Draw the floor below first
Begin with the existing landing, rooms and stair. Compare possible openings above or beside the existing flight, but do not assume that stacking the stairs will fit every house. The proposed opening must provide safe access and enough space for the stair geometry, landings and headroom shown in Approved Document K. [1]
Show the consequences downstairs on the same drawing. A useful option comparison identifies any space taken from an existing room, changed door positions and alterations to the landing. Then draw the loft rooms around the arrival point, rather than leaving the staircase until the roof design is finished. This is a practical way to test the requirements together. [1] [2]
Check headroom along the whole flight
Approved Document K normally provides for 2 metres of clear headroom above the pitch line of the stair and above landings. Its special loft-conversion illustration allows a reduced arrangement where space is insufficient: 1.9 metres at the centre of the stair and 1.8 metres at the lower side. This is a specific sloping-roof detail, not a general 1.8-metre allowance. [1]
Ask for a section showing the finished stair, roof lining and new floor thickness. A drawing measured to bare rafters can overstate the headroom remaining once the construction is complete. The new floor structure and ceiling finishes must therefore be coordinated before the stair is ordered. [1] [3]
Keep the route out protected
For the usual conversion creating a floor more than 4.5 metres above ground, Approved Document B's house guidance normally requires a protected stair arrangement or another suitable solution. The route has to continue towards a final exit; stopping the protection at the first-floor landing does not solve an open-plan ground floor. [2]
An entrance through another room or a staircase discharging beside cooking facilities needs particular scrutiny. Moving a door or partition below the loft can be part of the fire strategy even when the main building work is in the roof. Resolve that layout before agreeing the finished room sizes. [2]
Coordinate the opening with the structure
The floor around the staircase opening needs designed support. Cutting a convenient gap between existing joists is not a substitute for checking the loads and the new floor arrangement. Beam locations may also affect the landing level and headroom. [3]
What should the drawing package show?
Ask for plans of both affected floors and a stair section. Together they should identify finished levels, rises and goings, landings, door swings, headroom, guarding and the fire-protected route. The structural drawing should agree with that opening, not show an alternative position. [1] [2] [3]
Discuss unusually compact or alternative stair designs with the designer and building control before selecting a product. Approved Document K contains restricted alternatives; a supplier's description of a staircase as suitable for a loft does not establish that it suits the proposed accommodation. [1]