House conversion to flats, 4 year rule & continuous use

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    House conversion to flats, 4 year rule & continuous use

    I have some experience of the planning system and have obtained lawful development certificates in the past to confirm the lawfulness of the planning status of a building. However, I currently have a situation I have not seen before with regards to the "4 year rule" and the concept of "continuous use" so thought I would reach out here and see if anyone has any experience of it as I have seen some good advice on threads on this site over the last few years.

    Background - we have a residential building that was converted from one large residential house into 6 residential flats around 8 years ago. We have good evidence of the existence of these 6 flats going back at least 8 years e.g. tenancy agreements, council tax bills and utility bills for each flat. We are therefore interested in confirming the legal planning status of these flats with a lawful development certificate using the "4 year rule". However, there are periods during the last 2 years when one of the more of the flats were either:
    1. vacant (for up to 9 months in one case); or
    2. let on a short term basis with Airbnb (for up to 6 months).

    Therefore all 6 flats do have periods of 4 years where we can demonstrate they were in continuous use and occupied as a residential flat, however, it is not necessarily the most recent 4 years eg for one flat we can demostrate continuous use from 2012 to 2016, but not from 2016 to the present when it has had periods when it is empty.

    So my question therefore is - if we can demonstrate that the flats have existed for at least 8 years, and we can evidence they were continuously occupied by tenants between 2012 and 2016, do the void periods since 2016 matter in terms of obtaining the lawful development certificate under the 4 year rule (given that after 4 years of continuous use the rules (as we understand them) say that a residential property that has been split into flats should be immune from prosecution)? Please note that nothing changed about the flats during their void periods / periods on Airbnb, they were were still individual self contained flats (as they remain today), they were simply empty.

    Thank you for any input.

    Are you sure that this falls under the four year rule exemption. It seems to me that the property as a whole has a suffered a change of use to block of flats, so might be covered by the ten year rule.


      Situation would definitely be covered by the 10-year rule as indicated by Leaseholder64.


        Hi leasholder64 and vmart,
        Thank you for your responses although they are a little off topic as my query was not actually about the 4 year vs 10 year rule, it was more specific than that. In fact my query regarding continuity of use can be applied in both the 4 and 10 year rule scenarios.

        I don't really want to continue to move the thread off topic but for completeness, and with all due respect, I think you are incorrect regarding the fact that this change is covered by the 10 year rule. The relevant act(s) state that the time limit for enforcement action is "four years for the change of use of a building, or part of a building, to use as a single dwelling house." - following the conversion of a building to self contained flats each flat represents a "single dwelling house" and therefore they each fall into this 4 year category, not the 10 year category.


          But the building itself has been converted into multiple dwelling houses!


            In my experience that is not how the legislation is interpreted but again, I don't really want to turn this into a "4 year vs 10 year" thread - that was not my query.


              Probably won't have Building Regs. approval/certificates either. Not sure if this affects the legality of selling/letting, etc.


                Section 191(2) Town and County Planning Act 1990 as amended by Section 10 Planning and Compensation Act 1991.

                (2)For the purposes of this Act uses and operations are lawful at any time if—

                (a)no enforcement action may then be taken in respect of them (whether because they did not involve development or require planning permission or because the time for enforcement action has expired or for any other reason);
                After 4 years had passed no enforcement action was possible so that after that period had elapsed each flat was in lawful use as a single dwelling.
                That did not change during any period of vacancy.


                  Thank you pilman. That is good news.

                  In terms of actually making the application on the planning portal, would you make 6 separate lawful development for existing use applications i.e. one for each flat? Or would you make one application for "change of use from a single dwellinghouse to use as 2 or more single dwelling houses"? Or doesn't it make a difference? There doesn't appear to be any difference in application cost, it's either 6 x £462 per application or one fee of £2,772 down the second route.



                    Hi everyone,
                    I just thought it might be useful to someone in the future reading this blog to know what happened with this topic. The council agreed with everything that Pilman said basically. The 4 year rule does apply and that a period of vacancy did not invalidate this as long as the use had not changed eg to commercial. Hence we have now received a lawful development certificate confirming the building's lawful use as 6 flats.

                    FYI re: my last comment which went unanswered - we did submit them all under one application with one application fee of £2,772.

                    The council did not argue with us at all on any point when we called up offering a meeting and/or site visits, we did have a LOT of third party evidence though (tenancy agreements, utility bills, council tax bills, housing support receipts) going back well in excess of 4 years for all 6 flats. They also did not wish to meet us or to visit the property since they said that they wouldn't be able to tell from a visit whether the property met the 4 year requirements, therefore they relied entirely on the evidence provided.

                    Hope that's helpful to anyone coming across this entry in the future.


                      An application for a lawful development certificate needs to have evidence of the separate use of the two flats.

                      When I converted a house into two flats that were to be rented out to tenants, the original gas and electricity services were not changed so showing the utility bills that were paid did not prove single use.

                      The various tenancy agreements with the tenants who occupied the flats during the years they were rented out did show such use, as did the council tax payments made by the respective tenants after the flats were notified as separate dwellings to the council after the conversion was completed without the benefit of planning permission.
                      That was when the value of each flat for Council tax banding was assessed by the Inland Revenue Valuation Officer responsible for doing that who visited the flats to confirm the banding as Group A.

                      It also helped that some of the tenants claimed Housing Benefit that had been paid by the council.

                      It was a fact that the separate departments of the council never referred to each other once the development had been completed.

                      The Council Tax department and the Housing Benefit department never notified the Planning Department about the development, leading me to surmise that the council were glad to receive extra income rather than have the development stopped with a planning enforcement notice.

                      If you have not created two separate council tax accounts, you may be liable for a retrospective bill if you are able to provide other evidence to prove more than 4 years have passed since the two separate flats were created and lived in, but if there is other evidence that prove use and occupation as two separate dwellings then the LDC has to be issued, whether or not the local planning authority approve of the development.

                      The building control aspects of converting a house into two separate flats is not covered by the LDC so that is another aspect of the law that may come into play.

                      However if on the available evidence the LDC is issued, then that will confirm the lawful use of the two flats under planning law.

                      Then each can be sold off by granting a lease for each one of them, although some buyers' solicitors will raise queries about the building control requirements not being complied with, since planning law and building regulations are two separate matters that a solicitor and a mortgage company will have to take into consideration when acting for a prospective buyer of a leasehold flat.


                        Thank you Pilman, very helpful info,

                        what made you decide to pay the council tax individually for the flats, were you sure that they would not inform planning or just took the chance?

                        so if I have enough other evidence such as utility bills, tenancy agreements ect would I be able to pay council tax as a house and get the certificate with other evidence it has been converted?

                        thanks again,

                        kind regards,



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