As property prices continue to rise, many homeowners are looking to expand their living spaces instead of moving to a new house. A two-storey extension can be a fantastic way to increase both space and value in your home, whether you’re adding additional bedrooms, a larger living area, or a home office. However, understanding the costs associated with a two-storey house extension cost well is essential before you commit to such a project. In this guide, we’ll break down the key factors affecting the cost of a two-storey extension in 2025 and what you can expect.
What is a Two Storey Extension?
- A two storey extension is a structural addition to an existing property that expands both the ground floor and the first floor.
- It’s a popular design solution for increasing square footage while preserving outdoor space.
- Double storey extensions can be built on existing properties, including semi-detached and terraced houses.
- They’re a great way to add value to your property.
Types of two storey extensions (rear, side, wraparound)
- Double storey rear extension: extends at the back of the house, best suited to terraced houses with limited space, as well as semi-detached properties.
- Double storey side extension: extends to the side of the house, best suited to properties with the space for a side extension.
- Double storey wraparound extension: enables you to radically alter the layout of your home, great for increasing square footage while preserving outdoor space.
Factors Affecting Two Storey Extension Cost
Size of the extension
- The overall square footage of your extension will greatly impact the price.
- Working with an architect can help forecast financially, as well as provide you with accurate site plans, measurements, and drawings.
Complexity of design
- Unique designs, rooflines, and architectural features can add to the cost of your double storey extension.
- Aim to work with an architect to design the extension so that you can make the right creative decisions to keep costs down while still being happy with the final build.
Location and regional prices
- Costs can vary depending on the location within the UK due to regional price variations.
- For example, if you live in a conservation area, you will need to take the appropriate steps as per local planning regulations.
Material costs (labor, materials, equipment)
- Material costs will be one of your highest outgoings.
- Consider everything you need for the entirety of the project, including structural material, bricks and mortar, glazing, roof tiles, and insulation.
Two Storey Extension Prices
Average cost of a two storey extension
- The average cost of a two storey extension can vary from £1200/m² to £2200/m² in 2025.
- Factors affecting the final costs include the size and design of the build, the quality of the build, and the internal features.
Labour costs and timescales
- Labour costs will also count for a lot of your project budget.
- Tradespeople and specialists will be needed from the very start of your project, and will usually charge at an hourly or daily rate.
Types of Extensions
Double Storey Rear Extension
- A double storey rear extension extends at the back of the house.
- This type of extension is best suited to terraced houses with limited space, as well as semi-detached properties.
Double Storey Side Extension
- A double storey side extension extends to the side of the house.
- This type of extension is best suited to properties with the space for a side extension.
Double Storey Wraparound Extension
- A double storey wraparound extension enables you to radically alter the layout of your home.
- It’s a great way to increase square footage while preserving outdoor space.
Benefits of a Storey Extension
Adding value to your property
- A two storey extension can add significant value to your property.
- The amount of value added depends on the type of room added, such as a bathroom, bedroom, or en-suite.
Increasing living space
- A two storey extension can increase living space and add value to your home.
- There are many ways to increase living space, including adding a new room or floor.
Improving functionality and layout
- A two storey extension can re-imagine the layout of your home.
- It’s a great way to improve functionality and add more living space to your home.
Planning and Regulations
Planning permission requirements
- Planning permission is required for most extensions, unless they fall under permitted development rights.
- The cost of planning permission is around £206.
Building regulations and compliance
- You must check if you need approval prior to commencing your build and should not confuse this with planning permission – you may need both.
- The cost of submitting a full plans application is around £180, but there will be an additional cost for the subsequent inspections – this could vary from £200 – £550.
Party wall considerations
- If there is a wall on your property that stands on both your and your neighbour’s land and is part of a building, or if there is a garden wall standing on both pieces of land, or a wall that is used to separate two buildings, this is considered a party wall.
- You will need to review the Party Wall Act if you are doing work to an existing party wall, building on or at the boundary of two properties, or are excavating near to or below the foundation level of neighbouring buildings.
Construction Process
Initial building work
- The initial building work includes groundwork, foundation work, and structural elements such as adding additional walls, floors, and roofing.
- New roofing will require a mix of construction materials as well as roof tiles, the cost of which will depend on the roof design.
Secondary building work
- The secondary building work includes windows, doors, and landscaping.
- The cost of windows can vary depending on the type and size of the extension.
Interior work (finishing touches)
- The interior work includes installation of a new kitchen and bathroom.
- The cost of a new kitchen can vary depending on the size and specification.
Cost-Saving Tips
Project managing the build yourself
- Project managing the build yourself can save you around 15-25% of the labour and materials cost.
