Planning permission for a new or replacement staircase is not normally required. However, if you live in a listed building you may have to apply for listed building consent.

Part K of the building regulations requires that stairs, ladders and ramps shall be so designed, constructed and installed as to be safe for people moving between different levels in or about the building.
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Loft conversions: To ensure adequate fire safety for the dwelling a new stair serving a new room(s) will be needed. Where there is not enough room for a full traditional stair, it may be possible to use a space saving stair. Retractable ladders or stairs are not normally acceptable.