Class AA Permitted Development-Adding storeys to existing properties

October 12, 2021 by Ant Homin in forum Planning Forum

#1132 Ant Homin, 12 October 2021, 22:28

Can anybody provide insight / confirmation on eligibility criteria for the new Class AA development category that allows new storeys to be added to existing buildings. In particular, would a property that has already had a 1st floor extension be excluded ?.

The regs state that development will not be permitted if

"the existing dwellinghouse has been enlarged by the addition of one or more storeys above the original dwellinghouse, whether in reliance on the permission granted by Class AA or otherwise;"

Seems straight forward if a building has already been extended upwards and the extension covers the entire ground floor but what about the situation when an extension has already been carried out which only covers part of the property ? When I originally read the Order my first impression was that any extension already constructed ontop of the original property would be considered part of a storey and therefore the property would be excluded from Class AA. On this basis a significant number of properties would be excluded - doesnt seem unreasonable in current times to give the impression of a significant relaxation but only very limited application !!.

The other (optimistic) interpretation on second (and more careful) reading is that a property with a 1st floor extension would only be part of the storey, and only extensions covering the entire ground floor would preclude Class AA permitted development rights.

I am sure the words in the Order have been chosen with great care to avoid unintended interpretations. My query relates to a “dormer style” house which was originally constructed with a single storey kitchen extending out the rear of the property and the habitable floor space upstairs (1st floor) is only about 2/3rds that of the ground floor. A bedroom has been added above the kitchen (ie adding to the first storey), by raising the hipped roof which now finishes just below the main ridge of the house.

We are seeking to increase the upstairs floor area and add a second floor bedroom which will require the existing ridge height to be increased. What is the chance of being able to apply the new permitted development and avoid the resistance to increasing the ridge height through the usual planning process ?.

#1135 Damian, 15 October 2021, 20:02

You cannot add on top of an existing extension and therefore only above the original/as-built dwelling.

Just out of interest, how much would you need to raise the ridge by, in excess of 1m?

#1137 Ant Homin, 16 October 2021, 10:30

Thks for the response.

To get a 2nd floor room will require raising the ridge by 1.6 / 1.7m.

I had appreciated that you couldnt add on top of an existing extension but was concerned that any previous extension to a property would exclude using this new PD from adding any new storey. In my case the previous first floor extension (above the single storey kitchen) is outside the envelope of the main body of the house so should be ok. Also, since making the original enquiry I have seen several successful applications for properties that have already had extensions.

However, if a house has already had a second storey extension over part of the original house would it be possible to use this PD to complete the reminder of the storey over the unextended part of the property ?

#1138 Damian, 16 October 2021, 18:01

The thing that may catch you out is, is the existing extension something that would meet the new PD guidelines, e.g. above the original part of the house, roof pitch same as existing, no side facing windows, etc…? If so, then the new floor together with the existing should all meet those guidelines and therefore be considered PD.

#1139 Ant Homin, 16 October 2021, 23:35

Interesting thought, which becomes more intriguing for an extension partly within the original part of the house.

We are still considering layouts and developing options but I expect it will be 4 – 6 weeks before making any submissions but will endeavour to update the forum with the outcome.

Going down the PD route is not the preferred option but (if permitted) would establish a ridge height about 2.7m above the existing which is considered to be one of the main obstacles of planning consent to add a second storey room. Overall both options provide similar floor area albeit the PD option would be less well configured having reduced area on the first floor but gains a room on the second floor. The planning option as currently envisaged (to minimise the ridge height) would have a lower ridge with hipped sides to avoid a blocky appearance. One thought is to make a submission for the PD. If successful we could then try and get planning consent in the knowledge that it would be possible to fall back on the PD option.

#1140 Damian, 17 October 2021, 10:30

On an application I have recently come across, the condition (as you mentioned) states…

“the existing dwellinghouse has been enlarged by the addition of one or more storeys above the original dwellinghouse, whether in reliance on the permission granted by Class AA or otherwise”

On that particular application, the Planning Officer stated…

“the existing dwelling has not been enlarged above first floor level, therefore the proposal would comply with this criterion”

Because yours does already have the additional storey, it technically wouldn’t comply with that condition. But if you were to remove it and re-build as part of the Prior Approval process, then that ‘should’ be permitted. Not ideal but the wording of these conditions/restrictions is done in a way to catch people out on a more practical front.

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