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When is an Annexe Not an Annexe?

By: Helena Stratford - Updated: 10 Jun 2024 | comments*Discuss
Annexe Extension Planning Entrance

Planning issues with any extension build project have the potential to be complicated but when considering an annexe, there are several points to take into account.

Whether a property already has an existing, interconnecting 'granny' annexe, a completely separate unit or whether the plan is to separate part of the home to potentially let it, the configuration can all make a big difference to how a Local Planning Authority is likely to view the situation - as well as what the owner wishes to do with it.

Definition of an Annexe

An annexe is defined in planning guidance notes as:
Accommodation which is ancillary to the main residential dwelling and used for this purpose. It may be interconnecting within the property as a whole (for instance via doorways) or it may be accessed via a completely separate external entrance, but if it forms separate and additional accommodation for the main house, it will be viewed as an annexe.

Council Tax and Annexes

Contrary to popular belief, a home does not have to have a separate entrance or front door to be liable for a separate council tax charge. The Valuations Office, a branch of HMRC and the department responsible for setting Council Tax on properties, deems an annexe to be liable for separate banding if it could be classed as a self-contained unit - i.e. it has its own kitchen area, bathroom and sleeping/living space - even if it shares other services and entrances with the main house. Two sets of Council Tax could be levied if a property has an annex, so you'll need to consider that if you are:

  1. building an annexe
  2. buying a house with an annexe
  3. designing an extension to include an annexe

You may be able to apply for a 'Class T' exemption to the second amount of tax if it is possible to prove that the annexe is :

  • for sole family use
  • for someone who is substantially mentally or physically disabled
  • for a relative over the age of 65

Flexibility of an Annexe

Annexes seem to have grown in popularity over recent years as they are a relatively simple way of utilising a home or extension in the most flexible way. For some, they can provide a useful extra income through renting out the additional space whilst for others, an annexe can provide future security as families plan for ageing relatives and 'boomerang' children who return to live at home after university.

Letting an Annexe

What is crucial, however, is to be clear as to how the annexe may be used right at the planning stage. If the annexe is to be commercially let at any time, then Change of Use Planning will be required and it varies hugely from LPA to LPA (Local Planning Authority) as to how such projects are viewed. Back in 2012, there was talk of permission being scrapped for annexes but so far nothing has happened and it is vital to check with the council before commencing any work. Detail of exactly what is permitted can be found on page 40 of the government guidance notes: Permitted Development for Householders - Technical Guidance.

Wider Implications of Letting an Annexe

It follows that if the annexe is to be let, then there will be further implications and responsibilities to consider. The mortgage lender will need to be informed and again, depending on the provider,attitudes will vary as to whether they look favourably on this or not. Insurance will also need to be checked as some home insurance companies, such as Direct Line, don't take on residential landlord's insurance and of course there will be tax implications from the resulting revenue stream in renting the property.

Becoming a Landlord should not be taken lightly and it would be wise to consider legal obligations such as gas safety checks, fire regulations and access to the annexe at an early planning stage as it could mean expensive alterations to the house as a whole.

Letting Rooms within the Home

If the property already has an 'internal' annexe - i.e. it isn't completely separate from the main house but has its own bathroom, then one option available, in consideration of any extension build plans, is to let the rooms to a lodger. This is certainly possible - and financially very beneficial - under the Government's Rent-a-Room scheme. This scheme allows a person to earn up to £4200 per annum tax free by letting out a portion of their home. What is clear, however, is that:
  • The owner of the property must be living at the home
  • The property owner must have regular access to the lodger's area
  • The kitchen must be shared. If the annexe section has its own kitchen and is separable from the main part of the house then this, under council legislation, is deemed to need separate planning.

An annexe then, can be a flexible, useful and potentially profitable addition to a home - but it can also bring with it a minefield of red tape - mainly between the Valuations office and the Planning office - and could saddle the home owner with the unanticipated role and responsibilities of acting as Landlord. So before making any plans to buy, build or alter a property with an annexe, it is important to have that conversation with the Local Planning Authority first.

