Metal roofs have become really popular over the last few years and are starting to emerge from the shadow of the ever-popular asphalt shingles. Metal roofing systems have incredible strength, last much longer than other roofing materials, and are available in a variety of color options.
But even with all these benefits, many homeowners still face a dilemma. Metal roofs are typically associated with sloped or pitched roofs, where their installation is straightforward. So does this transfer to other roof designs, specifically, flat roofs?
If you are a flat roof owner and are wondering, can I install a metal roof on a flat roof? You are in the right place. We will answer this question and more in this blog post.
What Are Flat Roofs? Are They the Same as Low-Sloped Roofs?
When we talk about flat roofs, many homeowners believe that, because of their name, these roofs are completely flat. This is not true. Contrary to the name, flat roofs aren’t completely level. They typically have a slight slope (usually about ¼:12 or 1/4 inch per foot) to allow for water drainage. This minimal pitch is what distinguishes them from traditional sloped roofs.
So all flat roofs can be categorized as ‘low-sloped’ roofs, as it’s a pretty general term, however not all low-sloped roofs are flat roofs. Low-sloped roofs have a better slope than flat roofs. For instance, a low-sloped roof can have a slope more than ¼ inches per foot and can even be as high as 3:12 (3 inches per foot)
Can You Install A Metal Roof On A Low-Sloped Roof?
To answer the question, yes, you can install a metal roof on a low-sloped roof. However, when it comes to flat roofs, there are challenges and we generally don’t recommend it.
Why Installing Metal Roofs On Flat Roofs Is Difficult
While metal roofs offer numerous benefits, their installation on flat or low-slope roofs presents unique challenges. Here are some problems you may face:
- Metal roofing systems are typically designed for steeper slopes where water runs off quickly. On flat or low-slope roofs, water tends to pool, increasing the risk of leaks and water damage.
- Standing water on a flat roof can more easily penetrate these seams, which are exposed in traditional metal roofs.
- Metal expands and contracts with temperature changes. On a flat surface, this movement can stress the fasteners and seams more than on a pitched roof.
- Proper installation on a flat roof often requires specialized techniques and materials, such as enhanced underlayment or a different paneling system, making the process more complex.
What Do Building Codes Say?
There are certain building codes that govern how roofs on residential properties are constructed. Adherence to these codes is necessary, and your roofing contractor should make sure that your roof is built in adherence to them.
The International Residential Council (IRC) has several codes for roofing assemblies that specify the slope required for a metal roof.
According to Section R905.10.2
- The minimum slope for “lapped, non-soldered metal roofs” without lap sealant should be at least 3:12.
- The minimum slope for “lapped, non-soldered metal roofs” with lap sealant should be at least ½:12.
- The minimum slope for a standing seam metal roof should be at least ¼:12.
So if your flat roof does not meet one of these requirements, you cannot install a metal roof.
I Still Want To Install A Metal Roof, What Are My Options?
If your roof slope is negligible, but you still want to install a metal roof, there are some ways to do so. Here are some things to consider:
Retrofit Framing System:
A popular solution is to retrofit your flat roof. This is a practice in which you install a lightweight steel framing system over your existing flat roof. This creates a slight pitch, typically around ¼:12 or more, which is permissible to install a metal roof. The slope also allows for better water drainage. Metal roofing panels can then be installed on this new framework.
Retrofitting is now becoming more common due to its several benefits. They can extend the life of the existing roof by providing better drainage and ventilation, as well as increasing energy efficiency.
Specialized Low-Slope Metal Roofing Systems:
Some manufacturers offer metal roofing products specifically designed for low-slope applications. These systems often feature:
- Mechanical seaming for watertight connections
- Higher rib profiles to enhance water shedding
- Special sealants and gaskets at the seams
Install A Standing Seam Metal Roof:
There are two main types of metal roofing systems available: standing seam panels and corrugated panels. The former is much better for flat roofs.
Standing seam roofing systems offer a robust solution for very low-slope applications, including roofs with pitches as minimal as ¼:12. These systems feature thicker, more rigid panels that provide enhanced strength and durability.
A key advantage is their hidden fastener system, which uses specially designed clips to secure the panels without penetrating the metal surface. This clip system not only ensures water tightness but also allows for thermal expansion and contraction, reducing the risk of leaks and improving long-term performance. The raised seams between panels further aid in water shedding, making a standing seam metal roof an excellent choice for those determined to install a metal roofing system on a nearly flat surface.
Tapered Roof Insulation
Another effective strategy for improving drainage on flat or low-slope roofs is the installation of tapered insulation. This method involves adding insulation boards that are thicker on one side, creating a slight slope where none existed before.
Tapered insulation can be installed beneath the metal roofing system, providing a stable, sloped surface for the metal panels. This combination of tapered insulation and metal roofing panels not only addresses drainage issues but also enhances overall energy efficiency.
Other Alternatives
While the methods we talked about above make it possible for you to install a metal roof on a flat roof, there are some concerns too.
Installing framing or tapered roof insulation can be quite expensive. Also, these need specialized equipment and professional roofing contractors which can further increase the cost. But don’t worry, there are several other materials that can protect your roof well.
TPO (Thermoplastic Olefin):
TPO is a single-ply roofing membrane that offers excellent energy efficiency and UV resistance. It’s lightweight, reflective, and can be heat-welded at the seams for superior waterproofing. TPO is also resistant to mold growth and chemical exposure.
EPDM (Ethylene Propylene Diene Monomer):
EPDM is a synthetic rubber roofing membrane known for its exceptional durability and longevity. It’s resistant to UV radiation, ozone, and extreme temperatures. EPDM is also easy to install and repair, making it a cost-effective choice for flat roofs.
Modified Bitumen:
Modified bitumen combines asphalt with plastic or rubber polymers for enhanced performance. It offers excellent tensile strength and flexibility, making it resistant to tears and punctures. This multi-layer system provides robust waterproofing and can withstand foot traffic well.
Trust Our Flat Roofing Experts
As we can see, the answer to the burning question, can you put a metal roof on a flat roof, is yes. However, it is important to hire a roofing contractor with the necessary experience.
If you are looking for a roofing company that has expertise in installing quality metal roofing systems, look no further than the team at A. Fricker Roofing and Waterproofing. We also install other flat roofing materials such as TPO and EPDM. Contact us today at (918) 402-7167 to learn more about us.
