Lambeth Building Alterations and Extensions Supplementary Planning Guidance gains approval

On Monday 14th September Lambeth Council gave the green light to the long anticipated Lambeth Building Alterations and Extensions Supplementary Planning Guidance (SPD).

Up until now many homeowners and landlords wanting to extend or convert their properties found their hopes thwarted having their plans turned down by restrictive regulations.

The new planning guidance which comes into force on 23rd September 2015, is great news for many of those people as they may find their plans are now acceptable.

Rising stamp duty and skyrocketing house prices have meant many Lambeth residents have taken a ‘don’t move – improve’ approach, extending or improving their existing homes by converting the loft into extra living space. By extending their homes with a loft conversion, growing families are able to meet their need for extra living space without leaving the borough they call home.

To answer the growing demand for space and acknowledging that existing legislation was too restrictive, Lambeth Council's new Building Alterations and Extensions SPD is substantially more permissive. In terms of roof extensions to non heritage buildings, residents will now have much greater ability to expand their current properties than ever before.

The new planning guidance is quite in-depth covering a broad range of alterations. To help, we've made a brief run-down of the new planning guidance as it applies to roof alterations and loft extensions:

Dormers (that are subordinate)

  • Traditional single dormers may be considered acceptable on front roof slopes, but may be turned down if they are not characteristic of the group, building or street
  • In conservation areas where floor space is limited, linking two small dormers may be accepted to increase headspace
  • Although as a whole not appropriate on heritage assets, inset dormers where appropriate, must retain adequate sections of the roof either side of the inset
  • Horizontal box dormers are acceptable providing that outer edges are aligned with the windows below


The details on the new allowances for mansards on non heritage builds or assets, goes into much further detail than other sections of the SPD but with the main points being:

  • Rear mansards that are in pairs or groups must be regular in shape, with a roof ridge that is no higher than the existing one
  • The number of dormers must be equal or fewer in number than the windows on the level below
  • London roofs (butterfly roofs) on non-heritage builds can be extended and replaced with a traditional mansard subject to meeting overall design criteria
  • The mansard should have two lower pitches and two upper pitches. However, where an existing traditional mansard exists or has been approved the new mansard should replicate it

Roof Lights (roof windows)

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  • Roof lights are more likely to be allowed on the proviso that they are symmetrical and aligned with windows or other features below
  • On heritage builds, windows must be small and flush with the roof and must not open up into roof terraces
  • Roof windows should be minor features on the roof and not given prominence
  • Roof windows should be positioned at the rear where they tend to be featured historically

The new supplementary guidance goes into a lot of detail and has far reaching and positive effects for many Lambeth homeowners and landlords thinking of converting their loft space.

We work closely on our loft conversions with Landmark Architects' RIBA accredited team. They stay completely up to date with all new planning regulations across all the London boroughs we serve including Lambeth. This means you can rest assured that any loft extension managed by Landmark Lofts will be built within the existing parameters of your borough.

To maximise the potential of your loft space with designs that work within your borough's planning guidance, phone us on 020 3150 0505 or contact us today and get a free assessment.

You may download the full Supplementary Planning Guidance from the website.

Landmark Lofts are part of the Landmark Group – the only loft conversion and extension company in London who are affiliated with and recognised by The Chartered Building Company (CIOB), Chartered Architectural Practice (RIBA) and also Chartered Building Surveyors (RICS).

Click here to learn more about these regulators and why they're so important for you.

Royal Institute Chartered Surveyors
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