How should I carry out a Loft Extension?

There are different types of loft extensions, their costs, and considerations as follows:

1. Simple Dormer Extension:

• Most common and affordable.
• Creates a box shape out of the rear slope of the loft.
• Avoids planning permission with permitted development.
• Cost: £30,000 – £40,000.
• Additional bedroom and possibly an en-suite.
• Duration: 3-4 months.

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2. L-Shaped Dormer Extension:

• Similar to a simple dormer but includes an extension over the rear outrigger.
• Cost: £50,000 – £80,000.
• Offers double the space for slightly more cost.
• Duration: 3-4 months

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3. Mansard Loft Extension:

• Aesthetically pleasing, involves raising party parapet walls in brick so the neighbour can connect.
• Planning permission likely necessary.
• Cost: £35,000 – £75,000.
• Duration: 4-5 months.

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4. Hip to Gable Conversion:

• Found in end of terraced, semi-detached, or detached properties.
• Involves extending the inwardly sloping roof to create a vertical wall.
• More expensive than mid-terraced dormer extensions.
• Cost: £40,000 – £60,000.
• Duration: 4-5 months.

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Considerations:

• consult with a good architect to maximize space within your budget.
• determine which options require planning permission.
• obtain planning/conceptual drawings and drawings suitable for Building Regulation approval.
• involve an engineer for loading calculations, especially for steel beams.
• consider the Party Wall Act if the property is not detached.
• inform neighbours in advance for a favourable response.
  

For leaseholder, a loft space valuation is required and a premium must be paid to the freeholder. Typical premium for a London 2-bedroom flat worth £500,000 might be est. £40,000. Freeholders also often insist on a licence to alter to protect their interests and surrounding flats. Contact our team to organise advise by a party wall surveyor and/or a Registered Valuer.