Home Extensions: What Can I Build for my Budget?

There’s no doubt that extending your home is usually more affordable than moving to a larger property. But even when extending, it’s important to understand what your budget can realistically achieve. Here’s how to plan, assess costs and make the most of your investment.

Plan the project

Start by identifying what you want from the extension. Different needs suit different extension types — for example, creating a home office requires different features than adding an extra bedroom. Consider how the new space will affect the flow of your home and whether internal alterations may also be needed. Creating a clear brief and working with an architect or builder helps define what is achievable within your budget.

Cost versus value

Extensions can add significant value, but it’s important to ensure the cost aligns with the potential return, especially if you may sell in the future. Research local properties and compare how different extension types affect market value. Government data and online valuations can also provide useful insights.

Planning permission and a project schedule

Many extensions fall under Permitted Development, but always check with your local planning department to confirm. Regardless of permissions, building regulations will always apply. Once approved, establish a project schedule — allowing for potential delays — and confirm your insurance covers renovation work. You may also choose to hire a project manager to coordinate contractors and keep the build on track.

What can you get for your budget?

While exact costs vary based on location, specification and design, there are general guidelines that can help you estimate your expected spend.

Generally, you can expect to pay around £1200 per square metre for a single-storey, basic-quality extension.

It’s wise to share your budget with your builder from the start, ensuring accurate material and specification recommendations.

Types of extension

Many extension styles can bring in natural light, improve the layout of your home and enhance the connection between indoor and outdoor spaces. Conservatories offer extensive glazing, while orangeries balance brickwork with roof lanterns. Architects can also incorporate materials like zinc, timber and stone to create unique, statement designs.

Examples of projects

Self-managed Victorian property

A 30m² extension managed by the homeowners themselves, costing just over £88,000.

Oak extension to an Edwardian home

A 14m² oak-framed sunroom using reclaimed materials, costing £110,000.

Two-storey extension

A steel-framed addition adding 100m² to a converted stone mill, costing £161,000.

Second-storey timber frame

A full second-storey timber-frame addition adding 114m² for £200,000.

1960s bungalow remodel

A variety of improvements adding 271m² for £275,000, with advice to keep 10–15% spare budget.

Glazed extension

A steel-and-glass Edwardian extension added 20m² after redesign, costing £414,000.

Brick conversion and extension

An 86m² addition to a 1960s home costing £507,000, with lessons learned about going for the lowest quote.

Loft conversions

Loft conversions remain one of the best ways to add space and can increase property value by up to 20%. Costs depend on roof structure, conversion type, finish level and any additional internal works required, such as fire-safe access or strengthening floors.

Also see our full guide to home extensions for further details.