Loft Conversion Planning Permission - when is it required
Most loft conversions are completed under the sites permitted development rights but this
legislation is riddled with requirements and clauses and sometimes a loft conversion will require planning
permission. When a loft conversion does require planning permission first, the final design may be different from
what could be achieved under permitted development.
This is because Planning Policy seeks to control the external sign and neighbour impacts and this is based upon
planning policy wording and a Case Planning Officers opinion which can be a very subjective issue which can often
lead to a refusal.
A formal planning application for a loft conversion can also trigger other tick box planning requirements and
testing such as the sites off road car parking facilities for the extra bedroom created. Many houses in urban town
environments do not have any off road car parking spaces at all or are already deficient in numbers with
problematic on road displaced car parking. Again, this is another valid planning reason for the Planning Department
to refuse planning permission for your loft conversion.
You can see why, most loft conversions are often ‘reversed engineered’ for the permitted development route in
order to avoid formal planning permission. Here are a few reasons why a loft conversions may require formal
1 - The new dormer window affronts a highway and is the principal elevation of the property.
2 - The roof has already been extended by over the required volume (40 and 50 cubic meters per type of
3 - Part of the loft conversion works extend higher than the existing roof ridge line.
4 - The property is within a conservation area or AONB (Article 1(5( land).
5 - Includes for an external balcony, veranda or raised platform.
6 - The external materials do not match the existing (similar appearance)
7 - The new dormer window is less than 200mm from the existing roof eaves edge.
8 - A side facing dormer does not have obscure glazing or has an opening sash below 1.7M off the floor.
There can be other technicalities that would trigger the requirement for a formal planning permission for a loft
conversion and your experienced house extension designer or architect can explore and explain these issues with you
during the design build up process of your particular scheme.