There are several parts of legislation in England and Wales that affect this question. Perhaps four main ones apply: Health & Safety (HHSRS), HMO, Overcrowding and Planning Rules.HMOThe Housing Act 2004 schedule 14(6) states that the maximum number of lodgers living in a property, before it is classed as an HMO is two.So, if three or more lodgers live in a property, in addition to the landlord and his or her family, the property will be defined as an HMO.To decide whether the property is a licensable HMO it must be classed as a Prescribed HMO meeting these conditions:1 The HMO or any part thereof comprises three stories or more2 It is occupied by five or more persons3 It is occupied by persons from two or more households.OvercrowdingIf accommodation is much too small for a household it may be considered to be overcrowded under the law. A home may be legally overcrowded if there are not enough rooms or space for the number of people who live there.Currently (2009) there are two applicable standards in force: the Statutory Overcrowding standard under the Housing Act 1985 and the Crowding and Space Hazard, assessed under the Housing Health and Safety Rating System (HHSRS).Statutory Overcrowding (Housing Act 1985)Overcrowding can be caused by too many people living in a room or too many poeple for the size of the room.If two people of the opposite sex have to sleep in the same room, the accommodation will be overcrowded unless the two people are:- a married or cohabiting couple, or- at least one occupant is under ten years old.The number of people of the same sex (unless they are a same sex couple) who can sleep in one room is restricted by the size of the room.Rooms that are counted include living rooms, bedrooms and large kitchens. Space and floor area calculations:- children under one year old are ignored- children under ten years old and over one count as a half- rooms under 50 square feet are ignored.As a general rule:1 room = 2 people2 rooms = 3 people3 rooms = 5 people4 rooms = 7.5 people5 or more rooms = 2 people per room.Also, the floor area of a room determines how many people can sleep in it:- floor area 110 sq feet (10.2 sq metres approx) = 2 people- floor area 90 - 109 sq ft (8.4 - 10.2 sq m approx) = 1.5 people- floor area 70 - 89 sq ft (6.5 - 8.4 sq m approx) = 1 person- floor area 50 - 69 sq ft (4.6 - 6.5 sq m approx) = 0.5 people.Crowding and Space Hazard (HHSRS)The HHSRS is a new tool for local authorities to tackle overcrowding.HHSRS assesses deficiencies in a home in terms of the impact on the occupiers. Local authorities use the system to risk assess properties for 29 health and safety hazards, one of which is crowding and space.'a dwelling with one bedroom is suitable for up to two people regardless of age; two bedrooms for up to four people; three for up to six people; and four for up to seven people. Living rooms and kitchens are also considered. Whether a dwelling is actually overcrowded depends on the age and circumstances of the family in it.'�A dwelling may not match the ideal, but unless the hazard is a high-scoring Category I, the authority's decision to act is discretionary.PlanningIn some cases, especially where an HMO is being created, the property may be subject to Planning and Building Control rules, especially in respect of fire regulations.(The Regulatory Reform (Fire Safety) Order, June 2005, Effective 1 October 2006)HMO also have specific management rules (Statutory Instrument 2006 No. 372 The Management of Houses in Multiple Occupation (England) Regulations 2006) and are subject to annual Fire Risk Assessments. If in any doubt and before you commence any work or lettings you should contact your local authority planning and evironmental health departments and/or fire officer.�LandlordZONE All Rights Reserved - never rely totally on these standard answers which apply primarily to England & Wales. Before taking action or not, always do your own research and/or seek professional advice with the full facts of the case and all documents to hand.