Adding Rooflights to an Existing Flat Roof

If you are planning on adding a roof light to an existing flat roof extension it is important to conduct a thorough investigation of the structure and to talk to experts in the trade in order to work out whether planning permission will be required or whether you can go right ahead and install without any issues. There are many types of rooflights, sky lights and roof lanterns that can be applied to an existing flat roof. It depends on the type of property you have and the existing footprint of the property structure, as well as a few other factors, as to whether or not planning permission is required.

In terms of general planning permission it is usually required on any building project that will see a significant change in either the use or appearance of a building. In these cases careful consideration is required. When adding a rooflight to a roof there are a few cases where planning permission might be required, for instance where a sliding box rooflight is concerned, but in the majority of cases, such as a rectangular lantern skylights, it is unlikely that planning permission will be required.

Where Planning Permissions is Not Required 

When planning to add a rooflight to your existing flat roof extension there should be few problems with planning permission as long as your plans do not include an extension of the overall footprint of the existing building. Installation of rooflights and skylights are permitted under certain conditions according to building and planning regulations in England and Wales.

These conditions include the fact that any new flat roof skylights or roof lantern project no further than 150 millimetres away from the existing roof plane. Another factor is that any alterations made cannot be any higher than the existing roof height and all side-facing windows must be obscure glazed, with all openings made 1.7 metres above ground level.

Installation of Rooflights 

The guidelines above would mean that the majority of straightforward roof light installations would be covered by general permissions, however it is worth seeking planning permission guidance from experts in the field due to the upstand that will be present as part of the installation. For most rooflights there will be a requirement for an up-stand to offer something for the roof lantern to be securely fixed to, built in a way that also allows for water to drain off the roof lantern. It is likely that in some cases this will project the rooflight further than the 150mm from the existing roof plane as mentioned previously.

Building Regulations 

Whether you require planning permission or not to install a roof lantern there will always be building regulations to adhere to for a project such as this, ensuring that all structural and electrical work is conducted efficiently and safely. As a rooflight is altering the existing roof structure there will be building regulations to follow relating to the loading, insulation, ventilation and fire performance of the flat roof structure. Once a rooflight has been installed it should never affect the roof performance so these guidelines are required for the building and installation process itself.