Can You Put Shingles On A Flat Roof?

Short Answer

Shingles shouldn’t be put on flat roofs that have a pitch of less than 2:12 due to poor water drainage. Flat roofs need materials like EPDM, TPO, or modified bitumen for better water management and durability, especially in colder climates.

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Welcome to the Lindholm Roofing resource library. We often encounter a common query from our Chicagoland clients: “Can you put shingles on a flat roof?” This question is crucial, especially in a region like ours where architecture varies greatly. Today, we’ll dive into the feasibility, pros, and cons of using shingles on flat roofs.

What is a Flat Roof?

A flat roof, unlike traditional sloped roofs, has a very slight pitch, almost appearing flat. This design is prevalent in both commercial and residential structures in urban settings. Anything under a 2:12 pitch is considered to be a flat roof (2 inches of rise for every 12 inches of run).

The Traditional Approach

Traditionally, flat roofs are not adorned with shingles due to their unique structural and functional requirements. Unlike sloped roofs, flat roofs have minimal pitch, making them prone to water pooling and retention. This necessitates the use of specialized roofing materials that are designed to handle these challenges effectively.

In the past, flat roofs were typically covered with materials like tar and gravel, also known as built-up roofing (BUR). This method involves layering several sheets of roofing felt, embedded in bitumen, and topped with a layer of gravel. This gravel layer helps protect the roof from UV rays and provides a degree of fire resistance, making it a durable choice.

Can Shingles Be Used on Flat Roofs?

The short answer is, technically, yes. However, in most cases you really shouldn’t. Shingles are meant to be used where the roof pitch is greater than 2:12. It’s not a standard or recommended practice to use shingles on a flat roof for a few reasons:

  • Water Drainage: Shingles are designed for sloped roofs where gravity helps in shedding water. Flat roofs, with their minimal slope, can lead to water pooling, which shingles aren’t equipped to handle.
  • Warranty and Lifespan: Many shingle manufacturers do not warranty their products if installed on a flat surface. Additionally, the lifespan of shingles on a flat roof is typically shorter than on a sloped roof.
  • Building Codes and Regulations: Local building codes in Chicagoland may have specific requirements that prohibit the use of shingles on flat roofs.

Shingles Suitability for Flat Roofs

Flat roofs in Chicagoland present unique challenges when it comes to roofing materials. Shingles, commonly used for pitched roofs, are designed for slopes of at least 15° or 2:12. This slope is crucial for effective water drainage.

In contrast, flat roofs have a very small pitch, inadequate for draining water off shingles. When water sits on shingles, it can lead to leaks and significant damage. Understanding this limitation is key to selecting the right roofing material for flat surfaces.

Alternatives to Shingles for Flat Roofs

Given the limitations of shingles on flat roofs, there are several modern and more effective alternatives that homeowners and business owners in the Chicagoland area can consider:

  • Modified Bitumen Roofing: This is a modern take on the traditional built-up roof. Modified bitumen roofing involves layers of bitumen interspersed with polyester or fiberglass matting. This combination provides excellent durability, flexibility, and resistance to temperature changes. It’s often applied using heat, which creates a seal that is both water-resistant and durable. Homeowners favor it for its relatively easy maintenance and modern appearance.
  • EPDM (Ethylene Propylene Diene Monomer): EPDM, commonly referred to as rubber roofing, is a single-ply membrane known for its cost-effectiveness and durability. It’s extremely resistant to weathering, UV rays, and abrasions. EPDM is lightweight, making it a good choice for buildings with weight-bearing concerns. It’s also environmentally friendly, often made from recycled materials, and is fully recyclable at the end of its lifespan.
  • TPO (Thermoplastic Polyolefin): TPO roofing is another single-ply roofing membrane that has gained popularity for its energy efficiency. It reflects UV rays, helping to reduce cooling costs in buildings. TPO roofs are heat-welded at the seams, creating a watertight bond that is strong and resistant to leaks. It’s also resistant to mold growth, punctures, and chemicals, making it a low-maintenance option for commercial and residential buildings.
  • PVC Roofing: PVC roofing membranes are similar to TPO but are made from polyvinyl chloride. They offer excellent water resistance and are also resistant to fire and chemicals. PVC roofs are lightweight and can be installed over existing roofing materials in some cases, making them a versatile option.
  • Green Roofs: An increasingly popular choice, especially in urban areas, green roofs involve the installation of vegetation layers on top of a waterproof membrane. They not only provide excellent insulation and reduce runoff but also contribute to urban biodiversity and aesthetic appeal.

Roof Transition from Pitched to Flat

Many Chicagoland homes feature a combination of flat and pitched roofs. Achieving a seamless transition between these two types is vital for water management and preventing leaks. Roofers must be meticulous in creating a smooth junction.

A common error is placing flat roof materials directly on top of shingles, which can lead to water ponding at the transition and increased leakage risks. This area requires careful design to ensure water flows smoothly from the pitched part to the flat section.

Drainage Considerations

Proper drainage is paramount for flat roofs, especially in a climate like Chicagoland’s with its varied weather conditions. Both internal and external gutter systems must be designed to prevent freezing and accommodate the volume of water typical for the area.

For larger flat roofs, a siphonic drainage system might be necessary, offering efficient water removal while maintaining the property’s aesthetics. Consultation with a roofing expert is essential to determine the most effective drainage solution for your specific roof.

Insulation and Ventilation

Flat roofs over enclosed spaces, such as home additions or garages, require adequate insulation and ventilation, just like any residential roof. This is essential for energy efficiency and preventing moisture-related issues. Proper insulation ensures that the indoor temperature remains stable, reducing the risk of ice dams and condensation, which are common problems in colder climates.

Aesthetic and Color Matching

The appearance of your flat roof should complement your home’s overall aesthetic. Fortunately, modern roofing materials offer various color options, allowing homeowners to match their flat roofs with existing shingles. This coordination is key to maintaining curb appeal and ensuring a cohesive look. When choosing materials for your flat roof, consider the visual impact alongside functionality to achieve the best results for your home.

Expert Advice for Your Roof

At Lindholm Roofing, we believe in providing the best solution for your specific roofing needs. Whether you’re considering a new flat roof installation or maintenance for your existing roof, our team of experts is here to offer tailored advice and high-quality service.

Final Thoughts

While you technically can put shingles on a flat roof, it’s generally not advisable due to potential issues with water drainage, warranty concerns, and building regulations. Alternative materials like modified bitumen, EPDM, and TPO offer better performance and longevity for flat roofs in the Chicagoland area.