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How much does a loft conversion cost in the UK: breakdown and tips

By Heather · 12 May '22  · 

10 min read

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No matter what project you undertake, working out the costs involved are always going to be high on the agenda - and loft conversions are no exception!

From your materials to your contractor; architectural fees to your structural engineer costs; not to mention, you’ll also need to factor in new insurance policies. Yes, there are certainly a lot of numbers involved.
Luckily, Resi is here to help. We’ve helped over 4000 people grow their homes, including hundreds of loft conversions. And with our all-in-one platform, plus a dedicated finance team, there’s no better team to help you balance the books.

Below is a concise guide to the loft conversion costs you’ll need to factor in. However, for more tailored support, don’t forget you can always enjoy a free consultation with our experts here.

What is the average cost of a loft conversion in the UK?

On average, a loft conversion will cost between £55,000 - £80,000.

However, it’s worth noting there are a lot of different factors which will push up or reduce those numbers.

The main factors which will affect costs are…

  • Your location
  • Size of conversion
  • The type of loft conversion
  • Quality of build and materials

In actuality, the cost of a loft conversion can range from as low as £25,000, all the way up to £200,000!

Cost of a loft conversion in London vs outside of London

Where you sit in the UK can have a big impact on costs, no more so than in London. More than anywhere else in the UK, Londoners will see big inflation in the cost of renovating a loft. Why?

The reasons are multiple. The biggest contributing factor will be that most of your contributing experts will be living in and around London themselves, so charge a premium. Transporting materials can also be a challenge, especially given the premium for parking, and the large variety of period stock in the capital also bears special consideration.

Take a look at these rough costs for an idea of what location can do to your budget…

  • The average cost of a loft conversion in London: £60,000 - £100,000
  • The average cost of a loft conversion outside of London: £50,000 - £70,000

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Average cost to build different types of lofts

Another contributing factor will be the type of loft conversion you want to pursue. Simply room in loft renovations can cost as little as £25,000 and hip to gables (including dormers) can go up to £200,000.

Choosing the best loft extension for you will therefore depend not only on the amount of space you require but also on how much your budget can stretch.

London averages

Loft Conversion Small (30sqm) Average (45sqm) Large (60sqm)
Low end High end Low end High end Low end High end
Skylight conversion £30,000 £55,000 £50,000 £90,000 £70,000 £125,000
Mansard dormer £40,000 £70,000 £65,000 £110,000 £90,000 £150,000
Hip to gable, no dormer £45,000 £80,000 £65,000 £120,000 £90,000 £155,000
Main dormer £40,000 £65,000 £60,000 £100,000 £80,000 £140,000
L shaped dormer £45,000 £80,000 £70,000 £120,000 £90,000 £155,000
Hip to gable with main dormer £50,000 £100,000 £80,000 £150,000 £105,000 £200,000

Outside of London averages

Loft Conversion Small (30sqm) Average (45sqm) Large SQM (60sqm)
Low end High end Low end High end Low end High end
Skylight conversion £25,000 £45,000 £40,000 £75,000 £55,000 £100,000
Mansard dormer £35,000 £60,000 £55,000 £90,000 £75,000 £125,000
Hip to gable, no dormer £35,000 £65,000 £55,000 £90,000 £75,000 £125,000
Main dormer £30,000 £55,000 £50,000 £85,000 £70,000 £120,000
L shaped dormer £35,000 £65,000 £55,000 £100,000 £75,000 £125,000
Hip to gable with main dormer £40,000 £80,000 £65,000 £120,000 £85,000 £160,000

Please note: these estimates do not include VAT, nor do they cover the cost of glazing or fittings, such as ensuites. These are the costs associated with labour and materials, so also do not include further professional fees or legal costs.

For a more thorough and tailored quote, you can always book a free consultation with our team.

Otherwise, why not try our new construction calculator?

Cost breakdown for a loft conversion

The price tags you’ve been seeing in this article aren’t just one set number, they’re made up of a range of different fees and considerations. On top of these build costs, you’ll also have to add in other key services, such as design, planning, building regulations, and party wall matters. Overall, this could add an extra £8,000 or more to the figures above.

