Cost of Bathroom Extension

Looking for the cost of building a bathroom extension?

For a basic bathroom extension with just the bare essentials, the average cost will be around £900-£1700 per m².

But, if you're looking for a top-of-the-range build and finishing, it'll cost around £1750-£2200 per m².

So, how can this guide help you?

This ultimate price guide can help you calculate exactly how much a bathroom extension will cost you, as there are many factors that can affect the overall cost.

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For a more detailed look at bathroom extension costs - read on...

How Much is a Bathroom Extension?

When it comes to building a bathroom extension, the final price will depend on a wide range of factors.

These factors can include the size of the extension, the quality of the finish, and your location within the UK.

For a basic bathroom extension with just the bare essentials, the average cost will be around £900-£1700 per m². If you are looking for a top-of-the-range build and finishing, you will be looking at costs of around £1750-£2200 per m².

Depending on the type of bathroom products you add to your extension, you may be looking at additional costs of around £4,400 and £8,800 for a medium-sized bathroom. However, new bathroom suite prices can be higher for a larger space or higher specification products.

Bathroom Extension Prices

Below is an overview of the different bathroom extension costs that you can expect.

It's important to note that a double-storey extension can be cheaper per m² than a single-storey extension, as most of the cost is in the foundations and groundwork.

Supply Only Costs

Below is a list of the costs of supplies when it comes to building a bathroom extension. This indicates all of the costs that may come up without the cost of labour:

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Additional Costs

There are several additional costs associated with building a bathroom extension. Below is a list of the additional costs that you may need to think about with this type of work:

Underfloor Heating

Underfloor heating is a great addition to a bathroom extension. It provides a cosy feel and heats the room quickly.

It also means that you won't need to have a radiator installed in your extension, which will avoid the need for extra pipework.

Underfloor heating can be either electric or connected to the central heating system.

Electric underfloor heating costs around £700 to £1,200 on average, while piped in underfloor heating costs around £1,000 to £1,500 on average.

Bathroom Extractor Fan

A bathroom extractor fan will ensure that your new bathroom extension is properly ventilated.

If your bathroom is not ventilated properly, it will remain damp, leading to severe problems such as mould, mildew, and rot in the walls.

The average bathroom extractor fan installation cost is around £150 to £300.

Labour Costs and Timescales

The total cost for labour will vary depending on several factors, including your location in the UK, the number of contractors working on the job, the size of the extension, and the difficulty of the job.

Below is a rough guide on the costs that you can expect to spend on labour for this type of work:

Those based in London can expect to pay a bit more for labour than those based in the North or other parts of the UK.

The timescales for building a bathroom extension can vary greatly depending on a number of factors, including the size of the extension, the ease of access, the difficulty of the job, and how many contractors are working at any one time.

On average, you can expect a bathroom extension to take around 5-10 weeks.

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Cost Factors of a Bathroom Extension

There are several cost affecting factors when it comes to building a bathroom extension.

Below is a list of the main factors that can affect the overall cost of the job:

Size of Extension

The size of the extension can affect the overall cost of building a bathroom extension.

A larger extension will require more materials and will also take much longer to build, resulting in higher labour costs.

Quality of Finish

The quality of the finish is a huge factor in the overall price you will pay for your bathroom extension.

A basic single-storey extension will cost around £1,500 to £1,700 per m², whereas a premium single-storey bathroom extension will cost around £1,900 - £2,500 per m².

Plumbing Work

When installing the bathroom in the extension, there will be a lot of plumbing work involved. Some plumbing jobs may be more difficult or intricate than others.

With this in mind, your new bathroom's plumbing can affect the overall cost of the job.

A plumber will charge around £35-£45 per hour, so these costs can add up if there is a lot of plumbing work involved.

Ease of Access

The ease of access to the worksite can affect the overall cost. If the worksite is difficult to access, this will result in the job being more difficult and will add extra time to the length of the job.

The longer the job takes, the more you can expect to pay for labour.

What's Involved in a Bathroom Extension?

There is a lot of planning that goes into a bathroom extension. You will need to research everything and decide exactly what you're looking for.

You can then contact designers to create the exact final design of your new bathroom extension.

Once you know exactly what you want, you can start contacting contractors for quotes on the work.

Once everything is arranged, your new extension build will begin.

