What Is A Flat Roof With A Slope Called?

Imagine having a roof that seems flat at first glance, but upon closer inspection, you notice a slight incline. Have you ever wondered what this type of roof is called? Well, look no further! In this article, we will explore the fascinating world of flat roofs with slopes and uncover their true identity. Curious? Let’s dive into the details and unravel the mystery behind this architectural wonder! A flat roof with a slope is commonly referred to as a “low-slope roof.” This type of roof combines the benefits of a traditional flat roof with the added advantage of a slight pitch or slope. Instead of having a completely flat surface, a low-slope roof has a gentle slope that helps to promote proper drainage.

What Is A Flat Roof With A Slope Called?


A flat roof with a slope is characterized by its nearly flat surface that is slightly inclined to allow water to drain off. While it may not have the same steep pitch as a traditional pitched roof, the slight slope of a low-slope roof is enough to prevent water from pooling and causing damage. This type of roof is commonly used in commercial and residential buildings where a completely flat roof is not feasible or desirable.


One of the main advantages of a flat roof with a slope is improved drainage. The slight pitch allows rainwater to flow off the roof, preventing standing water and potential leaks. This helps to extend the lifespan of the roof and reduces the risk of water damage to the building. Additionally, the slight slope offers better stability and resistance to heavy wind loads compared to a flat roof.

Another advantage of low-slope roofs is their versatility. They can be used with a variety of roofing materials, including modified bitumen, EPDM rubber, TPO, and PVC. This allows you to choose the material that best suits your needs and preferences in terms of durability, cost, and appearance.

Furthermore, low-slope roofs are energy-efficient. The minimal pitch of the roof allows for the installation of insulation, which helps to reduce heat loss or gain, leading to energy savings and increased comfort within the building. This insulation also helps to minimize sound transmission, providing a quieter indoor environment.


Despite their many advantages, flat roofs with slopes do have some disadvantages that should be considered. One potential drawback is the increased complexity of installation compared to a traditional flat roof or pitched roof. The slope must be carefully calculated and constructed to ensure proper drainage and prevent water ponding. Improper installation of the slope can lead to recurring water issues and damage to the roofing system.

Another disadvantage is the increased risk of leaks. While the slope helps promote drainage, it also introduces additional seams and joints in the roofing system, which can be potential areas for water penetration. Proper installation and regular maintenance are crucial to minimize the risk of leaks.

Additionally, low-slope roofs may require more frequent maintenance compared to other roofing types. Debris such as leaves, branches, and dirt can accumulate on the roof, hindering proper drainage and causing water to pond. Regular inspections and cleaning are necessary to ensure the roof’s optimal performance and longevity.

Types of Flat Roofs with Slopes

There are several types of flat roofs with slopes to choose from, each offering different characteristics and benefits. These include:

Modified Bitumen Roofing

Modified bitumen roofing is a popular choice for low-slope roofs. It is composed of multiple layers, including a base sheet, reinforced with fiberglass or polyester, and a surface layer of modified bitumen. The bitumen is modified with rubber or plastic materials to enhance its durability and resistance to weathering. Modified bitumen roofs are known for their excellent waterproofing properties and can be installed with a torch-down, cold-applied, or peel-and-stick method.

Built-Up Roofing (BUR)

Built-up roofing, commonly known as BUR, is a traditional roofing system that has been used for decades. It consists of multiple layers of bitumen and reinforcing materials, such as fiberglass or polyester felt. These layers are applied directly to the roof surface and are typically finished with a protective coating of gravel or a reflective coating. BUR roofs are known for their durability, longevity, and fire resistance, making them a reliable option for low-slope roofs.

EPDM Rubber

EPDM (ethylene propylene diene monomer) rubber is a versatile roofing material that is commonly used for low-slope roofs. It is a single-ply membrane that is installed in large sheets, minimizing the number of seams and joints on the roof. EPDM rubber roofs are lightweight, durable, and highly resistant to UV rays, extreme temperatures, and weathering. They are also cost-effective and relatively easy to install, making them a popular choice for both commercial and residential buildings.

