How to Design a House Extension Using AI – and Why You Still Need an Architect

With artificial intelligence tools now available to everyone, more homeowners are exploring how AI might help them design a house extension. From floor plans to 3D visuals, AI can offer surprisingly helpful early-stage ideas. But while the technology can be exciting and accessible, it still can’t replace the value of a good architect — especially when it comes to developing the brief, meeting regulations, and managing the planning and construction process.

Here’s how you might begin designing a house extension using AI — and where a professional architect makes all the difference.

Step 1: Measure Your Existing House

The first step in any extension project is understanding the existing layout and dimensions of your home. For AI tools to generate useful output, you’ll need an accurate base plan.

There are two main ways to do this:

Option 1: Use LIDAR on an iPhone or iPad Pro

Modern Apple devices equipped with LIDAR (Light Detection and Ranging) can scan your home in 3D. Several apps, such as RoomScan, Polycam or Magicplan, allow you to capture the layout of a room or entire house and export it as a floor plan or 3D model. These scans can be used as the starting point for generating extension options or visuals using AI tools.

Option 2: Manual Measurement

If you don’t have access to LIDAR, you can measure the rooms by hand using a tape measure or laser measurer. Record room dimensions, ceiling heights, door and window positions, and any fixed features like boilers, services, or structural walls. You’ll then need to draw this up manually in a CAD program (or use a free tool like SketchUp or Floorplanner) before inputting into any AI tool.

Step 2: Draw Up Floor Plans and Elevations

Once the measurements are complete, you’ll need to draw up your existing house in plan and elevation. These drawings form the base information that both AI tools and human consultants will rely on.

Plans show the layout of each floor from above, while elevations show the outside face of each wall — vital for any planning application or design study. AI tools often need a clean, dimensioned plan to work from. Depending on the platform, you may need to upload your drawing in a specific format (e.g. PDF, DWG or SVG).

If you're not confident with this step, it’s worth involving a surveyor or architect early on. Inaccurate or poorly drawn base plans will cause problems further down the line.

Step 3: Generate Extension Ideas Using AI Tools

Once you’ve prepared your base drawings, you can explore design ideas using AI-based platforms. A few popular tools that homeowners have begun experimenting with include:

• HomeDesigns AI: Upload floor plans or photos and receive suggestions for layout changes and extension configurations.

• Interior AI or Reimagine Home: Generate interior visualisations to test different styles and configurations.

• SketchUp with generative design plugins: Use AI to propose massing or space planning options based on your inputs.

These tools can offer:

• 3D visuals of potential extensions

• Alternative layouts based on your room sizes

• Style suggestions for interiors or exteriors

• Solar studies or rough planning feasibility (in some cases)

While the results can be inspiring, they’re often very conceptual — not fully resolved, and not designed with your specific planning authority or technical constraints in mind.

Step 4: Understand the Limitations — and Where Architects Come In

AI is brilliant for generating initial ideas. It can quickly test out layouts, create moodboards, and even produce basic 3D visuals. But this is only one small part of what’s involved in a successful home extension.

Here’s why working with an architect is still essential:

1. Forming the Brief Is a Process

From experience, most clients’ briefs evolve a lot in conversation with their architect. What you think you need at the start (e.g. “a bigger kitchen”) often expands into deeper questions: how you want to live, what spaces you really use, and what kind of home you want over time.

AI can’t challenge your assumptions or help uncover what you didn’t know you needed. A good architect will.

2. Planning and Building Regulations Must Be Met

Even the most attractive design from an AI tool still needs to comply with:

• National and local planning policy

• Permitted development rights (if applicable)

• Building Regulations (covering structure, energy, fire, ventilation, access, etc.)

An architect understands how to design in a way that maximises your chances of approval while delivering the space you want. They can also adjust proposals if issues arise during consultation with planners or neighbours.

3. Surveys and Specialists May Be Needed

Depending on your property, you may need:

• A structural engineer’s input

• A arboricultural report

• A ecology report

An architect can manage these relationships and ensure the right information is integrated into the design.

Final Thoughts: Use AI to Explore, Use an Architect to Deliver

AI design tools are a brilliant way to start exploring your ideas. They can help you visualise the potential of your home and give you inspiration before you even speak to a professional.

But they are only tools — not designers, not planners, and not problem-solvers. A qualified architect can take your ideas further, challenge assumptions, and guide you through the complex process of getting your project built. That includes helping form a brief that’s right for your life, securing planning permission, and delivering a finished space that’s well-built, compliant, and joyful to live in.

Thinking about an extension? We’re happy to offer a short discovery call to explore your ideas — whether you’ve sketched something out, played with AI, or are starting from scratch. Get in touch and let’s see what’s possible.