Bear in mind that building control officers will need to attend at various points within the construction process. Seek advice from your contractors and stick to it.

Below is a list of the steps involved with building an extension:

• Foundations and Groundworks - Foundations will be laid and reinforcement bars installed, if necessary, before concrete is poured.
• Ground and Low-Level Work - Once the foundations are set, trenches and drains are dug up, and bricklayers will begin constructing the walls. At this point, a damp-proof course will be put in and lintels added before more concrete is poured in to create the flooring base.
• External and Internal Walls - Bricks are laid, and the cavity wall insulation is installed. All door and window frames are then added, and the internal blocks are laid.
• Roof Structure and Covering - The frame of the roof will be built and will then be covered with roofing felt. Roofing battens are then secured in place before roof tiles, ridges, fascias, and soffits are installed. The roof is then left to set.
• Windows, Doors and Rendering - The windows and doors will now be added, and the external walls can be rendered, if required.
• Guttering, Plumbing and Electrics - All rainwater pipes, guttering, plumbing, and electric wiring are added.
• Plastering - The joining wall will now be knocked through if necessary, or space will be created to install a door. Finally, the plastering can then be applied.
• Final Work - Remaining plumbing and electrical work is completed, and any testing is completed. At this point, the bathroom suite can be installed, and the room can be decorated to your liking.

Can I Build a Bathroom Extension Myself?

It's highly unlikely that you will be able to undertake a bathroom extension as a DIY job.

Any extension requires numerous skills, and many aspects of the build must be signed off by professionals and comply with building regulations.

Building a bathroom extension can take an extremely long time, even when completed by a team of qualified and highly experienced professionals.

It's imperative that the extension is built safely and securely.

With this in mind, you shouldn't attempt a DIY bathroom installation. Instead, you should look to hire reputable contractors who have all the relevant skills and experience necessary to build your bathroom extension.

However, there are elements that you may be able to do yourself, such as painting, decorating, or tiling. In addition, by managing the overall project yourself, you may be able to coordinate different tradesmen to get the extension completed as quickly as possible.

Building Regulations and Planning Permission for a Bathroom Extension

Many extensions are covered under permitted development, which means they don't require any planning permission to go ahead.

To be covered under these rights, the extension must be:

• No more than four metres high.
• Not extended more than six metres beyond the rear of the house if it is an attached house or no more than eight metres for a detached house.
• All side extensions must be single-storey and no more than half the size of the original house.

However, there are exceptions, particularly if your home is listed or in a conservation area.

If you live in a semi-detached or terraced house, then you may need a party wall agreement if you're working on a joint wall.

You will need to notify your neighbours of the intended work and get a surveyor to come out and make sure the work won't have any negative impacts on your neighbour's property.

Always check if you need planning permission for your extension by asking your local council directly. Don't simply assume the work is permitted, or you may end up having to reverse it all and remove the bathroom extension.

Building Regulations

Your extension work will require building regulations approval at various levels of the build.

The contractors that you hire should have a complete understanding of the building regulations that must be followed.

A building control officer will review and sign off on the work completed.

Benefits of a Bathroom Extension

There are several benefits to building a bathroom extension. Below is a list of the main advantages of choosing to build a bathroom extension on your home:

• More Room - Adding a new bathroom can reduce frustration in a busy or growing household.
• Convenience - If you add a new bathroom downstairs, this adds an element of convenience as you won't need to go all the way upstairs to use the bathroom.
• Great for Guests - A downstairs bathroom extension is great for when you're hosting guests, as it means that the upstairs of your home can remain private.
• Adds Value - An extra bathroom in the home can add significant value to your property. This is useful when you come to sell your property.

Hiring Contractors to Build a Bathroom Extension Checklist

You will need to consider a few things before hiring contractors to install an extension for you.

Below is a list of some of the main things that you should consider when looking for the right contractors for the job:

• Does the contractor offer any guarantees with their work?
• How much is the work to complete? – Ask for a breakdown of costs so you can ensure you are paying a good price for each element of the job.
• Is the contractor experienced in building the type of extension that you are looking for?
• How many years' worth of experience does the contractor have in building extensions?
• How many contractors will carry out the job?
• Will the contractor fix any issues that may arise?
• Will the contractor take care of any relevant waste removal?
• Do you need to hire any additional contractors for different parts of the work?
• Will the contractor follow all of the relevant building regulation guidelines?

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