How to Order a Custom Size Rooflight: Sizing, Lead Times and What to Expect
Not every flat roof opening matches a standard rooflight dimension. Extensions with unusual proportions, structural beams in complex positions, or openings that fall outside the standard range are common, particularly in older properties or architect-designed projects. When the opening does not match a standard size, a custom flat roof skylight is the appropriate solution. This guide covers everything you need before placing a custom rooflight order, how to measure correctly, what information to provide, what options are available, how long it takes and what to expect when the unit arrives on site.
When Do You Need a Custom Size Rooflight?
The standard rooflight range from Rooflights and Skylights UK covers sizes from 500x500mm up to 1000x3000mm (internal dimensions). If the roof opening falls within this range, a standard unit can be dispatched within 3 to 4 working days. A custom size is needed when:
- The internal opening dimension is wider or longer than 1000x3000mm
- The opening is narrower than 500mm in either dimension
- The opening falls between standard sizes and an exact fit is required for structural or aesthetic reasons
- The project specification calls for a non-standard proportion, such as a very long narrow opening or a large square format
- The project is a commercial or architectural build with bespoke dimensional requirements
Step 1: How to Measure for a Custom Rooflight
The most important rule when ordering a custom rooflight is to measure the internal opening, not the external upstand. The internal opening is the clear aperture inside the upstand, the dimension the rooflight will cover. This is what to provide when ordering and it is what we manufacture to.
Internal Opening Measurement
Measure from the inside face of the upstand on all four sides. Take the measurement at the top of the upstand rather than at roof level. Measure in millimetres and confirm both the width and the length.
If the upstand has not yet been built, measure the structural opening in the roof deck and deduct the upstand thickness on all sides. The builder or roofer can confirm the internal opening dimension once the upstand is in place.
Confirm all measurements before placing the order. A custom rooflight is manufactured to the dimensions provided and cannot be adjusted after production begins.
Important: Never use the external footprint of an existing rooflight or the overall upstand base dimension as the order size. Always measure the internal clear aperture.
Ready to Order Your Custom Rooflight?
Share your opening dimensions and our team will confirm your specification, pricing and lead time before production begins.
Explore Rooflight Collection →Step 2: Choose Your Product Type and Specification
Custom rooflights are available across the full product range from Rooflights and Skylights UK. Once the internal opening dimension is confirmed, the following options need to be selected.
Framed or Frameless?
Framed rooflights have a defined thermally broken aluminium frame in Anthracite Grey (RAL 7016) or Jet Black (RAL 9005) as standard. Frameless rooflights are precision-fitted with minimal visible edging for a clean, contemporary appearance. Both are available in custom dimensions.
Glazing Specification
Custom rooflights are available with double or triple glazing. Three glass types are available: clear Low-E glass for maximum light transmission, solar control glass for south-facing or exposed installations and satin privacy glass for bathrooms and overlooked spaces.
Frame Colour
Standard frame colours are Anthracite Grey (RAL 7016) and Jet Black (RAL 9005). If the project requires a specific RAL colour to match existing metalwork, window frames or architectural specifications, this is available on request. Contact our team on 0331 6303 671 to discuss colour options before placing the order.
Step 3: Place Your Order
To place a custom rooflight order, contact the Rooflights and Skylights UK team directly.
- Phone: 0331 6303 671
- WhatsApp: 07840 049231
- Contact form: rooflightsandskylightsuk.co.uk/pages/contact
When getting in touch, have the following ready: internal opening dimension (width x length in mm), product type (framed or frameless), glazing specification (double or triple, glass type), frame colour (standard RAL or specific colour if required) and delivery address with any site access considerations.
We will confirm the specification, pricing and lead time before the order is placed and send written confirmation of the details before production begins. Review all dimensions and the specification carefully at this stage before manufacturing starts.
Step 4: Lead Times and Delivery
Custom size rooflights from Rooflights and Skylights UK are delivered within 7 to 10 working days to all UK mainland addresses, covering the manufacturing time for the specific dimensions plus standard delivery.
Delivery is free to all UK mainland addresses. A £250 surcharge applies to Scottish Highlands, Northern Ireland and the Channel Islands. Every custom order is tracked from dispatch and handled by specialist delivery partners with experience in transporting glazed products safely to site. We will confirm the delivery date once the unit is complete and ready for dispatch.
