House With A Granny Flat – Everything You Need To Know

Ad Banner
Granny flat

You may see the words granny flat, annexe and annex and wonder what’s the difference? The truth is that they’re all different ways of saying the same thing. Granny flats are generally little known and talked about, but it is suggested they could actually help reduce your stamp duty bill (Daily Mail). Granny flats can ALSO increase the value of your house and help you earn an extra stream of income.

But what is a granny flat? And HOW could they help you earn an extra bit of money, whilst also helping you save on stamp duty? We have all the answers to these questions…

If you’re here to get a quick answer, this menu will help you get around:

Subscribe To Our Newsletter

We ask this in order to deliver you a better experience.


What is a House Annex?

An annex is a self-contained accommodation which is either attached to or built within the grounds of a house. An annex offers a degree of independent living, with them often containing a bedroom, bathroom, living room and kitchen. The general idea of an annex is someone can live in it without needing use of the main house.

An annex is a good option if you have an elderly relative who needs extra care but doesn’t want to go into a care home, as it allows them to still have their independence but also be close to the family, should they need some help.

What is the difference between an annex and an extension?
An annex requires there to be at least 50cm of space between the boundary and the building, whereas an extension can be built closer to the boundary, when attached to the main building.

Even if the part of the building in question is ‘self-contained’, having its own bedroom, bathroom, kitchen etc, if it’s attached to the main house then it will be classed as an extension rather than an annex.


Are granny flats worth it?

Obviously, people will have differing opinions on whether a house with a granny flat is worth it for them. Granny flats are good for those who have an elderly relative who may need extra care but doesn’t want to go into a care home. A granny flat could also act as an extra stream of income, should you choose to let it out.

As we mentioned earlier, the Daily Mail has also suggested that having a house with a granny flat can also help lower your stamp duty bill! How? Well, with a granny flat you’re able to claim for multiple dwellings tax relief. This is calculated by looking at the average price per dwelling, which is then multiplied by the number of dwellings, so in the case of a house with a granny flat would be multiplied by 2. The relief has a minimum amount of tax payable, which is 1% of total price.

This may sound a little confusing, so to help let’s work through an example…

Let’s say you bought a house with a granny flat for £1.5million (pricey we know, but bear with us)

The amount of stamp duty paid on this would be £78,750 (without the tax relief)

To work out how much you would pay with the tax relief:

The price paid is divided by 2 (as there’s 2 dwellings)

This is £750,000. The amount of stamp duty you would pay on this would be £12,500

This is then multiplied by 2 = £25,000. This is now the amount of stamp duty paid with the multiple dwellings tax relief on the house with a granny flat

That’s a saving of £53,750! WOW, maybe buying a house with a granny flat is worth considering!

*These calculations are based on the current stamp duty holiday, with the £500,000 nil-tax band ending on 30th June 2021.*

Granny flats are generally fairly quick to build and a good solution to those who may need extra space. A granny flat may also add extra value when it comes to selling the property. That leads us perfectly onto…

How much value does a granny flat add to a house UK?
Adding a granny flat to your property increases its square foot and therefore is most likely to increase the value. How much value the granny flat adds is dependent upon the size of the building and also the quality. However, it’s estimated most granny flats will add between 20-30% onto the market value.

A granny flat also gives your property a unique selling point and gives the property great ‘saleability’ as it can be let out, providing an extra stream of income. There are also not many properties that have a modern and good quality granny flat with the house and so if you market your property well, emphasizing the unique opportunity of a well decorated annex, then it’s likely to help it sell a little faster AND at a higher price!

If you’re blocking off already existing rooms in your house and converting them into a granny flat, this won’t really do much to increase the value of your home as you’re not increasing the square footage of your current property.


Can I build an annex in my garden UK?

The short answer is yes! You can build an annex in your back garden, BUT you will need to obtain planning permission first (which we’re going to cover in more detail later!)

If you have a smaller garden, it may be better for you to build the annex as an extension attached to the main house. This way the edge of the building can be closer to the boundary, unlike when an annex is built unattached as there must be at least 50cm of space between the edge of the building and the boundary.

How long does it take to build a granny flat?
This will be different from situation to situation. If you’re building a big granny flat of the highest quality, then it’s naturally going to take longer. If you’re blocking off existing rooms in your house to convert into a granny flat this may not take as long, mainly due to the fact you don’t need to gain planning permission first, which can take 8 to 10 weeks on its own.

The size and ambitions of your granny flat will be the main aspects determining the length of time it takes to build, but as a general idea, building a granny flat can take anywhere between 3-12 weeks. To give you a more specific time scale, suggests it will take around 5-7 weeks.

How much does a granny annex cost UK?
According to the daily mail typical costs to build an annex building are around £20,000 but may be more or less depending on size and quality. Most builders will base their prices off the size of the project and also the standard of the work, for example the intricacy of the design, quality of the materials, etc.

Area of the country will also play a role in the cost of building your granny flat, with the south of England generally being more expensive.

