This is exactly what we have just done in our clients home and is shown here https://www.houzz.co.uk/projects/2446242/stairs-and-balustrade-hanger-green. It is usually desirable to make the new attic stairs an equal pitch to the existing ones, however often it is necessary to increase the new upper flights pitch to avoid the window, if carried out skillfully and with a proper thought out design the stair and the space it sits in can be manipulated to enhance each other and either not impact on the available light or increase it. Unfortunately, most attic conversion companies will be looking for the fastest and most cost effective solution and a feature staircase may not fit into their scope. Often clients approach a specialist to design and make the stairs and work along side their contractor. The new flight could be designed to sit well next to the existing flight and the details like handrail and newel post of the existing could be copied so that both work together as a single entity. See this project that we also completed https://www.houzz.co.uk/projects/2044758/attic-stairs-and-stairwell we used the existing lower staircase as a starting point for the new stairs to the attic, while they are not the same they appear to have come from the same workshop whilst being constructed 100 years apart. Robert

We used to have something similar - we’re in a Victorian terrace that had a very old attic conversion when we bought it. The stairs were off the middle bedroom - the landing wasn’t altered in any way. The door to the middle bedroom was taken off (architrave remained in tact) - you walked through this gap and turned immediately 90 degrees to go up the stairs (the stairs ran along the bedroom wall). A new doorway was built immediately in front of the old one to preserve the bedroom (you wouldn’t need that in your plan!) The bedroom is quite big, so still felt quite spacious. My sons bed (an Ikea mid height thing) used to go under the stairs quite comfortably. A few years ago, we moved the stairs to come off the landing. The reason we did this was because the stairs off the bedroom effectively ran up the middle of the house - it meant that the attic conversion was two rooms. By moving the staircase to the landing and running them above the main staircase, we now have a large attic master bedroom and en-suite. It’s a much more usable space.

I was one of the original poster. Eventually in our case, building control wouldn't allow this - they originally OKd the plans, but then wouldn't allow the removal of the ceiling from the box room. There was a "galleries" approval that we explored but they weren't having that either.

A picture would help.