Build programme note: Place the custom rooflight order as early as possible in the build programme. A 7 to 10 working day lead time is fast for a bespoke glazing product, but avoid removing an existing rooflight or leaving the opening exposed until the replacement unit is confirmed and dispatched.
Step 5: What to Expect on Delivery
Custom rooflights are delivered fully assembled and ready to install. Each unit is individually inspected before dispatch to confirm it matches the specification provided. Every order arrives with the custom rooflight unit packaged for transit, full installation guidance and quality inspection confirmation.
Every custom rooflight from Rooflights and Skylights UK carries a 10-year guarantee, the same guarantee that applies to every standard unit in the range. Our team is available on 0331 6303 671 or via WhatsApp on 07840 049231 for any questions after delivery.
Custom Roof Lanterns and Walk-on Glass
Custom sizing is not limited to flat rooflights. Bespoke dimensions are also available for two further product categories.
Roof lanterns: Standard sizes start from 1000x1000mm. Bespoke dimensions are available for non-standard openings. Contact our team for lead times on bespoke roof lanterns as these may vary from the standard 7 to 10 working day window.
Walk-on glass panels: All walk-on glass is manufactured to order in custom dimensions. Contact our team with the opening size and structural requirements for a confirmed specification and lead time.
Custom size rooflights are available in any dimension (framed and frameless) double and triple glazed, any RAL colour on request. Delivered within 7 to 10 working days with a 10-year guarantee on every unit. Browse the full range at rooflightsandskylightsuk.co.uk/collections/bespoke-rooflights
Frequently Asked Questions
- What is the largest custom size rooflight available?
- How do I measure for a custom rooflight?
- How long does a custom rooflight take to deliver?
- Can I get a custom rooflight in a specific RAL colour?
- Is the 10-year guarantee available on custom size rooflights?
- Can I get a custom rooflight in triple glazing?
- What is the difference between a standard and a custom rooflight?
- Can I order a custom size roof lantern?
Custom rooflights from Rooflights and Skylights UK are available above and below the standard range of 500x500mm to 1000x3000mm with no fixed upper size limit. Contact our team on 0331 6303 671 with the required dimensions and we will confirm whether the specification can be manufactured and advise on structural considerations for very large units.
Always measure the internal opening, the clear aperture inside the upstand, measured from the inside face of the upstand on all four sides. Do not use the external footprint of an existing rooflight or the outside dimension of the upstand. Measure in millimetres and confirm both the width and the length. Contact our team on 0331 6303 671 if you are unsure how to measure correctly before placing the order.
Custom size rooflights from Rooflights and Skylights UK are delivered within 7 to 10 working days to all UK mainland addresses. Delivery is free to UK mainland. A £250 surcharge applies to Scottish Highlands, Northern Ireland and the Channel Islands. We will confirm the specific delivery date once the unit is manufactured and ready for dispatch.
Yes. Standard frame colours are Anthracite Grey (RAL 7016) and Jet Black (RAL 9005). Custom RAL colours are available on request for projects requiring a specific frame finish to match existing metalwork, windows or architectural specifications. Contact our team on 0331 6303 671 to discuss colour options before placing the order.
Yes. Every custom rooflight from Rooflights and Skylights UK carries the same 10-year guarantee as standard size units. Each custom unit is individually inspected before dispatch to confirm it matches the specification provided and meets our quality standards.
Yes. Both double and triple glazing are available across the full custom size range. Triple glazed custom rooflights achieve a U-value up to 0.5 W/m²K, significantly better thermal performance than double glazing. Contact our team to confirm pricing for triple glazing in your required custom dimension.
Standard rooflights are available in fixed dimensions from 500x500mm to 1000x3000mm and are dispatched within 3 to 4 working days. Custom rooflights are manufactured to the exact internal opening dimension and are delivered within 7 to 10 working days. Both carry the same 10-year guarantee and are available in the same glazing and frame finish options.
Yes. Bespoke roof lantern dimensions are available for non-standard openings. Contact our team on 0331 6303 671 with the required dimensions and we will confirm the specification, pricing and lead time. Standard roof lanterns start from 1000x1000mm and are delivered within 10 to 14 working days.