Flat conversion through Permitted Developments (B1 to C3)

Last year we were instructed to convert a disused office building into apartments. A small end of terrace Victorian house in South Bristol, the building had been used as an office for the last thirty years. The clients' brief was to create 3 new dwellings - utilising the roof space to increase the accommodation if required. 

The design of the new dwellings has to comply with DCLG's nationally described space standards ("Technical housing standards") which prescribe minimum floor areas and room sizes for new dwellings (see table). According to this table, the smallest acceptable development is a '1bed - 1 person unit' which requires a floor area of 39sqm. However when adopting the "Technical housing standards" Bristol City Council has stipulated that the minimum acceptable unit is a '1bed - 2person unit' which necessitates a floor area of at least 50sqm. 

 

In the case of this particular development, with an existing overall floor area of 122sqm it would have been impossible to gain planning consent for 3 units. That's why we considered using the Permitted Development route. Since 2013 office premises can be converted to residential use, subject only to local authority prior approval of a limited range of matters – as opposed to a more ‘traditional’ application for permission being required. The key difference is that when converting under Permitted Developments, the space standards don't apply. We submitted an application for "prior approval' for the new residential units (showing also refuse and bike storage) and consent was duly granted for 3 units of 45, 35 and 32 sqm respectively.

Having worked on numerous flatted schemes of various sizes, I think that it is possible to design good one-bed apartments from 36-37sqm onward - other considerations such as layout, outlook and amenity will be more important than mere floor area. To set a 50sqm minimum for all new homes means limiting the possibilities for creative solutions in smaller developments; it is all the more illogical when Permitted Developments conversions are not subjected to any space standards at all.

The main limitation is that Permitted Development conversions don't allow for any alteration to the exterior of the building and any external building work associated with a change of use will require planning permission. The skill is being able to fit the conversion within the existing building envelope; there is no impediment in submitting a separate application seeking consent for the work that might be needed to make the scheme workable or more appealing once the residential use has been confirmed.