The average bathroom extension
cost is £1,300 per m2
Pricing guides

How much do bathroom extensions cost?

Exploring what it might cost to add an additional bathroom to your home and make your en-suite dreams come true? Wondering how much you’d pay to extend your existing bathroom and finally make space for that coveted claw-foot tub on your Pinterest board? Find out the true cost of your bathroom extension using our handy guide. All estimates and prices are accurate as of 2024.  

The price of a bathroom extension varies hugely depending on the project you have in mind. For a budget, small bathroom extension, the cost could be over £100,000 less than it would be for a premium, double-storey extension involving multiple new rooms. Budget effectively for your extension using our price guide, with costs for everything from labour to supply to disposal.


Average bathroom extension costs

Bathrooms are a popular target for transformation, whether because the existing suite has become outdated, the style isn’t to a homeowner’s liking or there’s an issue with the current size or location. If you have one of the first two problems, you’ll usually opt for a straightforward bathroom renovation at an average cost of £5,000 to £10,000

If your primary problem is the size, shape or location, things will be more complex, and you’ll need to get to grips with the average cost of a bathroom extension or new bathroom addition. With an extension or addition, you’ll be paying for building work, room repurposing and all those aforementioned renovation costs. Use the table below as a starting point for your cost calculations.  

Average costs table:

Bathroom extension typeAverage price range per m2Average price for a 20m2 extension
Budget single-storey bathroom extension£1,000 to £1,700 £20,000 to £34,000
Standard single-storey bathroom extension£1,700 to £1,900 £34,000 to £38,000
Premium single-storey bathroom extension £1,900 to £2,200 £38,000 to £44,000
Budget double-storey bathroom extension£950 to £1,500 £19,000 to £30,000
Standard double-storey bathroom extension£1,500 to £1,850 £30,000 to £37,000
Premium double-storey bathroom extension£1,850 to £2,200 £37,000 to £44,000

Note that these figures are averages based on available data but are a good starting point. The best way to get an accurate quote for your planned bathroom extension project, inclusive of all those specific, cost-impacting details that the figures you find online can’t account for? Head to MyBuilder, post your job for free, and gather detailed, itemised quotes from available extension specialists and bathroom fitters in your area.

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How much does a bathroom extension cost?

Though you’re looking at an average of around £1,300 per m2 for extending a bathroom, the cost for bathroom additions will depend on numerous factors. It’s far from set in stone or simple to predict. For example, the cost of a master bathroom addition that repurposes a bedroom into a bathroom or adds to your home’s structure might be significantly higher than that of a small en-suite extension that steals some space from the main bedroom. Ask yourself:

What are the specifics of my existing home?

How much will things need to change in my home to achieve my bathroom extension?

How large an area will my extension/addition cover?

Will I choose budget, standard or premium options during the renovation phase and how much will tile, toilet, shower, bath, hardware, etc. cost?

Will my location make bathroom installation or disposal of an old bathroom more challenging?

Will my location affect the rates of tradespeople (e.g., London prices)?

The high price of most bathroom extension projects could lead you to consider a DIY approach, but we’d exercise caution here. Improvements to your home connected to electrics and plumbing can be costly if anything goes wrong, and in many cases, unlicensed work carried out by a non-professional could void your home insurance.

Plus, even beyond the safety and insurance concerns, extending a bathroom takes a lot of time and effort. Going it alone could unnecessarily prolong your stress and inconvenience while still costing you a lot of money. Hire a trusted, proven extension specialist, and save yourself the headache.

Cost to extend an existing bathroom

The cost of extending an existing bathroom will depend on how much you want to expand and what you’ll be expanding into. Will you be adding to the footprint of your house in a traditional extension format, or will you be reducing the size of another room to extend the bathroom? If you’re reducing the size of another room, the price will likely be lower, but the exact cost will be very much dependent on your individual home. 

