How Much Does A Granny Annexe Cost?

How Much Does A Granny Annexe Cost?
Diane Cossie
How much does a granny annexe cost?

How Much Does A Granny Annexe Cost?

One of the most frequently asked questions we get asked is “how much does a granny annexe cost?”

As this is a major construction project it really does depend on the size of the annexe you want us to build, what style of annexe you prefer and whether you want a pitched roof (like a bungalow) or a flat roof with a canopy to give it that contemporary look.

Once we have discussed those details with you, the other key factor to consider for a true costing is where you are thinking of putting the granny annexe in your garden and how close the mains services of electric, water and sewerage are which is something we can do for you as part of our free on site consultation service.

Our Huscore annexes are granny annexe floor plans, designs and sizes that have been inspired by our most requested floor plans and sizes over the many years we have been designing and building annexes.

We have also considered certain factors your Local Planning Authority will consider for successfully obtaining planning permission within the HUScore annexe ranges.

So in a round about way if you are looking for the most cost effective way to build a granny annexe in your back garden start with our HUSCore range.

Our HUScore range of annexes start from just £58,750 for the Cantley one-bedroom annexe with a flat roof.

With most people financing their granny annexe from equity released from the sale of their main home it pays to play it smart and keep in control of your budget when building an annexe for a family member in the back garden.


Some Factors That Affect The Overall Cost Of A Granny Annexe

  • Size : the bigger the granny annexe, the more it will cost.
  • Distance from mains connections : (10 metres is included in the price), if the distance is more than 10 metres there is a simple price per metre additional cost.
  • Pitched roofs cost slightly more than flat roofs and the larger the annexe, the larger the pitched roof cost will be.
  • Ground levels, pumps and septic tanks : Ideally your annexe needs to be at a slightly higher level than your services to allow for a natural fall into your mains sewerage. If the ground level is too flat a pump will be required or in some cases a septic tank might be the best option.
  • Internal and external specification upgrades, including decking, external lighting, upgraded appliance & kitchen choices, upgraded flooring and any special adaptations needed for your granny annexe.

When you are thinking about an annexe for a loved one, cost is a major consideration which affects everyone involved.

There are considerations as a family for where Mum & Dad are going to live on a permanent basis and with which member of the family.

There are also considerable benefits to the main house owner for the future resale value of their house as a  “house for sale with a granny annexe” being currently one of the most searched for terms on Google for the term “granny annexe.”

Ideally people would love an instant solution where they can buy a house with a granny annexe ready to move into.

Customers tell us all the time that they have researched the options available and found them either completely unaffordable, in the wrong location or are not what they would call a self-contained annexe that would like their relatives and loved ones living in.

The vast majority of our annexe customers ideally want to spend between £70,000 and £100,000 in total for their annexe build.

It should be a move that is primarily about a better quality of life and for some of our customers it’s a much needed new lease of life.


Granny Annexes And Council Tax

In 2014 the Government scrapped what it called the “unfair surcharge” on family annexes, which saw two separate council tax bills levied on the same home if it had a ‘granny flat’, ‘granny annexe’ or similar extension.

The two dwellings were treated as separate dwellings, each requiring Council Tax to be paid under the relevant Council Tax Bands.

This was then quickly revised and as long as the annexe is in use by a family member or the main house owner, Council Tax is payable at the reduced rate of 50% of your banding.

You can read more about this and whether you qualify for the discount on the Martin Lewis Money Saving site by clicking here.


Granny Annexes And Council Tax Exemption

As a lot of our annexes are for dependent relatives and elderly care you may be exempt from paying Council Tax completely if the annexe is your only main home.

For example on the website it states:-

An annexe will be exempt (which means you don’t have to pay council tax) if it is separately banded for council tax but forms part of another property and a dependant relative is living in it as their main or only home.

A relative is classed as dependant if they are:

  • over the age of 65
  • substantially or permanently disabled, or
  • severely mentally impaired.

You can find out more about annexes and Council Tax by clicking here or finding out from your Local Council.


Granny Annexes And The 7 Year Inheritance Tax Rule

If you are looking to sell a main family home and use the equity released to finance your annexe project, you will need to check with a qualified Financial Advisor the best way to manage any inheritance tax with regards to the 7 year inheritance tax rule that could work in your favour.

According to the Gov.UK website with regards to inheritance tax:-

If you leave your home to your children (including adopted, foster or stepchildren) or grandchildren, your tax-free threshold will increase to £425,000.

Giving away a home before you die

There’s normally no Inheritance Tax to pay if you move out and live for another 7 years.

If you want to continue living in your property after giving it away, you’ll need to:

  • pay rent to the new owner at the going rate (for similar local rental properties)
  • pay your share of the bills
  • live there for at least 7 years

You don’t have to pay rent to the new owners if both the following apply:

  • you only give away part of your property
  • the new owners also live at the property


Resale Value Of The Main Home With A Granny Annexe Attached

Garden annexes are popularly known in the UK as granny annexes but they are still a relatively new idea for what is a very traditional property ladder historically here in the UK where an Englishman’s home has always been his castle.

However in recent years we have seen significant changes in UK house prices especially in London which according to the HM Land Registry and Office looks like this:-

"house price index January 2017"

The knock on effect of these significant house price increases have created problems for many of our younger generations for whom a home of their own seems an unlikely prospect.

With our smallest one bedroom HUScore Cantley annexes starting from £58.750 we see the future of our annexes as being an attractive way to help family members both young and old.

Although the resale value of the main house with a granny annexe in the garden will obviously be determined by the area in which it is built, the demand for a property for multi-generation living is increasing year on year.

Granny flats in Australia are already booming and we see the same trend emerging here in the UK.

We recently learned that an ex-council house in London with one of our annexes built in the garden sold for £1.1 million pounds, having been valued without the annexe just a few years ago at £600,000. (Obviously this is in a prime location but it certainly shows how desirable an annexe can make a property for resale and investment purposes.)



  • With no stamp duty on annexes
  • 50% Council Tax reductions or complete exemption
  • Possible inheritance tax savings
  • And a potentially considerably more desirable resale property for the main house owner.
  • It is easy to see why granny annexes offer not only a solution or lifestyle choice but incredibly good value for money in the short, medium and long term.