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We have a garden room that we built 15 years ago, separate from our house, as an office. 10 years ago we started letting it on airbnb. It has one room with an attached shower and an area with a sink where we have put a toaster, kettle and microwave. We never allow longer stays than 7 days as it's not habitable. We've always called it'glamping'. We thought that it would qualify as a room in the house, as it uses the same services as our house. The council now want us to fill out a complex holiday let form, to assess us for council tax/ business rates. We don't make much money out of it and will make very little indeed if we have to pay tax or rates. Can you help....is it a separate dwelling? Thank you for any advice, Pippa
Pippa - 10-Jun-24 @ 10:46 AM
We brought a repossessed property which is a detached 4 bedroom and it came with a live/work unit. The planning is for sole use with the main dwelling. The live/work unit is huge and crosses 4 garages (1 garage belonging to the house) it has it's own entrance separate Kitchen/Bathroom and 2 separate main rooms although no parking. The water/sewage is connected although there is a separate water meter at the front and it has it's own electricity supply.The repossession was linked to the previous occupants taking out a mortgage as a separate dwelling to the house.When we moved in we were told 'family' could stay in the live/work unit. We did not realise until the council slapped us with a bill, it was subject to it's own council tax which we do get a 50% Annexe discount on. Our kids (young adults) did live over there for a while but now it is just an expensive storage unit! I did try for planning as full residential use but then was told I had to apply for retrospective change as was using as an Annexe?? I did not change the original use as this was how we brought it with no mention of the separate charges. The unit is on it's own title deed and separate address to the main house as well as we even have to pay a separate TV licence.Just wondered what I can do to make it less complicated if I were to sell the property as new buyers will need to know the costs of running the 2 properties? Can these be separated or can I get Annexe classification? It's not lived in so can I claim the council tax back?
LH - 22-Jan-24 @ 3:31 PM
We purchased our house 9 years ago as a whole property with an office annexe which had a bathroom and kitchen of sorts. It has a separate electricity supply but water sewage and heating is shared with the main house. We did up the annexe for my mother who lived there until her death last year. She insisted on having a separate address which sparked a visit from the local council who immediately slapped a council tax bill on it and deemed it separate albeit nil rated as she was a dependent relative. Now we have a potential buyer for our house who is being refused a mortgage and want the house to be returned to one address. Is this a possibility and if so what do we do.
Nellie - 12-Jul-22 @ 6:13 PM
I gained planning for a garage, gym, shower room, WC and playrooms above. For one year my elderly parents stayed using the playrooms above. The permission does not describe the property as an annex and there are planning restrictions as to its use. The VO have say “We have split the title” the building from the main house and now the garage has a class T exemption. By doing this the VO now say they have the right to revalue my main house. However I own the main house but the land the garage sits on I don’t own and was allowed to obtain the permission for the garage and gym etc and build at my own cost. The land is owned by my parents and has been since 1997. The splitting of the “title” has trigged the revaluation of my property even though a sale hasn’t taken place. Can I stop the revaluation? Regards Robert
Robert - 25-Jul-21 @ 10:06 AM
I have just had a recent conversion of an existing workshop into a annex.It only has a toilet and sink, small area with microwave, kettle, fridge and toaster I have put a bed setee in it but there is no separate bedroom.It adjoins the garage with access to be able to get out.It also hasfrench windows. Would I need permission for anyone to stay overnight? Kind regards.
Penny - 23-Jun-21 @ 5:02 PM
Difficult one this.So we have permission granted to build an annex.The planning quote as follows. . The proposed residential/ business accommodation/annex development hereby approved shall only be occupied and be used as ancillary accommodation to the main dwelling known at the time of decision as ....our address.....and at no time be subdivided from the curtilage of, or used as an independent unit of residential/business accommodation separate from .....our address... So we know we are the only ones to uses it, we know we cannot separate it. It will contain a bedroom and bathroom, office which has been granted. How ever we want to rent the main house out for occasional holiday let, airbnb,so when some one stays in the main house we can let them use the whole house, NOT the annex,as we will use that when customers stay.We will still use the main house when no holiday lets staying , so can anyone tell me if my neighbours from hell can stop us.
franki - 17-May-21 @ 3:43 PM
I've moved into a house that has an annexe.It was the garage and has been converted into a room with a small kitchen area and bathroom.I use it for storage, nothing else.Do I still have to pay an additional council tax?
MJW - 21-Apr-21 @ 4:10 PM
Hi, Can someone build annexe and have a back door put in that opens on to someone else land or a alleyway that they never had access for until they put this door in.
G - 17-Apr-21 @ 3:10 PM
My son had his garage that was attached to the house demolished and a one bedroom self contained annex built for me, I am disabled, I have recently moved out of this dwelling and pay council tax in my new home. The council say it is now empty and because my son owns the house he has to pay council the for the annex.
