Ribrob

Thanks both. Given there's both changes the original application and new works not even hinted at on the planning application I was going to contact planning enforcement, but i think i may also contact building control too.

Last year a business property that backs on to our home was granted planning permission to tear down and old single story extension and build a new one in it’s place. The new plans seemed reasonable, building a little bit further out than the old one to add about 15m2, but still about 4 to 5m from the boundary line, and using materials that would match the existing extension and surrounding buildings. They recently completed the work and it was okay, despite some different and additional extraction / air-con units they hadn’t properly illustrated in the plans that were made available during the planning consultation period. But not different enough to make a big deal about. However this week they’ve quickly built a second extension attached to the newly built one, extending it a further +4m to add another ~25m2, stopping about 50cm from the boundary. The new one is marginally lower and slopes down to be under 3m at the boundary. Wall and roof materials are entirely different to their first new extension, and the surrounding properties. I’m assuming that ending up with an extension this size was the plan all along, get planning permission for one thing, and tagging something else on using permitted development. Have any rules been broken here? Thanks in advance.