Evs2033

Hi, I’m looking at making an offer on a maisonette that has been deemed unmortgageable for two reasons. The first is a short lease and the second because of a lack of fire doors/exits. The estate agent gent has been very unclear on the fire door problem and only states that it’s because of a lack of fire doors. Is this something that would make the maisonette unmortgageable? The entrance to the maisonette is through a communal front door with the entrance to the maisonette and ground floor flat. There is only one entrance/exit to the maisonette As part of the deal I intend to purchase the freehold of the building. Would it be my responsibility as the freeholder to ensure that there are fire doors fitted for both properties or just the one that I own? Sorry for the long post. Andrew