Fixed Rooflights for Flat Roof Extensions: Pros, Cons & Must-Know Specs
Thinking about adding a flat roof extension and wondering if you should install a rooflight—but not sure which kind? Maybe you’ve searched:
“Are fixed rooflights worth it?”
“Best rooflight for flat roof kitchen extension?”
“Do I need an opening roof window?”
Let’s clear things up.
If you're going for a flat roof extension—whether it’s a kitchen, living room, or home office—fixed rooflights are one of the smartest and cleanest ways to bring in natural light. But they’re not always the perfect fit for every project.
Here’s everything you need to know about fixed rooflights: the pros, the cons, and the key specs that matter in 2025.
💡 What exactly is a fixed rooflight?
A fixed rooflight is a glass panel set into your roof that does not open. It’s designed to bring in daylight—not ventilation.
These are especially popular on flat roof extensions because:
They look minimal and modern
They can be large and frameless
They’re easier and cheaper to install than opening models
They sit on a kerb (a raised frame), and modern versions are often frameless from below, so you just see the sky—no chunky borders.
✅ Pros of fixed rooflights for flat roof extensions
1. More natural light = brighter interiors
Fixed rooflights flood your space with natural light from above, even if your extension only has walls on two or three sides. Perfect for:
Deep-plan kitchen-diners
Rear or side return extensions
Garden rooms and studios
You’ll notice the difference immediately—even on cloudy days.
2. Minimalist look, clean ceiling lines
Because they don’t open, fixed rooflights can be installed with slim or no visible frame from inside. That gives you a sharp, architectural finish that works beautifully in modern homes.
Bonus: if you go frameless, the view up to the sky is completely uninterrupted.
3. Lower cost and simpler installation
Fixed rooflights are typically cheaper than opening models—both to buy and to fit. No hinges, motors, or electrics. Just a solid, sealed unit set into the roof.
Installers love them because they’re quicker to fit and don’t need extra wiring or planning.
4. Low maintenance and great insulation
No moving parts = fewer things to break. And in 2025, most fixed rooflights come with high-performance glazing:
Low U-values (often under 1.2 W/m²K)
Solar control coatings (reduces overheating)
Self-cleaning glass (yes, really)
So you get thermal performance and less upkeep.
⚠️ Cons to consider
1. No ventilation
This one’s obvious, but it’s important. Fixed rooflights don’t open, so they don’t ventilate the room. If you’re relying on that for airflow, you’ll need to:
Include an opening window elsewhere in the room
Use an extractor fan (for bathrooms or kitchens)
Or install mechanical ventilation (like MVHR)
But for many homeowners, that's not a deal-breaker—especially in large open-plan spaces with sliding doors or windows.
2. No emergency egress
If your rooflight is in a loft or bedroom, it may need to double as a fire escape. Fixed rooflights can’t do that. In those cases, a roof window or vented unit is required.
For most flat roof extensions, though, this isn’t an issue.
📐 Must-know specs for 2025
When choosing a fixed rooflight, don’t just go by how it looks. Here’s what to check:
| Spec | Why it matters |
|---|---|
| U-value | Lower is better. Aim for 1.2 W/m²K or below (meets UK Building Regs). |
| Glass type | Look for toughened (outer) and laminated (inner) for strength and safety. |
| Solar control | Keeps heat out in summer and reduces glare. Useful for south/west-facing roofs. |
| Self-cleaning coating | Helps rain wash away dirt—less cleaning needed. |
| Kerb height | Should be at least 150mm to meet flat roof standards. |
| Frameless design | Frameless inside = cleaner lines and more sky views. |
Most quality brands will list these specs clearly. If they don’t—ask.
🛠 Top fixed rooflight brands in the UK (2025)
Here are some UK homeowner favourites for flat roof fixed rooflights:
Korniche Flat Glass – slimline frame, fast-fit design, very popular with builders
Roof Maker Luxlite Fixed – ultra-clear, frameless from below, beautiful finish
Wendland Flat Skylight – high energy performance, cost-effective and modern
Mardome Trade Glass – affordable, reliable, UK-manufactured options
Coxdome Flat Glass – solid build quality, available with solar and self-cleaning glass
- Saris-Extensions Fixed Rooflights — Premium quality, excellent thermal performance, sleek frameless design, and backed by expert advice and a 20-year guarantee.
🏡 Final verdict: Are fixed rooflights worth it?
If you’re building a flat roof extension and want to maximise light, minimise cost, and keep your ceiling lines clean—yes, absolutely.
Fixed rooflights are:
Budget-friendly
Easy to install
Beautifully minimal
Thermally efficient
And available in lots of sizes and finishes
Just make sure you plan ventilation elsewhere in the room if you need it, and always check the product’s U-value, kerb requirements, and glazing performance.
Thinking about adding one to your project?
Ask your builder or architect about kerb dimensions and solar control glass. Or better yet — speak directly to the experts.
👉 Contact the Saris-Extensions team today for tailored advice and to compare the best rooflight options for your home.