Thermoplastic Olefin (TPO)

TPO roofing systems are becoming increasingly popular for low-slope roofs. They are made of a single-ply membrane composed of a blend of polypropylene and ethylene-propylene rubber. TPO roofs offer excellent resistance to UV radiation, chemical exposure, and punctures. They are also highly energy-efficient, reflecting sunlight to reduce heat absorption and contribute to lower cooling costs. TPO membranes are typically installed in large sheets, minimizing the number of seams and making them less vulnerable to leaks.

PVC Roofing

PVC (polyvinyl chloride) roofing systems are another option for low-slope roofs. They consist of a single-ply membrane made of PVC, which offers excellent durability, flexibility, and resistance to chemicals and UV radiation. PVC roofs are known for their superior weathering properties, fire resistance, and ease of maintenance. They are also highly reflective, contributing to energy efficiency and lower cooling costs. PVC membranes are typically installed in large sheets, minimizing seams and potential areas for leaks.

What Is A Flat Roof With A Slope Called?

Installation of Flat Roofs with Slopes

The installation process for a flat roof with a slope involves several key steps to ensure proper functionality and longevity. These include:

Creating the Slope

The first step in installing a flat roof with a slope is creating the necessary pitch. This can be achieved using various methods, such as tapered insulation or structural slope systems. Tapered insulation involves adding layers of insulation that are tapered to create the desired slope. Structural slope systems, on the other hand, use built-up slopes that are constructed with materials like lightweight concrete or gypsum board. The method chosen will depend on factors such as the building’s structure, budget, and desired slope angle.

Membrane Installation

Once the slope is constructed, the roofing membrane can be installed. The type of membrane chosen will depend on the specific roofing material selected. For instance, modified bitumen roofing typically requires torching the membrane down, while EPDM rubber and TPO membranes are typically adhered or mechanically fastened to the roof. Proper installation techniques must be followed to ensure a watertight seal and minimize the risk of leaks.

Flashings and Edging

To complete the installation, flashings and edging must be properly installed to ensure the roof’s integrity. Flashings are materials used to seal joints, transitions, and penetrations on the roof, such as around vents, skylights, and chimneys. Properly installed flashings help prevent water intrusion and are essential for a watertight roof. Edging, also known as perimeter flashing, is installed along the roof’s edges to provide a clean, finished appearance and protect against wind uplift.

Maintenance and Repairs

Regular maintenance and timely repairs are essential to extend the lifespan of a flat roof with a slope and prevent damage. Here are some key maintenance tasks and repair considerations:

Regular Inspections

Regular inspections are crucial for detecting any issues early on and preventing costly repairs. Inspect the roof at least twice a year, during the spring and fall, and after severe weather events. Look for signs of damage, such as cracks, punctures, blistering, or loose membrane seams. Check the flashings and ensure they are secure and intact. If you notice any areas of concern, it is best to consult a professional roofer for further evaluation and repair recommendations.

Cleaning and Debris Removal

Regular cleaning is necessary to maintain the optimal performance of a flat roof with a slope. Remove any debris, such as leaves, branches, or dirt, that may accumulate on the roof surface or in gutters. This will help prevent water ponding, clogged drains, and potential roof damage. Use caution when cleaning the roof and avoid using sharp tools that could puncture the membrane or cause damage.

Repairing Leaks

If you notice any signs of leaks, such as water stains on the ceiling or walls, it is crucial to address them promptly. Locate the source of the leak and determine the appropriate repair method based on the roofing material and extent of the damage. Small leaks may be temporarily repaired with patching materials specifically designed for the roofing material. However, for larger or more complex leaks, it is recommended to consult a professional roofer to identify the underlying cause and perform a thorough repair.

