The London planning application guide for your loft conversion

After years of neglect an empty loft tends to collect cardboard boxes peppered with dust. It may seem obvious to grab your step ladder and a vacuum cleaner, however, the thought of accidently stepping through your bedroom ceiling is not reassuring. The good news is, there is a safer option for your loft conversion and I have proposed 3 questions below for you to get started.

Here we go:

1. Will I bump my head if I stand upright?
2. Can I fit another staircase above my existing one?
3. Have my neighbours done the same?

If you answered yes for all three, read and select from one of the top 6 developments I shortlisted below:

1. Roof-light loft conversion.

An out-looking window is an essential planning requirement to convert a space into a habitable room which makes it a great way to develop your loft within a modest budget and reasonable time-frame.

Planning requirements

• Minimum headroom of 2.1m/ 2.3m subject to local authority.
• Skylights should be in verticle alignment with your existing windows.
• The depth of each skylight should be no greater than 150mm.
• Any window below 1.7m should be fixed.
• Maximum of two roof light’s on your front elevation if facing a highway.
• Minimum staircase headroom of 1.9m at pinch points.

Application type: Householder Planning Application.
Cost: £86.
Decision period: 6-8 weeks.
Construction cost: £900 per m2.

2. Dormer windows.

If your home is located within a sensitive location such as a corner-plot, conservation area and/ or is a listed building, a dormer window will have minimal impact on the character of your property for your loft conversion.

Planning requirements

• Vertically aligned with your existing windows.
• Minimum of 500m from the roof ridge, eaves and party wall.
• Sub-ordinate to the main ridge height.
• Match the materials of the existing roof and walls.

Application type: Householder Planning Application.
Cost: £172.
Decision period: 6-8 weeks.
Construction cost: £1,000 per m2.

3. Rear dormer extension.

For a terraced Victorian property, the ‘box’ dormer is the most appropriate development to convert your loft. A well thought-out layout can help you achieve a large bedroom with an en-suite.

Planning requirements

• Minimum of headroom of 2.1m/ 2.3m subject to local authority.
• Maximum allowable volume for a terraced property is 40 m3 and 50m3 for a semi-detached/ detached property respectively.
• Should be sub-ordinate to the main ridge height.
• Minimum of 250mm set-back from the eaves.
• Consult neighbours on sharing the Party Wall.
• Match the materials of the existing roof.

Application type: Certificate of Lawfulness Proposed Use.
Cost: £172.
Decision period: 6-8 weeks.
Construction cost: £1,100 per m2.

4. L shaped rear dormer extension.

This larger form of the dormer is best suited for Victorian and Edwardian properties with an existing double storey extension. The additional floor space will allow you to create two bedroom’s with one en-suite and/ or a large bedroom with an en-suite; an independent bathroom.

Planning requirements

• Minimum of headroom of 2.1m/ 2.3m subject to local authority.
• Maximum allowable volume for a terraced property is 40 m3 and 50m3 for a semi-detached/ detached property respectively.
• Should be sub-ordinate to the main ridge height.
• Minimum of 250mm set-back from the eaves.
• Considerate of the party wall.

Application type: Certificate of Lawfulness Proposed Use.
Cost: £86.
Decision period: 6-8 weeks.
Construction cost: £1,200 per m2.

5. Hip to gable roof conversion.

If you are living in a semi-detached/ detached property, you can convert your slopped hipped roof to a verticle gable-end to create three single bedroom’s and/ or two large bedroom’s with an en-suite.

Planning requirements

• Minimum of headroom of 2.1m/ 2.3m subject to local authority.
• Maximum allowable volume is 50m3 for a semi-detached/ detached property respectively.
• Should be sub-ordinate to the main ridge height.
• Minimum of 200mm set-back from the eaves.
• Consult neighbours on sharing the Party Wall.
• Match the materials of the existing roof.

Application type: Certificate of Lawfulness Proposed Use.
Cost: £172.
Decision period: 6-8 weeks.
Construction cost: £1,500 per m2.

6. Mansard roof conversion.

The high roof and slanted angle allows for greater floor space and should be prioritised in converting your property into flats as you can create an additional unit subject to the existing floor space.

Planning requirements

• Minimum of headroom of 2.3m subject to local authority.
• Maximum allowable volume is 50m3 for a semi-detached/ detached property respectively.
• Maximum 70 degree lower roof slant and 30 degree upper roof slant.
• Minimum of 250mm set-back from the eaves.
• Reconstruction of party wall.
• Match the materials of the existing roof.

Application type: Householder Planning Application.
Cost: £86.
Decision period: 6-8 weeks.
Construction cost: £1,500 per m2.

If you need the momentum to formulate ideas for your loft conversion, one of the shortlisted development types above will help you narrow down your options with confidence. Send us an email with the subject ‘sketch to application’ to help you develop, refine and finalise that option.

*All requirements are subject to your local authority and location.

Semsettin Karahan is the architectural designer at Zanoply Ltd. As a graduate of the Oxford School of Architecture, Semsettin has been shortlisted and featured in a number of exhibitions; publications. He worked for the top architects within London as a designer and an associate director on a range of design builds ranging from residential to commercial projects. At the age of 22, Semsettin secured his first private planning permission for a residential flat conversion. A year later he became the youngest designer in London to proposed and construct a new-build dwelling. Semsettin’s attention for detail derives from his 7 years of experience within the design industry from being the Editor at OSA, Photographer at Cowley News and leading installation builds as a set designer, product designer for film companies and International drinks manufacturers.