I have a similar request about installing a stairlift. Approved Document B says 1000mm width for escape stairs. The block in question is mid 20th century so doesn't comply anyway (930mm width). The request relates to installing a stair lift that will stow on the landings and not the stair itself. However does the track that will be installed 90mm from the handrail mean the stair width would then be 840mm? Any dispensation awarded for low numbers/ stay put policy? Very aware equality/ discrimination could be thrown should advice not be fair.

The Regulatory Reform (Fire Safety) Order 2005 is all about Fire Risk Assessment and the guides are guides, there is nothing cast in stone. During the FRA the assessor has to consider many things, to decide if modifications can be allowed to the guidance and not all fire safety related. The assessor has to make his/her decisions based on risk assessment and if necessary defend it in court.

Without knowing all the necessary details it is impossible to give a definitive answer.