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Granny Flats – What are some of the things to consider when building?

Granny Flats – What are some of the things to consider when building?

A granny flat is a kind of extension to your main home that allows for self-contained accommodation. This can be a separate annexe or a building that is attached to the main home or even a separate granny flat in the house.

Most of our constructions are separate buildings, built in the garden of a property. Essentially a small bungalow which is entirely self-contained and has its own facilities such as kitchen, shower room and living room.

The size of accommodation that can be built, will depend on a variety of factors. This includes the size of your garden, local planning authority rulings and whether you are in a conservation area or not.



What are some of the considerations when building a granny flat?

  • If a granny flat is considered to be a separate dwelling, you will need to apply for planning permission.
  • Size of the annexe compared to the size of your main house. A granny flat must never be more than 50% of the total size.
  • The building needs to be considered separate and ancillary to the main building.
  • Planning authorities will want to know how the building will be used and who will be using it.
  • Planning permission for an annexe will only ever be granted for a family member.


Every local planning authority is slightly different and might ask for varying requirements for fulfilling the application. At Granny Annexe we use a specialist planning company who is familiar with the planning process for annexes and granny flats and know how different local planning authorities work and particular requirements for certain areas. We offer a complete turnkey service meaning that we take care of every aspect of the build from start to finish. We can submit an application on the client’s behalf at an additional cost of £1672.00 inc VAT.



Unlike some companies, we do not recommend using the Caravan Act instead of obtaining planning permission. This is because, in order to build under the Caravan Act, a building needs to be classed as temporary and mobile. Our annexes are neither of these things and we believe a home should be a solid and permanent structure. As such our buildings are constructed using solid concrete pad foundations and robust structurally insulated panels.

It is important to choose a company that understands the process and is able to design a building that will comply with certain LPA regulations. We have designed 1000’s of granny annexe for customers all over the country taking into consideration particular planning requirements. The requirements might include external design such as the colour of the render, cladding in particular colours or whether it is a flat-roofed or pitch-roofed building.


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Is my garden suitable for a granny flat?

In order to have an annexe built in the garden, there are a number of things to consider to determine if your property is suitable for this sort of building. Some of the main considerations are whether your garden is big enough, where your main house’s services are located, and where your house is located in relation to neighbouring buildings.

Size of garden

Your garden would need to be at least around 5 – 6 metres wide to accommodate a granny annexe in the garden. Most peoples gardens are of the long and thin variety meaning that an annexe can be positioned lengthways rather than longways to fit in a narrower space.

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Typically the narrowest annexe we build is 3500mm and there would need to be a least 1 metre of space either side of the annexe to the boundary. We are able to design buildings that will work in a huge variety of spaces, so even if you think your garden might not be suitable, it can still be a good idea to phone us and check in case there is something we can suggest.

Another option when considering a granny flat in a smaller garden might be to opt for an annexe extension instead. A granny flat extension uses the same building techniques as our normal annexe buildings but with the advantage of being connected to your main house. This can be beneficial in a number of ways. Firstly our specially designed single storey extensions can often be built within permitted development. Secondly, if you have a small garden then an annexe extension might help you to make the most of your garden space. Thirdly an annexe extension can create a more versatile building that can be used for a number of functions if the house is sold later.



Even though annexes are ancillary buildings they still, in most cases, share services with the main home. Electricity, water and sewage connection is included in the price of our buildings up to 20m. In some cases where connecting to the sewage is not possible, then a septic tank can be installed instead. It is also possible to install separate meters for each property in case you require separate billing.  With this in mind, how your main properties services are laid out is a clear consideration when we are doing a site survey and planning the design of a new granny flat.


Location Location Location

Certain locations require some special requirements when it comes to planning and local authorities. If you are living in a conservation area or an area of outstanding natural beauty then there might be additional conditions asked from the planning authority regarding the look and design of the building. Also, the proximity to neighbours can have a bearing on the design of a building. Neighbours might ask for a certain material or colour to be used or the height of the building might be affected if the building is very close to the boundary.


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