MY basketA roof lantern is one of the most effective ways to transform a dark extension into a bright, welcoming living space filled with natural light. Whether you’re installing a roof lantern on a new extension, kitchen extension, orangery or renovation project, it is important to consider more than just the glazing and frame. One often overlooked component is the roof lantern upstand, also known as an insulated kerb.
While the lantern itself may be the focal point, the insulated upstand beneath it plays multiple purposes. From improving thermal performance and energy efficiency to helping prevent water ingress and ensuring compliance with building regulations, an insulated kerb is a vital part of any successful roof lantern installation.
In this guide, we’ll explain why use an insulated kerb with a roof lantern and why it should never be treated as an afterthought.
What Is a Roof Lantern Upstand?
A roof lantern upstand, sometimes called a raised kerb or raised frame, is the structure that sits between the roof lantern and the roof surface. The upstand elevates the roof lantern above the finished roof surface, creating a stable, level surface for installation while helping water drain away from the rooflight.
Roof lantern upstands are typically constructed from timber and are often built on site by an installer. However, modern insulated kerbs are supplied pre-manufactured and designed to fit snugly beneath the lantern frame.
The roof lantern sits directly on the upstand, which provides essential structural support and helps distribute the weight evenly across the roof structure. Without a properly constructed upstand, the installation may not sit evenly, potentially causing issues with drainage, weatherproofing and long-term performance.
Why Does a Roof Lantern Need an Upstand?
The upstand ensures that the roof lantern is raised above the finished roof level, helping to protect the installation from standing water and water pooling that can occur on flat roofs.
Building regulations require a minimum upstand height of 150mm, measured from the finished roof level. The minimum upstand height helps ensure proper drainage around the rooflight and reduces the risk of leaks or water ingress.
The upstand prevents water ingress by elevating the lantern above the roof surface, allowing rainwater to run away effectively. A properly constructed upstand ensures effective drainage on flat roofs and significantly lowers the risk of water pooling around the roof lantern.
Building Regulations and Roof Lantern Upstands
When installing a roof lantern, compliance with UK Building Regulations is essential.
Approved Document C focuses on resistance to contaminants and moisture, requiring roof structures to be designed to prevent water ingress. Building regulations specify proper drainage to prevent water ingress and ensure long-term weather resistance.
Building regulations require insulation to be continuous throughout the roof structure, and building control officers will typically assess how the rooflight installation impacts the thermal performance of the building envelope.
Failure to meet these requirements can result in non compliance, which may lead to costly remedial work later on. By choosing an insulated kerb rather than a standard timber upstand, homeowners can more easily satisfy building requirements.
The Importance of Thermal Performance
One of the biggest reasons to choose an insulated kerb is its impact on thermal performance.
Many traditional roof lantern upstands are typically constructed from timber. While timber offers strength and structural support, it does not provide the same insulation performance as modern insulated kerb systems.
An insulated kerb includes an insulation layer that acts as a thermal break between the warm interior and colder external temperatures. This significantly reduces thermal bridging and helps prevent cold bridging.
By preventing cold bridging, an insulated kerb helps maintain comfortable indoor temperatures throughout the year while improving the overall thermal efficiency of the roof.
Reducing Heat Loss and Improving Energy Efficiency
Heat loss is one of the primary concerns for modern homes. Although a high-quality glazing unit and aluminium roof lantern can offer impressive performance, poor insulation around the rooflight upstand can undermine those benefits.
An insulated kerb reduces heat loss by creating a continuous barrier between the inside and outside environment. This helps retain warmth during winter and can contribute to lower heating costs.
Using an insulated kerb improves energy efficiency and helps homeowners achieve better U value targets. Insulation must be continuous to comply with building regulations, making the upstand a critical component of the overall construction.
Preventing Condensation and Moisture Problems
Cold bridging at the upstand can cause condensation and moisture issues over time. When warm internal air meets colder surfaces around an uninsulated roof lantern upstand, condensation can form.
This can lead to:
- Damp patches
- Mould growth
- Moisture damage
- Reduced insulation performance
- Premature deterioration of building materials
An insulated kerb prevents internal condensation by keeping internal surface temperatures higher and reducing thermal bridging. Because it acts as a thermal break, the insulated kerb helps maintain a more stable environment around the rooflight installation.
Supporting the Weight of the Roof Lantern
Modern roof lanterns feature large glass panels and robust aluminium frames, making them considerably heavier than many homeowners realise.
The roof lantern upstand provides a secure raised frame capable of supporting the glazing unit while ensuring the roof lantern sits evenly and securely fixed in position.
An insulated kerb enhances structural stability and weight distribution by helping spread the weight evenly across the supporting roof structure.
This is particularly important on larger roof lantern installations where substantial loads need to be transferred safely to the surrounding roof.
Easier Installation and Better Performance
Modern insulated kerbs simplify the process of installing a roof lantern.
A typical step by step installation involves:
- Preparing the roof opening.
- Installing the insulated kerb onto the roof structure.
- Ensuring the minimum upstand height is achieved.
- Verifying the upstand is level and securely fixed.
- Completing waterproofing and membrane detailing.
- Installing the roof lantern frame.
- Fitting the glazing panels.
Because the kerb is pre-manufactured, the lantern can fit snugly into position and sit flush with the intended design requirements. This can reduce installation times while helping to ensure a professional finish.
Ideal for Existing Flat Roofs and New Extensions
Whether you’re upgrading an existing flat roof or building a new extension, an insulated kerb can improve both performance and longevity.
Flat roofs naturally experience greater exposure to standing water than pitched roofs. The raised kerb elevation helps manage drainage while protecting the rooflight installation.
The insulated upstand is equally suitable for:
- Kitchen extension projects
- Dining room extensions
- Orangeries
- Garden rooms
- Contemporary living space renovations
- Existing flat roof upgrades
In every case, the combination of insulation, structural support and weather resistance provides substantial long-term benefits.
Conclusion
If you’re wondering why use an insulated kerb with a roof lantern, the answer is simple. It improves thermal performance, reduces heat loss, prevents cold bridging, minimises condensation, enhances energy efficiency and helps meet UK Building Regulations.
Beyond its thermal benefits, the insulated upstand provides critical structural support, ensures effective drainage, helps prevent water ingress and creates a stable base for the roof lantern.
Whether you’re installing a roof lantern on a new extension or upgrading an existing flat roof, choosing an insulated kerb is one of the smartest ways to maximise the performance of your roof lantern. Combined with high-quality aluminium frames, energy-efficient glazing and professional installation, an insulated kerb helps create a brighter, warmer and more comfortable living space for years to come.
At Lantern Superstore, we offer a range of roof lanterns and a kerb for all projects. Get in touch today to discuss your requirements and find the right roof glazing solution for you.
