What Is The Cost Of Building An Annexe?

3 of the most frequently asked questions we get asked about annexes are:
What are the planning permission options?
How are annexes constructed?
How much do annexes cost?

If you have been following us for some time you’ll know we’ve been involved with annexes and annexe living since 2011 when we part of the Sales & Marketing team at the Ideal Home Show which featured a stunning Open Plan Contemporary style log home from Sweden.

Since then, we’ve been featured on Amanda Lamb’s My Flat Pack Homes TV Show, been featured at the National Home Building & Renovation Show & Grand Designs Live and spoken with literally thousands of people about the best way to go about building an annexe in the back garden.

We consider ourselves to be the best free advice you’ll get anywhere in the annexe sector and if you have a question, please feel free to contact us on the website or on our Facebook page if that’s easier for you.

So let's talk about costs and some of the reasons they vary so much

We believe in the saying “You get what you pay for.

Whether that’s planning permission for an annexe by way of either a Certificate of Lawfulness or Householder’s Planning Permission or the type of annexe you are thinking of buying.

Annexes are a major purchase and should be considered as such.

Chances are they will be the second biggest purchase you make (after you main home.)

And therefore weighing up all the options available can be difficult for many people as it is not something many people have ever done before.

In fact if you say to someone this week, “I’m thinking of building an annexe in the garden for my Mum” you may well get a very puzzled look back at you with the question, “What’s an annexe?”

This may help to visualise what a modern day annexe may look like, we think they are beautiful 

Annexes involve every trade a full house build would require

Why annexes cost as much as they do? It takes a huge amount of time, effort & skill from multiple trades & people to either manufacture & build an annexe to your specification or to build an annexe on site in your back garden.


You will need the design skills of an architect or an annexe expert (luckily all of our Garden Lodges are architecturally designed and we’ve been designing custom annexes ourselves for years so we know what works and what doesn’t.)


The Planning skills of an annexe expert. (even if you choose the Certificate of Lawfulness route. It is still highly specialised). Without planning permission or permission to site an annexe in your garden you simply cannot proceed any further. (We have a very high success rate in achieving this for you.)

Structural Calculations & Electrical Planning

You will need structural calculations and a full electrical plan. (We offer these as part of our full turn-key service.)

Mains Service Connections

Once planning permission is approved or a Certificate of Lawfulness is obtained you will need to prepare your foundations and connect to your mains services. (Again, we offer this as part of our turn-key service.) Annexes must be ancillary to the main house and share the mains water, electricity and sewerage.


You will need an expert team to construct your custom annexe. Our annexe installation teams are some of the most experienced in the UK. Or to supply & fit a Residential Mobile Home to BS3632 standards you'll need an expert team to manufacture, deliver, site & install your garden lodge. We offer both.

Roofing & Internal Fittings

Following on from all that is the finishing of the build itself which will require roofing, “A” rated windows & doors, a heating system or electric radiators, cladding, flooring, carpentry & joinery, kitchen, bathroom, plastering, electrics, heating, painting and decorating.

Turn-key Service

It’s an exhaustive list of skills & trades that combine to become zero rated for VAT when built as a turn-key service saving you 20% when compared to an extension.

Saving Budget

Most people quickly find their budget runs away with them if they try to source each element individually as they then attract VAT @ 20%. This makes it far less cost-effective than opting for an all encompassing turn-key service like ours.

Your Dream Annexe

You want to end up with a warm, stylish annexe that is great value for money & ticks all the boxes for the planners and for you as a family.

How to get the best price for an annexe?

Online Search

Google is one of the best inventions ever for researching and finding information about anything & everything today – but nothing beats talking to someone about your project. It is by far the best way to get a price for your annexe project and understand what’s involved.


Be realistic with your budget. If you have a budget of under £50,000 in mind for a building the size of a small bungalow, fully fitted out with foundations and services connected you are not simply not being realistic.

Price Expectation

Expect to pay between £89,000 and £130,000 for a high quality annexe build, either on site or manufactured and delivered. Our custom annexes and garden lodges offer you the widest choice available helping you match your perfect floor plan and budget whenever possible.

Online Calculators

Take online calculators with a pinch of salt, most of them do not factor in the man power or expertise required to build or manufacture an annexe.

Find Your Price

Our entry level custom annexes and garden lodges are both around the £90,000 price point for a turn-key service.

Cost Per Sq Metre

Cost per square metre are only a guide as economies of scale, site specifics and location will all be a factor in your final quoted annexe price.

High End

If you have a budget in mind of £150,000 or more, you can expect to be able to push the boat out when it comes to what is possible with annexe design today. However you will always need to bear in mind what may or may not be permitted by your Local Planning Authority.

The Popular Choice

With designs like the Hampton available you can see exactly why more and more people are choosing annexe living today than ever before.

Important considerations for getting the right annexe at the right cost

In Summary

Sharing is caring!

Custom Annexe & Garden Lodge Brochures

Please enter your details and press “submit” to immediately receive our latest brochures.

Don’t forget to check your ‘junk’ folder if you don’t immediately receive a thank you email from us.