involves several components, which we’ll discuss in more detail later.

The main reason why pitch is important is roof preservation: a metal roof with a low pitch is far more likely to deteriorate prematurely. It’s highly susceptible to leaks, since a low pitch makes it easier for ponding — the term used for water that pools due to no slope to facilitate runoff.

Another consideration is cost. A roof with a steep pitch, such as the aforementioned A-frame, will require more roofing material than one with a lower-angled pitch.  

Additionally, if a roof pitch is low in an area that gets heavy snowfall, the weight of that snow buildup and accumulation may add unnecessary strain on the roof and housing structure, which can lead to damage.

Learn more: Snow Load and Large Roofs in Commercial Construction


What Are The Different Types And Styles Of Metal Roofs?

Those who picture the old semi-rusted tin roofs when they think about metal roofs may be surprised to discover the variety of styles modern metal roofs come in. We’ll go over some of the more popular ones here. 

(For those installing a metal roof in wetter climates, applying a lap sealant around the seams and joints provides extra protection against leaks.)  

Standing Seam

A standing seam roof is made of panels that average about 16 inches in width. They are flat in the middle and have two raised seams on each side, running lengthwise.

Because the concealed fastener system — the fasteners that bind the metal roof panels together — are not exposed, it’s watertight. If properly built and ventilated, this style of metal roof can last up to 50 years.

Corrugated

Corrugated metal roofing is what many people think of when they think of metal roofs—wavy galvanized steel sheets that develop a rusty patina over time, and are commonly seen on older sheds and industrial-type buildings.

Due to recent innovations, this type of metal roof is becoming less common. It doesn’t hold up to weather as well as other types of metal roofs. Also, when it rains, it’s pretty noisy.

Metal Shingles 

For those who are not completely sold on the appearance of metal roofs but who love their durability, metal shingles are the way to go. They combine the appearance of traditional shingles with the durability of metal.

The cost varies depending on the type of metal shingle used. Due in part to the increased lifespan and durability, expect to invest more in metal shingles than you would for traditional or asphalt shingles.

Stone Coated 

A popular option for those who aren’t sold on the appearance of traditional metal roofs, stone coated metal roofs are dusted with a fine coating of stone granules to give them the look of traditional shingles. 

They can be stamped into different patterns, mimicking the look of various shingle options, such as clay and even wood.


What Types Of Metal Are Used For Metal Roofing? 

As well as styles of metal roofing, you can also get metal roofs made from different materials. Let’s take a look at a few of them and weigh their pros and cons.

Zinc

Zinc is a popular choice for many reasons. It’s long-lasting, lightweight, and — since it’s naturally occurring — completely recyclable. 

It’s also fire-resistant and low-maintenance. It naturally hinders the growth of mold, mildew, and other types of fungus.

Zinc’s malleability makes it easy to shape into different designs, such as curved patterns.  

However, that malleability also makes it vulnerable to denting; anyone living in a hail-prone area should be aware of this.

Additionally, it expands and contracts slightly, depending on the temperature. These fluctuations need to be considered during installation to allow for such expansion and contraction. 

Finally, zinc runoff from water shedding may stain asphalt or areas around the house, perhaps even the home itself, and should be mitigated if necessary. 

Aluminum

Similar to zinc, aluminum metal roofs are durable, lightweight, and eco-friendly. They are also fire-resistant and can be coated with different finishes to offset sun exposure, aid in cooling costs, and blend well with the color of the home.

Aluminum metal roofs cost a bit more than steel, and are also easily dented. In addition, they can be a bit noisy when it rains.

Copper

As one of the most durable options on the market, copper roofing stands the test of time; its lifespan extends well beyond a century. 

A copper roof is fire, pest, and mold-resistant and fares better in a hailstorm than some of the other metal roof types.

Copper also ages well, developing an aesthetically pleasing patina over time. This material is 100% recyclable, making it another eco-friendly choice.