If you’re adding to your house, you can use standard extension costs as a guideline for bathroom extensions, but you’ll need to add around £5,500 to £10,000 onto the total, as we’ve done below. This is because the bathroom extension process is more involved and complex than a standard room extension process.

Extension typeAverage price rangeAverage price range for a bathroom extension (+ £5,500 to £10,000)
Budget 20 m2 extension£40,000 to £56,000£45,500 to £66,000
Standard 20 m2 extension£40,000 to £56,000£45,500 to £66,000
Standard 30 m2 extension£60,000 to £84,000£65,500 to £94,000
Premium 30 m2 extension£75,000 to £110,000£80,500 to £120,000
Standard 50 m2 extension£100,000 to £140,000£105,500 to £150,000

Cost of a new bathroom addition

The table above can also be applied to an extension that adds a new bathroom. This is functionally very similar to extending an existing bathroom. However, the final cost to add an additional bathroom may be higher, comparatively, as there will be no existing plumbing points, fittings or items to incorporate into the new and improved space. You’ll be starting from scratch. 

Cost to move a bathroom

In many older UK properties, the bathroom is situated downstairs. This isn’t the preference in the modern era, and it tends to be one of the biggest reasons a homeowner will invest in moving a bathroom from one room and placing it in another, better-suited room. 

Similar to other room extensions and additions that don’t add to the home's footprint, this shouldn’t be too costly on the scale of bathroom transformations. The average cost to move a bathroom upstairs is currently £14,850, though it could easily be as high as £20,000 depending on project specifics. Moving a bathroom to the next room on the same floor should cost less, at around £7,150

Cost of additional extension work

The more area you plan to cover with your bathroom extension, the more it will cost you. That said, if you’ve been planning to extend another area of your home, a simultaneous extension process will be less costly than two separate extensions completed at different times. Especially if, for instance, you’d like to extend the same area of your home on both storeys. 

Cost of hiring tradespeople

A bathroom extension is by no means a minor job. Work is unlikely to be done within a month, and your project will require the hiring and management of numerous different tradespeople, from builders and extension specialists to electricians, plumbers and bathroom fitters. This table outlines expected hourly labour rates for the professionals you may need to work with during your project.

TradespersonAverage hourly rate
Architect£50 to £100 (though they may instead charge a percentage or a lump sum)
Bathroom fitter£25 to £60
Builder£25 to £50
Electrician£45 to £60
Joiner£15 to £40
Painter decorator£30 to £50 (usually charged as a day rate)
Plasterer£15 to £50
Plumber£25 to £80
Project manager£100 to £200
Roofer£20 to £40
Tiler£15 to £75

As you’ll see from the table, the most significant hiring expenses will come into play if you need to bring an architect or a project manager on board. For small extension jobs, you might not need either. For more extensive work, especially if you lack experience or don’t have the time to manage things daily, you might need both. Remember that though this is a notable short-term cost, it’s also hugely beneficial in ensuring that:

  • Your project is well designed, and the final result is as expected.
  • Your project is organised and on track throughout. 

Cost of planning permission (if required)

If you’re concerned that your project will need planning permission, speak with your contractor or project manager about this and contact your local planning authority for more information. The table below outlines the costs of a full planning application for this purpose, depending on your location. 

LocationCost of a full planning application for alterations/extensions to a single dwelling

Planning permission may add to the total price of your bathroom extension and delay your planned start date if there are any issues. Thankfully, you won’t need planning permission if your extension:

  • Doesn’t extend beyond the rear of your existing property by more than four metres (detached) or three metres (terraced or semi-detached)
  • Takes up less than 50% of the size of the land around your existing property
  • Is single storey, with a maximum height of four metres
  • Doesn’t include any roof ridges or top points that rise higher than the eaves of your existing property’s roof

For extensions that will add additional storeys to your property and more significant extensions to the rear, you’ll also need what’s known as ‘prior approval’ from your local authority, which will take around eight weeks to be assessed and cost you roughly £100.

