Hi all,
I know everyone's got a different opinion on Velux Cabrio Balcony System, but I think it's one of those things that could be argued either way. It's obviously not directly covered by the DCLG Technical Guidance, and I haven't seen any appeal decisions that have dealt with this particular issue.
If you were trying to argue that it's NOT PD, then you would have to argue that it falls within the scope of Class B (which contains restrictions against balconies), rather than Class C (which doesn't). This means arguing that it constitutes an "enlargement of a dwellinghouse", rather than "any other alteration", which means arguing that it should be assessed on the basis of its open state, rather than its retracted state. I think you could draw parallels to how a shop awning or a roller shutter normally constitute development on the basis of their open state, rather than their retracted state. You would also have to argue that the advice in the DCLG Technical Guidance that a juliette balcony doesn't constitute a "balcony" doesn't apply to a Cabrio Balcony - perhaps by drawing attention to the fact that the latter is designed to allow your upper body to be fully outside the envelope of the building.
If you were trying to argue that it IS PD, then you would either 1) accept that it falls within the scope of Class B but argue that it doesn't constitute a "balcony", or 2) argue that it falls within the scope of Class C. With regards to the latter, I think you could draw parallels to how a typical window or rooflight is normally assessed on the basis of its closed state, rather than its open state. For example, the fact that a typical rooflight would project more than 15cm from the plane of the roof slope when open wouldn't cause it to fail C.1(a) because it's accepted that it should be assessed on the basis of its closed state.
Thanks,
Steve