Roof Window FAQs

Our customer services team answers a lot of questions about roof windows as they help our customers get the right products at the right price.

To help you with your shopping experience, we've listed answers to the more common questions below. If you have a query that hasn't been answered, please feel free to contact us.

What's the difference between a roof window, skylight & rooflight?

Centre pivot vs top hung

Pine wood, white paint, PVC or PU internal finish?

What are roof window dimensions/sizes?

How do I find my VELUX, FAKRO or RoofLITE window size/code?

How do I find my Roto window size/code?

What roof window size qualifies as a means of escape?

What is the size of the hole in the roof I need to cut?

Are flashings essential?

Is there a cheaper alternative to VELUX windows?

How can I improve the thermal efficiency of my roof windows?

Do I need conservation roof windows?

Do I need planning permission to install a VELUX CABRIO balcony window?

I need to replace a glazing pane in my roof window and have the glass measurements, are you able to use this information?

 

What's the difference between a roof window, skylight & rooflight?

On Sterlingbuild, roof windows refer to windows that are installed on a pitched roof - you might call them VELUX windows; however, we sell a large range of other roof window brands to cater for every budget, room and purpose.

Rooflights are what we call flat roof windows, including flat glass rooflights, roof lanterns and walk-on glass windows.

However, if you're looking for a window to add natural light and ventilation to an uninhabited space, you will need a skylight. These windows don't meet building regulations for living spaces but will add daylight to lofts, sheds and stables.

 

Centre pivot vs top hung

Centre pivot windows are perfect for installation in high positions, such as extensions; that way the sash protrusion into your room won't mean you bump your head. They work just as well in rooms with low ceilings, providing a fast way to add natural light and ventilation to a room. To get the most out of your installation, we recommend an electric or solar powered roof window so you can open and close the window and blinds with ease using a remote control or wall switch.

Top hung roof windows give you more headspace, and a panoramic view of your surroundings. This design delivers the most amount of daylight, unobstructed views and the feeling of extra space. Most top hung windows rotate 180 degrees for easy cleaning of the outer pane.

 

Pine wood, white paint, PVC or PU internal finish?

The outer frame of roof windows are the same colour (RAL 7043) across all brands, chosen to complement any roofing material. If you live in a conservation area though, you'll need to fit conservation windows, which have a black (RAL 9005) outside frame and vertical bar. We also supply a range of windows with copper and zinc outer frames to fit seamlessly into metal roofs.

You have more choice with the internal frame finish:

  • Pine wood frames are the classic wood internal finish. Opt for this frame to complement other pine furniture and traditional décor.
  • White paint finish windows are made from high quality pine and finished in a stylish white paint. This finish creates a seamless fit for your roof window in your white ceiling, as well as complementing other white windows, doors and furniture. The white frame will enhance any daylight reflected into your room, giving you a brighter, more comfortable space.
  • uPVC frames will complement other uPVC windows and doors in your home. As with a white paint frame, the lighter finish will enhance any daylight reflected into your room, giving you a brighter, more comfortable space. The additional benefit of a uPVC finish is the material is durable, easy to maintain and resistant to humidity - perfect for kitchen extensions and bathrooms.
  • PU frames are made from an insulated timber core coated with polyurethane. Like uPVC frames, they add a brighter finish to any room, and are ideal for kitchen extensions and loft bathrooms due to their resistance to moisture. What makes this frame the ultimate choice is the bright, seamless finish.

 

What are roof window dimensions/sizes?

The product dimensions given on Sterlingbuild are all width x height for pitched roof windows and width x length for flat rooflights.

This refers to the external frame size, not the glazing area.

 

How do I find my VELUX window code/size?

It's easy when you know how! The VELUX - and other brand - data plate can be found on the side of the window's frame.



The data plate gives essential information about the size and model of your roof window so you can buy the right blind, replacement glazing or replacement window.

 

How do I find my Roto window model & size?

To ensure you get a perfect fit for your Roto blind, you will need the size and series of your Roto Frank window. There's no need to measure your window or glazing area. 

1. Open your window
2. Check the inside of the frame and/or sash to find a data plate
3. There may be a protective red, blue or grey case, simply open this to find your data plate
4. Note the series, e.g. 735
5. Note the size, e.g. 5/9

Find my Roto Colt window size/code

The position of your dataplate will vary according to your Roto model. If you have any questions, get in touch with our team who will be more than happy to help.

 

What roof window size qualifies as a means of escape?

For a roof window to be used as an emergency escape, it can be no less than 45cm in width or height, with a free space area of 0.33m, so it needs to be a larger size top hung window. The sash must be able to stay open so both hands are free.

For more information, read our blog post What Do You Need to Know About Escape Windows?

 

What is the size of the hole in the roof I need to cut?

When working out the size of the hole for your pitched roof window, you need to add 40mm to the width 50mm to the height of the roof window size.

What is a roof window flashing?

 

Are flashings essential?

Absolutely! Flashings are vital to the installation of your roof window. They enable the window to fit in to your roof, creating a weathertight seal to protect your roof and home.

Buying the right flashing is incredibly important, and ordering the wrong flashing kit can put back your renovation project as you wait for the right one to be delivered. 

We have lots of information on finding the right flashing kit for your ECO+, FAKRO, RoofLITE, Roto, and VELUX flashing for your roof window. 

Which flashing kit do I need?

 

Is there a cheaper alternative to VELUX windows?

Yes! You don't need to lose out on quality and performance when you buy an alternative to VELUX. RoofLITE is a sister brand of VELUX and one that's very popular with our customers. Read our blog post on RoofLITE Vs VELUX.

 

How can I improve the thermal efficiency of my roof windows?

We highly recommend an insulation collar, which you can find in the Flashings & Accessories section. They provide excellent insulation and weatherproofing properties for your loft conversion or home extension window – perfect for a more comfortable living space.

Other installation accessories that improve your installation are underfelt collars, which ensure a weathertight fit, vapour barrier collars, that stop condensation forming in your roof space, and lining frame kits, which create a mounting base for the internal lining of your roof window.

If your roof window is already installed, choose an energy saving blind. You might be surprised by the difference it makes to your room.

 

Do I need conservation roof windows?

Sometimes local authorities will insist on conservation roof windows for loft conversions and home extensions for older buildings. All conservation windows have the modern benefits of style, energy efficiency and ease of use. It's the external frame that makes them suitable for conservation areas. If you're in any doubt as to whether you need conservation windows or not, contact your local planning authority.

 

Do I need planning permission to install a VELUX CABRIO balcony window?

VELUX CABRIO (and FAKRO Galeria) windows are becoming more and more popular. A common question we're asked is do they need planning permission? The Planning Portal didn't give us a definitive answer but our friends at VELUX did. No VELUX window needs planning permission, but they can't guarantee the renovation work you're planning for your home won't.

If in doubt, we will always advise you to talk to your local planning authority before you invest time and money into renovations, particularly if your property is listed or in a conservation area.

 

I need to replace a glazing pane in my roof window and have the glass measurements, are you able to use this information?

We aren’t able to work off the glass measurements and will need the full window code. We have instructions on how to do this for VELUX, FAKRO, Roto and RoofLITE windows.