Hendo - 12-Apr-21 @ 1:32 PM
Many years ago the main house was extended with a hallway toilet off that study also part of that included a family room with a kitchenette a play room and a bathroom No extra council tax, done before we moved in We then had our son and his wife staying for several months and a council tax was slammed on a so called annexe! This was because our American daughter in law stated she was in an apartment in her in laws house. Totally incorrect but the damage was done, she used it in a visa application and someone came to investigate No one in the council has been easy to deal with or the appeal There is only one entrance into the house and so called annexe and no exit No one lives in the annexe it is just part of our house Never built or adapted as a annexe If we take the kitchenette out will we stop the annex council tax Estate agents/ friends were shocked but we did lose an appeal several years back The so called annexe used to be a hobbies room for the last owners. Why are we penalised having a bathroom downstairs and a kitchenette This is used because we have an Aga in main kitchen and it is turned off in summer so we use a free standing cooker in the kitchenette which we have done for years The council class us as having a flat, we could not even sell the property only as one property Impossible to let out as tenants would be coming into our main house all the time Are we totally at a loss cause
Hunt - 30-Mar-21 @ 10:00 AM
I live in a house with a 1 bedroom annex underneath the main house. The annex has its own entrance and can accommodate 2 people. We live upstairs. I have now retired and was thinking about letting the annex out for 6 months of the year, April to September. At the moment it is used for family members visiting. What do I need to do to in order to use the annex as a holiday let apartment.
Dicky - 28-Mar-21 @ 5:57 PM
Unfortunately you can’t do any of that - I have been through planning hell trying to have an annex which has its own CT changed to a separate dwelling - 3 Appeals - 2 HIgh Court Appeals and still being told that ‘severe adverse impacts’ of using the private motor car in respect of emissions outweigh any benefits - even P79 d - Sub division of a Main Dwelling didn’t help even though the appeal site is brownfield land and not isolated from the local village at 350 m
Annxeer - 24-Jan-21 @ 8:39 PM
Hi there - we converted a garage into a one bedroomed annexe for my elderly mother.It is a separate building in the garden.The main house is listed but we were given planning consent with a restriction that the annexe could only be used asancillary to main residence ie we can't rent it.We asked the council to reassess the whole property for council tax and they zero rated the annexe with the wording "empty annexe" although verbally told us it was zero rated as it had a planning restriction and therefore could not be rented My mother sadly went into care with dementia and we started to rent the annexe out under the rent a room scheme to pay for care fees.We thought this was OK (although we have now learnt we can't as the buildings are not connected). While we had a friend living there under the rent a room scheme we had a visit from the council tax assessor who rebanded it as Band A and our friend has now paid the council tax for four years. I am now told that if the council is charging us council tax for all this time then we could apply to have a change of use for the annexe and rent it formally as a separate residence.Is this correct?I find the whole planning vs council tax departments very confusing - particularly when they are all part of the same council! Any advice hugely appreciated
Concerned - 22-Jan-21 @ 5:57 PM
We build a studio flat . With separate bath and kitchen.Got side entrance.Can we put that on rent . What procedure we have to follow. Any permission required from Hounslow Council?? Do we have to inform any department.
Az - 16-Oct-20 @ 11:49 PM
Hi, I am on housing benefit at the moment because of COVID and have found a lovely landlord who has an annex he will rent to me. He’s in the rent a room scheme, and he doesn’t pay extra council tax on the annex as it’s attached to the house. His previous working tenants haven’t either. It has a kitchen and bedroom (all one room) and a ensuite shower room. It has its own front door. Is this okay to rent to me as a room £450 all bills included or will the council tell him he needs to pay more council tax as he’s renting it to me? Any advice helpful. Thank you.
Lizzy - 13-Oct-20 @ 9:33 PM
My parents are moving out of the cottage/annexe on my sisters land her house is also on aforesaid land.My parents didn't pay any council tax when they lived there as they are both over 70.However, I am 45 and will be moving in there, my question is, will I have to now pay council tax on this annexe
LCD - 1-Oct-20 @ 2:04 PM
Hi, I have rented out a 3-bed house, which also has side double extension connected to the main house with its own toilet. This double extension was built-in 1986 and also has its own exit at the back. Council planning history shows that it was built as a double extension as it has its own entrance exit along with the main house can I consider this extension as an annexe and rent out separately? as it was really old there no approved layout of this extension and all the bills are shared with main house. How can I make this extension as its own entity and rent it out separately? any help be appreciable.
Sam - 17-Jun-20 @ 10:56 PM
Hi I have a 3 bed house with a annex to the side, I wanted to seperate the annex completely so to sell the 3 bed house and my partner and myself can live in the annex, as I can’t do stairs anymore due to illness,what would the chances be please and what would we have to do? Thank you
Sue - 16-Feb-20 @ 3:29 PM
I have recently built a detached garage on my property i had planning permission to build it but I would now like to change this to a self contained annex where my mother in law can leave for free. Would this require additional planning and would this become its own dwelling meaning I would need to pay additional council tax ?
