The average price of a bathroom
extension is around £30,000
Pricing guides

How much do bathroom extensions cost?

The bathroom extensions costs in this article are correct as of 2022

If everyone in your family is fed up with waiting for the shower to be free in the morning, or you’re stuck trying to get ready in a tiny ensuite, you may have considered adding a bathroom extension to your home. A bathroom extension gives you more space, with a focus on adding a new bathroom with all the comfort and functionality it provides, but you may be wondering how much an average bathroom extension costs, or how to go about getting bathroom extension quotes. Our guide will talk you through the price of a bathroom extension so that you’re ready to get started with your project.


Bathroom extension cost calculator

There are two key factors to consider when looking at the cost of a bathroom extension, the price of the building work involved in the extension itself, and the cost of the new bathroom. These can all be done as part of the same project by the same team of general builders, or carried out separately by specialist extension builders followed by bathroom fitters. 

Speaking to our experts, we have established that the basic price of building an extension is £1,100 to £1,400 per square metre. So, for a 20msq extension (4m x 5m), the cost will range from £22,000 to £28,000. These prices don’t include VAT, charged at 20%. The price bracket reflects the variance of materials used, the complexity of design, quality of finish and where in the UK you live. This price covers the essential elements of the build, constructing the foundations, building the walls, insulating the new structure, fitting out with plasterboard, adding a subfloor, and installing a basic provision for plumbing and electrics.


Meanwhile, the cost of a new bathroom hinges on the cost of the actual new suite you will be installing. The price of a bathroom suite is dependant on the materials used, quality and specification - a simple acrylic or steel bathtub can be less than £100, whereas a high-end one can run to more than £1,000. Altogether, after speaking to experienced MyBuilder tradespeople across the UK, we estimate the average price of a bathroom renovation is between £1,400 and £6,000. A full bathroom extension will therefore cost around £30,000.

For more details on the cost of building an extension, you can read our full guide on how much a home extension costs.

For a detailed look at the costs involved in fitting a new bathroom, check out MyBuilder’s guide to bathroom installation costs.

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We can help you meet professional bathroom extension builders near you to get real quotes today.

How long do bathroom extensions take to complete? 

The amount of time it takes to construct a bathroom extension will obviously depend on the scale of the build. A rough time-frame would be between three and four months, from the start of the project - clearing the space and digging the foundations, adding the finishing touches, and dealing with any snags you encounter. This does not include time for drawing plans and obtaining planning permission, if necessary. Delays can be common, and are often due to bad weather, changes in the plans, and hold-ups in materials being delivered. With multiple trades working on an extension, backlogs can also occur, with certain elements relying on other parts to be completed first.

MyBuilder Top Tip

At MyBuilder, we tend to advocate for hiring specialists in their particular fields to help make sure a job is done well. When constructing a bathroom extension, you may want to hire bathroom fitters separately from the firm that builds the extension, particularly if it’s a high-end bathroom which requires particular skill and attention to fit. However, an experienced extensions firm may be able to carry out the entire job from start to finish - make sure you ask to see examples of their previous work so you’re happy that they are up to scratch.

How to keep your bathroom extension costs under control

There are a number of ways to ensure you’re getting value for money when building a bathroom extension. The most important thing is ensuring you hire tradespeople who are reliable and trustworthy, and who you’ll have good communication with. It’s easy to find quality tradespeople on MyBuilder, with reviews from their previous customers. You should meet with multiple extension builders to get bathroom extension quotes and get a range of how much the project will cost to complete.

It is important that you only embark on any major project, like building an extension, when you are fully aware of the scale of the job and the costs involved. Set a budget and get several quotations for the work. Allowing yourself a contingency is always a wise move, to help you cover any extra expenses that could arise as a result of delays or issues with materials.

If you’re buying the bathroom yourself from a store or online, make sure you shop around and compare prices, and look out for deals in sales, which will be held throughout the year.

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