Loft Conversion Costs & Prices in the United Kingdom

Converting your loft is a relatively cheap and easy way to increase the size and value of your property – but how much does a loft conversion cost?  Find out the average price of a loft conversion in our guide to loft conversion prices in the UK.



Why Convert your Loft?

Loft conversions are one of the most popular home improvement projects in the UK because they:

Loft Conversion

      • Add value – A loft conversion can increase the value of your property by as much as 15%, says the Federation of Master Builders and as much as 20% according to Nationwide Building Society.
      • Are cost-effective – Loft conversions are a cheaper way of expanding the size of your home; in comparison to a full extension or moving home completely, the cost of a loft conversion comes in a lot cheaper.
      • Are simple to carry out – Loft conversions are pretty simple and relatively hassle-free to carry out – they can usually be completed in a week or two.
      • Are extremely versatile – You can use your loft conversion for a variety of purposes; as an extra bedroom and bathroom, as a lounge or additional living area, as an office or even a gym or home cinema.

Average Loft Conversion Cost across the UK

Typical loft conversion costs will vary depending on a range of factors, including:

      • Where in the country you live
      • What size loft you have
      • Whether any work is needed to strengthen the loft
      • Whether you want to add roof or dormer windows
      • Whether you want to install a bathroom and therefore plumbing
      • Whether you need to install heating
      • How lavishly you want to decorate the loft

Find out more about what influences the price of an attic conversion here.

One of the biggest loft conversion cost factors is location. To illustrate this, below are some average loft conversion prices from across the UK. The loft conversion costs UK listed below are from WhatPrice. ‘Standard’ loft conversions consist of a basic conversion including two roof windows, ‘deluxe’ loft conversions include two roof windows, two dormer windows and an en suite bathroom.

Loft Conversion Prices UK

20m² standard 20m² deluxe 30m² standard 30m² super
Northern Ireland £8,580 £19,369 £9,539 £20,328
Scotland £12,012 £27,116 £13,355 £28,459
Wales £10,639 £24,017 £11,828 £25,206
Northern England £11,669 £26,341 £12,973 £27,646
Midlands £10,868 £24,534 £12,083 £25,748
Yorkshire £11,669 £26,341 £12,973 £27,646
East Anglia £11,097 £25,050 £12,337 £26,290
South East England £12,012 £27,116 £13,355 £28,459
South West England £10,686 £24,534 £12,083 £25,748


Loft Conversion Costs in London

If you live in London your loft conversion is likely to cost slightly more due to increased labour and material prices in the city. To get an idea of loft conversion cost London, check out the table below. Again, cost of loft conversion London figures are from WhatPrice.

Loft Conversion Prices London

20m²  standard 20m² deluxe 30m² standard 30m² deluxe
Inner London £13,156 £29,699 £14,626 £31,169
Outer London £12,355 £27,891 £13,736 £29,272


Dormer Loft Conversion Cost

Dormer loft conversionThe average cost of a loft conversion will also depend on what type of conversion you choose to have. One of the most popular options is the dormer loft conversion, which extends outwards from the back or side of the roof in a box shape. Dormers are sometimes referred to as kennel or box conversions and provide some additional space in the loft room. Dormer loft conversion prices vary depending on how many dormers you add and what else you do to the loft, but on average:

      • WhatPrice say a dormer loft conversion costs between £19,000 and £27,000
      • Evis Build put the average at between £25,000 and £30,000

Get more information about dormer loft conversions and how much they cost.

Hip-to-Gable Loft Conversion Cost

Another popular option is to carry out a hip-to-gable loft conversion. This involves converting the hip (sloped) side of the roof into a flat edge which provides additional space inside the loft. The hip-to-gable loft conversion price will also vary depending on what else you have done to the loft, however:

      • says that a hip-to-gable loft conversion costs between £30,000 and £35,000
      • put the average hip-to-gable conversion price at £32,000

Get more hip-to-gable loft conversion advice and prices.

Mansard Loft Conversion Cost

Mansard Loft ConversionMansard loft conversions are usually the most pricey options, but they also add maximum space.  A mansard conversion involves altering the entire roof slope to around 72 degrees, which means significant structural and building work needs to take place. On average:

      • Evis Build says a mansard loft conversion costs around £35,000
      • The loft kind puts the price of a mansard conversion at between £33,000 and £34,000

Find out more about mansard conversions and how much they cost.

