Are you considering a metal roof? Is your roof or a facet considered low slope?
There are a lot of things to consider before deciding if a metal roof is right for you. However, most homeowners don’t consider whether their roof fits the minimum pitch requirements for metal roofing.
This isn’t something roofers have control over, and for good reason. It’s actually a building code to prevent water damage and leaks.
For over 30 years, Bill Ragan Roofing has helped homeowners understand the intricacies of roofing, no matter how big or small. That’s why I’ll break down what you need to know about the pitch requirements for a metal roof.
This article answers the following questions:
- What is roof pitch?
- What’s the minimum pitch for a metal roof?
- What if your roof doesn’t meet the minimum pitch requirements for a metal roof?
- How much will a metal roof cost on a low slope roof?
What is roof pitch?
Roof pitch is simply a roofing industry term for the steepness (angle) of your roof, also called slope. It’s calculated by the number of inches or feet it rises vertically for every 12 inches or feet it extends horizontally.
Roof pitch will be in the form of a ratio, rise/extend horizontally. For example, a roof that is 4 inches (or feet) up for every 12 inches (feet) out is labeled a 4/12 pitch.
Your roof could have multiple pitches if it's complex, such as a low slope area or a different roof facet(s) with more or less steepness.
Knowing the pitch is important because it impacts a roof’s square footage, which greatly affects material and labor costs. The steeper a roof gets, the more roof surface area it creates.
What’s the minimum pitch for a metal roof?
According to section R905.10.2 of the 2021 International Residential Code, minimum slopes for metal roof panels shall comply with the following:
1.The minimum slope for lapped, nonsoldered-seam metal roofs without applied lap sealant shall be 3 units vertical in 12 units horizontal (25-percent slope).
2.The minimum slope for lapped, nonsoldered-seam metal roofs with applied lap sealant shall be 1/2 unit vertical in 12 units horizontal (4-percent slope). Lap sealants shall be applied in accordance with the approved manufacturer’s installation instructions.
3.The minimum slope for standing-seam roof systems shall be 1/4 unit vertical in 12 units horizontal (2-percent slope).
(Standing seam metal roof on a 2/12 pitch)
In layman's terms, a standing seam metal roof (seamed mechanically or by hand) can be installed on any roof over a .25/12 pitch (I recommend a .5/12 to be safe). If you go with snaplock standing seam panels (snaps on instead of seamed), your roof must be a minimum of a 3/12 pitch.
For exposed fastener metal roofs, the minimum roof pitch is at least a 3/12 (even if you apply a lap sealant). However, I don’t recommend this metal roof for low slope roofing simply because of potential leaks from the exposed screws.
What if your roof doesn’t meet the minimum pitch requirements for a metal roof?
Now you know the minimum roof pitch for a metal roof. So, are you out of luck if your roof doesn’t fit the requirements?
The answer is no, but you'll have to create more slope with a built-up roof system. A built-up roof (also called a tapered roof system) increases pitch by adding layers of tapered insulation boards to an existing low-slope or flat roof.
(Insulation boards being layered to create more pitch)
These boards vary in thickness, so they can be arranged to create the minimum pitch requirements for metal roofing. As the insulation boards are layered and fastened to the decking, a gradual and consistent slope will be created across the roof.
Once the desired pitch is created, your metal roof is ready to be installed. Just know that this will increase labor and material prices quite a bit.
However, the insulation boards also help with energy efficiency, condensation build-up, and reduce sound caused by rain.
How much will a metal roof cost on a low slope roof?
Metal continues to grow in popularity in residential roofing. However, cost is the one thing that stops homeowners from committing to a metal roof.
Unfortunately, it won’t be cheap. For labor and materials, a new steel standing seam metal roof costs around $16.00 per square foot.
It’ll be more expensive if you have to add tapered insulation boards to build the roof up to the required pitch. Just know that an exposed fastener metal roof is much cheaper at $4.50 to $6.50 per square foot.
However, this metal roof system is prone to leaks and needs consistent maintenance.
What are your other low slope roofing material options?
After reading this article, you now know everything you need to know about metal roofing and pitch requirements. If you want metal on a flat or low-slope roof, I recommend a standing seam metal roof system.
Unfortunately, the cost is a big pain point. This is especially true if you have to build up your roof’s pitch first.
Luckily, metal roofing isn’t your only low slope option. So, before making a final decision, you need to know what else is available.
That’s why I wrote another article breaking down the best roofing materials specifically for flat or low-pitched roofs.
Check out the 4 Best Roofing Materials for a Low Pitch Roof to learn which low-slope roofing material is right for you.
