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How Long Does It Take to Build a Granny Annexe?

image is a blog header for a blog post about how long it takes to build a granny annexe

One of the first questions you will want to ask when building a granny annexe is, how long will it take? This isn’t a straightforward question as there are quite a few variables we work with on builds, including site preparation, planning permission and of course, annexe size.

Below, you will find average turnaround times for most granny annexe builds, and some customer examples.


Planning Permission

The first step in building a granny annexe is obtaining planning permission from your local authority. If you come to iHUS and ask that your annexe be completed in three months, this would be impossible as planning permission itself can take three months.

We say to allow three months for planning permission as decisions are usually made in eight weeks, but it can take a few weeks to get the permission granting process.

When you work with iHUS to build your granny annexe, the planning permission stage is included as part of our service. This can save you a great deal of hassle having us handle the process for you. It’s unlikely that you will be denied permission for a standard annexe, but we can advise you with a free consultation and assessment of your garden how likely you are to be granted permission.

image shows a builder working on a granny annexe

Building Your Granny Annexe – The Process

Once planning permission has been granted, we can crack on with building your granny annexe. This is an exciting time for our customers and our team work quickly to ensure that the finished product is delivered as soon as possible.

To enable us to work as efficiently as possible, we come at your build with a two-pronged approach; we start groundwork on your property and at the same time, your annexe will be assembled in our factory.

It is exciting to watch your new granny annexe come together and whilst we are busy building the annexe structure at our site, our team will be on your garden getting the basics in place. The initial groundwork includes laying trenches for services and putting the foundations in place for your annexe to sit on.

Once the groundwork is complete (usually around two weeks), your annexe will be brought onsite, sort of like a flat pack house! Once assembled our team will continue working to get you in your new annexe as soon as possible.

This part of the build includes plastering, internal fixtures and fittings, plumbing and of course, the exterior of the annexe will be completed with your choice of cladding.


So How Long Does It Take in Total?

Our more compact annexes take around 7-8 to complete, on average, and a small two-bedroom annexe will take 8-11 weeks. So, including planning permission, you are looking at an average project time of 5-6 months. This is from sales consultation to having the keys in your hand.

Wilson Annexe iHUS Community
This custom annexe, built for customer Margaret Wilson took ten weeks to complete.


For a good example of what we can achieve, the above annexe, built for Margaret Wilson in Kent, took 10 weeks to complete. The bespoke flat-roofed 2 bedroomed annexe was finished with an oversail canopy, fitted with LED downlights. The external walls are clad in Dark Grey Marley Cedral composite weatherboard to give the annexe a very contemporary look.


Get in Touch

Why not take advantage of our free onsite consultation? We can run through what you are looking for, survey your garden and give you an accurate project timeline. Contact us today to start the process.