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How Much Does It Cost To Build House Extension

Building an extension is one best way to get the most out of your home by maximizing the living space. An extension provides families with a much-needed space without the need to move out. In this guide, you will find out how much it costs to build an extension.

No doubt, building a home extension is a huge project. It requires careful and practical steps from planning permission to final execution. There are several things you need to determine, particularly the house extension cost.

Having a clear idea of the cost is vital before embarking on this project to save you a lot of hassle. After all, you will only use the type of extension that best suits your budget. However, extension costs usually vary depending on the type of project.

open plan living room with bi fold doors

Do you want to embark on a building extension project and you are wondering how much it will cost? Take your time here, and let's help you! This guide offers everything you need to know about house extension costs for all types.

Cost of Various Extension Types

You might be familiar with how much it costs to build a house; it is time to check out the cost of adding an extension. There are various types of house extensions, and they vary in structure and in cost. The most common types of extension include;

  • Rear Single Storey extension
  • Double Storey extension
  • Side return extension
  • Glass extension

The Cost of A Single Storey Extension

The cost of single storey extensions usually falls within the range of £1,000-£1,600 per square metre for basic structures. Luxury extensions can cost somewhat more than this range, depending on the features you intend to include.

To create a more realistic cost, it is better to set the budget for your single extension cost around £2000 for each square metre. This budget will help you to get at least a mid-range single storey house extension.

The Cost of Two Storey Extension

modern residential room

Two storey or

  • double storey costs slightly more than a single storey. The cost usually falls within the range of £1,500-£2,500 per square metre. This project will definitely cost higher if you want to build a luxury structure. Other features you intend to include can also influence the overall cost.

    It is better to prepare a budget of around £3,000 for each square metre to execute a mid-range extension. This cost estimation will also help you to cover possible inflation and material cost variations.

    The Cost of Side Return House Extension

    Side return extension is one of the most impressive house extension projects. It costs a little more than double and single extension because it runs from the ground floor. The average cost of a side return house extension is usually within the range of £2,000-£2,500 per square metre.

    The project costs more if you want to build a luxury structure. Setting your budget for this home extension project at £3,500 for each square metre will help you add luxurious touches to your project.

    The Cost of Glass Extension

    No matter what the size, a glazed extension can be an impressive addition to a house of any style. Whether it's a matching addition to a modern home, or a contrasting extension to a traditional property, they bring in that openness that everyone wants in their living space.

    Glass extensions are usually delicate. It is also relatively expensive because of the type of materials required to execute the project. This house extension cost is usually within the range of £1,500-£2,500 per square metre.

    A larger percentage of the cost here is a result of the glass. Also, it is best to engage professionals to avoid material damage that will lead to additional building costs.

    Proficiency Bespoke helps homeowners to expand their home, we believe that every home deserve great design.

    Additional Costs of An Extension

    Glass house extension

    Certain additional costs can influence the total cost of your home extension. They might be a direct part of the construction costs, but they are an integral part of the cost of an extension. Let's check them out!

    Planning fees

    Planning fees are vital for obtaining planning permission. This cost varies depending on your council, location and region you want to carry out your project. On average, it ranges from £100-£300 depending on the local authority.

    Professional fees

    In order to build your extension project you will need the service of various professionals.Some of the professionals include a structural engineer, architect, and surveyor.

    Building Control Charges

    The Building Control Officers will visit the site at intervals to ensure work conforms to Building Regulations. Building control charges also contribute to the cost of an extension. This cost varies depending on the size of the extension. It usually varies between £200-£900 depending on your local authority or the building control company you chose.

    Certificate of Lawful Development

    rear house extension

    The certificate of lawful development is essential if you are developing under permitted development rights. It usually costs slightly above £100.

    Party Wall Agreement

    The party wall agreement fee is essential if any building works are near or on your shared property boundary, It is usually an agreement between you and your neighbours. This cost usually varies between £700-£1000 per neighbour.

