When you convert a loft in an old terraced house, the brick walls in the loft area (party walls) are normally made from solid 9 inch brickwork. So if I run the new stairs up the party wall, the wall below the ceiling is adjoining another ‘warm’ wall. But when it passes through to the loft area it will be adjoining a ‘cold’ wall. Is this normally ignored by the Building Inspector, or do I have to have a nasty looking step in the wall, with some form of insulation behind?
Ask the building inspector, you can bet whatever advice you get from this forum the BI will have a different opinion.
Have a look at the party wall in the loft area it is quite common for this wall to be single skin so you could add insulation without getting a step.