Loft Conversion: Mansard

Expanding into your roof with a mansard loft not only gives you an extra room (or two, or three), it increases your property’s value and — crucially — does so in a visually striking way. Seen those Instagram influencers’ beautiful attics? You can achieve that chic look too.

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Mansard loft conversion: key fact

This is one way of increasing usable space in your house amongst many others, so it’s worth thinking about the finer details, to be sure you choose the best option. Get to know more about this type with our guide. You can expect:


  • Attractive end result
  • Sizeable space added
  • Suitable for all properties: terraced/semi-detached/detached
  • Mid-price point compared to other styles
  • Considerable amount of construction work
  • Typically requires planning permission/building regulations approval
  • Usually built at rear
  • Flat roof and sloping, almost straight wall (72 degrees)
  • Small dormer windows
  • Juliet balconies possible


What could you use it for? There are lots of possibilities, including:


  • Bedrooms: most popular choice, consider if you’d prefer one large one with a walk-in wardrobe, en-suite bathroom etc, or two smaller ones
  • Office: work from home in style with a dedicated room away from living areas, helping to differentiate between family time and work mode
  • Nursery: baby’s own haven with plenty of opportunity to grow into
  • Bathroom: especially important when adding sleeping sanctuaries at the top of the house, choose from a WC only, shower cubicle, or full tub
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Mansard loft conversion: cost

  • Starting at £40,000

The question of price is an important one, of course. It can be useful to compare it to other options, so you know what will work best for you. This variety will typically cost less than a hip-to-gable or L-shaped dormer, but more than a Velux or standard dormer project. So it sits in the middle of the range.


The final amount you pay will be determined by many factors, including:


  • Size
  • Design
  • Windows
  • Finish

It’s vital to align your budget with your expectations, and that’s where the pros come in. We can explain where to save money, what you don’t want to scrimp on, and how to maximise the potential of your roof space to balance cost with quality.

Mansard roof loft conversion companies in London

Looking for a firm to complete your works to budget, on time, and to a high standard? Fittra Construction’s here to improve your home and realise your dreams. We offer:

  • Complimentary consultation
  • End-to-end project management
  • Full, tailored design
  • Building regs
  • Planning permission applications
  • Legal advice
  • 5% deposit
  • Straightforward payment schedules
  • Buyers’ discounts
  • Liability insurance at £10M employer’s, £5M public/products
  • NHBC-registered
  • Accreditations: FMB, NFB, TrustMark, Considerate Constructors

Contact us now to get the ball rolling.

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Interested in Mansard conversion?


Why Work With US

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at all stages

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with project manager

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liability insurance

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of works

Integrated, In-house Team Will Work On Your Project

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Benefits from our trade discounts
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£5M public & products liability
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10% only deposit payments
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Detailed cost breakdown

In the End You Will Get




Our Projects

Do you have questions?

Frequently Asked Questions

What is the difference between a dormer and a mansard?

The only difference with a mansard is that the slope across the face of the mansard will make the construction look softer from the outside. But it will sacrifice some head height compared to a dormer that is built vertical off of the back wall.

How long does it take to build a mansard roof?

For a mansard loft conversion, around six to eight weeks is a typical timeframe for the the actual building work. However, the planning stage can also take a considerable amount of time, especially if planning permission is required.

Can a mansard roof have a flat top?

The flat top of the mansard roof provides a very poor drainage system which could lead to leaks or even roof collapse. The complex design of the roof means that it takes longer for roofers to fix it, and most may not even be familiar with the design in the first place.

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