​How much does it cost to build a single storey extension: A comprehensive guide

Are you considering building a single storey extension to add more space to your home? One of the most important factors to consider is the cost. The cost of a single storey extension can vary depending on several factors such as the size, materials used, and location.

According to a cost guide by Checkatrade, the cost of a single storey extension in 2023 can range from £1,500 to £2,500 per square meter. However, this is just an estimate and the actual cost can be higher or lower depending on your specific requirements. Other factors that can affect the cost include the complexity of the design, the quality of materials used, and the location of your property.

If you're looking to build an extension on a budget, you can expect to pay around £1,500 to £1,900 per square meter for basic quality. For good quality, the cost can go up to around £1,900 to £2,200 per square meter. By understanding the factors that influence the cost of a single storey extension, you can make an informed decision and plan your budget accordingly.

Understanding Single Storey Extensions

If you're looking to add more space to your home, a single storey extension can be a great option. It's a popular choice for homeowners who want to expand their living space without having to move out. Here are some things you need to consider when planning a single storey extension:

Size and Layout

The size of your extension will depend on your budget, the available space, and your requirements. You need to consider the layout of your extension and how it will integrate with your existing home. You may want to consult with an architect or a builder to help you with the design.

Building Regulations

You need to make sure that your extension complies with building regulations. This includes things like structural integrity, fire safety, and energy efficiency. You may need to obtain planning permission from your local council before you can start building.

Cost

The cost of a single storey extension can vary depending on the size, materials used, and location. According to Checkatrade, the cost can range from £8.5k to £20k for a garage conversion, to £100k to £160k for a basement extension. However, Resi estimates that a single storey extension on a budget would cost between £1,250 to £1,800 per square metre, while one using premium contractors could cost about £2,600 to £4,000 per square metre. It's important to get a few quotes from different builders before you make a decision.

Timeline

The timeline for building a single storey extension can vary depending on the size and complexity of the project. It's important to factor in the time it takes to obtain planning permission, as well as the time it takes to complete the build. Your builder should be able to give you an estimate of the timeline for your project.

Value

A well-designed and well-built single storey extension can add value to your home. According to Homebuilding & Renovating, a single storey extension can add up to 20% to the value of your home. However, it's important to consider the cost of the extension and the potential return on investment before you make a decision.

Cost Factors

When it comes to building a single storey extension, the cost can vary depending on a variety of factors. Here are some of the key cost factors to consider:

Size of the Extension

The size of the extension is one of the most significant factors in determining the cost. Generally, the larger the extension, the higher the cost. The cost of a single storey extension can range from £1,000 to £4,000 per square metre, depending on the size and complexity of the project.

Type of Extension

The type of extension you choose can also impact the cost. For example, a rear extension may be less expensive than a side extension, as it may require less structural work. A wrap-around extension, which extends around the side and rear of the property, may be more expensive due to the additional work required.

Materials Used

The materials you choose for your extension can also impact the cost. For example, a brick extension may be more expensive than a timber-framed extension. Similarly, the quality of the materials used can impact the cost. High-quality materials may cost more upfront, but they may be more durable and require less maintenance in the long run.

Planning Permission

If you require planning permission for your extension, this can also add to the cost. The cost of planning permission varies depending on the local authority and the complexity of the project. In some cases, you may need to pay for a planning consultant to help you with the application.

Location

The location of your property can also impact the cost of your extension. For example, if you live in a high-end area, you may need to pay more for labour and materials. Similarly, if your property is in a remote location, this may increase the cost of transporting materials and equipment to the site.

Additional Features

Finally, any additional features you want to include in your extension can also impact the cost. For example, if you want to install underfloor heating or a high-end kitchen, this will add to the overall cost of the project. Similarly, if you want to include bespoke features such as a skylight or bi-fold doors, this will also increase the cost.

Cost of Planning Permission

Before you start building your single storey extension, you may need to obtain planning permission from your local council. The cost of planning permission for a single storey extension in England is currently £206, according to Resi. This fee is for a householder planning permission application for more minor alterations to a single dwelling house. If you need an outline planning permission application in England, the cost is £426 for each 0.1 hectares (up to 2.5 hectares).

