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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There is no single legal definition of "habitable room", as its use and meaning are subject to context. Generally, a habitable room is a space in a building that is designed for people to live, sleep, or spend extended periods of time in, but does not include bath or toilet facilities, corridors or utility rooms.

If you plan to put up a small, detached building like a garden shed, garden room, garden office, annexe or summerhouse (all classed as outbuildings), building regulations generally won’t apply if the building has a floor area under 15 square metres and does not include any sleeping accommodation.

For buildings with a floor area between 15 and 30 square metres, building regulations approval is usually not needed - as long as the building does not include sleeping accommodation and either:

• it is at least one metre away from any boundary, or

• it is built mainly from non-combustible materials.

Read more about the building regulations that apply to outbuildings.

Don't forget to check the permitted development rights for outbuildings.

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The conversion of a garage, or part of a garage, into habitable space, will normally require approval under the building regulations.

As part of the garage conversion, it is likely that the original garage door will be in-filled with a new wall and possibly a window or door, and a new foundation may be needed for the new wall. 

As well as the foundation, you also need to consider:

• Floor

• Walls  

• Ventilation

Read more about the building regulations for garage conversions

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Yes, but you will need to obtain planning permission. Converting a detached garage into a self-contained living space, such as annexe, studio flat, or retail unit, represents a material change of use, particularly if it will function independently from the main house. This is because the garage would no longer be used in connection with the main dwelling and would effectively become a separate residential unit.