What Size Rooflight Do I Need? A Guide by Room Type
Choosing the right size roof light is essential to creating a bright, well-balanced space. Go too small, and you miss out on natural light. Go too large, and you might deal with overheating or planning issues. So, what size roof light do you really need?
In this expert guide, we provide size recommendations by room type, practical planning tips, and real-life examples using frameless roof lights from Skylights.co.uk—a favourite among homeowners and architects for flat and pitched roofs.
Table of Contents
Recommended Rooflight Sizes by Room Type
Here's a breakdown based on typical UK room sizes and usage:
✅ Kitchen
Recommended size: 1.2m x 2.0m or multiple modular units.
Best for flat roof extensions.
Place over kitchen islands or dining zones.
Consider solar-control glazing to avoid overheating.
Popular Choice: Our frameless fixed roof lights offer a sleek design that is perfect for modern kitchen layouts.
✅ Bathroom or Wet Room
Recommended size: 0.6m x 0.9m to 1.0m x 1.5m
Keep proportions modest for privacy.
Use frosted or opaque glazing.
Opening rooflights helps with steam and humidity.
Best for: Sloped ceilings or above walk-in showers.
✅ Bedroom or Loft Conversion
Recommended size: 0.78m x 1.4m (standard Velux size) or custom flat roof options.
Use two smaller rooflights for symmetry and airflow.
Opening models may be required for fire egress.
“We installed two 1m x 1.5m rooflights from Skylights.co.uk in our master bedroom loft. They provide balanced light and meet escape standards.”
— Ella, homeowner in Edinburgh
✅ Living Room or Lounge
Recommended size: 1.5m x 2.0m or 2m x 3m for large open-plan spaces
Create a central design feature with a frameless unit.
Triple-glazed options improve insulation and reduce noise.
Modular installations work well with timber joist spacing.
✅ Hallways, Landings or Stairwells
Recommended size: 0.6m x 0.6m or 0.8m x 1.0m
Light these traffic areas from above to avoid shadows.
Fixed frameless units reduce maintenance.
Combine with downlights for night use.
How to Calculate the Right Size for Your Space
Follow this general formula used by architects:
Minimum recommended glazing area = 15–25% of floor space
Example: For a 15 m² kitchen, 15% = 2.25 m² of rooflight coverage. That could be:
One 1.5m x 1.5m unit, or
Two 1.1m x 1.0m frameless skylights
Pro tip: Always allow structural supports, flashings, and upstand clearances.
Comparison Table: Frameless vs Framed Rooflights (Size & Design Impact)
| Feature | Frameless Rooflights | Framed Rooflights |
|---|---|---|
| Visible Glass Area | Larger due to a minimal internal frame | Slightly reduced |
| Aesthetic Appeal | Clean, modern, architectural look | More traditional |
| Custom Sizes Available | Yes | Limited standard sizes |
| Best Use Case | Kitchens, flat roofs, and minimal designs | Pitched roofs, heritage homes |
| Ventilation Options | Fixed only or paired with a background vent | Often available in opening |
FAQs: Homeowners Ask These Rooflight Size Questions
For compact kitchens (under 10 m²), use one frameless rooflight around 1m x 1m. Go bigger only if your ceiling height allows it.
Yes — and it often looks better. Symmetrical layouts spread the light and reduce structural disruption.
Not directly, but roof lights must meet Part L for U-values and sometimes Part B (fire escape) if they are in habitable rooms. Check with a building control officer.
Only if poorly insulated. Triple-glazed frameless units from Regal Glass Group maintain low U-values even at large sizes.
Why Size Matters When Choosing a Rooflight
Rooflights bring in up to three times more light than vertical windows. But size isn't just about brightness. It affects:
Thermal comfort
Ventilation
Building control approval
Aesthetic proportions
Structural support and cost
“When advising clients, we typically suggest rooflight glazing equals 15–25% of the room’s floor area. But the shape, ceiling pitch, and glazing spec also play a role.”
— Anna Clarke, Architect, RIBA member
Calculate your Skylight Size By Room
Real Use Case Examples
🏡 Adam's Kitchen in Newcastle
"We installed a 1.2m x 2.4m frameless skylight from Skylights.co.uk above the breakfast bar. It changed the atmosphere completely — much brighter and airier."
🏡 Priya's Ensuite in Cheltenham
"The 800 x 1000mm fixed skylight in our ensuite is just the right size. It brings in natural light without compromising privacy. The frosted glass makes a difference."
🏡 Karen's Guest Loft in Bath
"Two 1000mm x 1500mm skylights from Skylights.co.uk made our guest loft feel much larger and compliant with escape regulations."
Rooflight Size Mistakes to Avoid
Ignoring structural requirements — Get engineering approval for larger units.
Skipping shading needs — South-facing rooflights may need solar-control glass.
Using vertical window sizing logic — Rooflights admit much more light!
Forgetting about roof pitch — Flat rooflights sit differently than pitched models.
Overlooking planning permission — Stay under 150mm projection or apply.
Support Videos & Installation Resources
Final Takeaways
✅ Use 15–25% of the room floor area to estimate the rooflight size.
✅ Choose frameless units for modern, seamless light entry.
✅ Match the rooflight to the roof type — flat or pitched.
✅ Consider layout, ventilation, and planning from day one.
✅ Explore custom-size frameless rooflights from Skylights.co.uk for the perfect fit.
Need help choosing your rooflight size? Contact us for a personalised consultation or try our size calculator tool.