On average, you should expect to see your total bill made up of the following…

  • Architects - 2% (based on Resi’s services)
  • Administration fees - 1%
  • Structural Engineers - 4%
  • Surveyors - 3%
  • Contractors - 30%
  • Materials - 20%
  • Fittings - 5%
  • Glazing - 15%
  • VAT – 20%

Cost of windows and glazing

As we keep saying, there’s no one cost involved when it comes to your home. The price of glazing will differ depending on how size, style, and insulation (refers to as its u-value).

Dormer windows will cost more than their Velux counterparts, which are commonly used in simple room in loft renovations.

  • Velux windows: on average cost £900 - £1300 each
  • Dormer window: on average cost £4500 - £6500

Roofing material

Roofing costs will vary depending on both the existing style of your roof and what end result you’re after. For instance, going from a hipped roof to a gable will cost more than just incorporating a simple dormer.

Here’s a sample of the associated price tags…

  • Hip to gable roof replacement £4250 - £5500
  • Gabled roof replacement £3500 - £4000
  • Hipped roof replacement £5250 - £7200

loft conversion glazing

Flooring

What kind of flooring do you want for your loft conversion? Bedrooms tend to favour vinyl and carpet, while ensuites will lean towards more expensive tiles.

You’ll find all of these materials priced by square metre, meaning the larger your loft, the more money you’ll need for these key fittings.

Type Average cost per M2
Vinyl £10-£35
Wood £20-£90
Carpet £8-£60
Tile £20-£90

Insulation

A lot of heat escapes your home via the loft, so one of the benefits of undertaking a conversion is that you’ll have a more insulated property in general. Of course, to get the best results, you should invest in good quality insulation materials.

Type Average cost per M2
Rock Wool £10-£15.50
Earth Wool £6.50 - £8
Celotex board £23 - £40
Sheet £17.50 - £28
Blanket £15-£30

Stairs

If you need to create a new stairway to your loft, you’ll need to decide which style is right for you and what kind of stairwell your space can accommodate.

Luckily, we have already created a guide to help you explore your options.
On average, common stair options cost…

  • Simple staircase: £1200 - £2500
  • Bespoke staircase: £6000 - £9000
  • Alternating tread staircases: £300 - £500
  • Fixed loft ladder: £250 - £400

loft conversion stairs

Surveys

One of the first stages of getting your loft conversion underway will be to get a set of existing drawings. They will map out your loft as it is today, giving a blueprint for all the consequential services.

On average, surveyors charge between £500 to £1,500.

Get a quote for Resi’s surveying and design service.

Building regulations

At a minimum, you’ll need to budget for having a structural engineer come on board and make key calculations that will help your loft stay standing. But structure isn’t the only thing building regulations is concerned with.

From fire safety to sound-proofing, there are a lot of regulations your space will need to meet. You can rely on a contractor to fill in these blanks, but this can put you at risk of mistakes being made on site.

At Resi, we always recommend commissioning a full building regulations package.

  • Structural engineers fees - £500 to £1,000
  • Building regulations package - £700 - £1,200

Party wall matters

If your project will affect a party wall (a wall or boundary shared with your neighbour), you’ll need to make sure party wall matters are sorted at least two months before construction begins.

In the best-case scenario, this can be achieved by serving a party wall notice, which you can do yourself. Otherwise, if they refuse to give written consent to this notice, you’ll need to account for the cost of hiring a party wall surveyor, who will need to draft a party wall agreement. All costs, including those of your neighbours, will be on you to pay for.

  • Party wall surveyor costs: £500 - £1500

Architectural fees

Traditional, high-end architectural practices tend to charge on a percentage basis, usually around 4-7% of your total project costs.

However, you don’t need to break the bank to get a great design. At Resi, we run a home extension platform which gives you access to not only architectural design, but also surveying, planning, building regulations and more.

Get a quote for our architectural, survey, and planning package here.