Replacing Damaged Membrane

In some cases, the damage to the roof membrane may be extensive or irreparable, requiring a partial or complete replacement. This may be necessary due to aging, severe weather events, or improper installation. Consult a professional roofer to assess the extent of the damage and determine the best course of action. Replacing the damaged membrane will help restore the roof’s integrity and prevent further issues.

What Is A Flat Roof With A Slope Called?

Costs and Lifespan

When considering a flat roof with a slope, it’s important to understand the costs associated with installation, maintenance, and the expected lifespan of the roofing system.

Initial Costs

The initial costs of installing a flat roof with a slope can vary depending on several factors, such as the chosen roofing material, the complexity of the slope construction, and the size of the roof. Generally, low-slope roofs are more cost-effective than pitched roofs due to their simpler design and fewer materials required. However, the specific cost will depend on the material chosen, with EPDM rubber and TPO generally being more affordable options compared to modified bitumen or PVC.

Maintenance Costs

Regular maintenance is essential for the longevity and performance of a flat roof with a slope. The maintenance costs will depend on factors such as the frequency of inspections, the need for cleaning and debris removal, and any necessary repairs. It is recommended to budget for annual or biannual inspections, as well as periodic cleaning to prevent debris buildup. The cost of repairs will vary depending on the extent of the damage and the specific repair method required.

Lifespan Expectancy

The lifespan of a flat roof with a slope will vary depending on the roofing material chosen, the quality of installation, and the level of maintenance performed. On average, low-slope roofs can last between 20 to 30 years or even longer with proper care. EPDM rubber and TPO membranes tend to have longer lifespans compared to modified bitumen or built-up roofing systems. Regular inspections, timely repairs, and proactive maintenance will help maximize the roof’s lifespan and minimize the need for premature replacement.

Building Codes and Permits

When installing a flat roof with a slope, it is crucial to comply with local building codes and obtain any necessary permits. Failure to do so can result in costly fines and potential legal issues. Here are some key considerations regarding building codes and permits:

Meeting Code Requirements

Building codes dictate the minimum requirements for constructing a safe and compliant roof. These codes typically include specifications for slope, fire resistance, wind uplift resistance, insulation, and waterproofing. Consult with a professional roofer or local building department to ensure your roof design and construction meet the applicable code requirements. Compliance with these codes will help ensure the safety, durability, and longevity of the roof.

Permits and Documentation

Before beginning any construction or roof replacement project, it is essential to obtain the necessary permits from your local building department. The specific requirements for permits may vary depending on your location and the scope of the project. Typically, you will need to provide detailed plans of the roof design, including slope calculations and materials specifications. A professional roofer or contractor can assist you in obtaining the required permits and ensuring compliance with all documentation requirements.

What Is A Flat Roof With A Slope Called?

Professional Installation vs. DIY

When it comes to installing a flat roof with a slope, you have the option of hiring a professional or doing it yourself (DIY). Here are some factors to consider for each option:

Hiring a Professional

Hiring a professional roofer for the installation of a flat roof with a slope is highly recommended. Roof installation requires specialized knowledge, experience, and equipment to ensure proper functionality and performance. A professional roofer can accurately calculate the slope, recommend the best roofing material for your needs, and ensure compliance with building codes and warranty requirements. Additionally, professional installation provides peace of mind and a guarantee of workmanship and quality.

DIY Considerations

While it is possible to install a flat roof with a slope as a DIY project, it is not recommended unless you have prior experience and knowledge in roofing. The complexity of properly constructing the slope and ensuring watertight seals requires professional expertise. DIY installation increases the risk of mistakes, inadequate drainage, and leaks. Furthermore, DIY installation may void warranties on roofing materials. It is always best to consult with a professional roofer to assess the project’s feasibility and ensure a successful installation.

