Rules for building Additional Storeys using Permitted Development

Transcription of the video

In this video, I go through the rules for building Additional Storeys using Permitted Development.

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Additional storeys

This is video No 7 in a series of videos that started with Video No 1 considering eligibility for Permitted Development.

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Start by watching video No 1

It is recommended that you watch video 1 before you watch this one.

This video has 3 sections:

(1) Exclusions, looking at which houses are excluded from eligibility for Additional Storeys

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Houses that are eligible

(2) Limits, examining the detail of what can actually be built

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Various dimension limits

(3) Conditions, looking mostly at how to engage with the planning authority

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Approval by planning authority

Exclusions

You cannot build additional storeys on a house if any of the following exclusions apply:

  • A change of use has been granted;
  • The house is on Article 2(3) land or on SSSI land;
  • The house is Listed.

The house must be constructed between 01 July 1948 and 28 Oct 2018.

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Date limits for construction

The onus of proof regarding the actual date of construction lies with yourself, not the council. And you need to prove that the entire structure was built in this period, not just part of the structure.

If the original house has been previously extended upwards (using Class AA or otherwise), the Additional Storeys benefit is not available.

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Excluded if previously extended upwards

Where a single-storey extension already exists, you can’t use the Additional Storeys provision to raise it upwards.

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Not applicable to single-storey extensions

However, it might be possible to do this under PD rules if it is a rear extension. Check out video 3 on Rear Extensions.

The building must not contain a flat (Part 20 of the Permitted Development Order allows for new flats on properties that are not dwellinghouses).

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Building must not include a flat

Limits on the number of storeys

There are limits regarding the number of storeys that you can build: 1 additional storey

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Limits on number of storeys

For a detached house, the roof ridge can be raised a maximum of 3.5m for an existing one-storey building, 7m for an existing multi-storey building.

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Raising ridge on a detached house

For a semi-detached house, the roof ridge can be raised a maximum of 3.5m above the highest part of the neighbouring building. For an existing one-storey house, you can go up one storey.

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Raising ridge on a semi-detached house

If your neighbour has already raised their house, then you can go up one storey.

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Neighbour has raised their house

For an existing multi-storey semi-detached house, you can go up one storey. In this case from 2 to 3 storeys.

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Multi-storey semi-detached

If your neighbour has already added another storey, you have a choice of adding one storey, or 2 storeys.

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Neighbour has raised their house from 2 to 3 storeys

For a terraced house, the roof ridge can be raised a maximum of 3.5m above the highest part of the terrace. For an existing one-storey house, you can go up one storey.

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Raising ridge on a terraced house

If your neighbour has already raised their house, then you can go up one storey.

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Terraced neighbour has raised their terraced house

For an existing multi-storey terraced house, you can go up one storey. In this case from 2 to 3 storeys.

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Multi-storey terraced house

If your neighbour has already added another storey, you have a choice of adding one storey, or 2 storeys.

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Neighbour has added 3rd storey

The overall height limit is 18m which, in practice, limits the building to just 4 storeys.

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Maximum height

Assuming 3.5m per storey and 3m for a pitched roof, adding 2 storeys to an existing 2-storey house results in a total height of 17m.

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Assume 3.5m per storey

The same height is achieved by adding 1 storey to an existing 3-storey house.

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Add 1 storey to 3 storey building

If the same house has a flat roof with a depth of half a metre, the overall maximum height achievable is 18m. This is achieved by adding 2 storeys to a 3-storey house … or by adding 1 storey to a 4-storey house.

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Maximum height with flat roof

Other Limits

The floor to ceiling height for an additional storey must be the lower of 3 metres, or the floor to ceiling height of any existing storey.

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Floor to ceiling height

Any additional storey can only be built onto the principal part of the house. This means the main part of the house excluding any front, side or rear extension of a lower height, whether this forms part of the original house or is a subsequent addition.

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Applicable to principal part of building only

Only the topmost storey of the house can be built on when constructing an additional storey.

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Topmost storey only

Existing accommodation within the roof of a house is not considered to be a storey or a topmost storey.

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Existing loft accommodation is not topmost storey

The roof pitch of the additional storey must be identical to the existing roof pitch. You cannot build an additional storey with a pitched roof if there was previously a flat roof.

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roof pitch must be identical

The development must not include a window in any wall or roof slope forming a side elevation of the house.

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Side windows limited

The materials in the development must be of a similar appearance to the rest of the house.

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Materials must match original

There must be no visible support structures on the exterior of the house upon completion of the development.

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No visible supports

Any external works added to strengthen existing walls or foundations must not be outside the curtilage of the house.

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Works must not be added beyond curtilage

Conditions

You will need to complete the development within 3 years and it must then be used as part of a C3 dwellinghouse or ancillary to the primary use as a dwellinghouse.

You will require Prior Approval from the local planning authority, who will consider its external appearance.

An appeal decision in 2021 has clarified the extent to which councils can make visual assessments. They only have the power to judge the appearance of the house as it looks itself – they cannot examine the development in context with the surrounding area.

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Visual assessments cannot be made in context

The planning authority will also consider the impact on adjoining property and on any protected views

Thats it for this video

That was the last one of this series. If you have suggestions for other videos or even a completely new series, I’d love to hear from you.