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How much does a loft conversion cost?

Are you considering a loft conversion and wondering how much it’s going to cost? Look no further. We’ve put together this comprehensive loft conversion cost guide to help you plan your budget and see a clear breakdown of the costs.

If you’re looking to gain extra space in your home, want to add value to the property, or you’re yearning for a room with a view, a loft conversion can be an excellent solution – particularly in urban areas where extensions can be more restricted.

We’ve broken down the different elements of a loft conversion project to show you the prices associated with each part. Having a rough idea of the costs of loft conversions will put you in a much stronger position when talking with suppliers and tradespeople, so you know you’re getting a fair price.

We spoke to the online estimators at My Build Estimate – a professional estimating company monitored by the Royal Institute of Chartered Surveyors (RICS). They’ve provided us with their estimated average prices for loft conversions in the UK.

Once you’re ready to get moving with your loft conversion project, we can help you find reliable, experienced tradespeople to help.

Type of loft conversionAverage costTimescale (weeks)

Our costs are ballpark averages – get a local tradesperson to quote now

How much does a loft conversion cost?

On average, a typical UK loft conversion will cost around £40,000. However this price tag can vary considerably depending on the size and complexity of the project.

It should take approximately 6-10 weeks to complete from the start of the construction, once you’ve obtained any necessary planning permits.

Some of the most important factors that will affect the total cost of your loft conversion are:

  • Size of loft
  • Existing roof structure
  • Type of loft conversion
  • Style and quality of finishings
  • How long the project takes
  • Where you live

In general, the bigger the loft conversion and the higher quality the finishes, the bigger your budget will need to be.

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Average cost of loft conversion

The size and type of loft conversion you choose are the two most influential factors that will affect the final cost. Based on a 30m2 loft space, a Velux loft conversion will cost £22,500-£30,000. A shell loft conversion will be around £22,500-£37,500.

A dormer loft conversion is more expensive and will cost in the region of £37,500-£60,000. At the more expensive end are hip-to-gable loft conversions, which will cost £45,000-£65,000 on average, and a Mansard loft conversion, costing about £45,000-£70,000. For a bungalow loft conversion of 50m2 you’ll be looking at a cost of around £62,500-£87,500.

Types of loft conversion

Loft conversion semi detached house cost

The loft conversion cost for semi-detached houses will depend on the style of roof you opt for.

The easiest and most cost-effective option is to install roof light windows without making structural changes to the roofline.

However, if you do want to create a new bedroom and en-suite under the roof, there is the option of rebuilding the side slope roof as a vertical gable end. The idea here is to create more internal loft space by extending the property by creating a hip-to-gable roof.

The average cost for loft conversion on a semi detached house is around £38,000.

Detached loft conversion cost

Homeowners angling for loft conversion on a detached property will typically employ a team of specialists to rebuild the rear roof slope as a gable end, and adjust the side roof slope to have a flat roof dormer.

Velux roof windows will be fitted to the front roof slope. These structural changes will increase loft space considerably, allowing the space for a new bedroom and staircase.

The total price for the job will usually be higher than the semi detached house loft conversion cost but will be returned in an increased property value.

The average detached loft conversion cost is £45,000. 

Velux loft conversion cost

Loft conversion cost UK
Velux loft conversions are the cheapest and easiest to do, as they involve the least disruption to the existing loft space. The only downside is that they provide the least amount of additional space to the property.

Due to the fact that you don’t change the roof structure, a velux loft conversion is only really suitable for properties with large existing loft spaces.

The average cost of a velux loft conversion is around £27,500.

Dormer loft conversion cost

If you’re looking to gain some headspace with your loft conversion, a dormer style could work well. By creating dormer window structures that protrude out of the existing roof, you gain valuable additional space.

The average dormer loft conversion cost is about £45,000.

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Hip to gable loft conversion cost

A hip-to-gable loft conversion involves altering the shape of your roof structure to gain space. The existing top line of the roof is extended to the edge of the building, giving an additional box effect to the roof.

This type of loft conversion is only suitable for semi-detached or detached properties with sloping roofs. Some homeowners in detached houses will do a double hip-to-gable loft conversion to add space to both sides of the roof.

An average hip to gable loft conversion costs roughly £55,000.

bungalow loft conversion cost guide

Bungalow loft conversion cost

Due to being a single storey property, bungalows are perfect candidates for loft conversions. Converting the loft into extra space for bedrooms, living space or bathrooms can make bungalows much more spacious.