BigD - 16-Apr-19 @ 9:57 PM
I bought a bungalow with large garden and moved in.The express purpose was to build a connecting annexe for my daughter who has illness that will eventually be wheelchair bound. Before purchase I checked with planning and they advised due to medical condition it would be passed. Submitted plans, objection by neighbour stating she will loose late afternoon sun off her patio. Does not believe my daughter is ill, despite providing all relevant professional health reports. She now wants full council planning meeting so she can convince Counsellors to reject this.Decision has been put back three times. Is there anything more I can do.It has got very nasty, lies and libel. I just want to help my daughter. Reason not able to live in existing bungalow too small and totally unsuitable for wheelchair.
Cas - 16-Apr-19 @ 4:57 PM
Hi, we are just about to buy our first property which is a 3 bedroom semi detached with a granny Annex on the side, it is accessed through the main house and does not have it's own external access. We are wanting to encorperate it into the main house to make it a 4 bedroom semi detached. We are making the kitchen our main kitchen and the living room in the annex will be the dining room which opens up into the kitchen. My questions are 1. Would we have to pay 2 lots of council tax on this? Or would it be classed as one property after we finish the work? 2. Do we need to get permission from the council to do this? The annex was built in 2003 and as far as I can tell from the council website the property is registered under Band A. Thanks!
Chels55 - 25-Mar-19 @ 11:09 PM
Hi, We have an annexe which was built when the house was built.There is a door from our main house (internal door) which leeds into the annexe, there is also an external door for entry to the annexe.We have not rented out the annexe for many years.Council Tax has now gone up and no relief is available on council tax for the annexe any more, it has stopped this year.Our total is now £2976 for council tax for the year for both.As the annexe is no longer rented out we want to take the very old kitchen out and change the room to a bathroom.Also take the shower room out and join it up with the bedroom that is in the annexe.We spoke this morning to the council and they say we cannot have running water in there, or at least as far as this person knew.Someone more knowledgable in this matter will contact us in 48hrs.What do you know about incorporating the annexe into the main house.
chris - 18-Mar-19 @ 10:32 AM
We are considering buying a detached house with an annexe. This is to live with my daughter and family and according to the advert there is an A rated council tax on the annexe. We were going to add a kitchen but could easily use the other kitchen if it means no council tax. My wife and I are in our seventies and would prefer no stairs.
Mike - 23-Oct-18 @ 6:07 PM
Hi, My husband and I bought a 3 bedroom house which already had and annex extension built above the garage attached to the house. The annex can be accessed internally as well as externally with stairs which lead to an door which opens outside on the side of the house. We have lived in the "main house" and rented the annex to a lodger. We are now renting the "main house " to a family as well as renting the annex to a separate individual. The council are now saying we need planning permission or consent to do this even through the property was already built in this way when we bought it. Please advise how if possible we can evidence that this is still a single dwelling house or that we have not changed the use of the property or obtain retrospective permission. Many thanks Lizzy
Lizzy - 7-Sep-18 @ 9:27 AM
Hi, It's me again, sorry to be so needy. The stables we wish to convert into a self contained granny annex was built by me and I used a concrete base (slab) with steel mesh reinforcement. It's quite substantial and have not seen any movement in 12 years. My question is, when we are converting these stables I understand Building control will monitor it to some extent. My question is, would they be happy enough with the concrete base already in place.? Many Thanks
felttip - 19-Jun-18 @ 2:48 PM
Hi We have some stables that are now redundant because the Council are going to build on the fields we rent to graze the horses. We are considering what to do with these stables and assume we will not need planning to turn it into something useful, such as a granny annex. However the stables are around 500 feet away from main house so for practical reasons would want to extend our drive down to new granny annex, My question is, will we have an automatic right to turn the stables into residential building (still tied to house) and is there any planning restrictions on extending our drive down the garden? The stables are about 6 x 8 metres Could my wife and I live in it and rent the house? Grateful for any advice.
felttip - 19-Jun-18 @ 2:18 PM
Louloubelle - Your Question:
My father has detached barn which he has converted into an Annexe with relevant permissions an plans and it has been occupied since 96. However there was a break in 2012 when my sister moved out and it was unoccupied til we took over the council tax and moved in May 2015. A neighbour has made a complaint an we are now having to get a certificate of lawfulness to prove someone has been living on the property. It is completely self contained. Some has always been paying council tax since 96, yet the council want us to have this certificate. Can my dad still gift this to us for IHT reasons with this certificate of lawfullness hanging over us. What should we be doing and why are they pursuing this when it’s been lived in for so long. Does the short unoccupation make a difference to the 4 year rule does it have to be continuous even though tax was paid in the unoccupation? I’m so confused.

