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Loft Conversion Cost – Price Comparison UK 2023

How Much Does a Loft Conversion Cost on a 3-Bedroom Semi

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Most people think of loft conversions as a quick and cost-effective way to add size to their homes, and while this is true, there are some things to consider when looking into a loft conversion.

Unfortunately, loft conversions do not come cheap. There are several factors to consider before you even start to arrange a builder. Let’s look at the things which will influence your decision about a loft conversion.

There are some things which will not be in your control, namely the age of your house, the area you live in and the type of roof you have. However, other things can influence the overall cost, such as where to place a bathroom and how you decorate it.

There are two types of loft conversion.

  1. A simple loft conversion. This one does not need any external or outer structure removed or altered.
  2. A complex loft conversion. This is one where you need to knock through the existing roof to add a dormer window. The more rooms in the loft conversion that you want, the more dormer windows you will need to add, so that the loft can be light and airy.

Zac building a house

What is involved in the cost?

There are many things which you need to factor into your expense list for a loft conversion. Remember that for more than one room in the loft the expenses will increase.

Relocating the water tank/tanks. Some houses have more than one tank and you may have to have these moved to another area of the loft, particularly if you plana to have more than one bedroom.

  • Clearing the area. You will need to have everything that is nor needed up in the loft removed. This may involve hiring a skip to dump old clutter as well as any old building materials which will not be used.
  • Whatever you plan to do with your loft conversion it is a good idea to have it insulated. For a three-bedroom loft conversation you will need to be sure that the conversion is dry and damp-proof. You will need both the walls and the ceiling to be insulated.
  • If you are adding bedrooms which need internal walls then you must allow for the softwood framing to separate them into rooms.
  • If you have children who will be using the loft, then you need to make sure that the stairs you install will be safe for them. While metal, spiral staircases look great, they may not be safe for small children who can easily slip through them. Neither would they be safe for animals who run up the stairs with you. Ideally you need a straight staircase or one with one turn in it and has no gaps between the steps. It should also have a side so that toddlers cannot slip through.
  • For a loft conversion to be liveable you will need to have plasterboard fixed to the walls and the ceiling. This will give you a base to start decorating the loft. It will also allow you to insulate behind it and keep the area warm or cooler.
  • New electrics and heating. If you are living in the loft conversion it will need to be heated during the colder months. You will also need new cables run to areas o that each room will have their own outlets for things such as lamps and computer terminals.
  • Décor. If you are planning on making a liveable conversion, then you are likely going to want to decorate it. Remember to add the cost of light fittings, door handles, wallpaper or paint, carpet and tiles, and furniture you want to place up there.

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Loft Conversion Cost: A Breakdown

Your loft conversion cost can range from £15,000 up to £70,000. We know, that’s quite a variation, so it is essential that you are confident with the decisions that you make. Each individual decision will determine where in that range your conversion sits.

However, the main factor in terms of impact of your overall cost is the design itself. Allow us to explain.

Rooflight Loft Conversion

The cheapest option available is the rooflight loft conversion. Here, rooflight windows are installed to allow for natural sunlight into the loft. Flooring, insulation, plaster boarding and fitting of lighting all add into the overall cost, although the alterations involved are generally minimal.

Basic doesn’t necessarily have to be a bad thing. Sometimes, less is more. If you aren’t looking to install extensive electrical work or plumbing, a rooflight loft conversion may be the ideal choice for your home – particularly when you consider the average price is between £15,000 and £25,000.

Dormer Loft Conversion

A dormer loft conversion consists of creating a boxe-shaped structure that replaces one of the slopes of a roof. The final result is brilliant in that it allows for full-sized windows and furniture in the flat-roof space. The rebuild of one roof pitch means that a dormer loft conversion costs that bit more than a rooflight conversion, but the flexibility is unquestionable.

You’re looking at between £25,000 and £50,000 for a standard dormer loft conversion, while an L-shaped dormer that has a corner can increase your overall price.

