Rules for building Rear Extensions using Permitted Development
Transcription of the video
In this video, I go through the rules for building rear extensions under Permitted Development
This is video No 3 in a series of videos that started with Video No 1 considering eligibility for Permitted Development. Video No 2 listed the 10 conditions applicable to all extensions.
It is recommended that you watch videos 1 and 2 before you watch this one.
Looking first at a SINGLE-STOREY rear extension, the overall height cannot be more than 4m.
The eaves of the rear extension cannot be higher than the eaves of the original house.
And, where the extension is within 2m of the boundary, the eaves cannot be higher than 3m.
The Maximum Depth
This increases if you secure prior approval for a longer extension.
Without prior approval ….A single-storey extension must not extend beyond the rear wall of the original house by more than:
3 metres for a terraced or semi-detached house
and 4 metres for a detached house.
The rear wall or walls of a house are those which are directly opposite the front of the house.
The maximum depth is measured from the base of the rear wall of the original house to the outer edge of the wall of the extension (not including any guttering or barge boards).
With prior approval, a single-storey rear extension can be up to 6 metres long for a terraced or semi-detached house
and, up to 8 metres long for a detached house
Note that prior approval for a longer rear extension is not available if the house is on Article 2(3) land or on a site of special scientific interest
Neighbour Consultation Scheme
Prior approval is achieved by engaging in a neighbour consultation scheme. Before the development is started, the local planning authority must receive:
- a written description of the proposed development
- a plan showing the
- original house
- any existing enlargement to which the enlarged part will be joined
- and, the proposed development
The local planning authority must then give adjoining neighbours notice of the proposal and the opportunity to object. If anyone objects to the proposed development, then the local planning authority must assess “the impact of the proposed development on the amenity of any adjoining premises”.
If the Planning Office does not make a decision regarding the prior approval within 42 days, work may commence on the extension. If the Planning Office does make a decision regarding the prior approval within 42 days, it is likely to be one of the following, Prior Approval is:
- Not required
- Granted with conditions
With the first 2 decisions, work can commence. With the latter 2 decisions, you have the option to appeal.
Where a new extension is joined to an existing extension, the limits described above still apply. On a terraced or semi-detached house with prior approval, the maximum allowable depth is 4m.
With a pre-existing 3m rear extension, you can only extend a further 1m under PD rules.
On a detached house with prior approval, the maximum allowable depth is 8m. With a pre-existing 3m rear extension, you can extend a further 5m under PD rules.
Where the original rear wall of a house is stepped, then each of these walls will form ‘the rear wall of the original dwellinghouse’.
In such cases, the limits on extensions apply to any of the rear walls being extended beyond. On this example, a semi-detached house has an original ‘stepped’ rear elevation.
If 3m extensions are added to each step, this complies with PD rules. In this example, the houseowner wants to extend the original ‘stepped’ rear elevation to achieve a continuous rear wall.
On the right, this part of the extension would be 9m long and so it cannot be achieved under PD rules
DOUBLE STOREY rear extension has the following limitations:
You are not allowed to build a double-storey rear extension on Article 2(3) land.
A double-storey rear extension has a maximum allowable depth of 3m on all types of houses (whether detached, semi-detached or terraced) There is no opportunity to extend further by prior approval.
Where a new extension is joined to an existing extension, the 3m depth limit applies to the total enlargement. For example, this detached house has an existing, single storey, ground floor extension (not part of the original house) with a depth of 4 metres. It is not possible to add a first floor extension above this under PD rules as the total enlargement of the house would then consist of more than one storey and would extend beyond a rear wall by more than 3 metres.
A double-storey rear extension must be at least 7 metres away from any boundary of its curtilage which is opposite the rear wall of the house being enlarged.
This example does not comply with this limitation
This example does comply.
The extension roof pitch must be same as the original house roof pitch.
Any upper-floor window situated in a side elevation of the dwellinghouse must be obscure-glazed to level 3 (One-way glass is not compliant)
Also, the window should be non-opening unless the opening part is more than 1.7 metres above the floor of the room
Where such a window is on a staircase or a landing (i.e. not in a room) the 1.7 metre measurement should be made from the stair or landing immediately below the centre of the window, upwards to the opening part.
Thats it for this video
In the next one, video No 4, I’ll go through the rules for building side extensions under Permitted Development.