FS Vet

A large residential building of five floors with a single a storey staircase & access to the roof area for maintenance,etc. There is a reciprocal means of escape with an adjoining building,however it has been securely fastened & not available for use. There is afd in the common areas on all floors & the final exit leads to fresh air, so my query would be: Should the reciprocal fire exit be reinstated or once persons are in the 30 minutes protected staircase would this be sufficient to relax this requirement? Apologies, one further question....I would be keen to extend the fire alarm system to provide a sounder at roof level, in order to give warning to contractors working at roof level....acceptable & would I require planning permission?