Hip to Gable Loft Conversion

You may never have realised just how lucky you are to live at the end of a terrace. Or perhaps you have, and that is the exact reason why you purchased your property in the first place.

Of course, if you live in a detached house, you have the flexibility on either side of your property.

The roof slope is completely replaced with a vertical brick wall and is combined with a dormer conversion to maximise the space. A brick gable wall is built, as opposed to a stud wall, which naturally bumps up the price.

The average price of such a project in the UK ranges from £30,000 to £60,000.

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Mansard Loft Conversion

Finally, a mansard loft conversion creates a flat roof space and can even create an additional storey on top of the existing building.

Such a project will always require planning permission and is without question the most expensive option out there, at between £40,000 and £70,000. However, the final design can be stunning and is very much an option that can be explored at Loftera.

Heating a Loft Conversion

Extensions, understandably, do tend to increase the heating requirements of a property. However, you might be surprised to hear that a loft conversion can often improve the overall energy efficiency of a house given that they are so well insulated.

If you are set on the idea of additional heating in your loft, radiators are a popular option. Some people opt for underfloor heating, or even both.

Aiko Houghton and Zac Houghton

Insulation in a Loft Conversion

The best way to insulate a loft conversion is via a cold roof method. In doing so, the space between the rafters is filled with 70mm thick slab foam, allowing for 50mm spacing between the roofing felt and insulation.

On the inside of the rafters, 30mm foam is also added, giving a total of 100mm of insulation.

The roof section requires 300mm of mineral wool insulation or 150mm of slab foam insulation, such as Celotex.

It is essential that the insulation between the walls and the roof remains consistent. In order for this to be the case, a 100mm quilt is inserted in the internal partition walls with plasterboard then attached to cover.

The floor joists will also be fitted with insulation, allowing for a fully heated loft extension.

Sounds great, right? We are experts in loft insulation and consider it very much part of the overall package.

Stages of a Loft Conversion

Wouldn’t it be nice to pick out a design of lost conversion and then, after a click of the fingers, it is completed?

We can take a lot of the hassle out of the building work, but there are different stages to the overall job before completion.

Planning Costs

A job of this size requires comprehensive plans to be drawn up by a qualified architect. They will be able to map out the exact design and the changes that are required before completion. Taking into account all of the necessary structural alterations, an architect will be able to make all the necessary calculations and ascertain how much the building work itself will cost. You can usually look to pay around £1,000 for this service.

Planning Permission Costs

For some of the aforementioned smaller loft conversions, planning permission won’t be required. This is because the changes will count as permitted developments. However, for mansard loft conversions and some hip to gable alternatives, planning permission may indeed have to be applied for. Expect to pay planning permission fees of £172 in the UK.

Building Regulation Costs

No matter whether planning permission is required or not, your conversion will absolutely have to be inspected by the building regulations department or your local authority.

Fire safety, access and floor strength are just some of the areas that will have to be assessed. Plans for this type of inspection can cost between £400 and £800.

Should your loft extension impact any adjoining properties, such as a terraced house or semi-detached building, you’ll require a Party Wall Agreement.

Put simply, your neighbours will have to agree to the work taking place, so you’ll want to be extra nice to them! You are liable for their surveyor costs and any damage to their home which may occur as part of the job. Damage like this is of course unlikely, but such eventualities have to be covered for building work of this size.

Building Work Costs

You’ve had your plans mapped out and approved, now it’s time to get down to the nitty gritty of the building work itself.

More often than not, external work will take place first with the use of scaffolding. Later on in the job, access will need to be granted via the property itself and the floor will be strengthened at this point. The interior walls will be fitted, roof altered, dormers constructed and then the insulation process can begin.

Essential features such as a staircase, windows and electrics will be fitted, with the option of plumbing if a toilet is being installed.

