Building a Home Annexe

Building a home annexe is one way to create more space within the boundaries of your property. It’s also a great way to maintain a degree of separation or privacy for the annexe building’s occupants, whilst retaining a strong link to the main heart of the family home.

For this reason a home annexe is also commonly referred to as a ‘granny annexe’, as they are an excellent way for an elderly relative to life in a self-contained annexe but hold on to more than a modicum of independence.

Whether you are planning on building a home annexe for this reason or not, there are several considerations you’ll have to make before you even begin to lay the first brick. This article looks at the basic fundamental planning permissions and regulations relating to the building of a home annexe.

Planning Permission & Buildings Regulations

When thinking of building a home or granny annexe, one of the first questions people often ask is whether they will need planning permission. It is nigh on impossible to answer this definitively, as each case is individual and can be subject to local planning by laws or restrictions placed on the house.

It also depends whether the annexe is classed as an extension (attached to the house and accessible from the interior, or not more than 5 metres from the house), or is going to be a detached self-contained building. If treated as an extension, you would most likely need to obtain planning permission.

If accessible from the interior of the house via an internal interconnecting, it will usually be treated as part of the main dwelling. So effectively the annexe would again be treated as an extension. If the annexe is a separate dwelling within the boundaries of the house and it’s land, then certain other buildings regulations will apply, such as fire safety routes and sound proofing.

You should note that anyone that intends to reside in the separate dwelling with a separate door for access would most likely have to pay additional council tax. The exceptions are usually relatives, dependents (including those that are mentally or physically impaired) and persons over the age of 65. In these cases you will need to complete a special annexe exemption form.

Use of Your Home Annexe

The classification of the new annexe will also depend on your intended use for it – it could be classed as a separate dwelling if self-contained and occupied by someone that doesn’t otherwise live in the house. If it’s intended for business use, it will definitely need an application. However, if the use of building is classified as ‘ancillary’, i.e. it may not need an application if it also applies to any of the following:

  • Under 10 cubic metres in volume
  • Not intended for business use, e.g. office from which a business is run, parking or storage related to the business
  • Under 3 metres tall with a flat roof or 4 metres high with a pitched roof
  • Not closer to any other highway (e.g. bridleway, road, footpath) than the main house
  • Not going to take up more than half of the area of the land around the original house
  • Not in an Area of Outstanding Natural Beauty, a National Park, a Conservation Area or The Broads
  • Not on the site of a house that is a listed building

This can vary between local planning authorities and the only way to be sure is to call your local planning officer for more information. Therefore the information submitted in this article relating to planning permission applications and buildings control approval is intended as a basic guideline only.

Converting an Existing Building to an Annexe

Many people may choose to convert an existing garage or outbuilding to create a home or granny annexe. This can require the material change of a building. You will have to meet and obtain building control approval, as many garages do not have adequate heating, insulation or fire safety routes. Installing or replacing a garage door with windows may also require building control approval.

You should consider that some houses with self-contained annexes would appeal to a smaller house buying demographic, therefore although the value of your house might increase, you will effectively be selling to a smaller market.

Alternative Annexe Buildings

Therefore a popular home annexe solution is to erect a log cabin in the garden. Log cabins are fantastically adaptable spaces, and many will not require planning permission (see above) if classed as an ancillary building.

If intended as a separate dwelling, they can be easily insulated and soundproofed, and fire safety routes and other buildings regulations are simple to comply with. Therefore, as long as your garden is big enough usually planning permission is easy to obtain. And the bonus is that a log cabin can be easy on the eye and form an integral part of your garden landscaping or garden design!