Flat roof extensions are more popular than ever! they make a home feel spacious and provide that essential extra space for a growing family.

While the benefits are clear, you need to consider how the flat roof extension will affect light in the rest of the house.  Then how your structure can best incorporate windows to compensate. Finding the perfect balance between position, size and number of windows is key to getting this right.  VELUX offer a wide selection of flat roof windows that will enable you to achieve this.

Lighting considerations

For homes that are lucky enough to be extending on a south facing elevation, in order to avoid harmful UV exposure and overheating, we recommend limiting the ratio of rooflights to floor area. Thereby providing enough light without the discomfort of overheating during the height of summer.


The right number, type and size of windows will help avoid dark spaces and will be key to a successful flat roof extension.

Whilst bi-fold and patio doors look great, extending into the garden moves daylight further away from the original house. Homeowners don’t want to end up relying on artificial lighting in the spaces that light from the bi-folds just can’t reach. Bring more natural daylight into these spaces, whilst increasing space and improving ventilation in the extension, with the perfect VELUX flat roof window.


Flat roof window options

Flat roof domes and windows have come a very long way since the early days when people worried about how they looked or even if they’d leak! Choices now include a fixed or electrically operated vented base unit, flat or curved glass along with the more traditional roof domes. If these options are not enough VELUX have also incorporated their pitched roof windows into the flat roof range using their Flat Roof Kerb.

There are also a range of glazing options to choose from, and triple glazing is available for optimal energy efficiency. Solar reflective glass can be specified, or glass with a low g factor, such as VELUX’s Glazing 60, which keeps the solar radiation levels down to as little as 30%.

Simply the glazing accounts for a large amount of a flat roof extension budget, so you want to get it right!


More about our VELUX flat roof windows range:

Curved glass rooflight -suitable for pitches 0°-15°

The Integra is the world’s first ever flat roof window with curved glass. It lets rain run-off preventing water from pooling or staining the glass, meaning it’ll stay clean for longer. This is the premium choice for homeowners with it’s stunning edge-to-edge glass design, which looks great from the outside and is brighter inside.

VELUX Integra green roof<


Flat glass rooflights – suitable for roof pitches between 2-15°

Discreet, stylish design with maintenance-free PVC frame, resulting in high performance insulation. These windows also provide excellent noise reduction.

VELUX Flat roof window


Flat roof domes – suitable for roof pitches between 0°-15°

This is the modern version of the ‘roof bubble’ often used on commercial buildings, they are either clear or have an opaque dome for privacy.. They’re low maintenance, and are double glazed for excellent sound insulation and energy efficiency. Both options provide good levels of daylight and are scratch resistant.

(When ordering your flat roof window please ensure you order a base unit and compatible top cover)

VELUX flat roof dome


Flat Roof Kerbs - suitable for roof pitches between 0°-15°

These insulated timber kerbs allow you to choose the most appropriate type of VELUX for your living environment. Choose from a manually operated window or a stylish polyurethane INTEGRA solar operated top hung roof window.


Modular Skylights

Fitting multiple or larger roof windows will maximise exposure to daylight. For larger flat roof extensions, these windows create a glass roof effect. Designed by architects, they have a slim frame design, but still come as modules for ease of installation.


Sun Tunnelsuitable for pitches between 0°- 60°

For locations where a conventional rooflight isn’t suitable, the sun tunnel (or sunpipe) is a clever solution. It  brings natural daylight to those hard to reach areas.  Positioned on a south-facing roof, where the light intensity is at its greatest, the glazed dome with rigid or flexible tube allows natural light to travel down into a room.


Specialist flat roof windows

Where access and emergency escape is necessary, we have 3 sizes of manually operated exit available.  If smoke vents are required, 2 windows sizes are available (100x100cm or 120x120cm). Smoke sensors, control systems and break glass units can also be purchased separately.


Accessories - the finishing touch

We’ve a wide choice of internal blinds whether the aim is to diffuse the light, add that decorative touch or blackout remote controllable.


Want to help the environment?

Why not consider alleviating the traditional black appearance of flat roofs by adding a wildflower and sedum roof garden onto your VELUX extension.