Cost of removals

The demolition and removal side of a bathroom extension can be more costly than you’d expect. Waste is easily forgotten when budgeting for this kind of project, but from the construction phase to the renovation phase, it’s being produced, and it must be dealt with. You’ll need to confirm with your builder that elements like skip hire and disposal are included in the quote you’ve received from them. A full bathroom removal could be anywhere from £300 to £2,500 of your total budget. 

Cost of materials

Material and supply costs will apply during your bathroom extension's construction and renovation phases. The table below should help you budget for the various items you’ll need, which you can either ask your tradesperson to source or you can buy in advance and provide for them to install. 

ItemAverage price range
Bathroom door£50 to £300
Bathroom window (often frosted)£200 to £600
Wall décor (paint, tiles and/or wallpaper)£20 to £50 per m2
Flooring£10 to £30 per m2 budget, £30 to £60 per m2 standard, £50 to £100 per m2 premium
Bathroom towel radiator/standard radiator£60 to £300
Bathtub£80 to £500
Shower£60 to £1,000
Toilet£50 to £500
Sink/basin£50 to £300
Taps£50 to £100

As you can see, the averages range significantly depending on your choices with these materials. A £60 shower and a £1,000 shower are clearly two very different options. Do your research and identify your ideal price point for all of the above. If your quote for a bathroom extension is coming back to you over budget, this might be an area where you can make some considerable savings by shopping around, searching for deals and utilising sale prices. 

Cost of bathroom renovations

As mentioned, a straightforward bathroom renovation costs between £5,000 and £10,000, including labour and materials. This is the same for the bathroom renovation phase of an extension (though more work will need to be done on the plumbing side of things to prepare a space that’s never been used as a bathroom before). The table below outlines how renovation costs break down, job by job.

Bathroom renovation jobAverage cost
Installing a toilet£150
Installing a sink/basin£175
Installing a bath£350
Installing a shower£500
Installing a heated towel rail£250
Installing a shower enclosure£400
Installing a radiator£250
Installing underfloor heating£40 per m2, £700 to £1,500 
Installing an extractor fan£150 to £300
Electrical works £600
Tiling the walls£900
Laying laminate or vinyl flooring£250 to £950
Replastering £1,000
Painting and decorating £400
First fix plumbing£25 to £40 per m2

Cost of accommodation

A bathroom extension could last as long as two months for a simple addition and double that for more complex projects. If you know that you’ll lose access to one bathroom for months and feel that living in your home will become stressful, inconvenient and disruptive during that time, you may want to budget for other accommodation arrangements. 

If you can afford it, consider booking into a hotel or finding a short-term rental property while the extension is completed. The average price per night for an Airbnb in the UK is £70, while the average price per night for a hotel in the UK is £100. Alternatively, you could consider staying with family and friends, if that’s feasible.

Cost to run your new bathroom

Whether you’ve added a luxuriously deep new bath to your extended-size bathroom or put in a brand-new bathroom where there wasn’t one before, there’s a chance that your addition will impact your household running costs, primarily through upping your water usage. 

The average water bill in England and Wales is £37 a month, and the change shouldn’t be too noticeable post-extension, but it’s certainly worth preparing for if you’re concerned about the current price of your utilities.


How long does a bathroom extension take?

With a better idea of bathroom extension costs, you may now wonder precisely how long a project like yours will take. It isn’t easy to pinpoint an exact timeframe for something like a bathroom extension since it depends so much on the scale and complexity of the project and the availability of your chosen tradespeople. 

That said, a bathroom extension takes around five to ten weeks on average, and this table outlines various jobs and usual timeframes that you might like to be aware of.