    Classification and Stages of Home

    Extension Costs

    A house extension project is not a one-off payment. Each stage of the development comes with specific costs. Establishing the cost estimate of each stage will give you better insight into the overall final cost.

    Below is a breakdown of the individual development stages of a home extension cost.

    Design Cost

    Every building project starts with a vision that is transformed into an actual design. Hiring a professional architect is essential so you can have all the correct measurements, floor plans and building regulations to give to your builders to follow.

    Nevertheless, hiring a firm to design and build your extension will help with the stress of having to deal with different companies. The cost of architectural design varies depending on the extensiveness and complexity of the design.

    You might not be able to separate the cost if you are hiring a firm to design and build your extension. But fees for professional architects fall within the range of £1000- £2,500.

    Planning Cost

    Single storey extension

    Like every other project, a new extension requires proper planning. An adequate plan will help you optimize the construction cost, create extra space, and ensure basic quality. Extension specialists usually consider law and regulations as part of the planning stage, including the planning application.

    Some extensions require permission from the local authority. There are various building regulations in the United Kingdom. It is best to plan according to these regulations to avoid any legal consequences. Besides, these regulations ensure that you have a safe, standard, water and energy-efficient structure.

    Design costs will vary depending on the type of extension and its size. For instance, a single storey extension cost might not be as much as a rear extension cost. On average, the planning costs can range between £300-£700.

    Groundwork Cost

    Of all the costs involved in building an extension, the groundwork costs seem to be the most complicated. It often takes a significant part of the extension budget. It includes digging foundations and preparing the site for safety and structural integrity. Structural engineers and builders have the most tasks in the groundwork of an extension. You might have questions to ask the builder when building an extension, ensure you get answers to these questions before the project begins.

    The cost is often difficult to separate, especially with complex site constraints like uprooting trees and dealing with drains. You have to figure out the cost based on the existing structure and project complexity.

    Construction Cost

    The construction stage is where the bulk of work takes place. It is where you put up the actual building. The major building cost on materials comes in here. First off, you must decide if you want to use a timber frame, block, or bricks.

    The building contractor usually takes charge of this step, including roofing, interiors, loft conversions, sub-floor, plasterboards, and the likes. The average costs are typically dependent on size, building materials, and some other similar factors.

    Fitting Cost

    Your extension task and project management are far from complete without proper fitting. Some essential fitting materials include gas meters, electrical fittings, radiators and other necessities. The cost of fittings is dependent on the type of extension you intend to construct.

    You will have to cover extra costs if you are adding a kitchen extension and bathroom extensions. But the cost varies, depending on how much materials you intend to add and if they are basic or luxurious. It can also be dependent on the size of your building extensions.

    Finishing Cost

    Finishing is the icing on the cake of your building extension. There is no limit to how much you can spend on finishing. It all depends on your taste and how much you can afford to spend.

    Finishing materials include home decor and designs, flooring, and other accessories. It is the point where you top your building project with luxury and a customized feel.

    front of house extension

    Factors that Influence the Cost of Building an Extension

    The cost of building an extension in the United Kingdom can vary greatly or slightly depending on several factors. Some of these factors include;

    • Size of your extension, specification, and finishes
    • Type of home extension
    • Contractors and subcontractors
    • Design and planning
    • Building site constraints and ecological challenges
    • Necessary changes in the existing structure
    • The specific location within the United Kingdom
    • Fittings, finishes, and other specific features you intend to add
    • Home insurance

    Wrapping up, adding a home extension will not only help you to add extra living space. It will also add value and help you to maximize space. But like every other building project, a home extension comes at a cost. The overall cost is an aggregate of several individual expenses, including materials and labour costs. With this guide, it should help you better to understand the cost of building a house extension.

    It is best to have an insight into the cost required to build your desired extension. The cost varies depending on several factors, including location and type of extension in view. Ensure that you hire luxury house builders to mitigate costs and maximize output.