Expanding your space is one of the best ways to improve space, improve comfort, and add value to your property. In 2025, homeowners in London and across the UK are looking for clever ways to upgrade their liveable space, without moving home. The House Extension Cost can assist with planning to avoid unexpected costs.

Studio 20 Architects has a wealth of experience in guiding homeowners through any stage of extensions, from initial designs and planning applications, right through to full construction. Knowing how extension costs are packaged can save you both time and money and enable you to achieve your desired space.

“Did You Know? In 2023, the value of new construction work in Great Britain reached a record high of £139,029 million, marking a 4.2% increase from the previous year.”

This makes careful budgeting and expert advice essential for homeowners planning extensions in 2025.

What factors influence the House Extension Cost in 2025?

The House Extension Cost depends on numerous factors, size, location, design and materials. Generally, London projects will be on the expensive side due to higher labour costs and regulations. Additions to aspects such as energy saving ideas, bespoke features, or heritage issues can all increase costs.

Here are a few pointers:

• Generally, larger house extensions give you more for your money per square metre.
• Quality of materials and finishes directly impacts final costs.
• You may also find added costs and time in regards to planning permissions.

How to calculate House extension cost per m2 for your project

House extension cost per m2 is a common way to give a clear, scalable estimate of prices. You can see how each part of your extension—walls, flooring, roofing—affects your budget by figuring out how much it costs per square meter.

Pointers:

• A 30m² single-storey extension can cost anywhere from £54,000 to £75,000.
• Always plan for extra costs in case something goes wrong.
• Work with your architect to make the design as cost-effective as possible.

Why hire house extension architects London for your project?

Collaborating with house extension architects London guarantees that your project is well designed, will adhere to building regulations, and will add value to your property. An architect can either take your vision and implement a feasible plan or take your ideas and create a suitable design, thinking about considerations like design, structure, and planning application. 

Studio 20 Architects provides a range of services including: 

• Residential house extensions
• Overall Design and Architectural Planning 
• Submission of Planning Applications 
• Consultation on renovations/refurbishments 

Their knowledge will help you avoid potential mistakes and save time in obtaining approval, which will keep your project moving forward.

How does house extension design affect your budget?

The house extension design will have a significant effect on the eventual costs. Generally, simple house extension layouts will be less expensive and take less time to build than bespoke or modern shapes or bespoke extensions with large windows or skylights will add to labour and material costs.

Pointers:

• Straight rectangular extensions are usually cheaper.
• Sustainable materials can help save in the long run.
• Modern layouts add value aesthetically and when reselling your property.

How much do Extension builder prices London influence total costs?

The cost of house extension includes a lot of money for contractors. Prices for extension builders in London stay high because there aren’t many experienced teams and there is a lot of demand for qualified workers. Choosing respected builders makes sure that the job is done well, that safety rules are followed, and that deadlines are met.

Tips: 

• Always get many bids and a full analysis.
• Builders who charge less may not be able to meet quality or deadlines.
• When you choose both skilled architects and builders, you can be sure that the design can be carried out.

Is front house extension a smart investment in London?

A front house extension can greatly improve both the amount of room and the curb appeal. This could mean adding a porch, a corridor, or more living space. However, expansions that face the front of the house frequently have to have stricter planning clearances because they change the way the house looks.

Tips: 

• It adds useful living space and raises the value of the home.
• Needs careful planning and permission from local councils.
• The decisions you make about design here will affect both how it looks and how easy it is to keep up with.

How planning applications and legal approvals affect House Extension Cost

Apart from construction, your cost of house extension includes planning applications, a survey, and building regulations (building codes). Architects who work at Studio 20 Architects can undertake the applications on your behalf, ensuring that our design works within the council’s parameters and obtains approvals without delays.

Important Pointers:

• It’s not uncommon for planning applications to be required for some front aspects and double-storey additions.
• If there is no application process for your build, failing to secure, enforce and follow regulations can lead to fines or costly modifications.
• Seek consultation with an architect as early as possible to build the extension plans around your council compliance regulations and reduce unexpected compliance costs or rainy day funds.

How to make your extension investment worthwhile in 2025

To make sure your extension is worth the money, it is worthwhile to plan ahead of time. A good extension represents a careful and thought-out balance between budget, design, and purpose. By using Studio 20 Architects for your extended consultation, planning, and build, you are able to minimise the House Extension Cost whilst achieving your extension dream space.

Take the first steps in the right direction. By using Studio 20 Architects – your trusted partner for home extensions, architectural design and planning service in London – we will transform your living space with confidence. Our guidance through the concept and planning to completion, your dream home isn’t as far away as you may think!

FAQs

What is the price of a house extension per m² in London?

The price depends on the design and scale and tends to be between £1,800 – £3,200 per m², depending on whether it is single or double storey, materials and finishes.

Will I need to have permission for a front house extension?

Yes, typically front-facing extensions have planning permission (if permitted development is not applicable) to comply with regulations set by your local council.

Why hire house extension architects in London?

An architect will ensure your design is feasible and compliant as well as maintain as much value as possible while trying to avoid costly mistakes.

What hidden costs should I budget?

When budgeting, account for any cost of moving any utilities, structural reinforcements, scaffolding and also allow a contingency of 10 – 15% for any hidden expenses.