A double storey extension is a popular way to add extra living space to your home. London’s property prices are amongst the country’s highest; many homeowners are choosing to extend their existing homes rather than move to a larger property. However, the cost of a double storey extension in London can vary greatly depending on several factors. In this article, we will explore what affects the cost of a double storey extension and provide an average cost for this type of project in London.
Factors that Affect the Cost of a Double Storey Extension
Design and Architectural Features
Planning Permission and Building Regulations
Financing a Double Storey Extension
Double Storey Extension Before And After
Choosing Powerpillar For Double Storey Extension
Factors that Affect the Cost of a Double Storey Extension

Several factors can affect the average double storey extension cost. Some of the most significant include:
Size of the Extension
The size of the extension is one of the main factors that affect the double storey extension cost. The larger the extension, the more materials and labour are required, increasing the project’s overall cost.
When considering the size of the extension, it’s essential to consider its intended use. For example, adding one or two bedrooms will be less expensive than adding a living room, kitchen, or bathroom. Additionally, more significant extensions may require more extensive excavation, foundation work, and other structural support, increasing the cost.
Another important consideration is the size of the property; if the property is small, extending it will become more costly as the extension will become more complex, and it will need to be designed to maximise the space available.
Additionally, it’s also essential to consider the potential return on investment for a side double storey extension. While a more significant extension will cost more, it can add more value to your home. Therefore, it’s essential to weigh the costs against the potential benefits when deciding on the size of the extension.
Quality of Materials
The quality of materials used in the construction of a two storey extension can have a significant impact on the overall cost of the project. Higher-quality materials will cost more, but they can also add value to your home in the long run.
Higher-quality materials can create a more durable, energy-efficient and comfortable living space. Higher-quality materials often have better insulation properties, which can reduce energy costs and increase comfort levels. They can also require less maintenance and longer lifespan, saving you money in the long run.
For example, high-grade insulation can improve energy efficiency and reduce heating and cooling costs. Using more expensive but better-quality windows and doors can improve security, and soundproofing, while high-quality roofing materials may last much longer, require less maintenance and provide better insulation.
However, using higher-quality materials can also increase the project’s cost. The cost of the materials used in constructing a double storey extension can vary considerably depending on the type of materials used. For example, natural stone or hardwood flooring can be much more expensive than ceramic tile or laminate flooring. Similarly, using high-end cabinetry and countertops can add significantly to the project’s cost.
Design and Architectural Features
Design and architectural features can significantly impact the average cost of a two storey extension. Some features that may affect the cost include:
Roofing
A pitched roof will typically be more expensive than a flat roof.
Windows
The type, size, and location of windows can also impact costs.
Exterior finishes
The type of exterior finish, such as brick, siding, or stonework, can also affect the cost.
Interior finishes
The type of interior finishes, such as flooring, cabinetry, and appliances, can also impact the cost.
Additional Rooms
Additional rooms, such as bedrooms, bathrooms or kitchens, can also affect costs.
Glass features
Features such as skylights, sliding/folding doors, balconies or conservatories also can be costly.
Planning Permission and Building Regulations
Planning permission and building regulations can impact the average double storey extension cost by adding additional costs and requirements to the project.
Planning permission
Depending on the specifics of your proposed extension and local regulations, you may need to apply for planning permission. This can add additional costs in the form of application fees and the cost of hiring an architect or planning consultant to help with the application process. If your proposal does not comply with local regulations and planning permission is not granted, it could lead to additional costs if design changes are required.
Furthermore, All building work must comply with building regulations. You must submit a building regulations application, which can add to the project’s cost. You may also need to hire a building inspector to conduct construction inspections, which will add to the overall cost.
Labour cost
Labour cost is one of the significant factors that can affect the average cost of a double storey extension. Labour costs include wages and benefits paid to construction workers and tradespeople, such as carpenters, electricians, and plumbers, who are involved in the building process. The labour cost will vary depending on several factors, including the region you are based in and the local cost of living. In general, labour costs will be higher in urban areas such as London due to the high cost of living, which can increase the average cost of a double-storey rear extension. Also, specialised labour like heritage building and conservation labour can increase costs.
Labour costs can also be affected by the project’s complexity and the skill level required for the work. For example, a more complex or custom project will likely require more specialised labour and, therefore, be more expensive. In addition, if the workers are required to work under challenging conditions like high heights, remote areas or adverse weather, that can add to labour costs.
Double Storey Extension Cost
The average double storey extension cost in the UK can vary greatly depending on several factors, such as the size of the extension, the quality of materials used, the design and architectural features, and the location and access to the property. The cost also depends on the region you are based in and the local cost of living and labour costs, which can significantly affect the cost.
In London, the double storey extension cost can be higher due to the high cost of living, high labour costs and high demand for construction services. According to some industry sources, a double storey extension in London can cost between £50,000 and £150,000. However, this can vary greatly depending on the project and can go significantly above or below these numbers. It’s always recommended to get detailed quotes from several builders to get a more accurate estimate of the cost of your project.
Financing a Double Storey Extension
Financing a double storey extension can be done through various options such as loans and mortgages. It’s essential to consider the potential return on investment when planning a double storey extension, as adding extra living space to your home can increase its value. Additionally, there are ways to budget and save costs while planning the extension, such as opting for lower-cost materials or simplifying the design.
Double Storey Extension Before And After
A double storey extension is a type of home renovation that involves adding a level to an existing structure. Before the renovation, the building may appear smaller and more modest, with a single floor and a traditional layout. After the renovation, the building will have an additional level, including additional bedrooms, bathrooms, living spaces, and other amenities. The overall appearance of the building will change, with the extension appearing as a larger, more modern and spacious structure.
Choosing Powerpillar For Double Storey Extension
Choosing Powerpillar for double storey extension can provide several benefits. First, Powerpillar contractors have the knowledge and expertise to install the equipment correctly and safely, ensuring that they meet building codes and regulations for the double storey extension.
Furthermore, they can provide an estimate of the cost of the installation, including materials and labour; this allows you to budget for the extension more accurately. They can also take care of obtaining any necessary permits and inspections required by local regulations, saving you time and effort.
Choosing Powerpillar for your double storey extension can provide you with expertise, convenience, and quality work, ensuring that your extension is functional, efficient, and visually appealing. They can take care of the installation process and provide after-sale service, saving you time and money and ensuring that you have a beautiful and functional extension for years to come.
Conclusion
In conclusion, a double storey extension can be a cost-effective way to add extra living space to your home in London. However, the double storey extension cost can vary greatly depending on the size, materials, design, planning permission, location and access of your property. By understanding these factors and researching the average cost for a double storey extension in London, you can budget for your project and make informed decisions about the best way to add extra space to your home. It’s also worth considering the potential return on investment, as a well-designed and executed extension can add significant value to your property.