Builder fees

When you get a quote for your build (as seen above), a percentage of this will be going towards the cost of labour and the rest towards materials. How this balance places out can depend on several different factors…

  • Cost of labour, at the time
  • Inflation
  • Quality of materials
  • Size of contactor company

As a rough estimate, you’ll find builder fees make up between 40-55% of the quote costs.

To understand what you’ll be getting for your money, make sure you’re getting a full breakdown at the tender stage, whereby each penny has been accounted for.

Other costs to consider

While we’ve covered all the main costs, there could be some other expenses that raise their head.

Ecological surveys: if you have a protected species potentially on-site, specifically bats, then a survey will need to be carried out. This can range from £350 - £450.

Contingency fund: to stop yourself from falling short on cash while on-site, we always recommend you give yourself a contingency fund. 10% of your construction costs would be the safest bet and can be factored into any loan or remortgage you’re taking out.

5 ways to reduce costs when converting your loft

If you’ve been crunching the numbers and finding a loft conversion a little financially daunting, have no fear!

We asked our in-house designers to share with us their top tips for keeping down costs.

Plan in advance

When it comes to any big home improvement project, you can never plan enough. This will inevitably save you costs in the long run, as it avoids the need for rectifying any possible mistakes once work on your loft starts.
Run through these questions in your head:

  • Why do you want to convert your loft?
  • How will it be used?
  • Is your aim to add value to your home?
  • Who will be using your loft?

These questions will help establish what costs might be involved. If you want an en-suite bathroom, you’ll have to factor in expensive plumbing.

Likewise, if you want to incorporate a balcony or extensive glazing, this will come with some sizeable price tags.

loft conversion balcony doors

Hire an architect

Depending on the size of your project, an architect can make all the difference when it comes to getting the most out of your budget. Though many are put off by the extra expense, the benefits an architect brings to a project make them a great investment.

Benefits of using an architect...

  • They can help you set a realistic budget
  • Maximise the amount of space you get from the project
  • Ensure your designs are tailored to you
  • Find the best planning route and manage the process
  • Guide you through all the necessary steps before construction begins

An architect has the relevant knowledge to advise you on your proposed budget and help make sure you stick to this throughout your project. This helps eliminate those oh so scary mid-build financial surprises.

Could you project manage?

Many people admit their main regret when converting their loft is that they didn’t project manage it themselves. However, as you may have guessed, this endeavour is not for the faint-hearted.

While self-managing could very well save you money in the long run, you have to feel confident in your abilities in order to avoid far-reaching errors. The position entails being clear on what needs to be done, managing deliveries, nailing down timings, liaising with contractors, ensuring you’re sticking to a budget... the list goes on. In order to do the job justice, you have to have faith in your skillset and have plenty of time to spare.
However, if you are up to the task, you might be able to shave thousands off your construction costs.

loft conversion dormer underside

DIY decisions

DIY is a great way to save money on your loft conversion. While it is obvious that, unless you’re Bob the Builder himself, you cannot undertake everything as DIY, you can give the smaller jobs a go.

Here are a couple of tasks that are within most people’s abilities and will save on handyman costs:

  • Painting walls
  • Laying floor tiles
  • Installing shelves and curtain rails
  • Putting up wallpaper

Be smart with your finance

Contrary to popular belief, you don’t need to be sat on a massive pot of savings to convert your loft. There are a number of ways to finance your project and each has its pros and cons.

For those who have lived in their property for some time, you might find the most cost-effective way to fund your build is by releasing existing equity in your home. This helps negate the troubles you might face by relying on a simple savings account, as costs are liable to jump up and down, and you never want to be caught short of cash during crucial moments. This option can be even more beneficial if you live in an area that has seen prices increase in recent years.

Of course, whether you opt for a loan or remortgage, there are risks involved and you will need to make sure you have the means to pay back these loans.

To understand your finance options, it’s always worthwhile to talk to a lender who has specialist knowledge of the property sector. At Resi Finance, our brokers are unique in that they bring together residential, architectural, and financial expertise.

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