Whenever you are considering changes to your Property, it is always best to consider whether you require Planning permission.
Planning may be required for many scenarios. In Particular if you have a listed property, or live in a conservation area.
Some work is allowed under Permitted Development Rights, however there are many grey areas, so if in doubt, it’s best to check.
You can often get pre- application advice too, this will help with understanding the rules and regulations as well as which forms need completing.