Should I go for an annexe or an extension for planning?

11 March 2014

My husband and I are buying a house with my daughter and her family. We plan to rebuild the garage and other rooms which already have planning and add a new bedroom, ensuite and study which doesn’t. The property is in an area of outstanding natural beauty so we cannot use permitted development rights.

Can you please tell me which is the best way to apply for planning permission. Would it be as an extension to the main house or as a granny annexe? Which one could have its own address and which one has the most to gain financially regarding council tax etc? Also, which would be most likely to get planning? The planning officer has told us we will get it as there are no planning issues with what we want to do, but I think she was looking at it as an extension.

We’d also be interested in finding out which system is cheapest to build with – a 12′ x 7′ wall in insulation block or the same wall in timber partition and insulation.

Thank you for your valued help!


Hi Jilly. As a rule, an extension is likely to be less contentious than an annexe at the planning permission stage, especially if the latter is self-contained.

Your mention of a separate address and council tax liability are both things that are suggestive of a new, separate dwelling – rather than an annexe – and should be avoided. If the planning officer is happy with the layout and regards it as merely an extension, then apply for it as such. As you are one family then how you divide up and use the internal space of the dwelling, once built, is of no interest to the planning system – assuming you don’t entirely subdivide the property. Maintaining internal doors between the main house and annex is important in this regard.

If your application suggests you’re trying to create what is effectively a new self-contained dwelling, then it’s likely to prove far more contentious, especially in AONB countryside.

Mike Dade, Build It expert and planning consultant at Speer Dade

11 March 2014

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