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Can You Install A Skylight On A Flat Roof?

If you’re thinking about upgrading your home to let in more natural light, a skylight is often an attractive option. But what if you have a flat roof? The common perception is that skylights are best suited for sloped or peaked roofs. However, that’s a myth. Installing a skylight on a flat roof is not only possible but also comes with its own set of advantages and considerations. In this comprehensive guide, we’ll walk you through the essential factors you need to know, from choosing the right type of skylight to understanding building codes and more.

What Types of Skylights Are Suitable for Flat Roofs?

When it comes to installing a skylight on a flat roof, choosing the right type of skylight for flat roofs is crucial. Your options are somewhat different than those for peaked roofs. Primarily, you have three types to consider: fixed skylights, roof access skylights, and tunnel skylights.

  1. Fixed Skylight: A fixed skylight is an economical choice for bringing natural light into dark spaces. They are designed to provide a constant source of light but do not offer ventilation. Velux is one brand known for high quality, fixed skylights.
  2. Roof Access Skylight: If you’re interested in a skylight that offers both light and access to your roof, this is your go-to option. It’s perfect for any flat roof that might need regular maintenance access.
  3. Tunnel Skylight: Also known as TCR Sun Tunnel, these are ideal for areas where you want to channel light from the roof to another level of the house.

Fixed skylights are generally more expensive but offer superior glaze and curb features. On the other hand, tunnel skylights are relatively easier to install and are a practical choice for smaller spaces.

Are There Any Specific Building Codes or Regulations to Follow for Skylights on Flat Roofs?

Absolutely. Before you proceed with skylight installation, expert advice on local building codes is essential. These codes dictate critical areas like the maximum size of the skylight, how far it must be from the roof’s edge, and what type of roofing material is compatible with flat roof skylight installation.

For instance, some codes require that skylights installed on a flat roof must have a slight angle to allow the water run-off. This helps to prevent rainwater collecting on top, which is a common issue with flat roofs. Also, be aware that some areas require a permit for any significant changes to your existing roof, including options made for skylights.

It’s always safer and more efficient to consult a professional installer or roofer who is familiar with local regulations. Ignoring building codes can result in fines and could make your home more likely to leak or suffer from other issues.

CXP Roof Hatch

What Are the Pros and Cons of Installing a Skylight on a Flat Roof?


  1. Natural Light: One of the most significant advantages is the influx of natural light. A skylight transforms dark spaces into vibrant areas filled with vitality.
  2. Ventilation: Certain types of skylights also come with ventilation features. This is a fantastic way to add fresh air into your home, enhancing the indoor environment.
  3. Energy Savings: With additional natural light, you can cut down on electricity costs. Quality skylights are designed to keep heat in during winter and out during summer.
  4. Aesthetic Appeal: Modern homes with skylights benefit from an architectural standpoint. They add a unique design element that’s both functional and beautiful.


  1. Cost: Skylight installation requires a substantial investment. From the skylight unit to the installation process itself, it can get pricey.
  2. Potential for Leaks: A flat roof doesn’t allow water to run off as easily as sloped roofs, making skylights on flat roofs more likely to leak. Proper installation and design features like flash the curb can mitigate this.
  3. Maintenance: While they bring in a lot of light, they also require periodic cleaning, especially if you opt for types featuring CurveTech glass.
  4. Building Codes: You have to be aware of local regulations and potentially acquiring a permit, adding to the complexity.

How Much Does It Cost to Install a Skylight on a Flat Roof?

When considering installing skylights on a flat roof, one of the most critical areas to think about is cost. This isn’t a minor undertaking, and it’s best to be prepared for the financial aspect. The cost can vary widely based on the type of skylight, material, and labor involved.

A basic fixed skylight can cost anywhere from $300 to $500 for the unit alone. Add installation fees, which can range from $500 to $3,000 depending on complexity. If you’re looking at high end options like Velux No Leak Fixed or roof lanterns, you might be looking at a total cost upwards of $5,000.

Moreover, if your roofing material is unique or complicated to work with, expect to pay a premium. Plus, if you need to build the curb or want additional features like a rain sensor that automatically closes the skylight at the sign of rain, that’s going to add to your overall cost.

Hip Ridge Skylights

Is There a Specific Angle or Slope Needed for Proper Drainage on a Flat Roof with a Skylight?

If you’re planning to install a skylight on a flat roof, drainage is a key concern. Unlike sloped roofs where water naturally flows down, flat roofs pose a unique challenge for water runoff. For this reason, many building codes and expert advice suggest installing the skylight at a slight angle. This angle is critical for preventing rainwater from collecting on top of the skylight, which can lead to leakage and other moisture problems.

Essentially, the goal is to allow rainwater to run off the skylight smoothly. Typically, an angle of at least two degrees is recommended for adequate drainage. Some advanced skylight designs, particularly those featuring CurveTech glass, already account for this slope. When installed correctly, these are less likely to suffer from water pooling and subsequent leaks.

