Roof terrace structural plans

I have an end of terrace Victorian house with a 3 storey flat roof. My plan was to replace the roof now in a way that can have the terrace added at a later date once planning permission has been obtained. This work also involves removing the chimney breast on all three floors of an external non party wall. The builder has removed the chimney breast and has replaced the roof using 8inch joists (so I am water tight again). I have stopped the work because I have concerns the builder is not following building regulations and we agreed work will continue only when we have received professional advice. Firstly I need advice on the correct way of extending the joists that were previously against the chimney breasts. Secondly I need advice about and changes we should make to ensure the final result does comply with building regulations and can be used as a terrace. Thirdly I would need some plans so I can apply for planning permission for the roof terrace.