Granny Annexes: The Complete 2026 Guide for Families

The short answer

A granny annexe is any self-contained space for a relativeAttached to the house, converted from existing rooms, or a separate building in the garden. All three need their own kitchen and bathroom to count as self-contained.
It sits between staying at home and moving into a care homeA parent keeps their own front door and routine, and family is close enough to notice if something changes.
Planning permission and council tax both usually applyA self-contained annexe almost always needs planning permission before it is built, and its own council tax band once it exists, though a dependent relative living there can remove the bill entirely.
Building one is a five or six-figure decisionA standard one-bedroom annexe costs £70,000 to £115,000 to build, so it is worth weighing against buying a house that already has one, or paying for care in the home your parent already has.

This page is the overview. Five linked guides below go into the cost, the planning rules, the council tax, the value it adds, and how to find one for sale, in full.

What it is

What a granny annexe is, and the three ways to set one up

Granny annexe is not a legal term. It is the everyday name for any self-contained space, attached to a house, converted within one, or built separately, where a relative can live with their own front door, kitchen and bathroom.

The three types of granny annexe

Attached annexe

A portion of the main house sectioned off, usually on the ground floor, with its own kitchen and bathroom built in.

Entrance:: Its own front door, or the main entrance shared
Planning:: Almost always needed once it has its own kitchen and bathroom
Best for:: A parent who wants to be under the same roof but living independently

Granny flat (a converted floor or rooms)

An existing floor, wing or set of rooms turned into a self-contained flat within the building, common where a house is already split over floors.

Entrance:: Its own front door built into the existing structure
Planning:: Not needed while it stays non-self-contained, needed once it has its own kitchen and bathroom
Best for:: A larger or multi-floor house with little or no garden to build in

Detached ancillary building

A separate structure in the garden, built new or converted from an outbuilding, connected to the house's utilities rather than standing alone.

Entrance:: Fully separate, with its own front door
Planning:: Almost always needed, though a caravan-style annexe kept for family use can sometimes avoid it
Best for:: A parent who wants full privacy and separation, where there is enough garden to build in

The dark block in each diagram is the annexe. The pale block is the rest of the house.

What makes any of the three a genuine annexe, rather than just a large bedroom, is being self-contained: somewhere to sleep, somewhere to cook, and somewhere to wash, that the rest of the household does not need to use. That single test decides most of what follows in this guide, including whether planning permission is needed to build it and whether it gets its own council tax bill once it exists.

An annexe is one of several ways to keep a parent close without a care home. The best kind of house for an older person and community retirement living are two of the others, and the full comparison of care at home against a care home sets out the whole picture, including what changes if your parent needs nursing care rather than help with everyday life.

Why families consider it

What a granny annexe can offer that staying put or a care home cannot

An annexe is a compromise between two harder choices: a parent alone in a house that is getting difficult for them, or a parent in a care home they did not choose. It is worth being clear about what it solves, and what it does not.

Easier to spend time together

Visiting or having a parent round for dinner stops depending on a car journey. Family can look in on the way to work, or hear if something is wrong, without planning a trip.

More independence than a care home

A parent keeps their own front door, their own kitchen, and visitors whenever they like. Family involvement grows without anyone else deciding when they eat or who they see.

Care can be added without another move

Hourly visits, then more visits, then live-in care if it comes to that, can all happen in the same annexe. Moving between homes as needs change is unsettling, and an annexe avoids at least one of those moves.

The proceeds of a parent's own house can fund it

Many families building or buying an annexe are also selling a parent's existing home, and the proceeds can go towards the annexe, towards care, or towards both.

None of this makes an annexe the right answer for every family. It works best when a parent wants to remain independent and is well enough that living semi-separately is realistic, and when the family has the garden, the rooms, or the budget to create one. Where nursing needs are frequent, or a parent would be lonely without company through the day, a care home or community retirement living can suit them better than living alone a few steps from the back door.

