Do loft/attic conversions fall under the requirement for statutory certification?
Generally, they do not fall under this requirement. Where upgrade works may combine a loft/attic conversion with an extension, it’s the size of the extension only (i.e. not counting the pre-existing attic space) that determines whether the requirement applies. The Department of the Environment, Community and Local Government has produced a guidance note on this matter:
Homeowners, builders and designers should remember that the relevant Building Regulations requirements generally apply to works irrespective of whether they are subject to building control procedures.
Works should not be of a nature so as to create a new or ensure a greater contravention of Building Regulations requirements.
If you are in any doubt, contact your local Building Control Authority.