In Wales, the fees are slightly higher. A full planning permission application for a dwelling house costs £460 per house. It's important to note that fees for planning permission are subject to change, so it's worth checking with your local council for the most up-to-date information.

In addition to the planning permission fee, you may also need to pay for a certificate of lawful development, which costs £103 in England. This certificate confirms that your proposed extension meets the requirements for permitted development and does not require planning permission. You may also need to pay £34 per request for discharging planning conditions.

It's worth noting that if your extension does not meet the requirements for permitted development, you will need to apply for planning permission. Failure to do so could result in enforcement action being taken against you, which could be costly and time-consuming.

In summary, the cost of planning permission for a single storey extension can vary depending on your location and the type of permission required. It's important to factor in these costs when planning your extension and to ensure that you obtain the necessary permission before starting work.

Design and Architectural Costs

When building a single storey extension, it's important to consider the design and architectural costs. These costs can vary depending on several factors, including the size and complexity of the project, the location, and the experience of the architect.

According to HomeOwners Alliance, typical architect fees for a single storey extension planning application can range from £1,000 to £2,500. For a new build planning application, the cost can be between £3,000 to £5,000.

In addition to planning applications, you may also need drawings and plans for building regulations approval. The cost for this can be between £3,000 to £5,000 for a single storey extension, and up to £10,000 for a double storey extension.

It's worth noting that some architects may charge a fixed fee for their services, while others may charge a percentage of the total project cost. It's important to discuss these fees with your architect before starting the project to avoid any surprises.

When choosing an architect, it's important to consider their experience and qualifications. Look for an architect who is registered with the Architects Registration Board (ARB) and a member of the Royal Institute of British Architects (RIBA). This will ensure that they have the necessary qualifications and experience to design and oversee your project.

Overall, design and architectural costs can add up quickly when building a single storey extension. However, investing in a good architect can help ensure that your project is a success and meets your needs and budget.

Construction Costs

When it comes to building a single storey extension, the construction costs can vary depending on various factors. The size of the extension, the materials used, and the complexity of the design are some of the factors that can affect the cost of construction.

A general rule of thumb for the cost of extensions is around £1,000-£1,500 per m2. Thus, the difference between a 25 sq. m extension to a 30 sq. m extension will be at least £5,000.

Another cost factor is the use of the new extension. For example, if you are planning to use the new space as a kitchen or a bathroom, the cost will be higher due to the need for additional plumbing and electrical work.

It is also important to keep in mind that the cost of construction can vary depending on the location of the property. For instance, building an extension in London can be more expensive than building the same extension in a rural area due to higher labour and material costs.

When planning your budget for a single storey extension, it is important to consider all of these factors and to work with a reputable builder who can provide you with a detailed breakdown of the costs involved. By doing so, you can ensure that you have a realistic budget in place and that you can avoid any unexpected costs or delays during the construction process.

Interior Finishing Costs

Once the structure of your single-storey extension is complete, you will need to consider the interior finishing costs. These costs can vary depending on the materials you choose and the level of finish you desire.

Flooring

Flooring is a crucial aspect of your extension as it sets the tone for the entire space. The cost of flooring will depend on the material you choose. Here are some average costs per square metre for different types of flooring:

Laminate: £10 - £30

Carpet: £15 - £50

Vinyl: £20 - £50

Hardwood: £40 - £100

Tiles: £30 - £80

Walls and Ceilings

The cost of interior walls and ceilings will depend on the type of finish you choose. Here are some average costs per square metre for different types of finishes:

Plastering: £15 - £25

Wallpaper: £20 - £50

Paint: £10 - £30

Timber cladding: £50 - £100

Lighting

Lighting is an important aspect of any living space. You will need to consider the type of lighting you want and the cost of installation. Here are some average costs for different types of lighting:

Recessed lighting: £50 - £100 per light

Pendant lighting: £50 - £200 per light

Wall sconces: £50 - £150 per light

Roof window - Dependant on brand. See all pricing for roof windows.

