How to Fit a Velux Roof Light

Installing a Velux roof light is one of the most effective ways to bring natural light into a loft or attic space. It can transform a dark and unused area into a bright, welcoming room. Whether you are converting a loft, improving ventilation, or simply adding daylight to an existing room, a roof window makes a noticeable difference. Fitting one is a job that requires care and precision, and while many homeowners prefer to hire a professional, it can be carried out as a DIY project by someone with solid carpentry and roofing experience.

Planning and Regulations

Before beginning, it is important to consider planning permission and building regulations. In most cases, fitting a Velux window does not require planning permission if it falls under permitted development. The roof light must not project more than 150mm beyond the plane of the roof, and it must not be higher than the ridge line. However, if the property is in a conservation area or is a listed building, additional consent may be required. Building regulations always apply. The installation must ensure that the roof remains structurally sound, that the window is energy efficient, and that it provides adequate ventilation if used in a habitable room.

Choosing the Right Velux Roof Light

Velux windows come in a wide range of sizes and finishes, so choosing the correct one for your project is vital. Consider the size of the room, the slope of the roof, and how much light you want to achieve. Larger roof lights can flood a space with daylight but may require extra support in the roof structure. The pitch of the roof is also important, as certain models are designed for specific roof angles. It is also worth deciding whether you want a centre-pivot window, which opens in the middle, or a top-hung style that opens outwards for a clear view.

Preparing the Roof Opening

Once the correct window has been chosen, the first stage of fitting is to prepare the roof. The exact position should be marked between the rafters, ensuring that it is level and centred. Cutting into the roof must be done carefully to avoid weakening the structure. Typically, tiles or slates are removed from the marked area, then the felt or underlay is cut back to expose the rafters. A horizontal support known as a trimmer is fixed between the rafters at the top and bottom of the opening. These provide the framework that will support the window.

Installing the Window Frame

With the opening prepared, the Velux frame can be fitted into place. Velux windows are designed to be installed in two stages, with the frame secured first before the sash or opening section is added. The frame is lifted into the opening and fixed to the trimmers and rafters using the brackets supplied. A spirit level should be used to check that the window is square, as even a small misalignment can affect the way it opens and seals.

Fitting the Flashing Kit

The flashing kit is one of the most important parts of the installation, as it ensures the window is fully weatherproof. Each Velux window requires a specific flashing kit to suit the type of roof covering, whether tiles, slate, or corrugated sheets. The flashing is installed around the frame in overlapping sections, directing rainwater away from the window and back onto the roof. Proper fitting of the flashing is essential to prevent leaks, so the manufacturer’s instructions should be followed closely.

Reinstating the Roof Covering

Once the flashing is in place, the removed tiles or slates can be refitted around the window. They should sit neatly against the flashing, with cuts made where necessary to ensure a tight fit. Care should be taken not to force or crack the tiles, as this can lead to problems later. With the roof covering reinstated, the sash can then be slotted back into the frame and locked into position.

Internal Finishing

The final stage is to finish the inside of the roof light. Insulation should be fitted tightly around the frame to minimise heat loss and prevent draughts. A vapour control layer is often added to stop condensation forming. Plasterboard is then fitted around the opening and finished with plaster or paint. A well-finished interior not only looks professional but also helps the window perform efficiently.

Costs of Fitting a Velux Roof Light

The cost of fitting a Velux roof light depends on the size of the window and whether you do the work yourself or hire a professional. The windows themselves start from around £300 for a small unit, with larger models and those with advanced glazing costing £600 to £1,000. A professional installation typically costs between £400 and £800 depending on complexity, which brings the total cost to somewhere between £700 and £1,800. If additional structural work is needed, such as cutting rafters or adding support, this can increase the cost.

Suitability and Safety

Not every roof is suitable for a Velux window. The pitch of the roof, the position of rafters, and the overall condition of the structure all play a part. It is important to ensure that cutting into the roof does not compromise its strength. If you are in doubt, a qualified builder or roofer should be consulted. Safety is another consideration. Working at height carries risks, so suitable scaffolding or a secure working platform is essential. Protective equipment such as gloves, goggles, and safety harnesses may also be required.

Maintenance and Longevity

Velux roof lights are designed to last many years with minimal maintenance. Occasional cleaning of the glass and frame, along with checking the flashing for signs of wear, will help keep them in good condition. The seals and hinges should also be inspected periodically. Many modern Velux windows come with features such as self-cleaning glass and enhanced thermal performance, which reduce the need for upkeep and improve energy efficiency.

Conclusion

Fitting a Velux roof light can transform a room by bringing in natural light and fresh air. While the process involves careful preparation and attention to detail, it is achievable for skilled DIYers and straightforward for professional installers. With the right choice of window, correct installation, and proper finishing, a Velux roof light can provide decades of reliable use and add real value to a property.