Once the final inspection has taken place and approved, the decoration can begin. All in all, the building work is where the bulk of the cost is spent.

Additional Costs

A slate roof tends to cost more (how much is a new roof) in terms of alterations than concrete roof tiles. If your property is a bit older, usually pre-1960s, it will likely be bult with a frame. Replacing these frames can take more work and, as a result, increase the overall cost of your loft conversion.

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Traders Required to Install a Loft Conversion

As you may have gathered, or are probably already well aware, building a loft conversion is far from a one man job.

There are multiple expert tradesmen that will need to pull together to ensure that your dream loft conversion is completed to the standard that you require.


All of the above building work will need to be performed by, you guessed it, a builder. They’ll be able to paint a clear picture of what is structurally possible and fit the sound proofing and insulation. A little pointer is to ask your builder what type of insurance they have.


The beautiful natural sunlight that the fitted windows will allow for is fantastic, but you’ll absolutely need electrical lighting fitted, unless you only plan on using your loft in the daytime. A qualified electrician will be able to provide a BS7671 test certificate once completed to allow you to pass building regulations.

Window Fitter

About that natural sunlight. You’ll require a glazier to come and advise on the best place to have your new windows fitted. Once decided, they’ll have to fit them, making sure that the correct standard of double glazing is followed to allow for the necessary noise proofing, insulation and security standards.

Heating Engineer

We live in England, guys. Heating is an absolute necessity, unfortunately. A heating engineer should, of course, own the process of installing your heating options. They should also advise on where best to fit any radiators so that the heat adequately reaches the rest of the conversion.

Have you considered solar panels? If your conversion is on a larger scale, these may be the ideal option for your property, saving you money in the long run.


Larger conversions may benefit from an en-suite, particularly if the new room is being used as an additional bedroom. A sink, toilet and shower may be required in this instance.


Often known as the jack-of-all-trades, a joiner will be essential to the completion of your loft conversion. The chances are that you’ll require new ceiling joists given the fact that a lot more people are going to be passing through. Anyone that already has a loft conversion will be only too aware of the awkward shape that the design can leave them in. A good joiner will be able to advise on the best storage solutions for your situation.


With any new internal building work, you’ll want to be sure that the walls are plastered as smoothly as possible so that any painting or wallpapering can be done to the required standard.


Larger loft conversions such as mansard and hip to gable will require scaffolding in order for the building work to take place.


If you’re planning on a bit of DIY work, painting may well be the best area to try your hand. Failing that, a painter and decorator will be the last port of call to put the finishing, and often most visible, touches on your loft conversion.

Of course, all of the above tradesmen come with a cost. They are essential to the work being completed, but you’ll want to know how much they are going to cost.

Tradesman Average Hourly Rate
Builder £20-£35
Electrician £50-£120
Window Fitter £10-£15
Heating Engineer £30-£100
Plumber £35-45
Joiner £10-£20
Plasterer £30-£50
Scaffolder £10-£25
Painter £20-£50

Loft Conversion Flooring

You’ll want your brand new loft conversion to look as comfortable and cosy as possible. Making the correct choice in terms of flooring goes a long way to ensuring that the new room feels exactly how you want.

There are multiple options to choose from, each with different costs involved:

Type Average Cost (Per M2)
Vinyl £7-£20
Wood £10-£70
Carpet £4-£40
Tile £10-£60

What are Velux windows?

These are windows that are not added onto your loft conversion, they are in fact installed level with the roof, and are flat, unlike dormer windows which add a little more height to the roof.

If you are doing a loft conversion and can work with these windows, then you will find that they are your cheapest option for an extension. For more information on the best windows in Liverpool visit maghulldoubleglazing.com.

So, down to the cost of a three-bedroom loft conversion.

Generally, a loft conversion in the north would cost you less than down in the south. Additionally, because land is at a premium in the south, you can expect a loft conversion to add more to the value of your house in the south than up north.