Generally, bungalow lofts are larger in area than regular houses and so come in slightly higher in cost. The average bungalow loft conversion cost sits around £75,000.

Mansard loft conversion cost

With a Mansard loft conversion, the whole shape of the existing roof is changed. You end up with an essentially flat roof and vertical outer walls. This type of loft conversion will give you the most space, but consequently is one of the most expensive to do.

The average Mansard loft conversion cost is around £57,500.

Terraced house loft conversion cost

The average cost of a terraced house loft conversion will depend on the type of conversion that is carried out. You can opt for a simple Velux loft conversion, which is the simplest and cheapest option. The cost of a Velux loft conversion in a terraced house is around £27,500. However, for a terraced house, it doesn’t usually often provide enough room to actually make proper use of the loft space.

To add real usable space and open up your loft to potentially being used for one or two rooms, you’ll need to spend a little more. A dormer loft conversion in a terraced house will cost in the region of £45,000. Alternatively, a Mansard loft conversion is the most extensive but also most expensive option – with an average cost of around £57,500.

It’s also important to remember that there are a lot of factors that will influence the cost of a loft conversion in a terraced house, such as property size, the complexity of design, and the quantity and quality of materials used.

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Modular loft conversion cost

A modular loft conversion involves using a prefabricated unit that is built off-site. It’s effectively a modular construction that is built and then delivered to the property and attached to your existing roof space.

Although they may seem like a quicker, easier to install loft conversion, they aren’t as straightforward as they seem. Your loft will often need to be cleared out a lot earlier than a traditional loft conversion as the company building the module will need easy access to take precise measurements.

Modular loft conversions are more affected by bad weather, and can cause more disruption to your neighbours – you may need to obtain a road closure permit for the loft delivery.

The average modular loft conversion cost is about £50,000.

Shell loft conversion cost

A shell loft is a basic loft conversion where all major structural work is carried out, including the new structural floor, joists and dormer(s). The interior design and finishes are then left for the homeowner (or another third party tradesperson) to complete.

This type of conversion is perfect for homeowners who love DIY, or have a limited budget. As the most basic loft conversion, the cost is generally more affordable.

Your average shell loft conversion cost comes in around £30,000.

DIY / part loft conversion cost

If you’re working with a strict budget you may want to look at doing a DIY or part loft conversion to save money. A part loft conversion is where you hire professionals to create the shell (or ‘skeleton’) of the new loft space, including stairs, flooring and wall structures. You then complete the rest of the conversion work yourself.

The average cost of a part loft conversion is typically in the region of £30,000.

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JobAverage cost (30m2)
Project management£2,500
Scaffolding (excludes temporary roof)£3,500
Internal preparation£6,000
Alterations to roof structure£3,500
Steelwork to support structural changes£4,500
Roof coverings£7,500
Electrics and plumbing£2,500
Joinery (excludes staircase)£4,000
Total £40,000

Loft conversion cost breakdown

In order to help you budget for the different aspects of your loft conversion project, we’ve provided a breakdown of average costs for a typical loft conversion in the UK.

For the purpose of this cost breakdown, we’ve based it on a £40,000 conversion to create a loft space of approximately 30m2 with a dormer and a roof light.

Loft conversion stairs cost

The staircase is one of the fundamental elements in a loft conversion, and there are a variety of options available at varying costs. For this guide we’ve based the costs on price per m2.

A basic staircase will cost around £1,000-£1,500. If you want custom-built stairs you’ll be looking at £5,000-£10,000. For a spiral staircase, the average cost is around £2,500-£9,500.

For homeowners who want a slightly quirky set of stairs, the average cost of alternating treads is about £400-£850 per tread. Finally, the cheapest option is installing a fixed ladder with a bannister at a cost of £200-£500 per m2.

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Loft conversion flooring costs

The cost of the flooring for your new loft space will vary, depending on the type and quality you choose. For an average loft conversion, here are some of the prices for the most popular flooring choices:

  • Vinyl – £15-£25 per m2
  • Wood – £20-£85 per m2
  • Carpet – £10-£65 per m2
  • Tile – £50-£100 per m2

Loft conversion insulation costs

It’s important to make sure your loft is properly insulated. The different insulation options come at different prices. Sheet insulation costs around £15-£30 per m2. Loose-Fil insulation is around £7.50-£15 per m2. And blanket insulation will set you back about £14-£29 per m2.

