Double Storey Extension

Extension Planning Experts

A double-storey house extension is a simple way to create more space without moving. Whether you need extra bedrooms, a bigger kitchen, or more living space, a double-storey extension makes it possible to do more with your existing home. A well-designed two-storey extension adds both function and value.

Many homeowners choose to build an extension to make better use of their space, especially where outdoor room is limited. Building a double-storey extension can improve the layout of your home across both floors. We handle single and double-storey extensions, working closely with you to plan an extension that fits your needs. If you’re thinking about a two-storey extension, we’re here to support you through every stage.

What Is a Double Storey Extension?

A double storey extension is a type of house extension that increases the size of a home by adding new accommodation at both ground floor and first floor level. It is a popular choice for home owners who need more space but want to remain in their current property, offering a practical alternative to moving. A well designed double storey extension can significantly increase overall floor area while improving how the home functions day to day.

Because it extends over two levels, a double storey extension often makes more efficient use of the available plot than a single storey extension, typically providing better value per square metre. It also gives greater flexibility to redesign the internal layout, making it ideal for adding bedrooms, creating a larger family bathroom or ensuite, expanding the kitchen, or improving living and dining space. When carefully proportioned and detailed, a double storey extension integrates seamlessly with the existing house through appropriate scale, materials and window alignment, while enhancing comfort, functionality and long term property value.

Our Double Storey Extension Projects

Richmond

Bromley, London

Thames Ditton, London

Windsor

Why Choose a Double Storey Extension?

A double storey extension is one of the most cost effective ways to add significant floor area to your home while making efficient use of your existing plot. It is ideal for terraced, semi detached and detached houses, allowing you to create additional space across two levels in one coordinated build, often with better value per square metre than separate projects.

Key benefits
• Add substantial extra space across two floors without needing to move home
• Increase property value by creating high demand accommodation such as extra bedrooms and bathrooms
• Improve the ground floor layout with a larger kitchen, open plan kitchen diner, utility room or family space
• Create better first floor accommodation such as a master bedroom suite, ensuite, or larger family bathroom
• Achieve improved room proportions and a more practical internal layout compared to smaller extensions
• Maintain more of your garden space compared to single storey extensions with the same overall floor area gain
• Improve natural light with well planned window placement, roof detailing and circulation design
• A single build programme for both floors can be more efficient than carrying out works in stages

With the right design approach, a double storey extension can look and feel like it was always part of the original house. Careful attention to scale, materials, window alignment and internal planning helps achieve a seamless result that improves day to day living and provides strong long term value.

Our Featured Works

Our Approach to Double Storey Extensions at Salstan Architecture

At Salstan Architecture, our approach to double storey extensions is focused on creating additional space that feels fully integrated, performs well, and adds long term value. We start by understanding exactly what the home needs to achieve, whether that is extra bedrooms, a larger kitchen, an additional bathroom, improved storage, or a better overall layout. From the outset, we consider how the extension will improve flow across both floors, not just add rooms.

We then develop a double storey extension design that is proportionate to the existing house and appropriate for the street scene. This includes careful attention to massing, roof form, window alignment, and material choices so the new addition sits naturally with the original building. Internally, we focus on room proportions, circulation, natural light and privacy, ensuring the extended ground floor and first floor layouts work together as one cohesive home.

We also design with approvals and construction in mind from day one. Where planning permission is required, we shape the proposal around relevant policy and neighbour considerations, such as overlooking, daylight and boundary relationships. We progress each scheme with clear, coordinated drawings and build ready detailing, supporting a smoother route to tender and construction. The result is a double storey extension that looks considered, functions effortlessly, and is properly resolved for delivery on site.

Our Process Explained in Six Easy Steps

Step 1 - Your 3D Site Survey

An appointed surveyor will come around for a full measured survey of your property. They will also note down all your desired requirements for your proposal.

Step 2 - Drawings Initiated

The project is allocated to one of our architectural designers who will design your project from the ground up, taking into account all your needs.

Step 3 - You Review It

We promise you will have your first draft within 10 working days unless agreed otherwise. You send your designs and get back to us with any changes required. We will then wrap up your drawing to be ready for submission.

Step 4 - Submission & Decision

Your plans will be submitted strategically for swift approval by the council. Expect a decision in 6-8 weeks. We’ll handle any required changes for free!

Step 5 - Technical Design

Once plans are approved, our engineers manage design and regulatory compliance. Get construction quotes from us & compare with others.

Step 6 - Construction

If you decide to move forward with our services, we will promptly arrange a detailed, comprehensive consultation to discuss and finalize your specific requirements, ensuring everything aligns perfectly with your vision.

What Our Clients Say About Us

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Frequently Asked Questions

Do I need planning permission for a double storey extension?

In most cases, yes. Double storey extensions typically require planning permission due to their size, impact on neighbours, and changes to the appearance of the property, although this can vary depending on the site and local constraints.

Is a double storey extension good for adding value?

A well designed double storey extension can significantly increase usable space and market appeal, which often improves long term property value.

How much space can a double storey extension add?

It depends on the available footprint, boundaries, and design constraints, but a double storey extension can provide substantial additional accommodation such as extra bedrooms, an ensuite, a larger family bathroom, and expanded kitchen or living space downstairs.

How do you make a double storey extension look like it belongs to the existing house?

We focus on scale, proportions, roof form, window alignment, and material choices so the extension integrates naturally with the original building and feels cohesive from both inside and outside.

How long does planning permission take for a double storey extension?

In most cases, planning permission takes around 6–8 weeks from validation of the application by the local authority. If amendments are requested, neighbour comments raise issues, or the case is more complex, the process can take longer.