Garage Conversion Granny Flat - are they allowed under planning?
Most garage conversions can be built without the requirement for formal planning
permission. This is called permitted development rights or allowances. The use of your garage conversion is not
really relevant for this Permitted development so to use a garage conversion as a granny flat is quite
However, problems can arise if the proposal does require formal Planning Permission because of a condition on a
previous implemented planning consent seeking to control the use of the garage solely for that purpose for
Planners often see the formation of any annexe accommodation as a back door approach to establishing a separate
residential dwelling and all the undesirable problems that often brings such as additional on road car parking
problems, over crowding, sub-letting etc.
Therefore, a garage conversion for use as a granny flat needs to be considered carefully on how it is presented
if formal Planning permission is actually required as the Planners will have final and total control of what you
can do. As a general guide for presenting garage conversions as granny flats you may want to make the proposal
reliant and interconnected with the main dwelling with a degree of shared facilities. Any attempt to make the
granny flat garage conversion fully independent and with its own front door for example will probably be resisted
and refuse formal Planning permission.
So, is there a way around this if formal Planning Permission is required for the granny flat within the
converted garage and you do require a high degree of separation for a fully independent granny flat? Well yes but
it is a devious approach and not without risk.
You simply show the proposal with a high degree of interconnection shared facilities for Planning and then do
what you want to the internals during the build and through Building Regulations to keep it legal. Perhaps a
doorway does not get installed as shown on the planning scheme. Perhaps the shared utility suddenly becomes the
main kitchen for the granny annexe. As a rule, most Planners have little control of the internal layout of a
property so their continued control for such minor internal alterations after approval is somewhat constrained.
A clever and well experienced house extension designer or architect will be able to manipulate a design for a
granny flat garage conversion without too much fuss or complication and re-engineer it slightly for the build after
Planning Approval has been obtained.
The risk is that the Planners find out and do take action to enforce the originally approved layout. Again there
are ways and techniques to avoid compliance but it can be stressful and expensive.
So, in conclusion, any garage conversion for use as a granny flat is fully acceptable if it falls under the
sites permitted development rights (works you can do on a property without the requirement for formal Planning
Approval). Each home owner is to establish this fact as a basic first step principle and present a scheme to the
Council for a Certificate of Lawful Development to obtain legally binding written confirmation that the garage
conversion to granny flat is indeed PD or permitted development.