In dealing with an appeal against the refusal of a certificate of lawfulness for the residential occupation of a barn in the garden of a Kent dwelling in breach of a planning condition, an inspector has usefully set out the legislation in such situations (DCS Number 400-036-533).
The inspector recorded that Section 191(2) of the Act states that uses are lawful at any time if: (a) no enforcement action may be taken in respect of them, including if the time for enforcement action has expired; and, (b) they do not constitute a contravention of any of the requirements of any enforcement notice then in force. Section 171B sets out the relevant time limits for enforcement action. Section 171B(1) sets out the time limit for operational development as four years; Section 171B(2) sets out that, where there has been a change of use of any building to use as a single dwellinghouse, no enforcement action may be taken after a period of four years beginning with the date of the breach. Section 171B(3) states that in the case of any other breach of planning control, no enforcement action may be taken after the end of a period of ten years beginning with the date of the breach.
The inspector noted that a condition on the planning permission for the barn stated that the building permitted should not be occupied at any time for residential purposes, but should only be used for agricultural storage and a workshop in association with the host property. Therefore, the inspector explained, use of the barn as a residential dwelling would be a breach of planning control under Section 171B of the Act both as development without planning permission (a material change of use from barn to residential dwelling) and as a failure to comply with a condition attached to a planning permission.
The LDC application sought to confirm that the use of the barn as a residential dwelling was lawful on the basis that the time for taking enforcement action had expired. The inspector further explained that whilst ordinarily a breach of planning control comprising a failure to comply with a condition on a permission would fall within the ten-year time period set out in Section 171B(3), it was held in FSS v Arun DC & Brown  that the four-year limit in Section 171B(2) applies where a building is being used as dwellinghouse in breach of a condition which serves to prevent that use. As a result, regardless of whether the breach amounted to a material change of use without planning permission or a breach of condition on a planning permission, the four-year time limit under Section 171B(2) applies.
It’s worth remembering this one: if it’s a house it’s not ten years, it’s four.
Section 4.535 of DCP Online covers immunity from enforcement.