Common Issues and Challenges

Flat roofs with slopes, despite their advantages, can face specific issues and challenges that should be considered. Some common problems associated with low-slope roofs include:

Drainage Problems

While the slope of a low-slope roof promotes drainage, it is important to ensure that the roof’s design and construction allow for proper water flow. Improper slope calculations, inadequate slope construction, or clogged drains can result in drainage problems, leading to water ponding and potential leaks. Regular inspections and maintenance are necessary to identify and address any drainage issues promptly.

Ponding Water

Even with a well-designed slope, low-slope roofs can still experience ponding water if there are uneven areas or blocked drainage points. Ponding water occurs when water collects and forms pools on the roof surface. This can lead to accelerated deterioration of the roofing material, increased risk of leaks, and potential structural damage. Promptly identify and address areas of ponding water to minimize the risk of damage.

Snow and Ice Accumulation

In regions with cold climates, snow and ice accumulation can be a challenge for flat roofs with slopes. Snow can accumulate and cause additional weight on the roof, potentially compromising its structural integrity. Ice dams can also form at the roof’s edges, preventing proper drainage and causing water to back up. It is important to take proactive measures to prevent the accumulation of snow and ice, such as using snow guards or heat cables, and promptly remove any buildup to prevent damage.

Waterproofing Challenges

Proper waterproofing is essential for the longevity and performance of a flat roof with a slope. The numerous seams and joints in low-slope roofs pose a challenge in achieving reliable waterproofing. Special attention must be given to the installation of flashings and the sealing of seams to prevent water penetration. Regular inspections, maintenance, and the use of high-quality materials are crucial for minimizing the risk of leaks and ensuring effective waterproofing.

What Is A Flat Roof With A Slope Called?

Energy Efficiency and Insulation

Flat roofs with slopes can offer excellent energy efficiency and insulation benefits when properly designed and installed. Here are some key considerations:

Insulation Options and Considerations

Insulation plays a significant role in the energy efficiency of a flat roof with a slope. Proper insulation helps to minimize heat transfer, providing better temperature control and reducing energy consumption. There are various insulation options available, including rigid foam insulation, spray foam insulation, and fiberglass batts. The choice of insulation will depend on factors such as the desired R-value, budget, and local building codes.

When installing insulation on a low-slope roof, it is important to consider potential thermal bridging. Thermal bridging occurs when there is a break or discontinuity in the insulation, allowing heat to transfer more easily. To address this, additional insulation materials or techniques, such as staggered installation or the use of thermal breaks, may be necessary to create a continuous and effective thermal barrier.

Cool Roof Systems

A cool roof system is designed to reflect more sunlight and absorb less heat compared to traditional roofs. This helps to reduce heat transfer to the building’s interior, resulting in lower cooling costs and increased energy efficiency. Low-slope roofs can be designed as cool roofs by using reflective roofing materials, such as white or light-colored membranes. Cool roof systems can also incorporate additional features like insulation and proper ventilation to further enhance energy efficiency.

Benefits of Energy Efficiency

The energy efficiency of a flat roof with a slope offers several benefits. Lower energy consumption leads to reduced utility costs and increased savings over time. A well-insulated and energy-efficient roof also improves indoor comfort by maintaining more stable temperatures and reducing the need for excessive heating or cooling. Energy-efficient roofs contribute to a greener and more sustainable environment by reducing the overall demand for energy resources.


A flat roof with a slope offers the advantages of a flat roof’s clean, modern appearance and a slight pitch to promote proper drainage. This combination makes it an appealing choice for commercial and residential buildings, providing improved water management, increased stability, and versatility in roofing material options.

When installing a flat roof with a slope, it’s essential to consider factors such as the type of roofing material, slope construction, and compliance with local building codes. Regular maintenance, inspections, and timely repairs are crucial for maintaining the roof’s functionality and extending its lifespan. With proper installation, maintenance, and attention to energy efficiency, a flat roof with a slope can provide durable, reliable protection for your building while also contributing to energy savings and environmental sustainability.

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