Planning Permission for Windows: What Homeowners Need to Know

Replacing Your Existing Windows: Do You Need Permission?

In most cases, replacing existing windows with similar designs does not require planning permission. If your new windows match the original ones in size, colour, and overall appearance, and the property is a house (not a flat or maisonette), the work can usually go ahead under Permitted Development.

You may also change the material, such as switching from timber to timber-look uPVC—provided the visual effect remains consistent with the originals.

However, there are exceptions. Flats do not benefit from the same PD rights. For leasehold properties, you’ll also need permission from the freeholder—even for like-for-like replacements.

Conservation Areas and Listed Buildings

If your property is in a designated area such as a Conservation Area, National Park, Area of Outstanding Natural Beauty, or if it is listed, you must seek formal consent before changing any windows.

Listed Building Consent is always required for listed properties, and unauthorised changes can be a criminal offence.

Windows for New Openings

Creating a new window opening may fall within Permitted Development rights, but this depends on the location, design, and impact of the change.

If your new windows are at the back of the house, then typically this should be fine, but check with your Local Authority. Windows at the front of your home, facing the ‘highway’, usually require planning permission.

New Bay Windows

If you are changing regular windows to projecting bay windows, then separate rules apply for these, as they can be treated as extensions. New bay windows at the front of your house will need planning permission.

Replacing existing bay windows falls under the replacement of existing windows, and planning permission for windows is not required.

You may find more flexibility with new bay windows for the back or the side of your home, but again, do check with your local authority.

Unusual Window Configurations

Perhaps you are looking to go bold with your new windows and create unusual window designs, shapes or colours.

In this scenario, your windows are more likely to require approval for a significant change in the window layout or appearance.

Changing a Window to a Door

Converting a window into a door—commonly done when installing bifold or sliding doors at the rear of the property, beside existing windows—may be permitted without planning permission.

However, changes to the front elevation are far more likely to require consent. Regardless of planning status, any structural alteration like this must meet Building Regulations, and you’ll need approval from either a competent installer or Building Control.

Windows on the side of a house

Fitting a new window on a side elevation is allowed under PD in many cases, but there are specific privacy rules, which are designed to protect the privacy of your neighbours.

Any side-facing window on an upper floor must be fitted with obscure glazing.

The window should not open if the bottom edge is less than 1.7 metres from the floor inside the room.

Upgrading your glass in existing windows

There are many early generation uPVC, aluminium and timber windows with original single glass or basic double glazed units. Upgrading the glass only to higher-performance new units, such as double or triple glazing, doesn’t need planning permission.

However, restrictions apply in Conservation Areas and listed buildings, where maintaining the external appearance is critical. Some councils may even restrict the thickness of glazing that can be used. This is especially the case in sash windows.

If original glazing cannot be replicated, such as historic stained-glass windows, secondary glazing may be a suitable alternative. This non-permanent solution improves thermal and acoustic insulation without altering the building’s appearance.