Yes, but this type of conversion will require full planning permission. This is because you’d be changing the use of the ground floor from residential to commercial (typically to a use class such as E), while the upper floor would remain as a residential flat (Class C3). The change of use triggers the need for planning approval.  

Find out more about change of use

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Increasing the size of a window will often fall under permitted development rights, meaning an application for planning permission is not required to make the change, provided limits and conditions are met.

Any new window must be of similar appearance to the original which you are replacing.

Permitted development rights do not apply to flats. To increase the size of a window in a flat or maisonette you will require planning permission.

 If you live in a listed building, you will require listed building consent for any major changes.

Where the work has as significant impact on the external appearance of the house, especially on the principal elevation, planning permission may be required.

Building control approval will likely be required where the change impacts the structure of a building, this primarily occurs when an opening Is widened. When altering walls you may want to consult a structural engineer.

Building control will also consider energy efficiency, glazing, ventilation and fire safety.

If the garage will remain in domestic use - for example, as a personal hobby or home workshop - then planning permission is typically not required.  

However, it’s important to check whether there are any planning conditions, covenants, or restrictions attached to your property or the garage itself that may limit or prevent conversion.  

Read about planning permission for garage conversions on Planning Portal.  

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Bricking up an external door is classified as permitted development, meaning an application for planning permission is not required to complete the works. You will need to ensure that any materials used are of a similar appearance to the existing exterior of the house.

If you live in a listed building, then you will require planning permission and listed building consent for the change. In this instance it is best practice to talk to your local planning authority.

Find your local planning authority.

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Planning permission is unlikely to be required for the installation of external damp proofing unless the work will change the external appearance of the building or is part of a larger project.

If you live in a listed building you will need listed building consent for any significant changes, this can include external damp proofing. Additional rules may also apply if you live in a Conservation Area or other protected area.

Building regulations approval is not required for installing an external damp proof course (DPC).

Read further guidance on damp proofing.