1) Do I need to make an application to build an extension? Yes unless it is an exempt building.
2) Do I need an application to convert my loft into a room? Yes. See loft conversions
3) Do I need an application to convert my garage into a habitable room? Yes, if there are any structural alterations or alterations to the drainage. See garage conversions
4) Do I need an application to carry out repairs to my house? Possibly. Such works as replacement of windows and doors will require an application as will replacement boilers and most electrical works. However many of these may be self-certified by "competent persons". Since 6th April 2006 many works that would previously have been exempt may now require permission as a result of Part L. Structural alterations or those affecting means of escape also require permission.You are advised to consult the Building Control section for clarification about specific works.