HAS

I have an existing dwelling house under construction. I want to convert the attic space to bedrooms. I will not be altering the front elevation of the house or the height in any way. Permission was granted for a bungalow. Do I require planning permission to carry out these works?
My concern is that I will not get a Certificate of compliance with planning for the bank. The height etc of the space in the attic allow me to fully comply with the building regulations.