The loft conversion then depends on the size of the loft and the part of the country you live.

A one-bedroom loft conversion in the north of the UK will set you back about £16,000, while the same project in the south would be above £30,000.

A two-bedroom loft conversion in the north will be about £20,000 an in the south will be about £40,000.

A three-bedroom semi loft conversion in the north will be about £30,000 and in the south upwards of £50,000.

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What would you get?

For this you would get the basic shell of your loft conversion. It will come with all the framework completed, the wiring done, floors and windows installed, and windows in place.

Normally a loft conversion does not include finishing off the work, so you can expect to have to either do some things yourself or hire a decorator in to finish it all for you. You will also need to add your bathroom suite and any wardrobes in the bedrooms, as well as carpets and tiling in all the rooms.

What about planning permission?

Generally, a loft conversion that makes use of Velux or dormer windows does not need planning permission.

You should not need any planning permission if:

  • The added space does not exceed more than 40 cubic metres. This figure is 50 cubic metres for detached or semi-detached houses.
  • There are no balconies or verandas on the conversion.
  • It does nor extend beyond the end of the existing roof at the front of the house.
  • Windows at the sides are glazed or frosted.
  • Side windows are more than 1.7 metres above the floor.
  • You have used the same or similar materials.
  • You are not on an area of Outstanding Beauty, a World Heritage Site, the Broads or a conservation area.

Top Tip: How to Reduce the Overall Cost of a Loft Conversion

As far as we’re concerned, the best way to ensure that your loft conversion costs are kept to a minimum is to hire experienced and reliable experts who are committed to seeing the job through from start to finish.

That’s exactly what the team at Loftera can provide. We have been perfecting our craft for a number of years and are proud to provide our famous service to the people of Merseyside and beyond.

A job of this size, whether you are opting for a mansard or rooflight loft conversion, is bound to encounter one or two snags along the way. We’re used to that, and are beyond confident in our ability to iron out any such issues.

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Location, Location, Location

In general, loft conversion prices tend to go hand in hand with the property market of the area in question.

Often, this difference is down to how densely populated an area is. In a busy city area, there is often little or no space for parking, rubbish skips, scaffolding, machinery. This does increase prices.

Naturally, a higher cost of living will coincide with higher salaries for works and increased daily rates. It goes without saying that this will all result in a bumper final price. Delivery and material costs should be factored in also. The size of a delivery vehicle, or distance that it needs to travel, will alter the final cost.

As we are sure you are now understanding, there are many factors to take into account to keep in mind in order to ensure that your loft conversion cost is kept to a minimum.

Reasons for a Loft Conversion

There are numerous reasons behind why people opt for a loft conversion in their home. One of the main benefits is that it adds value to your house.

Sure, if you’re putting this much time, effort and resources into such a big build, the last thing you are likely thinking of is selling your property.

However, it is always nice to know that your house has increased in value, it puts you in a strong position in the market at a later date if required.

On the topic of moving, if you are considering upgrading your home, perhaps because you are due to increase your family size, a loft conversion is a much less expensive way of doing this.

Adding natural sunlight into your home is never a bad thing. When building a new loft conversion, the choice is yours on where or how many windows you fit. We would advise to go for as many as possible, as allowing natural light into your home allows for a warm feel, and can save costs on electricity bills.

We spoke earlier about the insulation required when building a new loft conversion. It is no secret that the newer the insulation, the better it works. When fitting brand new insulation, you will be improving your insulation and making your home more energy efficient.

Growth is always a plus, right? In life and in your property. Building an extension or a conservatory is fantastic, and done right they can be stunning. No matter how good the work is though, there is one issue that is unavoidable – you lose space. The last thing most of us want is to lose garden space, those summer days in the back garden are priceless, and building outwards, in the shape of an extension or conservatory, reduces precious space.

