For many types of minor development, the owner of the property will not require planning permission. This is known as a permitted development right, which effectively means that Parliament has already pre-approved the work you want to do.

For the private rented sector, the relevant use classifications are:

• C3 Dwellinghouses - this covers residential dwellings where either a single person lives, or up to six people live in the home as a family. It also includes use by sharers where an element of care is provided (supported living) and use by groups of sharers who do not fall into the HMO category (like religious groups).
• C4 houses in multiple occupation - where a property is shared by between three and six unrelated sharers.

If you have a residential property that does not fit into the requirements for these categories, the property will be considered 'sui generis'; Latin for 'a class of its own'. For example, a HMO with seven or more people is too large to be classed as C4, so it must be 'sui generis'.

In the second half of this article we will look at a significant loophole within these classifications, in particular when there is an “element of care” promised by the “registered provider”, which then brings the property under the umbrella of “exempt accommodation”.

First though, excluding these “supported living” properties, if the local planning authority believes that in their area, or part of it, there is strong evidence to justify the withdrawal of this permitted development right that allows the conversion of family homes into small HMOs, they can use an Article 4 direction to do so.

Generally, there is a requirement for a consultation period, after which the direction will be confirmed, and it will then come into force on a specified date (although it can often be introduced immediately in a conservation area).

The Article 4 direction does not apply retrospectively, so any development undertaken before it came into force is not affected.