Bathroom extension jobUsual timeframe
Multi-room double-storey extension (including a bathroom)14 to 16 weeks
Full bathroom extension (including renovation)Five to ten weeks
Full bathroom renovationOne to five weeks
Adding to an existing bathroomTwo to ten weeks (depends on extension type)
Adding a new bathroomTwo to ten weeks (depends on extension type)
Plastering a bathroomA few hours to a few days
Tiling a bathroomA few hours to a few days
Installing underfloor heatingA few hours to a few days
Installing laminate or vinyl flooringThree to five hours (not including potential latexing time for concrete floors)
Adding a new shower or bathtubThree to five hours
Adding a new toilet or sink/basinTwo to three hours


How to reduce bathroom extension costs

Regardless of your budget and planned bathroom extension project, you don’t want to pay more than necessary to achieve your goals and get the bathroom you’ve dreamed of. If you’re looking for ways to reduce the total cost of a bathroom extension and renovation, these tips and tricks should help. 

  • Shop around for the best possible quote: This is arguably our most crucial piece of advice. If you fail to confirm that the quote you’ve received for your extension is a fair, competitive price, you could massively add to your total cost unnecessarily. Speak with multiple extension specialists, compare costs on a comprehensive, like-for-like basis and exclude anyone who doesn’t seem remotely in line with industry standards. 
  • Act as your own project manager: As we’ve mentioned in this guide, a project manager is a valuable addition to an extension job, managing a lot of the day-to-day so that you don’t have to. If you’re willing to become your own project manager, you could save £100 to £200 every hour that you’re not paying another person to outsource the responsibility. Weigh up the investment of time versus money to make the best decision for your personal situation.
  • Consider long-term savings, too: Saving money isn’t just about reducing the bill you’ll receive in the short term. Think about the future, and don’t cut too many corners in pursuit of a reduced quote if the corners you’re cutting may cost you more to fix at a later date. Buying poor-quality vinyl flooring, for instance, could mean replacing that flooring sooner than you’d need to if you’d chosen something more expensive with better longevity.
  • Reuse what you can: If you’re extending an existing bathroom into a larger space or swapping it from one room to another, consider whether any elements can be carefully removed from the old bathroom and placed into the new one. You don’t necessarily need to gut everything and start from scratch if that’s not what your project calls for, and there may be at least a few things you’d be happy to reuse in your new and improved bathroom.
  • Source materials and supply certain items yourself: Some tradespeople will charge a lot more for the time they spend sourcing your bathroom items, from tiles to toilets. Plus, they won’t be as concerned about getting the best price for you as you might be. Retain some control and reduce your labour costs by taking on sourcing responsibilities for specific items. Look out for sales, price cuts and deals, then strike when the time is right.
  • DIY the decorating stage: Though much of the bathroom extension process is better handled by a professional, you can definitely flex your DIY muscles during the decorating stage, whether that means trying your hand at tiling, giving the walls a fresh coat of paint, or hanging a few rolls of wallpaper. Labour costs add up, so why not save up to £400 a day by swapping hiring a professional decorator for picking up the roller and trowel yourself?


Do I need planning permission for a bathroom extension?

This is always worth confirming with your contractor, but unless you own a listed building, you’ll usually only need planning permission for an extension (whether it’s a bathroom extension or any other kind) if it will do any of the following:

  • Extend more than four metres (detached) or three metres (terraced, semi-detached) beyond the rear of your existing property
  • Take up more than 50% of the land around your existing property
  • Involve multiple storeys
  • Rise above a maximum height of four metres
  • Include roof ridges/top points above the eaves of your existing roof

Should I hire an architect for my bathroom extension?

This is ultimately your choice, and many building contractors are happy to work without an architect, especially on smaller projects. But, if you’re planning a more extensive project needing planning permission and careful design, we’d probably recommend footing the bill to ensure you get things right the first time. An architect can help with initial design ideas, drawing plans, meeting regulations and communicating expectations to your contractor/contractors. 

Do I need to tell my insurer about a bathroom extension/addition?

You need to inform your insurer about any changes made to your home that impact the overall structure, including extending a bathroom. Cosmetic changes like re-tiling or straightforward bathroom renovation don’t need to be mentioned, but if you’re planning an extension, you’ll need to check your insurance documents and confirm that your insurer will continue to cover your home after the changes.

Can I carry out my own bathroom extension?