These pros mean copper is more expensive than other metal roof options, and may even be susceptible to theft. Plus, it is a little heavier than other metal roof choices and might cause staining if there’s runoff. 

Additionally, copper expands and contracts significantly as temperatures fluctuate — a significant consideration that needs to be accounted for during installation (depending on the region). 

Galvanized Steel 

Many galvanized metal roofs are coated with zinc, which acts as a natural barrier against rust and makes the roof appear less industrial. 

Galvanized steel roofs have many of the same pros as the other options: they’re fire-resistant, environmentally friendly, low maintenance, and long-lasting. 

Many of the same cons apply as well: denting susceptibility, expansion and contraction fluctuating temparatures, and noise. In addition, there’s also the potential for rust and corrosion if not properly installed.


What Factors Should You Consider When Determining The Pitch Of Your Metal Roof?

It’s critical you consider all these factors to help determine the appropriate pitch when installing your roof:

Weather Conditions And Climate

minimum metal roof pitch requirements for snowy conditions

This is one of the most important variables that will help preserve your metal roof and maximize its lifespan. Not only does it affect the type of metal roof you choose, but it also plays a huge role in determining the appropriate pitch. 

If you live in an area with heavy precipitation, winds, and snow accumulation, opt for a steeper pitch. This allows the water and snow to run off and better offsets high winds.

Drier environments that don’t have such heavy winds are better able to withstand a less steep pitch.

Structural Factors

Another extremely important component related to determining the pitch of your metal roof is the structural factors. 

The pitch of the roof needs to be established in accordance with the home’s design and laid out in a way that preserves the integrity of the building without adding any unnecessary stress. 

Building Codes

Adhering to local building codes is an important aspect of any construction project. Codes cover things like the type of material used,  minimum pitch or slope requirements, and other building-related specifics.

Check with your local city or county officials for the codes that govern home construction in your area.

Roof Style And Building Aesthetics 

Style and aesthetics aren’t really structurally significant, but that doesn’t mean they should be dismissed entirely.

The wide variety of metal roof colors and styles makes it much easier to choose a roof that works well with all sorts of architectural designs. Weighing in the style of the home is another element to consider in determining both the pitch and the type of metal roof.

Just ensure that, first and foremost, the roof slope is able to mitigate the weather in the region, and is supported appropriately by the structure of the home.

Cost

Budget is a critical aspect of any project. Typically, the steeper the pitch, the more material used. Make sure that your budget covers both materials and labor.

The type of metal roof is another aspect affected by cost. When choosing the one that’s right for you, prioritize durability and longevity over aesthetics.


How Do You Choose The Right Roof For A Metal Building?

For homes and buildings made from wood, stucco, and other common structural materials, the metal roof and its pitch may be selected based on the nature of the building itself and the weather in that particular region.

If the building is made of metal, a common roof pitch is between 1:12 and 4:12. Typically, low slope roof pitches are used for metal buildings that also have metal roofs. However, flat roofs are not a great option since they impede runoff and are prone to water damage.


How Do You Replace A Traditional Roof With A Metal Roof?

Homeowners looking to replace an existing roof with a new one will be happy to know that a metal roof can usually be laid over the existing tile shingles.

This cuts down on the overall cost and time it takes to replace a roof. 

However, it’s important to check out a few things first.

For example, make sure that metal over shingles is allowed per local building and zoning requirements. If there are any existing leaks, those will need to be attended to first as well. Finally, confirm that the roof structure and overall foundation of the home are able to support the extra weight a metal roof will add.

If all these check out, it’s a good idea to lay out a protective barrier between the shingles and the metal roof to prevent the granules on the shingles from coming in contact with the metal, which may lead to premature corrosion.

Check with a roofing contractor to ensure this is a viable option.


Conclusion

For those looking for long-lasting functionality, a metal roof is the obvious choice. 

By closely adhering to the manufacturer’s installation instructions and considering climate, building codes, and the structural requirements of the home, a metal roof will likely be a one-time purchase. 

Contact FMP Construction today for help with your roofing renovation needs!

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