To determine which are the relevant Building Regulations for your property you need to know the date of the conversation. If the building conversion was completed pre 1st June 1992 it must comply with the Building Regulations in force from 1st June 1992 onwards. If the conversion took place post 1st June 1992, it must comply with the Building Regulations in force at the time of conversion.
It is important to note that some London Councils, such as Camden, operate this scheme if less than 50% of the flats within the building are owner-occupied as opposed to two thirds.
In a nutshell a building that has been converted into self-contained flats and has both owner-occupied and rented flats, the whole building may require a licence. However it is important to note that the S257 licence does not cover the individual flats, thus mandatory licensing and the other licensing schemes running in that borough still apply to each individual flat, depending on how it is tenanted.
HMO management regs 2007 applies to all buildings falling into the S257 HMO definition.
It is worth noting that wither your building needs to be licensed, or not, if it has a common part ie. a shared entrance to flats, then a Fire Safety Risk Assessment is a requirement under the RRO 2005 to be held by the freeholder. HMO Services London carry out unique fire risk assessments, please contact us to book in your inspection.
This is a complex area of the licensing legislation, please get in contact for more information.