How Much Does a Side Extension Cost for a Detached House?

Adding a side extension to a detached house can be an exciting way to increase living space, improve functionality, and boost property value. However, understanding the costs involved is crucial before starting such a project. Side extensions vary widely in price depending on size, design, and structural complexity. This article breaks down the typical costs you can expect, helping you plan your home improvement with confidence.

What Is a Side Extension and Why Choose It?

A side extension involves building out from the side of your home, often taking advantage of available space on either the left or right side of the property. This type of extension is popular for detached houses because it can seamlessly blend with the existing structure, creating additional rooms such as kitchens, dining areas, or even extra bedrooms.

One of the main benefits of a side extension is that it typically requires less disruption to your garden compared to rear extensions. For detached homes with ample side space, it’s an efficient way to expand without compromising outdoor areas.

Moreover, a side extension can significantly enhance the overall aesthetic appeal of your home. By carefully designing the extension to match the architectural style of your existing property, you can create a cohesive look that enhances curb appeal. This can be particularly beneficial if you are considering selling your home in the future, as potential buyers often appreciate the added space and the visual harmony it brings.

Additionally, a side extension can provide unique opportunities for natural light and ventilation. With the right design choices, such as large windows or skylights, you can create bright, airy spaces that feel open and inviting. This not only improves the quality of the interior environment but can also contribute to energy efficiency, reducing the need for artificial lighting during the day. As a result, a side extension can be both a functional and aesthetically pleasing addition to your home.

Typical Costs of Side Extensions

When budgeting for a side extension, it’s important to understand the cost per square metre, as this is the most common way builders estimate prices. According to the National Association of Building Contractors, side extensions usually cost between £1,000 and £2,000 per square metre. This range covers standard single-storey extensions with straightforward construction.

For example, a 20-square-metre side extension could cost anywhere between £30,000 and £50,000, based on figures from Diogel Architecture. These prices include basic construction, but keep in mind that additional features like high-end finishes or complex layouts can push costs higher.

Why Do Prices Vary?

The wide price range for side extensions is influenced by several factors:

• Size and scale: Larger extensions naturally cost more due to materials and labour.
• Design complexity: Simple rectangular extensions are cheaper than bespoke or irregular designs.
• Structural work: Extensions requiring underpinning, new foundations, or alterations to load-bearing walls tend to be pricier.
• Access and site conditions: Limited access to the side of the house can increase labour costs.

Understanding Side-Return Extensions: A More Bespoke Option

Side-return extensions are a particular type of side extension that often involve extending into the narrow space between the main house and a boundary wall or fence. These are more bespoke and technically challenging due to restricted access and structural considerations.

Farook Member, Director of QS Supplies, explains that side-return extensions typically cost between £2,400 and £3,500 per square metre. This higher price reflects the complexity of the work involved, including underpinning, drainage, and sometimes the need to work around existing structures.

For homeowners considering a side-return extension, it’s important to factor in these additional costs and plan accordingly. While pricier, side-return extensions can dramatically improve the flow and usability of your home, often creating open-plan living spaces that are highly sought after.

Double-Storey Side Extensions: A Bigger Investment

If you’re looking to significantly increase your living space, a double-storey side extension might be the answer. These extensions add an entire additional floor, which can be used for bedrooms, bathrooms, or home offices.

According to Checkatrade, a typical 5m x 4m double-storey side extension costs between £66,000 and £100,000. The higher price tag reflects the need for more extensive foundations, structural reinforcements, and compliance with building regulations for multi-storey construction.

While more expensive, double-storey extensions offer excellent value in terms of added space and potential property value increase. They are particularly suitable for detached houses with sufficient side space and height clearance.

Factors That Affect the Final Cost

Beyond size and structure, several other factors can influence the overall cost of your side extension:

• Planning permission and building regulations: Fees and compliance costs vary by local authority.
• Materials: Choices range from standard bricks and mortar to premium cladding and glazing.
• Interior finishes: High-end kitchens, bathrooms, and flooring add to the budget.
• Professional fees: Architects, structural engineers, and project managers may be required.
• Unexpected issues: Older homes can reveal hidden problems such as damp or unstable foundations.

Tips for Managing Your Side Extension Budget

Planning and managing costs effectively can help you avoid unpleasant surprises during your extension project. Here are some tips:

• Get multiple quotes: Always obtain detailed estimates from several reputable builders.
• Define your priorities: Decide where to invest in quality and where to save.
• Plan for contingencies: Set aside at least 10-15% of your budget for unexpected expenses.
• Consider phased work: If budget is tight, plan the extension in stages.
• Consult professionals early: Architects and surveyors can help design cost-effective solutions.

Is a Side Extension Worth the Investment?

Side extensions are a popular choice for detached homes because they maximize available space without compromising gardens or rear views. They can add significant value to your property and improve your quality of life by creating more functional living areas.

While costs vary, understanding the typical price ranges and factors involved helps homeowners make informed decisions. Whether opting for a straightforward single-storey extension or a bespoke side-return or double-storey design, careful planning and budgeting are key to a successful project.

Final Thoughts

In summary, a side extension for a detached house typically costs between £1,000 and £2,000 per square metre for standard builds, with side-return extensions costing more due to their bespoke nature and structural challenges. Double-storey side extensions are a larger investment but offer substantial additional space.

By considering your home’s layout, your needs, and your budget, you can choose the right type of side extension that enhances both your living space and your property’s value. Always work with trusted professionals and plan carefully to make your home extension dreams a reality.