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How much does a house extension cost in 2022?

Additional costs

You may have to budget for some other costs to your home extension that were not covered in the above prices, and which vary, depending on the scope and specifics of your project.

These can include:

Cost of hiring a skip 

Skips are used to collect and dispose of the rubbish and excess materials that form when building work takes place. Sometimes, a skip will be included in your extension quote, but if it isn’t, you might have to pay between £100 and £400 a week, depending on where you live in the UK and how large you want your skip to be. You might need to hire more than one skip.

What does it cost to get a site survey?

It’s a very good idea to get a site survey done on your property before you begin work. This is because a surveyor will help you identify problems that could come up during the project, or any issues that stand out immediately. A survey will cost you between £600 and £1,400, depending on the size of your home. They’re useful because they can save you money down the line.


The ground over which your extension will be built needs to be prepared before building can begin. This means the foundations of the extension, but also other things like tree removals and the paths attached to your extension. You might also have to reallocate your drains, if they’re in the way. This kind of work can take up to two weeks to complete, depending on the project. Your main tradespeople will complete it, with a cost that can range from £500 to upwards of £3,000, depending on the cost of labour, and the size of your extension.

Cost of underfloor heating

Underfloor heating can be a great addition, especially in places like glass conservatories that don’t retain heat well. It’s easier and cheaper to install while the extension is being built, rather than retrofitting it later.

The price to have underfloor heating installed will depend on the size of the area being covered, and the type of underfloor heating you choose.

On average, installing electric underfloor heating costs between £600 – £850 for a 10m2 room, whilst wet (water) underfloor heating costs between £1,350 – £1,850 for the same sized room.

Additional costs for a home extension

Cost of hiring an architect 

You may feel more confident embarking on your extension project if you’ve shared your ideas with a professional who is equipped to help you make the most of your space. You don’t necessarily need one, especially not for simple extensions like a single-storey build, but whether or not you hire one is up to you. You will be charged around 10-15% of the cost of the extension for a plan. On average, the bill for this service might end up costing you between £700 and £1,200.

Planning application fee 

According to Planning Portal, the service that deals with all online planning applications, the cost to apply for planning permission is £206 plus a £32.20 service charge. This totals to £238.20.

Party wall agreements 

In some cases, the building of your extension might affect a neighbour’s wall or boundary. If this is the case, then your surveyor will need to serve your neighbour with a Party Wall Notice. This will cost you between £65 – £100.

You will then need to wait for your neighbours to give their written consent. If, within 14 days, they fail to do this, then there will be additional costs, as you will need to have a Party Wall Agreement arranged by a party wall surveyor. They charge between £80 and £300 an hour.

Post construction cleaning specialist 

If it isn’t included in your quote, then you might need to hire a post construction cleaning specialist, or team, to come and clean your extension before you can start using it. They can also clear around the site, depending on what you need.

Prices range widely, and will depend entirely on how much cleaning you need done to your extension. Bigger projects can require multiple cleaners and can cost upwards of £70 an hour, whilst other, easier cleans can cost £20 an hour.

If you think you need a post construction cleaner, then tell us about your project, and get a free quote now.

Building regulation costs

You will need to make sure that your extension project meets building regulations, as you cannot proceed without the appropriate certification. This includes ensuring the house is safe for habitation and also following all legal requirements. This takes place before building works begin.

Two additional services you might want to pay for are the cost of a structural engineer, which ranges from £1,200 and £3,000 and a CCTV surveyor, around £250 – £500. The former will plan out the calculations for the foundations of your extension, the latter uses CCTV to examine the condition of your drainage systems to ensure there aren’t any blockages or other problems.

You may not end up needing all of these things, but regulations are an important part of your home extension cost, so you should budget for them accordingly. Prices will of course vary widely, depending on how complex your project is, and where you live.

The best thing you can do is request a handful of quotes, to get a better sense of what a home extension might cost you.

Picture of a home extension
There are several additional costs you need to factor in when planning an extension

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