Some parts of your bathroom extension can be done on a DIY basis if you’d like to save money or prefer to do things with your own hands, like painting and decorating, but other elements need to be left to a qualified and appropriately insured/certified professional. Your insurance company will likely only be satisfied with the quality of your extension if you can provide evidence that a qualified tradesperson undertook any work associated with the structure, heating or pipework.  

Is extending my bathroom worth the cost?

Only you can determine whether extending your bathroom, at an average price of £1,300 per m2, is worth it. Some of the main benefits/reasons to consider a bathroom extension, which might apply in your situation, are as follows: 

  • A larger bathroom gives a young family room to grow
  • An upstairs bathroom is more convenient than a downstairs bathroom
  • Two or more bathrooms can be very convenient, especially in larger households
  • The ability to offer guests their own bathroom increases their comfort and privacy
  • Additional and larger bathrooms tend to add value to a property
  • Bringing a bathroom in line with modern plumbing and electricity standards can save on utility costs in the future

When should I book my bathroom extension?

You can book your extension as soon as you’re comfortable covering the costs. For bathroom fitters, the busiest time of year spans from September to December, so you may not have to wait as long to get your extension booked and completed if you reach out to a tradesperson in late winter or spring. Note that if you plan to extend your home’s existing structure, you’ll ideally want to do so during a period of nicer weather (spring or summer) to avoid disruption.

Your bathroom extension checklist

Whether you’ve never worked with a tradesperson before or you’ve never undertaken a project as significant as a bathroom extension before, it’s completely understandable to have some apprehension about the process. Thankfully, our bathroom extension checklist should enable you to tick every box, cover every base and turn your dream bathroom into a reality.  

  • Do your research to narrow down an estimate ahead of time: This guide is a great place to start when working out your estimated bathroom extension cost. Plus, look at where you’ll sit on the price ranges we’ve covered in this guide. For instance, do you plan to purchase a £60 shower, a £160 shower, or a £600+ shower? The more you know about what you’ll pay, the less likely you will be disappointed or confused by a mismatch between expectation and reality.
  • Post your project on MyBuilder: Post the details of your planned bathroom extension on MyBuilder, free of charge, and we’ll share them with professionals in your area. Appropriately skilled extension specialists with the right availability to help will then register their interest in working with you, and you’ll have essentially created a shortlist for yourself without any hassle. Over 90% of MyBuilder job posts generate interest, so you can be confident in finding a tradesperson who can help.
  • Look for quality customer care and relevant experience: As you look into the profiles of the extension specialists who’d like to work with you, pay close attention to their past customer reviews and the standard of care they provide. Then, pay equally close attention to the number of extensions they’ve done that seem similar to yours in terms of skill, scale, etc. Find someone who knows what they’re doing and does it well.
  • For more advice on choosing the right extension specialist, take a look at our hiring guide.
  • Gather quotes, ensuring everything is included: For price comparison purposes, it’s imperative that you ask for quotes from numerous contractors and compare them on a fair basis. Keep your eyes peeled for any costs that seem suspiciously high or low, or any prices that might not have been included to make the quote seem cheaper than it really is. Are supply costs accounted for? What about existing bathroom removal and disposal?
  • Ask about insurance, aftercare and guarantees: Insurance is a must for a big renovation like a bathroom extension. When you think you’ve found your tradesperson, ask for evidence of their insured status before you sign anything. Similarly, confirm that they’ll be happy to offer you a guarantee in the event that something goes wrong after completion. Most contractors will happily share insurance details and offer a guarantee. Anything else is a red flag. 
  • Make your final choice with confidence: Step into your final hiring decision with confidence, knowing you’re a) getting a good price, b) working with an experienced and reliable local professional, and c) protected if anything goes wrong. Then, before you know it, the construction and renovation will be underway, and you’ll be excitedly awaiting your new bathroom reveal!

Use MyBuilder to connect with a qualified, experienced extension specialist for free. Post your bathroom extension job today and find an available local tradesperson right away.

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