The ‘granny’ annexe has deep roots, but now it’s annexes of all kinds that are in high demand.
Councils received around 9,000 planning applications for them in 2019/20 — that’s 25 a day, according to Churchill Home Insurance.
Around a fifth of these are to convert existing outbuildings like a garage or a shed. But the large majority are for completely new premises in the garden — for childcare, home schooling, office space and shielding, which were cited among the biggest reasons.
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There’s a cash bonus to this. Churchill claims annexes add an average £91,000 to the value of a home and make it a far better proposition when it comes to selling.
‘Any property with a purpose-built office or studio gains more interest from purchasers.
It is also a common request from buyers on their wants-list,’ says Giles Davidson of Hamptons estate agency.
So how do you go about joining Britain’s annexe army? Firstly, decide on size and purpose. If it’s serving a single function — like a games space or a home office — it need only be a large room, perhaps with a loo and basic kitchenette.
If it’s for use as a home gym it may require stronger floors and walls; and if it’s for something like recording music (or playing music in the case of teenagers) consider the best soundproofing you can afford.
By contrast, if the annexe is to host people overnight — whether friends or Airbnb or holiday let guests — most annexes would have at least one bedroom and en suite bathroom, a living space and a modest kitchen.
Large purpose-built annexes are likely to require a full planning application
Secondly, choose whether you buy a kit or get a one-off purpose-built annexe.
Some companies offer flat packs: prices vary according to size and materials, with basic costs topped up by add-ons such as toilets, showers, air conditioning and extra windows. If you’re going for a purpose-built annexe, hire an architect or specialised company and expect to pay more.
Thirdly, submit a planning application — if required. It’s likely that a simple conversion of a garage or an existing garden house into living quarters may not need planning consent, but larger purpose-built annexes are likely to require a full application. These should take no more than eight weeks to be agreed or rejected.
The Government has relaxed so-called permitted development rules but there are strict limits on height, size and uses for annexes, plus extra controls if the main house is listed or in a conservation area. Check planningportal.co.uk.
Finally, treat the finished annexe as part of the house for insurance purposes.
‘Anyone considering constructing or converting a garden annexe needs to inform their insurer that work is taking place and consider the additional building and contents on their policy once it’s complete,’ says Pritpal Powar of Churchill.
Such is the growing popularity of annexes that many estate agents suggest sellers with sufficiently large gardens or land secure planning permission for one ahead of putting the property on the market — even if they don’t build it.
For the buyer, this consent gives a signal that they can build an annexe if they wish, including an idea of size and position. Consent also adds to the value of the property, so both sides of the deal gain.