Do You Need a Felt Collar with a Rooflight?

Installing a rooflight can completely transform a space, bringing in natural light, enhancing ventilation, and improving energy efficiency. But as with any roof penetration, there are critical components involved in ensuring the installation is weatherproof and long-lasting. One such component that often raises questions is the felt collar. So, do you really need a felt collar with a rooflight? Let’s dive into the details.

What Is a Felt Collar?

A felt collar is a pre-formed or custom-made piece of roofing felt that wraps around the upstand or frame of a rooflight. Proper frames are essential for ensuring a secure and weatherproof installation, as they provide the structural support needed for durability, insulation, and water tightness. The felt collar is designed to integrate seamlessly with the surrounding roofing membrane (usually felt, EPDM, or asphalt) to prevent water ingress at the junction where the rooflight meets the flat roof. The meaning of a felt collar in rooflight installation is that it serves as a critical barrier, protecting against leaks and enhancing the overall performance of the roof window system.

Think of the felt collar as the flashing for a rooflight, it helps direct water away and ensures the vulnerable joint between the rooflight and the roofing material is sealed.

The Function of a Felt Collar

A felt collar performs several important roles:

1. Waterproofing: The primary function is to prevent water from entering the building where the rooflight has been installed. Roof penetrations are notorious for leaks if not properly sealed. Fitting the felt collar precisely is essential to ensure a proper seal and prevent water ingress.
2. Seam Integration: It allows for a smooth transition between the rooflight upstand and the existing roofing membrane, creating a watertight envelope. During installation, installers may need to add sealant or other materials to enhance the effectiveness of the felt collar.
3. UV Protection: Some felts provide additional UV protection around the base of the rooflight, helping to extend the lifespan of the upstand.
4. Building Regulations Compliance: Proper detailing, including a felt collar, may be required to meet local building codes, particularly in climates with heavy rainfall or snow.

When Do You Need a Felt Collar?

The necessity of a felt collar depends on several factors:

If your rooflight is being installed on a pitched roof with a traditional tile or slate covering, a felt collar is often recommended. It acts as an additional barrier, helping to prevent water ingress around the window. However, for flat roofs or roofs with integrated waterproofing systems, a felt collar may not be required.

It is important to select a felt collar that suits the specific rooflight and roof type to ensure it fits properly and provides effective protection.

1. Type of Roof Window

• Fixed Rooflights: These types of roof windows require a felt collar, also known as an upstand.
• Opening Rooflights: Similar to fixed rooflights, a felt collar provides an extra layer of protection with an opening rooflight too.

For optimal performance, ensure that the chosen rooflight is compatible with the felt collar.

2. Roof Type and Material

• Flat Roofs: Felt collars are far more common and necessary on flat roofs, especially those using built-up felt systems. Water tends to sit on flat roofs longer, increasing the risk of leaks.
• Pitched Roofs: On sloped roofs, a felt collar also helps shed water away more quickly.

3. Roof Membrane Material

If your roof uses traditional bitumen felt, you should integrate a felt collar as a best practice. Make precise cuts to fit the collar snugly around roof features or battens, ensuring a secure and weatherproof installation.

4. Installer Preference and Warranty

Some rooflight manufacturers or professional installers insist on the use of felt collars for warranty purposes. If your installer recommends it, it’s wise to follow their guidance—not doing so may void your warranty.

Before making a final decision, be sure to review installer feedback and product reviews to ensure you are making an informed choice.

Benefits of Using an Insulation Collar

Even if not strictly required, there are several reasons why using a felt collar is a good idea:

• Increased Reliability: It reduces the chance of leaks, especially during heavy rain or snow melt. Ensuring the corners of the felt collar are properly sealed is crucial to prevent water ingress and maintain a tight fit around the window opening.
• Better Insulation: A well-installed collar can help reduce drafts and thermal bridging at the junction of the rooflight and roof.
• Professional Finish: It gives the installation a tidy, completed appearance, important if resale value and building quality are priorities.

Velux Roof Windows

Installers typically use a felt collar with Velux roof windows to create a weather-tight seal between the window frame and the roofing underlay, helping to prevent water from entering. While it’s a useful addition for added protection against the elements, it’s not always essential, especially when other weatherproofing measures are in place. At UK Rooflights, we supply high-quality roof lights and lanterns. While we don’t currently stock Velux windows, we provide an insulated upstand engineered for reliable performance in all weather conditions. This upstand pairs perfectly with our rooflights, enabling them to meet, and exceed, UK building regulations.

Key Takeaways

• Yes, in most cases, an insulation collar is strongly recommended when installing a rooflight on a flat felted roof.
• It significantly reduces the risk of water ingress, helps with insulation, and ensures the longevity of the installation.
• Always check with the rooflight manufacturer and your roofing contractor to ensure that their guidelines are followed.
• Skipping a felt collar might save time or money up front, but could lead to expensive repairs later.
• During installation, make sure to check each key point, such as measurements and positions, to ensure a successful and compliant outcome.

Final Thoughts

While a felt collar might seem like a small and optional detail, it’s a crucial component of a long-lasting, leak-free rooflight installation, especially on flat roofs with traditional felt membranes. The added protection, improved seal, and compliance with best practices make it well worth the minimal additional cost and effort.

In building and roofing, the devil is always in the details, and in this case, the felt collar could make all the difference between a cosy, sun-filled room and an annoying water stain on your ceiling. With a properly installed felt collar, you’ll be happy with the improved performance and peace of mind it brings.

At UK Rooflights Online we offer a range of stock and bespoke size options on our rooflights with upstands as an optional extra. To find out more, speak to our team on info@ukrooflights.co.uk today!