I recently had a double storey rear extension completed - both first fix and second fix. After moving in I realised that the space around the open living area is not as per my expectations and want to demolish one of the structural internal walls to help add some open space. This is a old external wall ( which has become internal wall after the rear extension ) - about 250mm thick and I want to demolish about 1.5m of this wall. Is it even possible to perform such structural alterations, potentially by adding a steel beam, after all the major build work is complete?