Do I need planning or just building regs to create an additional attic bedroom in my flat, with a velux window? There is an existing velux facing in the same direction to the rear of the flat. The room would be an additional bedroom in an HMO, council HMo department said it would meet their criteria for number of people in the building. The flat is in an article 4 area where I understand planning can restrict development, but is an additional bedroom affected by article 4 in this scenario?