Single Story Extension Cost Calculator

Use our single storey extension cost calculator to instant home extension costs. Our online extension cost calculator allows you to calculate the cost of a single storey extension, based on your unique specifications.

How Much Does a Single Storey Extension Cost?

An extension typically costs between £1,000 and £2,000 per square meter, with the price almost doubling to between £1,300 and £2,500 for a two-storey extension; however, a two-storey extension also needs additional joists and fixtures in order to make it structurally sound.

Home Extension Costs in the UK

Below we have listed some guide prices for single storey extensions in the UK.

It’s important to note that location is an important factor in how much your home extension will cost. Highly sought-after areas such as London having costs that skyrocket compared to other areas in the UK.

For instance, an extension in Kensington that could easily cost around £20,000 can cost less than £1,000 for a homeowner in Wales, despite being structurally and aesthetically the same in size and appearance. Because of this, estimations are not a guarantee on the final price.

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

Several factors need to be taken into account when figuring our the costing of your extension installation. The lump sum of the installation is made up of different things; including materials, labour, VAT and groundwork costs, all of which can be affected by the size of your desired structure.

Even what particular materials you are buying, and even what kind of soil you have could affect the progress of the initial groundwork.

All of these factors come together to dictate both the price of your extension and how much time is going to have to be spent on the installation.

Extension Costs per Square Metre

Extensions don’t just add an extra living space but can also increase the desirability and overall value of your property should you choose to sell on at any point in the future.

A property’s overall value is often measured in terms of how many square meters it covers. For example, 1 meters squared is around the same size as the floor of a red telephone box.

The more square meters, the more it will evidently cost you. It will however, earn you more of a profit in terms of added value.

An extension that covers 25 meters squared won’t cost you as much to build as a 50 meter squared extension, however a 25 meter squared extension will add less monetary value.

In a recent survey by Zopa, an estimation of the average extension cost was around £20,000, with an average return on investment of around 71%, with a profit of £14,000 in added property value. It is important to remember, however, that averages are taken from a range of data. The price and the profit can vary wildly from project to project.

The cost of an extension in London, such as in areas like Hackney and Richmond (who’s neighbourhoods have a high demand for larger properties within that area of London), a 25 meters squared extension can increase the value of a property by more than £169,000. However, a similar sized extension in other areas around the UK, while still adding to the value of the property, is more estimated at adding around £59,000.

However, there is a general estimate that an extension typically costs around £1,000 to £2,000 per square meter, with two-storeys almost doubling that price between £1,300 to £2,500.

Planning Permission Costs

Planning permission is often another factor that needs to be thought about, with that including additional costs, including standard fees and design costs, as well as taking more than a month for it to be processed by the local council. The government’s Planning Portal has a lot more information on the regulations in place, the allowed dimensions and features for extension installations, as well as the additional planning costs that have to be taken into account in your budget.

Certain dimensions of single-storey extensions are exempt from planning permission. However, it is still highly recommended that you familiarise yourself with Government regulations.

single storey extension

Will a Single Storey Extension Add Value?

Does an extension add value to your house? The additional space created by an extension often increases your properties monetary value, as well as its desirability as a property should you ever choose to sell on.

The multi-purpose nature of an extension is one of its greatest strengths, meaning that, no matter what you are planning on using it for, it can be adapted into any kind of room you want it to be.

The size of an extension isn’t the only thing that affects the price of the installation, however, as many other factors must be considered.

Whilst extensions are predominantly brick-built, things such as windows (including their size, materials and number of units), doors and roofing options can all increase both the price and the value of your home.

All these options individually need to be designed and decided on during your initial planning stages, as well as whether they will come from the same installation company as are building your extension, or if you can get a better deal elsewhere.

How Do You Plan On Using Your Extension?

As mentioned above, location is an important factor in the value of an extension, as well as what you are planning on using the extension for.

With a brick-based structure creating a brand-new multi-purpose room on your home, your new extension can be used as an expansion on a pre-existing room, such as a kitchen extension, or a completely new room that can be made into a living space, a sunroom, a study, studio or a playroom. The possibilities are endless, with wiring and plumbing able to be installed in the brick walls, giving you light, running water and heating.

If you want to utilise your new one or two storey extension to be an additional bedroom, this can add around 12% to the value of your property, whilst a bathroom adds around 6%; however, a combination of a bathroom with an en-suite can add as much as 23%.
As with most things, extensions cost more to build in London than in most other areas around the country but will also be worth more in terms of property value and desirability.

A house extensions highly adaptable and multi-purpose nature is one of its greatest strengths, being able to be made into basically any kind of room you want, with plumbing and electrics able to be installed in the brick walls like any other wall in your property. The possibilities are literally endless, and, even if you are only using it as a sitting room, any future homeowners will be free to change it and adapt it for their own needs.

How Long Does A Single Storey Extension Take To Build?

Building work on your property can be a bit of a hassle, causing disruption to your daily routine and getting in the way of plans. Because of this, when having any kind of extension installed on your property, it is important that you know exactly how long your installation work is going to take and when it will be finished so you can structure your life around the work.

As with the price of the extension, the length of the installation is often dependant on the size of the structure, as well as what materials it is being built from. Your average 3-meter single-storey rear extension typically takes between 3-4 months, while a larger or more complex installation can take around 6 months or more.

You may want to know whether it is worth moving out of your property for the duration of the installation, but that is entirely up to your discretion and the recommendation of your installers. A smaller extension can often go on without causing as much disruption, a larger extension may be more obtrusive, and you may wish to keep away from your house until the more drastic, base work has been completed.

DIY Extension

This is the cheapest option available, with you acting as both project manager, designer and builder. Buying in your chosen materials yourself from suppliers and either building the structure yourself or getting local subcontractors to help you. This is the most hands-on you can get, which is perfect if you want complete control over the cost and source of materials and the construction of your extension, but the overall quality of your installation is entirely dependant on your own skill.

Main Contractor and Subcontractors

Instead of having a single, main contractor installing your entire extension, this option saves you some money and allows you more control over the construction work being done.
Often relying on you buying in the materials yourself, acting as project manager for the construction, this option entails getting a main contractor in to build your base extension up to a weather-tight stage, and then getting additional subcontractors in to finish the remaining work.
This option doesn’t rely on your own building skill, but allows you a similar amount of control over your construction work.

Main Contractor

The most hands-off approach available, this option involves employing a single main contractor to act as builders and project managers for your installation.
Following your design, the contractor will buy in the necessary materials and oversee all of the construction work with very little involvement needed on your part. This is the most expensive option, but the best option is you do not want to get involved in the construction process yourself.