Do I need planning permission to make my window bigger?

One Answer

1. Georgina Crothers says:

   24th May 2023 at 12:20 pm

   Hi Maciej,

   Build It’s planning expert Martin Gaine says: “Making a window bigger is usually permitted development, meaning that planning permission is not required. However, there are some cases where it is not permitted development: flats do not have permitted development rights, for example (only houses do), and some houses have had their rights removed by way of a planning condition on an earlier grant of planning permission. You might also need planning permission in a conservation area or if the house has some special architectural merit. It is best to contact the council for advice. To be absolutely sure, you can apply to the council for a certificate of lawful development (a way of confirming that something is permitted development).”

   In terms of installing the new window yourself, it depends on your level of experience and skill. Generally speaking, it’s always advisable to get a qualified glazing installer on board, particularly one with experience installing your chosen product. Poorly fitted windows can mean there are gaps and cold bridges, compromising airtightness and its overall energy efficiency.

   You’d also need to ensure your measurements are extremely accurate, particularly if you’re making the window opening bigger, so that you purchase the correct size window. The frame material will also determine the installation process, as this can differ depending on whether it’s aluminium, timber etc. Depending on the manufacturer, installing the window yourself can also compromise the warranty, so if anything were to go wrong, you wouldn’t be covered. For these reasons, although calling in a professional will cost more, it can save you a lot of time, money and stress in the long run.

   Georgina Crothers (editorial assistant, Build It)

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