Why You Should Avoid Putting Shingles on a Flat Roof: Understanding Roof Pitch and Material Suitability

by William Jones / ⠀Experts / April 16, 2025

Choosing the right materials and techniques for your roofing can significantly affect the roof’s structure, longevity, and functionality. Shingles are one of the most common materials utilized in roofing projects. If you look around an average suburban neighborhood, the chances are high that most homes will have shingled roofs. However, a prevalent misconception is that roofing shingles, which are typically used for sloped roofs, can also be installed on flat roofs. This is entirely false, as the entire point of shingles is that they are interlocking and overlapping tools for use at a slanted degree.

As such, shingles are perfect for sloped roofs, but these elements that make them so effective for sloped roofs render them ill-fit for flat roofs. Shingles on a flat roof can lead to various problems that may jeopardize the roof’s integrity and the comfort of its occupants. To avoid such problems, hire experienced roofing experts such as Clearview Roofing and Construction. The team, including Chris Feniello, a roofing contributor, has decades of combined experience and expertise in the field and is prepared to guide you and ensure that your roofing project gets done with the correct materials.

Understanding Flat Roofs and Their Unique Challenges

Flat roofs with a pitch of 2/12 or less are designed to be almost level. They provide advantages such as easier maintenance access and additional usable space. However, for the benefits they bring, they also come with their unique challenges. A flat roof is an entirely different kind of roofing project, meaning that traditional roofing materials, like asphalt shingles, are ill-equipped to accomplish the job satisfactorily.

Flat Roof Problems

Water Drainage Issues

Due to their minimal slope, flat roofs are more prone to water ponding. Shingles are designed for pitched roofs, which allow water to run off easily. Conversely, flat roofs can accumulate water, leading to leaks and other damage. Even a slight pitch, like 2/12 (often still considered flat), fails to provide sufficient slope for effective water management.

Material Suitability

Asphalt shingles are asphalt-based and crafted to endure exposure to elements on sloped surfaces. They are designed to shed water rather than retain it. On flat roofs, they struggle with prolonged contact with standing water, UV rays, and various environmental factors as effectively as materials specifically engineered for flat roofing. This exposure to standing water can cause rapid deterioration of the shingles and lead to rusted nails, requiring quicker repairs and replacements than anticipated.

Installation Problems

Placing shingles on a flat surface can create challenges with proper adhesion and sealing, ultimately leading to failure. Flat roofs necessitate materials that can create a continuous waterproof barrier, such as rubber membranes, TPO, or built-up roofing. Shingles do not effectively seal joints, increasing the risk of leaks.

The 2/12 Pitch Perspective

Although a 2/12 pitch is not entirely flat—it equates to a 9.5-degree slope—the same risks are associated with it as those with truly flat roofs. Some may incorrectly believe that a slight pitch allows for using shingles; however, the fundamental principles remain the same.

2/12 Pitch Problems

Limited Water Drainage

Even with a 2/12 pitch, water can still collect in inadequate drainage areas. If shingles are installed, they may quickly become overwhelmed by accumulated water, resulting in leaks and moisture-related problems.

Potential for Ice Damming

In colder climates, snow and ice can quickly accumulate on lower-pitched roofs. Installing shingles on these roofs raises the risk of ice damming, pushing water under the shingles and into the building.

Warranty and Insurance Issues

Most asphalt shingle manufacturers specify that their products should only be installed on roofs with a particular pitch. Using shingles on flat or low-slope roofs can void warranties and lead to insurance issues if damage occurs.

Final Thoughts

Choosing the right materials is vital for preserving the integrity and value of any structure. Homeowners and builders should prioritize suitable roofing systems, like membranes or other flat-roof-specific materials, to ensure reliability, prevent leaks, and extend the roof’s lifespan. Consult with a qualified and experienced roofer, like Clearview Roofing and Construction, which has been serving Long Island since 1961. For more information on Long Island roof repairs, contact any local Long Island offices, such as Huntington, Rockville Centre, or Babylon, today.