Loft conversion labour costs

One of the single biggest costs for your loft conversion project will be the labour involved. Given you’ll need a range of different tradespeople to carry out the different work, the labour costs can quickly add up.

Depending on the type and size of your loft conversion, the average total labour cost is between £14,000 – £35,000.

To give you an idea of hourly rates for the different tradespeople, builders, tilers, plasterers and decorators all charge around £20-£35 per hour. Plumbers and electricians come in more expensive at about £35-£50 per hour.
loft conversion bathroom

Other loft conversion costs

There are a wide range of additional costs that you need to consider when planning the budget for your loft conversion project.

General building material costs

Here are the average costs for building materials used for a loft conversion in the UK:

  • Electrics – £500-£1,000
  • Structural beams, joists and masonry – £1,500-£4,000
  • Bathroom – £4,500-£6,000
  • Decorating materials – £1,000-£2,000
  • Built-in Storage – £2,500-£10,000

Architect plans cost

Not all building contractors will need full architect plans but it’s always a good idea to get them drawn up so you’re clear on the project scope. Simple architect plans will cost around £500, or more detailed plans can cost up to £2,000.

Underfloor heating cost

Installing underfloor heating is becoming more and more popular with British homeowners. For an average loft conversion, underfloor heating will cost between £450-£1,050.

Bat survey cost

As bats are a protected species, if you think you might have them nesting in your roof you’ll need to get an official bat survey done. You’ll then get a license to proceed with the loft conversion work. A bay survey generally costs about £400-£750.

Building regulations cost

If you decide to hire tradespeople who aren’t registered as part of the Competent Tradesperson Scheme then you’ll need to pay for your loft conversion to be approved by Building Regulations. The cost is usually between £500-£1,250.

Other additional costs

If you need to move your water tank as part of the loft conversion the cost is around £750. Painting the exterior of your house will be about £1,200. If you need to do the cladding it will cost about £2,000, and rendering will set you back about £4,000 on average.

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loft conversion for office

Reasons to get a loft conversion

There are a number of great reasons why converting your loft is a good idea:

  • Add value to your home in the region of 10%-25%.
  • Create more living space by making the most of the property you already own.
  • An extra bathroom built in a loft can be a valuable addition to a family home.
  • No planning permission is needed for most loft conversions.
  • Enjoy a room with a view thanks to the new height added by your home.
  • Build up not out so you don’t eat into any valuable garden space you may have.

Do I need planning permission for a loft conversion?

Not necessarily. In most cases, a straightforward loft conversion is considered ‘Permitted Development’, which means it shouldn’t need planning permission.

That said, if you’re planning on extending beyond the specified conditions of Permitted Development, you live in a conservation area, or you have a listed property, then you will need to apply for planning permission.

Also, if you’re planning to alter the shape or height of your roof structure then you’ll also need planning permission. That includes any windows or structural changes that will sit outside of the current dimensions of your roof.

To ensure your loft conversion project complies with all permissions and regulations, we recommend always checking with your local planning office before you begin the project.

Loft conversion building regulations

Loft conversions will need official Building Regulations approval. That means you need to get a registered building control surveyor to inspect your conversion at various stages of the project. They will also issue you a completion certificate following a final inspection once the conversion is complete.

If you live in a semi-detached or terraced property, you’ll need to notify your neighbours before you start any planned building work under the requirements of the Party Wall Act 1996.
Hourly rates of tradesman installing loft window

Hire a registered competent tradesperson

As it’s so important to meet all relevant Building Regulations, always hire tradespeople who are registered as part of the government’s Competent Tradesperson Scheme.

All tradespeople on this scheme will have already proven their ability to carry out certain work to required standards, which means you won’t need to apply for building regulations approval.

Useful loft conversion checklist

  • Plan, plan, plan. Loft conversions can be complicated so it’s important to be in control throughout the whole project.
  • Calculate your budget as a starting point and plan from there
  • Remember to include all potential additional costs
  • Factor in contingency for changes and extra costs during the conversion
  • Decide what you need the space for and research options
  • Contact your local planning office to confirm if you’ll need planning permission or not.
  • Speak to local builders for advice and discuss viable options
  • Ask friends and family for recommendations of loft conversion experts.
  • Shop around for fair and competitive prices.
  • When hiring a professional always choose registered competent tradespeople with a relevant loft conversion experience, qualifications and accreditations.

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