What tends to go wrong

What tends to go wrong, and how to head it off

An annexe changes a family's day-to-day life as much as it changes a parent's. Most of the problems families run into are foreseeable, and worth talking through before anyone builds or buys anything.

Worth agreeing before you start

Set times you expect to see each other, so neither side feels watched or ignored
Agree in writing how bills, food shopping or repairs are split before the annexe is occupied
Talk to every sibling about who is doing the caring and what that is worth, before resentment builds
Ask your parent directly whether they would rather try a retirement village or stay where they are
Revisit the arrangement after six months, since what works on paper does not always work in practice

What tends to cause trouble

Assuming a parent will feel more independent than they would in a care home; for some people it feels like less
Leaving money between the generations undiscussed until a bill or an inheritance forces the conversation
One sibling taking on the daily caring without agreeing what that means for time, money or a future inheritance
Building or buying before finding out whether your parent wants to move at all

An annexe puts a family in closer contact than most are used to, and that can be the whole point or the whole problem depending on the relationship. It is not a failure to decide, after talking it through, that a care home or community retirement living suits your parent better. The difference between a nursing home and a care home is worth reading before ruling either out.

The money question

How the three main routes affect your parent's money

Families choosing between staying at home with care, a care home, and a granny annexe are choosing between three different things that happen to a parent's house and savings. Here is what each route does to both.

	What happens to the house	Typical weekly cost	What it does to savings
Stay at home with care	Kept, and disregarded in the means test while your parent lives in it	£1,050 to £1,400 live-in, or £18 to £25 an hour for visits	Pays from income and savings until they near the £23,250 upper capital limit, after which the council may help fund care at home
Move into a care home	Usually sold, and counted in the means test unless a partner remains living there	£1,100 to £1,600, typically around £1,160	House proceeds and savings pay the fee until they fall to the upper capital limit, then the council contributes
Build or buy a granny annexe	A parent's own house is usually sold to fund the £70,000 to £115,000 annexe or the extra cost of a house that has one; the family home gains an asset rather than losing one	Building or buying is a one-off cost, then care on top: £18 to £25 an hour for visits, or live-in care if needed	What is left over from the house sale after the annexe stays as savings, rather than being spent on fees

Stay at home with care

What happens to the house: Kept, and disregarded in the means test while your parent lives in it
Typical weekly cost: £1,050 to £1,400 live-in, or £18 to £25 an hour for visits
What it does to savings: Pays from income and savings until they near the £23,250 upper capital limit, after which the council may help fund care at home

Move into a care home

What happens to the house: Usually sold, and counted in the means test unless a partner remains living there
Typical weekly cost: £1,100 to £1,600, typically around £1,160
What it does to savings: House proceeds and savings pay the fee until they fall to the upper capital limit, then the council contributes

Build or buy a granny annexe

What happens to the house: A parent's own house is usually sold to fund the £70,000 to £115,000 annexe or the extra cost of a house that has one; the family home gains an asset rather than losing one
Typical weekly cost: Building or buying is a one-off cost, then care on top: £18 to £25 an hour for visits, or live-in care if needed
What it does to savings: What is left over from the house sale after the annexe stays as savings, rather than being spent on fees

Figures are PrimeCarers pricing data and typical UK care home fees for 2026, and the England capital limits for the care means test (£23,250 upper, £14,250 lower), unchanged since 2010. They are not a forecast for any specific family.

The annexe route is the only one of the three that turns a parent's house into an asset the family keeps rather than money spent on fees, which is why it appeals to families who can manage the upfront cost. It is not automatically cheaper: building or buying still costs tens of thousands of pounds before any ongoing care is added on top, and how much it would cost to build a granny annexe works through that figure by size and construction type. If your parent's needs are more about company and everyday tasks than money, how many visits a week they need is worth reading alongside this, and local authority funding explains how the means test works and when the council starts to contribute.

