Single Story Extension Cost Calculator

Use our single story extension cost calculator to get instant extension costs online.

Are you looking to expand the size of your property?  A single storey extension will be a valued addition to your home, increasing its overall value should you choose to sell on.

Extensions are an amazing way of giving yourself more space, adding a whole new, additional room to your property that can be used as anything from a dining room, studio, playroom, sunroom or even an extension on a pre-existing room, including kitchens.

However, when looking into getting any kind of construction work on your property, it is important that you find out exactly how much everything is going to cost and how long it is going to take to build. Afterall, you will need to structure your life around the building work so it’s smart to be aware of the costs involved.

How much does an extension cost? Use our single storey cost calculator to find out.

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How Much Does a Single Storey Extension Cost?

Depending on your location in the UK, an extension can typically be estimated at around £1,000 to £2,000 per square meter, which itself can vary depending on the quality of the extension materials.

If you wanted a two-storey extension, however, this price almost doubles to around £1,300 to £25,000, and will overall cost more due to additional joists and fixtures.

Your location matters as properties in London can be expected to have a much larger cost, while also getting far more profit due to the desirability of extensions within the capital, especially in certain areas.

For instance, a £20,000 extension in Kensington and Chelsea costs less than £1,000 in Wales for the same amount of space. Location is a major factor in both costs and profit, so an average estimate isn’t a guarantee on price.

How Much Does an Average Single Storey Extension Cost?

In a recent survey of over 1000 home improvement projects, Zopa gave an estimation of an average extension cost being around £20,000, with an average return of 71% on investment and giving a profit of £14,000.

However, averages are made up of a combination of a lot of different ranges of data, and often times these prices for both costs and profit can fluctuate wildly from project to project.

How Much Does a Single Storey Extension Cost in the UK?

Take a look at our guide prices for extensions in the UK. Our single storey extension cost calculator will also provide you with a guide price based on your specifications.

Extension Width (mm) Extension Projection (mm) Guide Price
4000 3000 £23940 – £26460
4100 3000 £24538 – £27121
4200 3000 £25137 – £27783
4300 3000 £25735 – £28444
4400 3000 £26334 – £29106
4500 3000 £26932 – £29767
4600 3000 £27531 – £30429
4700 3000 £28129 – £31090
4800 3000 £28728 – £31752
4900 3000 £29326 – £32413
5000 3000 £29326 – £32413
5100 3000 £30523 – £33736
5200 3000 £31122 – £34398
5300 3000 £31720 – £35059
5400 3000 £32319 – £35721
5500 3000 £32917 – £36382
5600 3000 £33516 – £37044
5700 3000 £34114 – £37705
5800 3000 £34713 – £38367
5900 3000 £35311 – £39028
6000 3000 £35910 – £39690

Extension Costs per Square Metre

For an area in London, such as Hackney or Richmond, an extension of around 25 square meters can mean an increase in value of more than £169,000, because of increased demand for larger properties within the area.

However, a medium sized extension in other places around the UK still adds a considerable amount of value, estimated at an average of around £59,000.

All in all, the cost of an extension per square meter is around £1,000 to £2,000 for a single storey, with that almost doubling to £1,300 to £2,500 for two storeys.

10 Ways To Cut The Cost of Your Extension

Will a Single Storey Extension Add Value?

Does an extension add value to your house? Of course!

All home extension projects add value to a property one way or another, but the truth is, is that the amount of added value often depends on the overall size of the structure and how much you spent building it.

The value of a property being measured in terms of how many square meters it covers, 1 m2 being around the same size as the floor of a red telephone phone box.

The value of the additional extension also depends on where you live and what the extension is being used for. If, for instance, an extension is made to add an additional bedroom can add 12% to the value of the property, whilst a bathroom adds only around 6%, whilst a bedroom with an ensuite can add 23%.

Naturally, a relatively small 25m2 extension doesn’t cost as much to build as a 50m2 extension, and thus will add less value to your property in comparison. However, don’t let this put you off as there are many more things an extension can provide that can add additional value, such as the design of the extension and what you use it for.

single storey extension cost calculator

An Extension Will Improve Your Living

Overall, a house extension’s usability as a multi-purpose room is one of its greatest benefits, with brick walls able to have wiring and plumbing installed, meaning that the possibilities of its possible uses are endless.

Even if you only plan on using it as a sitting room, anyone who later buys your home can then use it as a freely usable space as anything from a utility room to a bathroom.

extension cost calculator

How Long Does A Single Storey Extension Take To Build?

When having any kind of extension installed on your property, be it a house extension or a conservatory, you want to naturally get it over with as soon as possible.

Building work can be a hassle and can often get in the way of plans and your day-to-day life, so finding out the length of your installation project can be vitally important to structuring your life around it and causing as little disruption as possible.

Your average, simple 3 meter single-storey extension on the rear of your property typically takes around 3 to 4 months, with a larger or more complex construction taking around double that, at 6 months.

Whether or not you want to move out of your property during the construction is entirely up to your discretion, as smaller extensions can be quite unobtrusive but larger or more complicated ones can cause a lot of disruption.

Your Extension Options

DIY Extension– -This option is for if you want a lot of control over your installation, and also save yourself more money. Buying in the raw materials directly and building the extension yourself may save you a lot of hassle from dealing with contractors, but the quality of your extension is entirely down to your own skill.

Main Contractor and Subcontractors – Save yourself some money by getting a main contractor to construct the extension up to a weather-tight stage, and then employing additional subcontractors to finish remaining work. Buying materials is often left up to you, directly from suppliers.

Main Contractor – This is the most hands-off approach, having a main contractor take up the role of project manager and constructing the extension to your design specifications. This is the most expensive option, as you are paying additionally for the project manager role as well as their purchasing of materials from suppliers.

When figuring out the cost of the home extension you are getting for your property, you need to take certain things into account; including additional costs, VAT, the size of the structure, the materials you want it built from and what kind of groundwork is needed to put in foundations. All of these factors can affect the overall cost of the installation, as well as the length of time it will take to build.

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