Heating and Ventilation

You will need to consider the cost of heating and ventilation for your extension. Here are some average costs for different types of heating and ventilation systems:

Radiator: £100 - £300 per radiator

Underfloor heating: £50 - £100 per square metre

Ventilation system: £500 - £1,500

Keep in mind that these are just rough estimates and the actual cost will depend on the size and complexity of your single-storey extension. It is always best to consult with a professional to get an accurate quote.

Additional Costs

In addition to the cost of building a single storey extension, there may be additional costs to consider. Here are some potential expenses to keep in mind:

Planning permission and building regulations: Depending on the size and location of your extension, you may need planning permission from your local council. This can cost anywhere from £206 to £462, depending on your location in the UK. Additionally, building regulations approval may be required, which can cost around £750 to £1,500.

Architectural and design fees: If you require the services of an architect or designer, their fees can add to the overall cost of your extension. Expect to pay around 10-15% of the total cost of the project for their services.

Structural engineering fees: If your extension requires structural changes, you may need to hire a structural engineer. Their fees can range from £500 to £2,000, depending on the complexity of the project.

Party wall agreement: If your extension is close to a neighbouring property, you may need to obtain a party wall agreement. This can cost around £700 to £1,000.

Site preparation and landscaping: Depending on the state of your current garden, you may need to pay for site preparation and landscaping. This can include removing trees or shrubs, levelling the ground, and laying new turf or planting new flowers. Expect to pay around £50 to £100 per square metre for landscaping.

It's important to consider these additional costs when budgeting for your single storey extension project. By taking them into account, you can ensure that you have a realistic understanding of the total cost of the project.

Reducing Costs

Building a single storey extension can be expensive, but there are ways to reduce the overall cost without sacrificing quality. Here are some tips to help you save money:

1. Consider the size and design of your extension

The size and design of your single storey extension can significantly impact the overall cost. A smaller extension will require less materials and labour, which can help reduce costs. Additionally, simpler designs with fewer complex features can also help keep costs down. You can use our guide to find out roofing sizes & structural opening sizes for fitting roof windows to your extension.

2. Choose the right materials

Choosing the right materials can help you save money on your single storey extension. For example, opting for cheaper materials such as uPVC windows and doors instead of timber or aluminium can help reduce costs. However, it is important to ensure that the materials you choose are still of good quality and fit for purpose.

3. Get multiple quotes

Getting multiple quotes from different builders can help you compare prices and find the best deal. However, it is important to ensure that you are comparing like-for-like quotes, as some builders may include additional costs or use different materials.

4. Do some of the work yourself

If you have some DIY skills, you may be able to save money by doing some of the work yourself. For example, you could paint the walls or install the flooring yourself. However, it is important to ensure that you have the necessary skills and tools to complete the work safely and to a high standard.

5. Consider financing options

If you are unable to pay for your single storey extension upfront, you may want to consider financing options such as a home improvement loan or a remortgage. However, it is important to carefully consider the costs and risks associated with these options before making a decision.

By following these tips, you can help reduce the overall cost of your single storey extension without sacrificing quality.

Conclusion

In conclusion, the cost of building a single storey extension can vary widely depending on several factors, including the size of the extension, the quality of materials used, and the complexity of the project. Based on the search results, a general rule of thumb for the cost of extensions is around £1,000-£1,500 per square meter. Thus, the difference between a 25 sq. m extension to a 30 sq. m extension will be at least £5,000.

It's important to note that the cost of a single storey extension can also be affected by other factors, such as the use of the new extension, the location of the property, and the contractor you choose to work with. For example, Resi suggests that a single storey extension on a budget would cost between £1,250 to £1,800 per square meter, while one using premium contractors could cost about £2,600 to £4,000 per square meter.

When planning your single storey extension, it's important to consider your budget and to work with a reputable contractor who can help you stay within your budget. You should also consider the purpose of the extension and how it will be used, as this can affect the final cost of the project.

Overall, building a single storey extension can be a great way to add space and value to your home. By doing your research and working with a trusted contractor, you can ensure that your extension is built to the highest standards and within your budget.