How Long Does It Take To Build An Annexe?

How Long Does It Take To Build An Annexe?

Granny Annexes are fast becoming annexes for alternative ways of solving some of today’s affordable housing issues.

They are perfect for retirement planning & elderly care (granny flats), young independents first homes, single parent & single income homes and they are also a great way to downsize & free up equity too.

The concept is simple. 

Annexes typically range from around £85,000 to £200,000 and are classed and built as mobile homes.

This means they attract zero rated VAT saving you thousands of pounds when compared to an extension on your main home.

Most annexes have one or two bedrooms, an open plan living / dining / kitchen area, a bathroom and come fully equipped and decorated ready for you to move in.

So how long does it take to build an annexe?

Let’s dive in to that in more detail in this week’s feature article.


The Decision Stage: Approximately 2 Months For Most People

The decision to build an annexe is probably the most difficult because it usually involves several or many members of your family deciding how it will work together.

With issues such as inheritance tax, council tax, running costs, moving costs and more to factor in financially, the process is not one to decide on without giving it clear and careful thought.

For the record, we’ve never known anyone build an annexe and regret it yet!

It’s typically a win / win for all concerned.

Once the family have decided that an annexe is the best solution for them, most people get 3 quotes from companies like us 😉 to see which one offers the best solution within their budget.

We’ve found that the quotation and deciding process can take as little as two weeks and as long as 3 months depending on the circumstances.


The Planning Permission Stage: 10 Weeks On Average

Once you have decided on the company you would like to build your annexe you will usually be required to pay a deposit and / or a planning fee to proceed to the next stage which is the all important Planning Permission stage.

Now everyone tells us they have the worst Local Planning Authority in the country,

A select few Local Planning Authorities have a no annexe policy in place. In which case you should consider the Certificate of Lawfulness route.

And of course if you live in a conservation area, have a listed building, or live in an area of outstanding natural beauty, this process may be more challenging although it has been done and can be done when you choose the right company to work with and deploy the services of annexe planning specialists.

Everything relies on this process.

You cannot live in a mobile home, annexe or caravan in your garden without it.

Once you’ve decided on the company you want to build your annexe, the company will need to prepare and submit your Planning Application or Certificate of Lawfulness to your Local Planning Authority.

They will then validate it. (If they are busy they can sometimes take several weeks to do this.)

Once it is validated, your appointed Local Planning Officer has 8 weeks in which to determine your application.

In rare cases, (depending on the level of work your Local Planning Authority is dealing with at any one time) an extension of time may be requested which can take a further 3-4 weeks.

The quickest we’ve ever come across is 4 weeks to approval, the longest we’ve ever experienced was 15 weeks.

Both were successful.

The Foundations And Services Stage: 1-2 Weeks (On Average)

Once Planning Permission is approved or a Certificate of Lawfulness is granted, we have the green light to proceed to the build stage of your annexe.

The next stage is to prepare the foundations and mains services connections for your annexe.

This process typically takes 1-2 weeks depending on where your services are , what ground preparation is required and the overall size of your annexe.

For most build on site annexes (our custom annexes) we use concrete pad foundations.

Some of our build off-site annexes (our lodge style annexes) may need a concrete pad foundation.

Either way, our team usually complete this stage of your annexe build in 2 weeks or less.


The Annexe Build (On-Site Annexes): 8 to 14 Weeks

We use timber-frame kits for our build on site custom annexes.

These require a short manufacturing time of typically 2-4 weeks.

To keep things moving along we usually plan and prepare the foundations during this time and go back through all your final interior choices ready for the build itself.

Once the kit is manufactured and delivered to site, it’s all systems go for the build.

From the erection of the frames, windows & doors, roof & cladding externally to the fitting of the bathroom & kitchen, flooring, plumbing, electrics, painting and decoration internally, the average build on site is typically 7-14 weeks to completion depending on the size and specification of the annexe.

We allow a couple of days at the end of the build to go through any snagging you may have before we complete the handover of your new annexe.


The Annexe Build Off-Site Model Typically Takes Around 10 Weeks To Manufacture

If the thought of having an annexe built on site fills you with dread, you may prefer a build off-site lodge style annexe instead.

It’s built to your final specification, put into manufacture for an average of 10 weeks and then delivered and sited in 4 days or less.

Manufacturing times can vary by a number of weeks depending on the time of year.

It’s a very simple, stress-free way of building an annexe in your back garden but you will need good access (at least 14 feet wide) to accommodate the delivery.

Once you decide on the model, specification and floor plan of your lodge style annexe, you will need to make a visit to the centrally located design centre and choose all your internal finishes.

We have mood boards to help make this process and easy as possible plus show models to pop into so you can see what everything looks like.

Once that’s done, you can put your feet up & relax!

We’ll prepare the foundations and services in the normal way and arrange for the delivery of your new annexe.

It really can be as simple as that.



  • We offer a full turn-key service for either a build on site annexe or a build off-site lodge style annexe that includes applying for the relevant permission from your Local Planning Authority.
  • Planning usually takes 8-10 weeks from the time your Local Planning Authority validates your application.
  • Foundations typically take 2 weeks or less.
  • Build on site annexes typically take 7-14 weeks depending on size and specification, you also need to allow extra time for manufacturing.
  • Build off-site annexes typically take 10 weeks to manufacture then 4 days or less to deliver and erect on site.

As always we look forward to your thoughts and comments below or join in the conversation on our Facebook Page! Use The Contact Us Page To Email Us With Your Enquiry.

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