You can perform certain types of work without needing to apply for planning permission. These are called “permitted development rights”.
However, the local planning authority may have removed some of your permitted development rights by issuing an ‘Article 4’ direction. This will mean that you have to submit a planning application for work which normally does not need one.
Article 4 directions are made when the character of an area of acknowledged importance would be threatened. They are most common in conservation areas. You will probably know if your property is affected by such a direction, but you can check with the local planning authority if you are not sure.
Before commencing any proposed works, you should contact your local planning authority and discuss your proposal. They will be able to inform you of any reason why the development may not be permitted and if you need to apply for planning permission for all or part of the work.