It depends if the premises are classed as a "shared House" (i.e four friends club together to rent the property) or a true HMO where the residents don't know each other and pay rent individually
The following is taken from the LACORS "Housing Fire Safety" document
If it is a shared house then a Grade D LD3 system required (AFD in escape routes, kitchen lounge and any cellar) There would be no requirement for emergency lighting. Walls and doors don't need to be fire resisting, but should be of sound traditional construction. Any cellar should however be seperated by 30 minutes fire resistance.
If it is a HMO a grade D LD2 fire alarm system will be required (AFD in escape routes, each bedroom, kicthen and any cellar) Means of escape should be via a protected route or escape windows can provided from first floor level in certain circumstances in lieu of a protected route. Emergency lighting to BS 5266 will be required in areas where there in no "borrowed light" available
It is asssumed in a shared house the residents will know each other and therefore will be more inclined to "take care of one another's well being". This is why a "lesser fire safety standard" is excepted in shared houses
Residents of a HMO however may not be so inclined to take care of each other, hence a higher standard of fire safety is expected.
Hope this helps if you need any further guidance please ask.YOu may also find the "LACORS Housing - Fire Safety" document invaluable -
www.lacors.gov.uk
