Planning permission is not normally required to turn two properties into one by knocking through a party wall provided the changes are internal and do not impact the external appearance of the property.

You should check with your local planning authority that they agree, and there are not any previous planning changes or conditions which may have an impact.

Additional permissions may be required depending on the building’s history and their location. If the building is listed, an application for listed building consent will be required before any major changes are made to the dwellings.

The work will have to comply with building regulations, the focus will be on structural work and safety.

‍Read more about how building regulations apply to internal walls.

Inefficient windows and doors can significantly contribute to heat loss. Replacing single glazed windows by installing double glazing can cut heat loss through windows considerably. Double glazing works by trapping air between two panes of glass creating an insulating barrier that reduces heat loss, noise and condensation.  

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If you can't replace all the windows, why not choose the rooms that cost you the most to heat? Other options to reduce heat loss through windows include sealing gaps or using thermal blinds.

You don’t usually need planning permission for repairs, maintenance and minor improvements or replacing windows and doors that are of a similar appearance.

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Building regulations apply to replacement glazing, in terms of thermal performance, air supply, ventilation, safety and means of escape.

Read about planning and building rules for doors and windows

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Deconversion is the process of restoring a previously subdivided house back to its original state as a single property. Merging flats to create a single house may require planning permission, so you should discuss proposals with your local planning authority before starting work.

Read more about converting flats back to a house.

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The principal elevation is the most visible or prominent side of a structure, typically facing a street or public area. While often considered the 'front' of the building, it may not always contain the main entrance. There can only be one principal elevation of a house.

A wall is a 'party wall' if it stands astride the boundary of land belonging to two (or more) different owners, for example the wall separating two semi-detached properties.

Some kinds of work carried out to a property may not be controlled by the building regulations, but may be work which is covered by the Party Wall etc. Act 1996. This is a separate piece of legislation with different requirements to the building regulations.

To find out more about party walls, visit Planning Portal.

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