What Kind of Maintenance is Required for Skylights on Flat Roofs?

Maintaining a skylight on a flat roof doesn’t have to be a daunting task. However, it does require consistent attention. Most importantly, you need to regularly check for signs of leaks, as flat roofs are more susceptible to this issue. Additionally, depending on your skylight features, you may need to clean the glass or polycarbonate dome at least once every few months to ensure optimal light and visibility.

If your skylight is designed to provide ventilation, ensure the flap or opening mechanism functions like it should. Many skylights come with rain sensors that automatically close the skylight when rain is detected. It’s important to test these features periodically to make sure they are working correctly.

Cleaning and upkeep are also essential for the curb and flashing that is perfect for your specific skylight type. Neglecting these areas can lead to issues like rust and leaks. Given that flat roofs already pose unique challenges, staying on top of maintenance can save you both time and money in the long run.

Can I Install a Skylight on a Flat Roof Myself, or Should I Hire a Professional?

The idea of a DIY skylight installation might be tempting, especially for those who enjoy home improvement projects. However, when it comes to skylights for flat roofs, our unequivocal recommendation is to consult a professional installer or roofer. There are many nuances — such as ensuring the skylight is installed at the correct angle to allow water runoff, flashing the curb, and choosing the compatible roofing material—that can make or break the installation.

A professional can also guide you through the permit process if your local building codes require it. Skipping professional installation is not worth the risk, as any errors could make your roof more susceptible to leaks, not to mention the potential fines for violating building codes. Additionally, professional installers are well versed in critical areas like skylight placement, type, and building materials, which will save you a lot of guesswork and potential mistakes.

Is There a Specific Brand or Manufacturer Known for Quality Skylights Suitable for Flat Roofs?

When it comes to quality skylights suitable for flat roofs, Velux flat roof skylights often come highly recommended. Velux offers a variety of options, including their Velux No Leak Fixed models, which are specifically designed to prevent leakage, a common concern with flat roofs. These models also come with advanced features such as CurveTech glass, rain sensors, and are designed to keep the interior climate comfortable.

Another reputable brand is Fakro, known for their high quality skylights that offer features like dome in acrylic or polycarbonate and options for added ventilation. If you’re looking for a skylight that offers both aesthetic appeal and durability, a Fakro skylight is also a solid choice.

Selecting a quality skylight from a reputable brand ensures that you are investing in a product that is both durable and functional, designed to provide your space with natural light as well as allow daylight and fresh air when applicable. While they might be generally more expensive, the investment is worth it for the long-term benefits.

Flat Roof Skylight Installation

How Long Does It Take to Install a Skylight on a Flat Roof?

If you’re pressed for time or simply eager to bask in natural light, understanding the time frame for skylight installation is essential. For a straightforward installation, where no structural modifications are needed, it could take as little as one day. However, more complex installations could extend into a week or more, especially if a new curb needs to be built or existing roofing material is hard to work with.

Skylights are relatively easier to install on new construction homes with flat roofs, as planning and placement can be integrated from the beginning. If you opt for special features like Velux’s TCR Sun Tunnel, you can expect the installation to take a bit longer due to the complexities involved. Pooling expert advice from your installer ensures that the skylight installation process remains efficient and high quality.

What are the Potential Leak and Moisture Problems Associated with Skylights on Flat Roofs, and How Can They Be Prevented?

Skylights on flat roofs are particularly prone to potential leak and moisture issues. The design of a flat roof doesn’t naturally allow rainwater to run off, making it imperative that the skylight is installed with particular care. Key prevention measures include using a wooden frame that has been treated for moisture resistance and ensuring the skylight is an economical choice for your particular type of roof. A proper installation with quality materials minimizes these risks substantially.

One option that’s gaining popularity is the use of curved flat roof skylights. These are designed to not only bring elegance into virtually any space but also to improve rainwater runoff, thus reducing the chance of water pooling. Employing a design featuring Curvetech glass can further help prevent rainwater from collecting on top.

When it comes to skylights, investing in quality is often better than seeking a quick, cheap fix. Brands like Velux offer features such as rain sensors that automatically close at the first sign of rain, effectively preventing water damage.

Conclusion: Is a Skylight on a Flat Roof Right for You?

In conclusion, adding a skylight to a flat roof can dramatically transform your home, filling dark spaces with natural light and fresh air. However, several factors demand your attention, such as your choice of roofing material, the installation angle, and strategies for preventing moisture. Trusted brands like Velux and Fakro offer high-quality skylight options, specifically designed for flat roofs, such as the Velux TCR Sun Tunnel and Fakro roof windows.

Though it might look simple, the complexity of skylight installation best suits professional execution. Professionals can help you navigate building codes and choose the ideal skylight for any flat roof, be it a workspace or a pool-side sanctuary.

If you’re on the fence, professional guidance can clarify the costs, benefits, and features that will make your skylight a valuable addition to your home. From options like polycarbonate domes to curved glass features for modern homes, the possibilities for transforming your space with natural light and ventilation are virtually limitless.

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