Would you say that, for example, an extended family of three generations who took in a lodger would require an HMO licence?
Only if you suggest that an extended family of multiple generations weren't related !
[Quite. When I moved into my present house, many moons ago, we had four generations here - myself+wife, our daughters and my mother and grandmother. Had the concept existed back then, is it seriously being suggested that would count as an 'HMO'?!
Ditto - I think you'll find that you were all related.
The definitions for HMO differ depending on whether it's for licensing and management, planning (there's a C4 category now which the described situation doesn't meet - sounds like C3(c)), or council tax.
For licensing and management, the definitions are :
An HMO [defined in ss.254 to 259 of the Housing Act 2004] is a building, or part of a building, such as a flat, that:
is occupied by more than one household and where the occupants share, lack or must leave the front door to use an amenity, such as a bathroom, toilet or cooking facilities
or
is occupied by more than one household in a converted building where not all the flats are self-contained (whether or not some amenities are shared or lacking). A self-contained unit is one which has inside it a kitchen (or cooking area), bathroom and toilet for the exclusive use of the household living in the unit. If the occupiers needs to leave the unit to gain access to any one of these amenities then the unit is not self-contained.
So from this it's clear that the exact arrangement of facilities, and who is allowed to use them, is key to whether it's an HMO or not. From the OPs description, it's not completely clear. If (for example) there are several rooms on one floor, where only the lodger on that floor is allowed to use them, and they form a self contained unit then it probably isn't an HMO. But if (for example) someone lodging on the second floor had to use facilities on the first floor, even if those facilities weren't shared with the lodger on the first floor, then you might find the local council arguing that it is an HMO.
Generally a household is a family (including cohabiting couples and same sex couples) or other relationships, such as fostering, carers and domestic staff. It includes cousins, aunties and uncles and step-relatives. Each unrelated tenant sharing a property will be a single household.
It gets a bit more complicated, the advice I have is that
Properties which are shared by two individuals are exempt from the HMO definition as are those with a resident landlord with no more than two lodgers.
Looking back,
at the moment it looks like it's not an HMO (since the father is related) and there are
TWO households - and I stand corrected (provided that the unrelated lodger does genuinely have his/her own separate facilities). Once the father is replaced with another lodger, then the situation changes - there will be
THREE households. If either of the current lodgers is replaced with a couple then that last exemption disappears.
Like I said earlier, one needs to read carefully the regulations as what may seem like fairly minor details can have great significance - in this case, whether the upper floors really are "self contained". Should the property fall into the definition of HMO, then in some areas the owner/manager must be licensed. Regardless of whether a license is required, there are a number of obligations that come with managing an HMO - failure to comply can result in prosecution and fines up to £5000.