What Size Rooflight Do I Need? A Guide by Room Type

Posted by Blagovest

24 October 2025

On 16 June 2025

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.

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

What size rooflight should I use in a small kitchen?

For compact kitchens (under 10 m²), use one frameless rooflight around 1m x 1m. Go bigger only if your ceiling height allows it.

Can I install multiple smaller rooflights instead of one large one?

Yes — and it often looks better. Symmetrical layouts spread the light and reduce structural disruption.

Do building regs limit how big my rooflight can be?

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.

Do larger rooflights lose more heat?

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.

Part of the "Planning & Regulations" series by Skylights.co.uk.