Build, buy, or convert

Deciding whether to build, buy a house with one, or convert what you have

There are three practical routes to an annexe, and the right one depends on your garden, your timeline and your budget more than on which sounds best.

Questions that point towards the right route

0 of 5 ticked

Your house and garden

Do you have space to build in the garden?Little or no garden usually points towards converting existing rooms or a loft rather than a new detached building.
Could an existing garage or outbuilding be converted?Converting is the cheapest route by a wide margin, though it will often share a kitchen or bathroom with the main house rather than being fully self-contained.
Are you likely to move house in the next few years?A kit-built or mobile-home style annexe can sometimes be taken with you; a brick-and-block extension cannot.

Time and money

How soon does your parent need somewhere to move to?A build, from planning application to moving day, usually takes four to nine months. Buying a house that already has one can be faster if the right property comes up.
What is your budget, and where is it coming from?Savings, a parent's own house sale, a mortgage advance, equity release or help from family are the routes most people use to pay for a build or a purchase.

If nothing in your garden or your house works, buying a house that already has a self-contained annexe skips the build and the wait, though genuine ones are not common on the market and searching for one takes a specific approach. How to find a house with a granny annexe for sale covers how to search Rightmove for one, since there is no tick-box filter for it. If building suits you better, how much it would cost to build a granny annexe breaks the cost down by size and by construction type, including the extra costs, VAT and timescales that sit around the headline build price.

Permission and tax

The two questions every annexe has to answer: planning and council tax

Whether an annexe is self-contained decides both of these, which is why the same design choices keep coming up throughout this guide.

	The question	The short answer
Do you need planning permission?	Before you build	Almost always, once the annexe has its own kitchen, bathroom and front door. A householder application in England costs £548 from April 2026, and most decisions come back within 8 to 13 weeks.
Will it be charged council tax?	Once it exists	Yes, once it is self-contained, it gets its own band. A relative living there halves the bill, and a dependent parent, 65 or over or disabled, removes it entirely.

Do you need planning permission?

The question: Before you build
The short answer: Almost always, once the annexe has its own kitchen, bathroom and front door. A householder application in England costs £548 from April 2026, and most decisions come back within 8 to 13 weeks.

Will it be charged council tax?

The question: Once it exists
The short answer: Yes, once it is self-contained, it gets its own band. A relative living there halves the bill, and a dependent parent, 65 or over or disabled, removes it entirely.

Both tests turn on the same detail: whether the annexe has its own kitchen, bathroom and somewhere to sleep, separate from the main house.

Neither of these happens automatically, and neither is optional once an annexe meets the self-contained test. Do you need planning permission for a granny annexe sets out what each type of annexe needs, the fee and timescale in full, and what to do if an application is refused. Is a granny annexe subject to council tax covers how a band gets assigned, the discounts and exemptions in full, and what happens while an annexe stands empty.

Once it exists

What the annexe is worth, and what to do if plans change

An annexe is rarely the last decision a family makes about it. What it adds to the house, whether it could be let out, and what happens if it stands empty for a while all come up sooner or later.

It usually adds to what the house is worth

A well-finished, self-contained annexe is estimated to add around 20% to 30% to a property's value, though a cramped layout or one that swallows the whole garden adds far less.

Letting it out separately is ordinary rental income, not tax free

A self-contained annexe let out as its own letting is treated as normal rental income, taxed and governed by tenancy law like any other let property. HMRC's Rent a Room Scheme, which lets you earn up to £7,500 a year tax free (£3,750 each for joint owners), only applies to a room or floor that still shares your kitchen or bathroom, not a fully self-contained annexe.

A mobile or park-home style annexe can be sold on

If the annexe was bought rather than built, some suppliers and dealers act as brokers for used static and mobile homes, and a private sale is also possible.

An empty annexe is not automatically exempt from council tax

Only if a planning condition stops it being let separately. Without that, some councils charge more for a long-term empty home rather than less.

