House Extension Builders

The precise cost of a home extension can vary significantly in accordance with a number of factors - particularly, design, and the need for additional services such as electrical and plumbing. In addition, the cost quoted for your extension may be influenced by your location, and the contractor you select. Whilst a small, one-storey extension’s price can start at approximately £15,000, larger projects including two-storey and bespoke extensions can cost upwards of £100,000. Due to this variation cost, it’s near impossible to get an exact price for your extension project without consulting a contractor - in fact, it’s advisable to reach out to multiple in order to get a good idea of costing and value.

Although a number of extension types will ultimately require planning permission, in some circumstances, a single-storey extension may be considered a permitted development. Although permitted developments do not require planning permission, they are still subject to regulation, which must be adhered to during both the design and construction phases. I order to avoid planning breaches, it’s essential to conduct research or consult an expert during the planning phase of your project in order to determine whether or not planning permission is applicable.

If you’re looking to add an extension to your home, reach out to our team of construction advisors for a free, no-obligation consultation, during which we’ll discuss your ideas, requirements, and concerns.

Completing a house extension can be a complex process from initial design through to your contractor’s first day on-site, meaning that effective planning is essential n order to ensure the best possible results. When putting together your preliminary plan, you should generally consider the following:

- Have all relevant initial site surveys been completed?

- Will your intended design require planning permissions or permits? If so, when, how, and by whom will applications be submitted?

- What safety regulations must your project adhere to? How will these be implemented?

- Have you selected an architect and project manager or construction contractor who can deliver on the above requirements and your vision?

- Do the completed design, and planned footprint suit the requirements of yourself and your existing property?

- How long will your project take to complete?

- How much will your project cost in total? Have you left leeway in your budget for unexpected costs?

The timeline and expected completion date of your project can be influenced by a number of factors - primarily the size and complexity of your design, the contractor chosen, whether or not you intend to live in your home during the construction process, and external influences such as supply shortages.

On average, a standard single-storey extension will be completed within approximately three months, whilst a two-storey extension may require an additional few weeks in accordance with the factors listed above. During this time, the site and foundations will be prepared before external walls are constructed and integrated into existing walls. Towards the latter half of the process, the roof and internal walls will be constructed, before the structure is weather-proofed, and windows and doors are fitted.

In the finishing stages, power is added to the extension, the space will be plastered, and finally, decoration will be completed.

In cases wherein an extension will require full planning permission, drawings completed by a professional architect are essential and must be submitted in order to gain approval.

In contrast, permitted development sites require only the submission of a ‘sketch’ and ‘letter of intent’, primarily to inform the planning department of your project’s intended aesthetics. This may be completed by an individual other than an architect, but poses the risk of breaches and planning enforcement in the case of common issues such as scale inconsistencies present once construction is complete. Your permitted development project plans are more likely to receive approval quickly and avoid future planning issues if a professional architect is consulted.

Outside of London, the average cost of a single-storey extension is between £1,200 - £1,500 per square metre.
It's important to consider at the outset what you are going to want out of your space. If it is an extension to your dining room or living space, for example, your costs are likely to be lower. If the project includes a kitchen, however, then the price will be higher and this should be accounted for. Other additional features such as underfloor heating or bi-fold doors rather than french doors can also see your budget heading up. You should weigh up the pros and cons of each feature you are looking to include. Will it fundamentally change the way you live, or is it a nice to have addition?

Adding an additional storey onto your extension can add up to 50% to the expense. So you can expect to pay £1,600 - £2,150 per square metre (of the overall footprint of the extension). Once again consider any additional features that you might want For example, a bedroom with an en-suite bathroom is going to be a higher spend than a back bedroom/study.