For any set of stairs in whatever situation, whether it is a loft or cellar conversion or just standard floor to floor, we need 3 dimensions. The width, outside to outside of stair strings. The rise, the distance measured vertically between the two finished floor levels. The going, the distance measured horizontally between where the stair will start and finish.
For giving you a quote we only need sizes to within the nearest inch or 25mm. assuming you will be happy with our exact quotation we will then visit you and take sizes to the nearest millimetre. This will not change the quote.
Most staircases are between 800mm and 900mm wide, they can be made wider or narrower, stairs wider than 1000mm will require handrails on both sides. Amazingly there is no minimum allowed width! See Document K for staircases, of building regulations.
All of our staircases comply with building regulations; it is not in our interest to be sued for not complying and creating a safety or fire hazard. We have replaced quite a few over the years that other companies have fitted, only for them to be rejected by building control, doubling the cost to the home owner!