House Extension Cost in London: How to Calculate Yours?
As a general rule, the house extension cost in London is at least £2,000 per square metre, so do keep this in mind. For example, if you were to build a 20 sqm extension in London, you could estimate initial costs to start from £40,000, exclusive of VAT.
With this said, many other factors will require consideration. As a starting point, we have created a list for you below:
- Extension design complexity
- Structural works
- Level of fixtures
- Fittings and material choices
Questions to Ask Before Establishing a London Extension Budget
To establish a realistic budget for your extension, you must initially determine the size of the extension. Factors influencing the size, in addition to the house extension cost, encompass:
Purpose of the Extension: a pivotal question, sometimes pondered too late in the process.
Intent to Utilise Permitted Development: is your goal to construct the extension within permitted development guidelines?
Sunlight Impact on Neighbours’ Windows: consider how far you can extend without obstructing sunlight to your neighbours.
Extent of Garden Utilisation: determine the portion of your garden you’re willing to allocate for the extension.
Engaging an Architectural Designer may alter your answers to these questions as could propose innovative design solutions that enable you to maximise space more efficiently than anticipated. At Christopher David Design, we want to bring your design ideas to reality. Contact our team for a consultation about your extension project today.
London House Extension Costs: Determining Your Layout
As part of the extension process, you should account for the expenses leading up to the construction phase. We advise our clients to be as deliberate as possible in the components that they wish to incorporate into their extension design. There should be consideration for integration into the current property and ask: is this an opportunity to reconfigure the layout of the rest of your home? For example, if you are constructing a kitchen extension, what will happen to the current cooking space? Similarly, for a wraparound extension, how will you create an open-plan living and dining area?
At the very least, optimising your home’s layout becomes essential. There is a likelihood that you may want to reevaluate internal walls, possibly demolishing some to expand your living room or adding a wall to establish a utility room.
Planning Permission Process and Associated Costs
Before going ahead with any extension, it is important to consider planning permission. Your house extension cost is just one part of the overall planning process – without the legal documentation in place, you will not be able to go ahead with construction.
For a single-storey extension in London, you may be able to go ahead and build with your permitted development rights, however, for most extension types, especially a double-storey extension, you will require planning permission.
In the case of a listed building, there are also very strict rules regarding extending. Whether you wish to go ahead with a rear extension or a basement extension, you will need to adhere to the special protection laws in place. It is recommended that you consult with your local authority regarding planning permission in your area. They will be able to advise on the likeliness of your extension being approved within permitted development rights or whether you will need to submit a full planning application.
The total cost of a planning application in London can vary depending on the type and scale of the proposed development. It is important to note that fees may be subject to change, and you should check with the local planning authority or the official government website for the most up-to-date information. In the U.K., planning application fees are set by the government, and local authorities are responsible for collecting them. The fees are categorised based on the type and scale of the development. Generally, larger and more complex developments incur higher fees.
Architectural Designer, Planning, and Specialist Services
We advise you to allocate a minimum of £4,000 for Architectural Designer, planning, and specialist services, encompassing comprehensive planning permission if required. Allocate £6,000 for Architectural Designers and structural engineers to address building regulations and produce technical drawings. Additionally, budget £700 for building regulations fees, and consider reserving up to 10% of the construction cost if you opt for professional services for contract administration and construction inspection.
Professional fees are often variable depending on the reputation of companies and their expertise. You should budget your total extension cost to consider these additional fees.
Types of House Extensions in London
There are various types of house extensions, as many of our other guides cover. In London, the most common type of extensions are rear extensions and double-storey extensions. Below, we have put together a small section with further details about each type of house extension and the associated benefits:
Rear Extensions
Extending the back of a property is a popular option for many people who live in London. where the space is available. This can involve adding extra rooms, expanding existing rooms, or creating open-plan areas. One of the most popular extension designs we come across is a kitchen extension with French doors opening into the garden space. Rear extension cost is generally the most affordable option for homeowners.
Side Extensions
Extending to the side of a property is another popular option, though many of the properties in London do not have an existing layout suitable for this option. Being able to proceed with this type of house extension also depends on local planning regulations and the distance from neighbouring properties.
Loft Conversions
Converting the loft into a living space is a common way to add bedrooms or other functional rooms without extending the footprint of the house. We have worked on several house extension projects in London consisting of loft extensions.
Basement Conversions
In some cases, properties may have the potential for basement conversions, adding additional living space below ground.
Two-Storey Extensions
Also known as double-storey extensions, these extensions involve extending both the ground and first floor, providing more substantial additional space. A double-storey extension option is great for growing families, though the planning consent process is often more challenging to navigate and you should expect to pay higher extension costs.
Wraparound Extensions
Combining side and rear extensions to create a wrap-around extension can be a way to maximise space. The extension cost for this option is generally on the higher end of the scale, so bear this in mind when planning for this type of house extension. The average extension cost for a wraparound extension is also higher than a simple rear extension, given the extra work involved.
Extension Cost Calculator for London Extensions
(House Extension Cost = Size of Extension (in square metres) x Average Cost per Square Metre + Additional Costs)
Size of Extension (in square metres)
Measure the length and width of the proposed extension area and multiply them to get the square meterage.
Size of Extension=Length×Width.
Average Cost per Square Metre
Research the average cost per square metre for house extensions in London. This can vary depending on factors like location, materials used, and the complexity of the project. For example, if the average cost is £2,500 per square metre.
Average Cost per Square Metre=£2,500
Additional Costs
Consider additional costs such as planning permission fees, Architectural Designer fees, structural engineer fees, VAT, and contingency funds (usually around 10-15% of the total). Add these to the calculated cost.
Additional Costs=Planning Permission Fees+Architectural Designer Fees+Structural Engineer Fees+VAT+Contingency FundsAdditional Costs=Planning Permission Fees+Architectural Designer Fees+Structural Engineer Fees+VAT+Contingency Funds.
Final Cost
(House Extension Cost = Size of Extension x Average Cost per Square Metre + Additional Costs)
From the information we have provided above, we hope that you have a clearer idea of house extension costs in London. Though we do not provide a specific cost calculator for house extension projects, we can provide advice on extension costs through a consultation with our design studio. Our expert team will happily discuss your house extension project and help you to get clear on the associated costs and steps involved in the design, planning, and construction process.
Would you like to discuss house extension costs and planning with Christopher David Design? Simply submit your contact details and we will be in touch.