Here are some example figures which are based on a project located in the south of England:

Basic build
£1500/m2 new build areas
£800/m2 refurbished areas

Standard, high-quality build
£1650/m2 new build areas
£875/m2 refurbished areas

Premium quality build
£1800/m2 new build areas
£950/m2 refurbished areas
Figures taken from Resi

There’s also an option of choosing a pre-built granny flat, which are generally manufactured off-site in advance and then assembled on site. This is a quicker alternative to building your granny flat ‘from scratch’ but doesn’t necessarily mean a cheaper build (booo).

To help you get an estimate for what building your granny flat (or extension) may cost, you could use this extension cost calculator.

How many bedrooms can a granny flat have?
An annex building can have as many bedrooms as you choose to have. Although, it’s worth bearing in mind that the annex must be no more than 50% of the total garden area. Generally speaking, most granny flats are 1 or 2 bedrooms, but that’s not to say, if you have the space, you can’t build a 3- or 4-bedrooms annex.

According to a survey by Foxtons, the average back garden in Britain is 15 metres long, with the width being a lot less, giving a long and thin appearance to the gardens. Because of this, most gardens only have enough space for a single bedroom annex.


Do you need planning permission for a granny annexe?

Much the same as any building work, you do need planning permission before building an annexe. You will either need planning permission or a certificate of lawfulness from your Local Planning Authority (LPA). However, some leisure style buildings which won’t be lived in may not need planning permission, but it’s always worth checking with an expert.

Before applying for planning permission, it may be a good idea to use the help of an expert to help draw up the plans for your annexe. This way you will be able to give tweaks on your design which will make it more likely the plans will be approved, saving you time.

For example, if you want your annexe to have a pitched roof but your garden is quite overlooked, an expert may advise that it’s better for you to have a flat roof as it’s less visible to neighbours, and so will increase chances of planning permission being approved.

Another possible route is submitting your plans for planning permission under the Caravan Act. Having read that, you may be wondering HOW does the Caravan Act relate to your annexe? Well, in the Caravan Act it clearly defines what’s classed as a caravan and mobile home. This definition states any structure which is designed for human residence that can be transported by road is classed as a caravan or mobile home, meaning if your annexe can be removed and transported then it will be fall under this category.

Normally, experts will submit for ‘normal’ planning permission for your annexe and planning permission under the Caravan Act as a sort of ‘safety net’, in case any objections are raised. However, under the Caravan Act there are certain dimensions which can’t be exceeded. These dimensions are:

  • Depth – external 6.8 metres
  • Length – external 20 metres
  • Ceiling height – internal 3.05 metres

Once you have your planning permission approved, you will work with your local LPA to develop the land into an annexe. After your final design has been decided and submitted, planning permission normally takes around 8-10 weeks to obtain.

What is the minimum land size for a granny flat?
The minimum land size for your granny flat may differ from council to council, but a good guide to go by is a minimum size of 450sq metres for the whole land area.

Can you build a granny flat before the main house?
Unfortunately, granny flats can’t be built on unoccupied land and if you’re wanting to build a house with a granny flat, the house must be build first. Granny flats can also only be built on residential property, meaning if it’s commercial land you won’t be able to build one.


Do annexes pay council tax?

Yes, just like any house an annexe has to pay council tax and the local council will determine the tax band, taking into account all the living space including the main house. If it’s possible for someone to live in your annexe independently, without use of the main house, then it may fall into a different tax band.

Also, most councils will offer a 50% discount on the annexe’s council tax bill, if it’s lived in by a relative.


Can I let out my annex?

Yes, you are able to let out your annex, allowing you another stream of income. If you are to let out your annex, it will fall under the category of a ‘lodger’ rather than an assured shorthold tenancy. An assured shorthold tenancy is the ‘normal’ method of renting, as it grants the renter more rights in terms of notice periods and evictions.

It’s worth bearing in mind that if you are to let out your annex, you will now be considered a landlord, meaning you have certain landlord responsibilities outlined by the government.

The duties a landlord is responsible for are:

  • repairs to the structure and exterior of the property, heating and hot water systems, basins, sinks, baths and other sanitary ware
  • the safety of gas and electrical appliances
  • the fire safety of furniture and furnishings provided under the tenancy
  • ensuring that the property is fit for habitation
  • repairing and keeping in working order the room and water heating equipment
  • the common areas in multi-occupancy dwellings

The landlord is entitled to go into the annex to inspect it and carry out repairs.

Under the rent a room scheme, you can collect up to £7500 a year of tax-free rent. If you want to read more about the rent a room scheme, this guide may help give you some more insight.

What do you think about looking for a house with a granny flat? Do you think it increases the value of a house? Is it something you’d want in your next house? Get in touch and let us know!

Subscribe To Our Newsletter

We ask this in order to deliver you a better experience.

photo of Millie Archer

Millie is a perfectionist with a passion for property and writing articles. You’ll find her researching the latest housing trends and the newest up and coming areas worth investing in. Read more about Millie here.

Ad Banner
About Millie Archer 142 Articles
Millie is a perfectionist with a passion for property and writing articles. You'll find her researching the latest housing trends and the newest up and coming areas worth investing in. Read more about Millie here.

Be the first to comment

Leave a Reply

Your email address will not be published.