- This type of extension is useful if you want to add more living space to your home.
Hiring a Contractor
Checklist for hiring a contractor
- A double storey extension is a huge job! Before you hire someone, there are some things you should consider.
- Get quotes from a number of labourers – the way these quotes are provided and how you are dealt with will give you a good idea of the company’s professionalism, and the varying quotes will give you an idea of cost.
Reducing the cost of building your extension
- A complex design will likely require more specialist/skilled workers, longer to build, pricier materials and longer design time by an architect.
- Another way to save money is to manage the project yourself – this will dramatically reduce your spend, but will take a lot of time and patience on your part.
DIY Considerations
Can I build a double storey extension myself?
- In short, no. You’ll definitely need to hire relevant tradespeople for certain tasks during the double storey extension build.
- You can complete some jobs DIY, like painting and decorating, if you don’t mind not having a professional finish.
Risks and challenges of DIY construction
- There are risks and challenges associated with DIY construction, including the potential for substandard work and increased costs in the long run.
Timeline and Scheduling
How long will my extension take?
- The size of the build, planning permission, and weather conditions can affect the duration of the project.
- Delays are common, especially when multiple contractors are involved.
Planning application approval times
- The time it takes for a planning application to be approved varies depending on the council and type of development.
- For household and minor developments, a decision is typically made within 8 weeks.
Value and Resale
Will a two storey extension add value to my property?
- There is no fixed answer to this. The value of your house will almost certainly increase – the appeal of more living space is always a draw to potential buyers.
Hidden Costs and Expenses
Additional expenses to consider
- Additional costs to consider include kitchens and bathrooms.
- A small kitchen can cost around £10,000 to £20,000.
- A small bathroom can cost around £7,000 to £15,000.
Average Cost of a Two Storey Extension in 2025
In 2025, the average cost for a two-storey extension in the UK can range significantly based on the factors above. On average, homeowners can expect to pay between £1,500 per square metre and £2,500 per square meter. This cost includes labor, materials, and associated fees, though it can rise for more luxurious or complex designs.
For example:
- A 30-square-meter extension could cost anywhere between £45,000 and £75,000.
- A 50-square-meter extension might range from £75,000 to £125,000.
These figures cover construction costs for the full construction process, but additional costs, such as landscaping, interior design, or furniture, should also be considered in the total project cost.
Cost-Saving Tips
While a two-storey house extension is a significant investment, there are ways to reduce costs:
- Choose Standard Materials: Opting for standard, readily available materials instead of bespoke ones can help reduce the overall cost.
- Simplify the Design: Keeping the design simple and functional will cut down on design and structural complexities.
- Get Multiple Quotes: It’s always wise to get quotes from several contractors to compare pricing and find the best deal.
- DIY Finishes: If you’re comfortable with DIY, you can save money on certain aspects, such as painting, tiling, or landscaping.
A two-storey extension in 2025 is a great way to add both living space and value to your home, but it’s essential to understand the factors that will influence the cost. By considering location, size, materials, and design choices, as well as planning for necessary permits and professional fees, you can better estimate your budget. Ultimately, whether you’re looking for a simple extension or a more luxurious addition, with careful planning, a two-storey extension can be a worthwhile investment for your home.
FAQs
- How much does a two-storey extension typically cost in 2025?
In 2025, the average cost of a two-storey extension in the UK ranges from £1,500 to £2,500 per square meter. A 30-square-meter extension could cost between £45,000 and £75,000, while a 50-square-meter extension may range from £75,000 to £125,000, depending on the design and materials used. - Do I need planning permission for a two-storey extension?
Yes, most two-storey extensions require planning permission, as they go beyond the scope of permitted development rights. You’ll need to submit a planning application to your local council, which can take several weeks to process. It’s important to factor in the cost of obtaining planning permission and building regulations approval. - What are the most significant factors affecting the cost of a two-storey extension?
The key factors include the size of the extension, design complexity, materials and finishes, location, and any structural work needed. Labor costs, especially in urban areas, can also significantly impact the final price. Choosing higher-end materials and custom designs can also increase costs. - How long does it take to complete a two-storey extension?
The duration of a two-storey extension project varies depending on the size, complexity, and design. On average, a project can take anywhere from 4 to 6 months to complete. However, delays due to planning approvals, bad weather, or supply chain issues can extend the timeline. - Can I save money on a two-storey extension project?
Yes, there are several ways to save on a two-storey extension. Consider opting for standard materials instead of custom ones, simplifying the design to reduce structural complexity, and obtaining multiple quotes from contractors. Additionally, you can take on DIY tasks like painting or landscaping to reduce labor costs.