Our Response:
Was planning permission given for the annexe to be for part of themain residence or as a separate dwelling? If the former, then change of use (hence the requirement for a certificate of lawfulness) might be needed.
ExtensionBuild - 15-Jun-18 @ 10:41 AM
My father has detached barn which he has converted into an Annexe with relevant permissions an plans and it has been occupied since 96.However there was a break in 2012 when my sister moved out and it was unoccupied til we took over the council tax andmoved in May 2015.A neighbour has made a complaint an we are now having to get a certificate of lawfulness to prove someone has been living on the property.It is completely self contained. Some has always been paying council tax since 96, yet the council want us to have this certificate. Can my dad still gift this to us for IHT reasons with this certificate of lawfullness hanging over us.What should we be doing and why are they pursuing this when it’s been lived in for so long.Does the short unoccupation make a difference to the 4 year rule does it have to be continuous even though tax was paid in the unoccupation? I’m so confused....
Louloubelle - 14-Jun-18 @ 7:51 AM
Tatiana - Your Question:
We want to build an annex and get planning permission for it for a family member to live in. Once we get planning for this, if we later want to let it out or allow an au-pair or nanny stay in it, can the council say we need to either stop or tear the building down? Will the council allow us to let it out at all, when they have originally given permission for a family member?

Our Response:
Talk to your planning officer about this - an annexe for say a teenager, will require different permissions than one that is rented out etc. The council are unlikely to force you to "tear it down" but you may not be able to use it as any other than your original application/intention.
ExtensionBuild - 11-Jun-18 @ 1:50 PM
We want to build an annex and get planning permission for it for a family member to live in. Once we get planning for this, if we later want to let it out or allow an au-pair or nanny stay in it, can the council say we need to either stop or tear the building down? Will the council allow us to let it out at all, when they have originally given permission for a family member?
Tatiana - 8-Jun-18 @ 10:48 AM
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