Renting under the Rent a Room Scheme only works if the arrangement is closer to a lodger sharing your home than a separate letting, since HMRC's own guidance limits the relief to accommodation that is part of your only or main residence. A lodger in that kind of arrangement usually has fewer rights than an assured shorthold tenant: a landlord generally only has to give around four weeks' reasonable notice to end it, well short of the two months an assured shorthold tenancy usually requires. Letting a fully self-contained annexe as a separate letting brings ordinary tenancy law and normal rental income tax with it instead. Gov.uk explains how the scheme works and what counts towards the tax-free amount.

How to start

From this page to a decision

An annexe touches money, the family and the law all at once, so it is worth taking the steps in an order that avoids committing to a design before the bigger questions are settled.

1
Talk to your parent, and to any siblings, before anything else
First
Whether they want to move this close at all, and how caring responsibilities and money will be shared, matter more than any design decision that follows.
2
Ask the council for a care needs assessment
Free
It settles what level of care your parent needs, which affects how big an annexe needs to be and whether a second bedroom for a live-in carer is worth building in.
3
Decide whether to build, buy, or convert
This month
Your garden, your timeline and your budget decide this more than preference does. Get quotes or start searching once you know which route fits.
4
Book care in the current home while the annexe takes shape
Ongoing
A build or a house search can take months. Hourly visits can start now and move with your parent once the annexe is ready.

Questions

Questions families ask about granny annexes

Any self-contained living space for a relative, with its own kitchen, bathroom and somewhere to sleep. It can be attached to the main house, converted from existing rooms, or a separate building in the garden. A large bedroom with an ensuite is not an annexe unless it also has its own kitchen and its own entrance.

In most cases, yes, once it is self-contained. Do you need planning permission for a granny annexe covers what each type needs, the fee and how long a decision takes.

Yes, once it is finished and self-contained, though the bill depends on who lives there: a 50% discount for most relatives, and a full exemption for a dependent parent aged 65 or over or with a disability. Is a granny annexe subject to council tax covers the discounts and exemptions in full.

A standard self-contained one-bedroom annexe costs £70,000 to £115,000 to build in 2026, with professional fees, planning costs and utility connections usually on top. How much would it cost to build a granny annexe breaks this down by size and construction type.

Usually, yes. A well-finished, self-contained annexe is estimated to add around 20% to 30% to what a house is worth. Do granny annexes add value works through what changes that figure.

Some come onto the market, though they are not common. How to find a house with a granny annexe for sale covers how to search Rightmove for one, since there is no dedicated filter for it.

Not necessarily, at least not upfront. Building or buying an annexe costs tens of thousands of pounds before any ongoing care is added, while a care home or live-in care has no upfront cost at all. What an annexe offers instead is an asset the family keeps: a well-built, self-contained annexe is estimated to add 20% to 30% to what the house is worth, in a way that weekly care fees never do. Do granny annexes add value works through what that means in pounds for a given house price. Care at home or a care home compares the ongoing costs of each route in detail.

Then it is not the right answer, whatever the financial or practical case for it looks like on paper. An annexe works best when a parent wants the arrangement, not when it solves a problem for the rest of the family alone. Choosing the best house for an older person and community retirement living cover two other ways to keep them safe and independent without this particular change.

Yes, if it is not needed for a relative, but a fully self-contained annexe let as a separate letting does not qualify for HMRC's Rent a Room Scheme: it is ordinary rental income, taxed and governed by tenancy law like any other let property. The scheme's £7,500 tax-free allowance (£3,750 each for joint owners) only applies where the arrangement is closer to a lodger sharing your home, such as a room or floor that still shares your kitchen or bathroom. Check the current position with an accountant before you commit to either route.

An annexe can usually keep up with rising needs for longer than families expect, since hourly visits, then more visits, then live-in care can all be arranged in the same space without a second move. How many visits a week does my parent need and live-in care cover the point at which care in the annexe may no longer be enough, and what the alternatives look like at that point.

The complete guide to granny annexes