DIY Loft Conversion Cost

It is possible to carry out loft conversions yourself to try and save cash. However, you should only attempt this if you have some experience and are absolutely sure you can carry out work safely and in accordance with both building regulations and planning permission guidelines. If your loft is already structurally sound, you have windows fitted and all the necessary electrical work completed and you’re only making cosmetic changes, it is possible to do this yourself. Prices will vary depending on what type of loft conversion you have; here’s a rough DIY loft conversion price guide to give you an idea:

      • According to Evis Build a DIY loft conversion could cost as little as £9,400

Get more advice about DIY loft conversions and information about prices.

Loft Conversion Planning Permission

Loft conversionAs with any conversion or extension project, you’ll need to make sure that you don’t need to apply for planning permission when considering a loft conversion. Fortunately, loft conversions, including roof extensions, are classed as permitted developments in the UK, however, this may not apply if you live in:

      • A listed building
      • An Area of Outstanding National Beauty
      • A Conservation Area
      • A World Heritage Site
      • A National Park

In the above cases you should consult your local building authority about whether you need planning permission for your loft conversion.  In all other cases, you won’t need to apply for planning permission for your loft conversion as long as you meet the following conditions:

      • You don’t extend your roof more than 40 cubic metres if you live in a terraced house of 50 cubic metres if you live in a semi-detached house
      • Roof extensions should be set back at least 20cms from the eaves of the roof
      • If you’re installing side windows, they must be obscure-glazed and non-opening
      • You don’t extend beyond the plane of the existing roof slope if it’s facing a highway
      • All materials must be similar to the existing property
      • No part of the extension should be higher than the original roof height
      • Your loft conversion shouldn’t include any verandas, balconies or raised platforms

If you’re in any doubt about whether you need to apply for planning permission for your loft conversion, consult your local council; a loft conversion company or architect may also be able to offer advice.

The Party Wall Act and Loft Conversions

In addition to planning permission, if your house shares a wall with a neighbouring property under the Party Wall Act 1996 you need to inform your neighbours in writing that work is taking place; they have the right to contest this if they want to. To make sure your loft conversion goes smoothly, it’s best to talk to your neighbours beforehand.

Loft Conversion Building Regulations

All projects undertaken in the UK need to adhere to building regulations. Loft conversions need to comply with the following sections:

      • Part A – Structural Safety: this involves making sure that the loft walls, floors and joists are sturdy enough and that there’s sufficient headroom in the loft
      • Part B – Fire Safety: you will need to make sure that there’s an escape route in case of fire and that proper smoke alarms are installed
      • Part E – Resistance to Sound: there should be adequate sound proofing in your loft conversion
      • Part F – Ventilation: there must be adequate air vents and windows to adequately ventilate your loft conversion
      • Part L – Conservation of Fuel and Power: the loft will need to be insulated to conserve energy
      • Part P – Electrical Safety: any electrics in your loft must be installed by a qualified electrician
      • Part G – Sanitation, Hot Water Safety and Water Efficiency: if you’re planning  to install an en suite bathroom as part of your loft conversion then you’ll need to make sure plumbing is correctly and safely installed

*Sources: Federation of Master Builders, Nationwide Building Society, WhatPrice, Evis Build,,, Planning Portal. All information is accurate as of December 2012.

Naresh says:

I just want loft conversion with diagram stairs and plumbing who are tth quality licensed builders

samrat says:

Hi Naresh,
If you are looking for loft conversion specialist then please fill out this free quote loft conversion form and up to 4 companies will contact you.

Damon says:

I live in London and prefer the aesthetics of a Mansard loft conversion to a dormer. A lot of my neighbours in identical properties have dormers and they did not need planning permission. As far as I can work out – if I want a mansard loft extension the only reason why I would not meet the demands of permitted development is due to the rule that the roof extensions should be set back at least 20cms from the eaves of the roof . How can this apply to Mansards when you are changing the rear roof aspect? Or does it not apply?

Thanks in advance for any clarification or guidance.

mjackson says:

Hi Damon,
Planning requirements can differ depending on many factors so the best thing to do at this stage is to visit the Planning portal website in order to see whether planning is required for your project.
Should you find that you do require planning then feel free to contact us on 0800 612 5305 and we will endeavor to get you up to 4 free quotes from local Architects.

Tom says:

I am looking into estimates of loft conversions for a property I have in mind to buy. I have looked through this page to see the estimated costs of London and can see that costs will be roughly 30k for this property in Wimbledon, SW London. However, I have asked 3 other companies and they have quoted me 50k which I though was crazy! Why is there such a big difference? Is there anyone I can send my architects drawings for the house I intend to buy that could give me a more accurate quote?

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