How Much a House Extension Costs

A house extension can cost anywhere from $20,000 to $100,000 or more, depending on various factors such as size, complexity, materials, and location. It is essential to consult with professionals and get detailed quotes to accurately estimate the cost of your desired house extension project.

Expanding your living space with a home extension is an exciting prospect, but one of the first questions that comes to mind is likely, “How much will it cost?” The cost of adding a house extension can vary significantly depending on numerous factors, such as the type and size of the extension, location, materials used, and professional fees. In this post, we will provide you with a general overview of the costs involved, allowing you to plan your budget accordingly.

Determining Factors

  1. Type of Extension: The cost of an extension greatly depends on the type you choose. Common types include single-storey extensions, double-storey extensions, conservatories, or modular extensions. Each type has different associated expenses, as well as unique advantages and limitations.
  2. Size and Design Complexity: Naturally, the larger the extension, the higher the cost. Moreover, complex designs with intricate architectural features such as vaulted ceilings or glass walls usually come with higher price tags due to increased labor and material expenses.
  3. Structural Changes: If your extension involves major structural modifications or requires removing load-bearing walls, additional costs will be incurred for necessary engineering calculations, permits, and the services of structural engineers.
  4. Material Costs: The choice of materials will have a significant impact on the overall cost. Common construction materials include brick, timber, uPVC, glass, and metal. Each material has its own price range and may require additional expenses for insulation, wiring, plumbing, and finishes.
  5. Utility Connections: Expanding your home often requires extending utility connections such as electricity, plumbing, and heating systems. These connections can contribute to the overall cost, especially if larger capacities or more efficient systems are needed.

Estimated Cost Range

How Much a House Extension Costs

To provide you with a rough estimate, based on industry averages, here is a general range of costs for house extensions in various size categories.

Table: Estimated Cost Range for House Extensions

House Extension TypeEstimated Cost Range
Single-storey rear extension$20,000 – $60,000
Double-storey side extension$40,000 – $100,000
Two-storey rear extension$60,000 – $150,000
Loft conversion$30,000 – $70,000
Basement conversion$60,000 – $150,000
Garage conversion$15,000 – $40,000

Keep in mind that these figures are just general estimates and can vary depending on your specific requirements, location, and the overall scale of the project.

Additional Costs

In addition to the construction costs, there are other expenses to consider:

  1. Planning Permission Fees: If your extension requires planning permission, there will be associated fees, which vary depending on your location.
  2. Building Regulations: Compliance with building regulations may require additional inspections and certification, which can add to the overall cost.
  3. Professional Fees: Architectural design, structural engineering services, and hiring a project manager or contractor will incur professional fees. It is advisable to obtain multiple quotes and do thorough research before finalizing these contracts.


Adding a house extension can significantly enhance your living space and add value to your property. However, it is essential to carefully consider the cost implications and set a realistic budget to ensure a smooth construction process. By taking into account the factors mentioned above and consulting with professionals, you can make informed decisions and create accurate estimates for your house extension project.