In theory, although perhaps not quite literally, when building upwards, you can go as high as you like. We wouldn’t recommend attempting your very own mini skyscraper, but the point remains. When building upwards, like with a loft conversion, you don’t lose any space. You only add.

Potential Issues With a Loft Conversion

Of course, any project of this size will face one or two issues. Please don’t panic, it is perfectly normal, and that is where experts like us come into play.

Party Wall Disagreements

Those years of making friends with your neighbours can really pay off when embarking on a job of this size. In reality, your neighbours are much more likely to agree to your loft conversion if you are on good terms.

Our advice would be to speak to your neighbours before any sort of work begins. Should you anticipate any problems, be sure to get a party wall agreement in place at least two months before starting.


Older properties may well come across asbestos in a loft space. There is no way to avoid this. However, you are best to have a survey carried out before committing to any building work so that this issue can be dealt with properly. Check out the cost of asbestos removal for more info.

Out of Place Furniture

We are sure that many people reading this will be experts in interior design. Your choice of staircase up to your loft can limit you in terms of the size of furniture items that you can take up there.

Speak with the contractor early on. There is a chance that you may be able to have the furniture taken up early on before the banister and door frames are built. If you don’t ask, you don’t get.

Planning Permission

There is so much to remember, that it is only natural that one or two items will be missed. Make sure that applying for planning permission isn’t one of them.

Failure to do so can result in a hefty fine, which just isn’t worth it considering that the local council can provide a notice of lawful development certificate for between £100 and £400.

Frequently Asked Questions

How Much Value Does a Loft Conversion Add to My House?

On average in the UK, a loft conversion increases a property value by 22%. This can fluctuate depending on the quality and size of work, and the area where the work is being carried out.

Will a Loft Conversion Impact My Council Tax?

In general, council tax bands are only reviews when a property is being sold, or if the tenants ask for a review. If neither of these take place, a loft conversion being built should have no impact on your tax.

I’m Converting the Loft Myself. Do I Need Insurance?

If you are planning on carrying out the work yourself, congratulations! You are set to save yourself an awful lot on your loft conversion cost. However, it is still worth taking out insurance. If nothing else, this covers you in case of damage to your property or injury to yourself.

To sum up

Consider whether you have the time to manage the conversion on your own or would be better hiring a company to do the entire job for you.

If you choose a company to do the work, you can expect it to take anywhere between 2 weeks and 2 months. This is also dependant on the time of year when companies are very busy or slower.

If you choose to manage the project yourself then please make sure that the contractors you hire are all fully qualified, can show you their references and qualifications and can do the work in the time you ask.

Other blog posts to check out:

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About Loftera

Loftera bridges the gap between homeowners and trusted tradesmen, serving as the go-to platform for top-notch home improvement advice and solutions. With a foundation rooted in hands-on construction expertise and a commitment to transparency, Loftera connects you with local, vetted professionals, ensuring quality and reliability for every project. Explore our carefully curated articles, benefit from expert insights, and discover a seamless way to transform your living spaces. Whether you’re contemplating a renovation or seeking the best tradesperson in your vicinity, Loftera stands as your reliable guide in the realm of home improvements.

Joe Bruckland

Joe Bruckland

Construction Expert and founder of Loftera

Having immersed myself in the construction and home improvement world for over two decades, I’ve developed a deep-seated passion and expertise in the intricacies of the industry. My journey, beginning on construction sites and evolving to helm significant home renovation projects, has provided me with a hands-on perspective and a wealth of knowledge that I bring to Loftera. Holding certifications from premier industry bodies, I’ve been a go-to consultant for leading construction magazines, participated in industry forums, and collaborated with renowned tradesmen and architects across the UK. My mission is simple: to demystify the complexities of home improvement, ensuring homeowners are empowered with information that is both current and reliable. Through Loftera, I aim to provide insights that are a blend of field experience and data-driven research, cementing my commitment to be an authoritative voice in the home improvement landscape.

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