Shared / Communal Rooms
The landlord is entitled to set which rooms/areas are shared/communal with the lodger- it’s typically the bathroom, kitchen and lounge. If you have multiple bathrooms, you can each have a dedicated one.
The important thing to remember, as discussed in the what is a lodger article, is that a lodger shouldn’t have exclusivity to a room, otherwise a ‘tenancy’ could be created, which would then give your tenant (not ‘lodger’) much more rights and control over your home. To avoid that from happening, the landlord should have access to all areas, including the lodger’s bedroom (but should respect privacy).
Lodger Agreement
The shared/communal areas are often defined in the lodger agreement. If they’re not, you can specify them in the written house rules.
It’s always a good idea to get it written down on paper and signed so there is no confusion about which rooms your lodger is allowed to access.